Dissertations / Theses on the topic 'Ultrasonic test'

This work describes a thirty-two channel programmable transmitter unit for driving an ultrasonic transmitting array using transducers with thickness resonances of up to 2 MHz. It has been developed to allow the performance of time delay focussed transmitting arrays to be thoroughly investigated before their eventual use in an imaging system. The unit will produce a pulse or continuous wave output which is programmable using either a microprocessor or a computer, in both amplitude and delay or phase. The unit's operation is discussed in some detail and the experimental underwater 1 MHz transducer array used for the functional tests is described. Results are presented showing the performance of the transmitting unit when used with this array and demonstrate that the system provides an effective tool by which a proper assessment of time delay focussing may be made. A computer prediction technique·has been introduced. The computer prediction of the field in the region in front of a focussed ultrasonic array has been obtained by the summation of the fields due to the individual array elements. The shape of the short duration acoustic pulses due to the individual elements is determined.by the electrical drive and transducer characteristics. The prediction technique is valid for any pulse shape which can be represented mathematically, however the results presented here have been limited to the pulse shape used in the experimental work. The algorithm used is suitable for a wide range of array formations and the close agreement of the practical and the simulation work shows the validity of the prediction technique. The experimental array has been used as the basis of a detailed investigation into the resolving power of focussed arrays and a number of results have been derived from this investigation. These are used to support extensive simulation studies and computer prediction techniques. The validity of the simulation techniques is assessed and the effect of considering each transducer in the array as a single small but finite sized centrally placed element is compared with that where each transducer is represented by a number of synchronously driven Huygens radiators. The significance of these results with respect to imaging is discussed. The effect on performance of system error is investigated and an assessment of the tolerance of the time delay technique to these errors is made.

Low alloy steels are widely used in components which operate at high temperatures and pressures, and thus are susceptible to creep. This process involves microstructural changes and degradation of the material which leads to rupture if not detected. Available methods for assessing these factors are currently limited to destructive tests, or to investigation of selected areas of the component surface. Consequently, reliable methods for the detection of creep damage are indispensable, both to guarantee safe operation during the designed lifetime, and to ensure that components possess the physical properties suitable for their required use. Presently, methods including magnetic particle inspection and replication metallography are available for the detection of surface cracks and creep damage. However, there are significant benefits to identifying damage at an earlier stage. A successful plant life strategy demands techniques capable of identifying the initiation of in-service damage within the bulk of structure. Due to the limited availability of test material which may be obtained and the demand for volumetric material characterisation, acoustic NDE techniques offer an attractive means to obtain this information. However, for the effective application of non-destructive characterisation of creep damage, it is fundamentally important to firstly establish an understanding of how acoustic NDE signatures relate to material properties. The research programme undertaken to meet these requirements involved the application of acoustic NDE techniques to meet this task. A specific test programme was developed so that variations in selected microstructural parameters were characterised in terms of structure and properties. These fully characterised specimens then provided the standards required for assessment of volumetric and surface ultrasonic techniques, in both the time and frequency domains.

Thesis (M.Sc.)--City University of Hong Kong, 2006.
"Master of Science in Materials Engineering & Nanotechnology dissertation." Title from title screen (viewed on Nov. 21, 2006) Includes bibliographical references.

Ces travaux de thèse portent sur l'étude expérimentale approfondie d'un composite à base polyamide 66/6 renforcé par des fibres de verres tissés suivant un motif sergé 2/2. L’objectif est de proposer des solutions de Contrôle Non Destructif (CND) basées sur les ultrasons afin de détecter différents niveaux d’endommagement induis. Pour cela, une étude approfondis des mécanismes d’endommagement apparaissant lors de sollicitations en traction suivant l’axe des fibres et hors axes est réalisé. Le cas d’impact induis par poids tombant est également étudiés. En effet, ces différents cas de sollicitions entraînent l’apparition de différent mécanismes d’endommagement. Ces derniers, ainsi que leur ordre d’apparition, sont caractérisés par Microscopie Electronique à Balayage (MEB) et tomographie à rayons X principalement. L’évaluation de la réduction du module élastique pré et post chargement ainsi que la fraction volumique de vide montrent une évolution de l’endommagement plus importante lors de chargement en traction hors axes des fibres que lors de chargement suivant l’axe. Lors des essais d’impact par poids tombant différents niveaux d’énergie sont considérés en restant proche du domaine des BVID en vue d’éprouver la sensibilité des méthodes de CND. Deux méthodes de CND par ultrasons étudiées durant ce projet peuvent être mises en avant. Premièrement, par mesure de la vitesse de propagation des ondes dans plusieurs directions du composites, le tenseur de rigidité est estimé dans tous ces cas de sollicitation mécanique pour différents niveaux d’endommagement. Des indicateurs d’endommagement basés sur ces mesures montrent une évolution de l’état d’endommagement similaire à celle discutée précédemment. Deuxièmement, une étude de la détection de l’endommagement par ondes guidées est menée. Aucun changement des modes transmit n’est visible lors de l’augmentation de l’état d’endommagement. L’évolution de l’énergie du signal transmis est alors proposée et validée comme indicateur d’endommagement efficace pour des chargements en traction mais pas pour l’impact. La mesure du décalage temporel à en revanche permis une localisation et une quantification de l’endommagement induit par impact
The present study is focused on the experimental study of a polyamide 66/6 based composite reinforced by a 2/2 twill weave glass fabric. The aim is to propose Non Destructive Evaluation (NDE) methods based on ultrasound that can efficiently distinguish different damage state. In order to do so, an investigation of the damage mechanisms induced by different type of mechanical solicitations. Tension along and off the axis of the fibers was considered as well as the case of drop weight impact. Those solicitations were shown to induce different damage mechanisms. The latter were characterized by means of Scanning Electronic Microscopy (SEM) and X-Ray tomography mostly. The decreasing of the elastic modulus and the void volume fraction evolution were shown to be more significant for the samples loaded in tension off-axis. During the drop weight impact tests, the energies were considered in order to remain close to the Barely Visible Impact Damage (BVID) regime in order to experience the capability of the ultrasound based NDE methods. Two NDE methods investigated during this study deserve to be highlighted. Firstly, the stiffness tensor was estimated by means of phase velocities measurements in different propagation direction. Damage indicators based on results from this method were proposed. They were found to give results similar with the one from the evaluation of damage discussed earlier on. Secondly, a study of the damage detection using guided waves was performed. No mode conversion effect was observed from this investigation. Consequently, the signal energy was proposed as damage indicator and was found to be suitable to detect damage induced by tension but not by impact. The measure of time shift allowed obtaining a localization and evaluation of the damage induced by impact

Non-destructive testing has become necessary to ensure the quality of materials and components either in-service or at the production stage. This requires the use of a rapid, robust and reliable testing technique. As a main testing technique, the ultrasound technology has unique abilities to assess the discontinuity location, size and shape. Such information play a vital role in the acceptance criteria which are based on safety and quality requirements of manufactured components. Consequently, an extensive usage of the ultrasound technique is perceived especially in the inspection of large scale composites manufactured in the aerospace industry. Significant technical advances have contributed into optimizing the ultrasound acquisition techniques such as the sampling phased array technique. However, acquisition systems need to be complemented with an automated data analysis procedure to avoid the time consuming manual interpretation of all produced data. Such a complement would accelerate the inspection process and improve its reliability. The objective of this thesis is to propose an analysis chain dedicated to automatically process the 3D ultrasound volumes obtained using the sampling phased array technique. First, a detailed study of the speckle noise affecting the ultrasound data was conducted, as speckle reduces the quality of ultrasound data. Afterward, an analysis chain was developed, composed of a segmentation procedure followed by a classification procedure. The proposed segmentation methodology is adapted for ultrasound 3D data and has the objective to detect all potential defects inside the input volume. While the detection of defects is vital, one main difficulty is the high amount of false alarms which are detected by the segmentation procedure. The correct distinction of false alarms is necessary to reduce the rejection ratio of safe parts. This has to be done without risking missing true defects. Therefore, there is a need for a powerful classifier which can efficiently distinguish true defects from false alarms. This is achieved using a specific classification approach based on data fusion theory. The chain was tested on several ultrasound volumetric measures of Carbon Fiber Reinforced Polymers components. Experimental results of the chain revealed high accuracy, reliability in detecting, characterizing and classifying defects.

Defected wheel are one the major reasons endangered state of railroad vehicles safety statue, due to vehicle derailment and worsen the quality of freight and passenger transportation. Therefore, timely defect detection for monitoring and detecting the state of defects is highly critical. This thesis presents a passive non-contact acoustic structural health monitoring approach using ultrasonic acoustic emissions (UAE) to detect certain defects on different structures, as well as, classifying the type of the defect on them. The acoustic emission signals used in this study are in the ultrasonic range (18-120 kHz), which is significantly higher than the majority of the research in this area thus far. For the proposed method, an impulse excitation, such as a hammer strike, is applied to the structure. In addition, ultrasound techniques have higher sensitivity to both surface and subsurface defects, which make the defect detection more accurate. Three structures considered for this study are: 1) a longitudinal beam, 2) a lifting weight, 3) an actual rail-wheel. A longitudinal beam was used at the first step for a better understanding of physics of the ultrasound propagation from the defect, as well, develop a method for extracting the signature response of the defect. Besides, the inherent directionality of the ultrasound microphone increases the signal to noise ratio (SNR) and could be useful in the noisy areas. Next, by considering the ultimate goal of the project, lifting weight was chosen, due to its similarity to the ultimate goal of this project that is a rail-wheel. A detection method and metric were developed by using the lifting weight and two type of synthetic defects were classified on this structure. Also, by using same extracted features, the same types of defects were detected and classified on an actual rail-wheel.
Master of Science

Ultrasonic transducers are used in many fields of daily life, e.g. as parking aids or medical devices. To enable their usage also for mass applications small and low- cost transducers with high performance are required. Capacitive, micro-machined ultrasonic transducers (CMUT) offer the potential, for instance, to integrate compact ultrasonic sensor systems into mobile phones or as disposable transducer for diverse medical applications. This work is aimed at providing fundamentals for the future commercialization of CMUTs. It introduces novel methods for the acoustic simulation and characterization of CMUTs, which are still critical steps in the product development process. They allow an easy CMUT cell design for given application requirements. Based on a novel electromechanical model for CMUT elements, the device properties can be determined by impedance measurement already. Finally, an end-of-line test based on the electrical impedance of CMUTs demonstrates their potential for efficient mass production.

Le projet de normalisation européenne c. E. N. /t. C. 138 présente des méthodes et des critères en vue de vérifier et caractériser les appareils et traducteurs utilisés en contrôle non destructif par ultrasons. Le but de cette thèse est de montrer l'applicabilité des méthodes proposées, et d'en effectuer une analyse critique. Nous avons porté notre attention sur les méthodes de caractérisation des traducteurs immersions proposées par le projet de norme c. E. N. /t. C. 138 n 237 et compare les résultats à ceux obtenus par interférométrie laser. Des simulations sur un modèle simplifié nous permettent de compléter l'analyse des différents résultats expérimentaux. L'influence de la taille du réflecteur sphérique sur le champ ultrasonore a été particulièrement étudiée. L'analyse des méthodes définies par le projet de norme c. E. N. /t. C. 138 n 230 sur la vérification des appareils ultrasonores utilisés en contrôle non destructif par ultrasons, est proposée par la mise au point d'un banc de mesure informatisé conforme aux textes de norme. Pour ce faire, nous avons développé un logiciel d'assistance informatique, Verapus qui guide l'operateur dans le déroulement des protocoles de vérification.

Cette thèse a pour objectif d’instrumenter un contenant familier dans le domaine du biomédical et de la chimie (un tube à essai) avec des éléments piézoélectriques à ondes longitudinales (L) et d’implémenter, en les optimisant, diverses méthodes ultrasonores pour mesurer les viscosités rapidement, sans changer de banc de mesure et cela de quelques Hz à plusieurs dizaines de mégahertz au voisinage de la température ambiante. Grâce au système mis en place il est possible en quelques minutes de déterminer le comportement rhéologique du liquide, étudié en mesurant sa viscosité de cisaillement. Par ailleurs, la gamme de viscosité atteinte est extrêmement large puisque les mesures sont possibles de quelques dizaines de mPa.s à plusieurs centaines de Pa.s. Enfin, au-delà de résultats quantitatifs en terme de viscosité, le banc de mesure peut être aussi utilisé pour suivre de façon qualitative des cinétiques de réaction (polymérisation par exemple)
The main goal of this thesis is to set specific piezoelectric elements emitting longitudinal waves (L) on a well-known container in the field of biomedical and chemistry (a test tube) and to implement with some optimizations various ultrasonic methods to measure viscosities quickly, without changing the measurement bench. The measurement has to be done from a few Hz to several tens of megahertz around room temperature. Up to now it is possible to determine in a few minutes the rheological behavior of the liquid studied thanks to the evaluation of its shear viscosity. Furthermore, the viscosity range reached is extremely wide: the measurements are possible from a few tens of mPa.s to several hundred Pa.s. Finally, beyond quantitative results in terms of viscosity, the measurement bench can also be used to qualitatively monitor reactions (polymerization for example)

In Diesel engine blocks properties such as tensile strength, heat conductivity, sound damping, engine vibration and noise are strongly influenced by graphite shape and volume percent in the matrix microstructure. In this study, the engine blocks were produced at ELBA Basinç
li Dö
kü
m Odö
ksan Cast iron foundry in Osmaneli Turkey by performing casting into furan resin sand and preparing cast iron liquid alloy in induction furnace that were treated with Mg by using ladle method. The main purpose of this study is to achive 0 &ndash
25% volume nodularity and remaining is compacted graphite in the produced engine blocks. The shape and volume percent of graphite particles were characterized by an image analyze system. In the first part of this work, after the diesel engine blocks were produced at ELBA Basinç
li Dö
kü
m Odö
ksan Cast iron foundry in Osmaneli Turkey, the blocks were cut and samples were obtained from 14 different thicknesses of diesel engine blocks. Afterwards, the samples were examined under optical microscope, Soif XJP-6A. The nodularity and compacted graphite values were obtained numerically with the help of Materials Plus image analyzer systems, which is attached to the optical microscope. v In the second part of the study, the diesel engine blocks which are produced at Odö
ksan were examined by ultrasonic test that was done by using USM 35 flaw detector test machine. Solidification &ndash
time and temperature &ndash
time simulations were also done by using NovaCast NovaFlow simulation code. Finally mathematical formulas for 13 different thickness of diesel engine blocks were obtained by using excel linest code. The compacted graphite volume percent observed at different sections of the diesel engine blocks were found to be a function of cooling rate and chemical composition. Best results were obtained when chemical Mg/S ratio was approximately 1 and C.E.V. was between 4.40 &ndash
4.50.

The measurement and monitoring of the elastic properties of cement-based materials is very important for assessing their quality, integrity and performance. Due to the nonhomogeneous and time-dependent characteristics of these materials, it is difficult to observe the developments in elastic properties with traditional destructive methods. The aim of this thesis is to determine and monitor elastic properties of mortar specimens made with different cements by using resonant frequency and ultrasonic pulse velocity test methods, and to obtain relationships between these elastic properties. For this purpose, eight different cement mortar mixtures were prepared with different constituent CEM I cements. Dynamic elastic moduli, static elastic moduli, dynamic Poisson&rsquo
s ratio and strength of these mixtures were observed for different ages. The relationships between these elastic properties are determined and the results obtained from two different nondestructive test methods are compared. Although nondestructive tests made it possible to obtain elastic properties of mortar mixtures, the results revealed that it is very difficult to develop a single relationship between different elastic properties of mortars with varying mixture proportions. This situation is mainly due to the anisotropy and nonlinear behavior of the mortar and the difficulty of describing the actual behavior of mortar by formulations defined for perfectly elastic materials.

This research presents a novel microfabrication approach and testing methodology for cylindrical ion trap (CIT) microarray tunable for mass- spectrometers. The growing interest in cylindrical ion trap (CIT) mass-spectrometers is primarily due to ease with which cylindrical geometry can be realized as compared to hyperbolic surfaces found in conventional quadrupole ion traps. Also due to the fact that the potential at the center of hyperbolic electrode in quadrupole ion trap and cylindrical electrode in cylindrical ion trap (CIT) does not differ significantly[2]. Since the RF voltage required to eject a given mass-to-charge ion scales as the square of the ion trap radius, a decrease in ion trap dimensions provides a significant reduction in electronics requirements, thereby providing a pathway for overall system miniaturization. The reduction in sensitivity due to reduced ion storage capacity as a result of miniaturization can be improved by employing an array of identically sized ion traps. Microfabrication approach promises excellent uniformity in the fabrication of identically sized holes which in turn leads to low-cost high performance CIT microarray for mass spectrometers[1,2]. The criterion used for the determination of trap diameter was to ensure that the hole to be 1.09 times the wafer thickness to provide optimal potential to trap ions[1]. The end- plates were designed to optimize the electron and ion transmission into and out of the ion trap and provide a high quality electric field definition within each cylindrical ion trap (CIT)[3]. Two different approaches, namely deep reactive ion etching (DRIE) and mechanical drilling using ultrasonic disc cutter were proposed and used for the fabrication of ring-electrode which forms the main body of the ion trap. Excellent uniformity in hole diameter was observed in both the approaches. The end-plates were fabricated using deep reactive ion etching (DRIE) which provided high transmission rigid grid structure for ions and electrons. Standard Bosch process was used for deep reactive ion etching (DRIE). The two electrodes were metallized using electroless plating which provides excellent uniformity of coating even on end-plate structures with 5micro m through holes. CYTOP[trademark], a cyclized perfluoro polymer, was used as an insulation layer and intermediate bonding layer between the ring electrode and end-plates. The breakdown voltage for a released 16 micro m thick CYTOP[trademark] layer was found to be 1.47KV. An assembly for testing miniature cylindrical ion trap (CIT) was designed and built. An electron impact ionization source was used for generation of ions. Mass selective instability scan was used to selectively eject ions with different mass-to-charge ratio. A cylindrical ion trap (CIT) with 4mm diameter was fabricated and tested for analyte gases such as krypton and xenon.

Environment conditions and moisture presence in masonry structures may affect durability or even mechanical properties of architectural heritage. Among all the deterioration causes, the degradation of historic masonry by freeze-thaw cycles and different moisture amount are considered to evaluate their influence on elastic properties. Therefore, two experimental campaigns were carried out in the present study. The first one was performed at the Dept. of Geotechincal Engineering at Tongji University, to assess the influence of freeze-thaw cycles on elastic modulus of historic Chinese brick. The static elastic modulus was evaluated from the compressive strength test on masonry specimens subjected to different numbers of freeze-thaw cycles. Moreover, strength decay of the masonry was investigated, also analysing data obtained during ultrasonic test (UPV, non-destructive test). The aim of this step was to obtain the dynamic elastic modulus. Thanks to interpolation of the obtained data it was possible to improve the knowledge of the Elasticity modulus’ reduction of historic masonry subjected to freeze-thaw cycles. The second experimental campaign was performed at DICAM, University of Bologna, on ancient Chinese and Italian bricks, to assess the sensitivity of dynamic elastic modulus to moisture amount. In particular the influence of water presence in the material pores on the UPV measurements. The close relationship between the ultrasonic pulse velocity and the moisture content was investigated on brick cores in dry, 50% saturated and saturated conditions. Practical value and one of the main contribution of the experiments was the investigation of external factor and intrinsic properties of porous materials which directly influence the ultrasonic pulse velocity test.

Excessive and compulsive ethanol drinking is one of the most serious public health issues. Therefore, it is vital to increase the knowledge about risks and protection for alcohol use disorders (AUD) to optimize prevention and treatment strategies. Ethanol consumption commonly initiates during adolescence when extensive neuronal maturation and development also occurs. Early exposure to ethanol is a risk factor for AUD, but the effects of adolescent drinking and the basis for the individual susceptibility to AUD are not fully understood. The interactions between genotype and environmental factors determine the individual risk for AUD and this thesis aimed to examine the environmental impact. The specific aims were to investigate 1) how early-life conditions affect adolescent voluntary ethanol drinking, behavioural profiles, endogenous opioids and response to treatment with an opioid antagonist (naltrexone), and 2) whether alterations detected in the offspring may be mediated by variations in maternal behaviour. A rodent maternal separation (MS) model was used to mimic a protective and risk-inducing early-life environment, respectively, with the use of 15 min (MS15) or 360 min (MS360) of daily MS. The main findings were 1) the MS360, but not the MS15 rats, responded to naltrexone following adolescent ethanol drinking; all adolescent rats had a high voluntary ethanol intake independent of early environmental conditions whereas in the adult groups the MS360, but not the MS15 rats, increased their ethanol intake and preference over time; adolescent ethanol exposure resulted in higher dynorphin levels in hippocampus and higher Met-enkephalin-Arg6Phe7 in the amygdala, independently of rearing conditions, 2) behavioural profiling using the multivariate concentric square field™ test showed: the young MS360 rats had increased risk assessment and risk taking behaviour compared to the young MS15 rats; the young MS15 rats increased, whereas the young MS360 rats decreased, their risk assessment and risk taking behaviour over time; differences in pup-retrieval strategies where the MS360 dams retrieved some pups into a safe area but as compared to MS15 rats they left more pups in a risk area; increased risk assessment behaviour in the MS360 dams immediately after weaning. Taken together, early-life environmental conditions alter adult but not adolescent drinking, the response to naltrexone, and behaviour in dams and offspring. Adolescent rats consumed more ethanol independent of rearing conditions and displayed increased opioid levels in brain areas related to cognition and addiction.

The diploma thesis deals with non-destructive testing of concrete as well as with the relationship between determined parameters and the compressive strength of concrete. The thesis is mainly focused on the ultrasonic pulse velocity method and the rebound hammer test. The experimental part of the thesis describes non-destructive tests performed on concrete blocks. The compressive strength was tested on the drill cores taken from the concrete blocks. The aim of this thesis is to find regression models of the relationship between the compressive strength and non-destructive parameters, and the subsequent analysis of the results.

Fresh properties of mortars are important factors in altering the performance of self compacting concrete (SCC). Measurement of the rheological properties of the fine mortar part of concrete is generally used in the mix design of SCC. It can be stated that SCC rheology can be optimized if the fine mortar part of concrete is designed properly. However, measurement of the rheological properties is often impractical due to the need for complex equipment. Therefore, more practical methods of assessing mortar workability are often preferred. In this study, four mineral admixtures, three superplasticizers (SP) and two viscosity modifying admixtures (VMA) were used to prepare self compacting mortar (SCM). The mineral admixtures included fly-ash, brick powder, limestone powder, and kaolinite. Two of the SPs were polycarboxylate based and another one was melamine formaldehyde based. One of the viscosity modifying admixtures was based on an aqueous dispersion of microscopic silica and the other one was based on high molecular weight hydroxylated polymer. Within the scope of the experimental program, 43 mixes of SCM were prepared from different materials with keeping the amount of mixing water constant. Workability of the fresh mortar were determined using V - funnel and slump flow tests. The setting time of the mortars, were also determined. The hardened properties that were determined included the ultrasonic pulse velocity (UPV) and the strength which was determined at 7, 28, and 56 days. It was concluded that among the mineral admixtures used, only fly-ash and limestone powder increased the workability of the mixes. The two polycarboxylate based SPs yield approximately the same workability and the melamine formaldehyde based SP was not as effective as the other two.

Cette these retrace les etapes rencontrees lors du projet de recherche et developpement: mise au point d'un anemometre ultrasonore correlatif. Dans la premiere moitie du rapport sont presentes differents elements devant permettre de poser rigoureusement et precisemment le probleme: caracterisation d'un appareil repondant a un ensemble de besoins et de contraintes. Dans la deuxieme moitie du rapport sont presentees les experimentations et les etudes necessaires a la mise au point d'un anemometre prototype. Ces experiences sont relatives a la faisabilite de l'appareil aux methodes de traitement de l'information (correlation, statistiques, redondance), et aux problemes technologiques rencontres (lies surtout a l'utilisation des ultrasons dans l'air). Enfin, les resultats de tests de validation en soufflerie sont exposes

Ultrasonic Pulse Velocity (UPV) and Rebound test as non-destructive techniques may effectively contribute to in situ analysis of bricks and masonries elements for the restoration, rehabilitation and strengthening of historic buildings. Fired-clay bricks were commonly used in buildings in ancient China, but there is few knowledge on their behaviour in environmental conditions. Moisture is one of the main factors that cause deterioration in historic building, in particular in areas with natural freeze-thaw cycles. In this work, two laboratory experiments were carried out, at Tongji University, China, and DICAM Department of Bologna University, Italy, respectively. Fired-clay bricks about 200 years old were collected from demolished buildings in Changzhi City in Shanxi Province, belonging to the Yellow River Region, where the climate involves natural freeze-thaw cycles. The aim was to evaluate how the frost damage changes the physical and mechanical properties of Chinese historical bricks and masonries. Several non-destructive methods were used, focusing on the effectiveness of Ultrasonic Pulse Velocity (UPV) for evaluating physical and mechanical properties of Chinese historic grey bricks and masonries. Destructive tests were also used to evaluate compressive strength and static elastic modulus. The samples showed a reduction of their properties due to freeze-thaw cycles. The presence of water affected the values of the analysed parameters, leading to a decrease of UPV. The trend determined by these methods can be used to assess the uniformity of bricks and to detect areas of poor quality or deteriorated masonry structures.

The diploma thesis deals with influence of the used adhesive to large format tiles properties after installation. Properties on large format tiles were monitored by ultrasonic pulse velocity method. Hydraulic setting adhesives were tested in second part. Strength and modulus of elasticity were tested. The development of shrinkage over time was also monitored. The results were summarized in tabular and graphical form and were examined by simple statistical analysis to determine resulting conclusions.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, 1986.
Microfiche copy available in Archives and Science.
Bibliography: leaves 31-35.
by Tien-when Lo.
M.S.

Present and future demonstrator designs were used to demonstrate the quality assurance of welds. The NDT methods tested on prototype demonstrator parts are: visual inspection, radius gauges, throat size gauge, liquid-penetrant testing, magnetic particle testing and ultrasonics with pulse echo and phased array. The other methods like eddy current, time of flight diffraction, radiography, impression test, macro test and infrared thermographs are currently being analyzed along with their inspection costs.   The control plans for present and future designs with corresponding present and future NDT methods are suggested to minimize a shift in process. Magnetic particle testing revealed a lack of fusion and cracks for fillet welds, whereas ultrasonic pulse echo and phased array identified an internal lack of fusion, inner pores/slag inclusions on butt welds. Ultrasonic PAUT & TOFD could be used for accurate defect identification and thermography for online identification of lack of penetration, depth of penetration and weld parameters.
Weight reduction by improved weld quality (WIQ)

Concrete structures may be at risk to deteriorate by alkali-silica reaction (ASR), when they are maintained under the conditions supporting the reaction. This reaction causes the expansion of concrete and generates microcracking in the interior part and macrocracking on the surface of concrete. This transformation can lead to serious durability problems in concrete structures, which decrease their technical and economical management. The aim of this study is to monitor the damage due to ASR progression using mechanical and nondestructive tests on specimens of various scales: mortars, laboratory concrete and cores collected from a large hydraulic structure. Two Canadian crushed aggregates were used: Spratt limestone as a reactive aggregate and Limeridge limestone as a non-reactive aggregate. Two mortars and two concretes were made from these aggregates. Mortars were made according to Canadian standard CSA A23.2-25A and stored at 38[degré]C in 1 molar NaOH, solution and concretes were made and stored at 38[degré]C in humid air (R.H>90%) according to Canadian standard CSA A23.2-14A. Also two types of concrete cores containing reactive aggregates (siliceous clayey limestone and Potsdam sandstone) from two concrete locks affected by ASR were kept at 38[degré]Cin 1 molar NaOH solution. Expansion and mass variation of all specimens were measured regularly during the reaction evolution. In a first step, the properties of aggregates were characterized and their reactive silica content was measured. Non-destructive test methods were based on measurement of ultrasonic pulse velocity and resonant frequencies (longitudinal and transversal) of mortar, concrete and concrete cores. Also some other investigations were performed on the specimens: compressive and tensile strength, modulus of elasticity, non linear acoustic test, petrographic analysis by SEM and Damage Rating Index measurement. The main observations and recommendations are: (1) Measurement of elastic modulus of elasticity is the best mechanical test to assessing ASR damage in concrete. (2) The relation was observed between the expansion of mortars and the variation in its petrography features. (3) There was a good relationship between expansion and the degree of damage associated by ASR in concrete and concrete cores assessed by Damage Rating Index method. (4) Measurement of non linear parameters and resonant frequencies are the best nondestructive techniques for assessing ASR progression. A direct correlation was shown between the expansion of concrete cores and the reduction of dynamic modulus and increasing the nonlinear parameters.

Orientador: Raquel Gonçalves
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agricola
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Resumo: é praticamente toda exportada em sua forma in natura sem que a ela seja agregado valor de beneficiamento. Um dos problemas enfrentados pela indústria moveleira é o fato da madeira não ser submetida à classificação, dificultando a elaboração de projetos e a certificação da qualidade do móvel confeccionado a partir deste material. Nesse contexto as empresas moveleiras brasileiras buscam parâmetros para composição e certificação de seu produto, sendo atualmente a norma brasileira ¿Projeto de Estruturas de Madeira¿ ¿ NBR 7190/97, o único instrumento norteador para a caracterização de propriedades da madeira. No entanto, nesse setor as dificuldades para a obtenção de corpos-de-prova nas dimensões especificadas por esse texto normativo têm gerado dúvidas quanto aos resultados de caracterização de propriedades, de maneira que este trabalho teve como objetivo principal verificar se os valores do módulo de elasticidade e da tensão de ruptura no ensaio de compressão paralela às fibras podem ser considerados estatisticamente equivalentes, desde que sejam mantidas a proporcionalidade da dimensão do corpo-de-prova. Para isso adotou-se, como alternativa ao corpo-de-prova proposto pela NBR 7190/97, a dimensão 0,03 m x 0,03 m x 0,09 m. Os ensaios foram realizados utilizando-se 7 diferentes espécies de madeira com densidades variadas, buscando-se, com essa amostragem, a generalização dos resultados. Como objetivo secundário se buscou avaliar a influência das dimensões do corpo-de-prova e da freqüência do transdutor na velocidade de propagação de ondas de ultra-som na direção longitudinal. As espécies adotadas foram: Cerejeira (Torresea sp), Perobinha (Paratecoma peroba) , Cabreúva-vermelha (Myroxylon peruiferum), Angico-preto (Anadenanthera macrocarpa), Garapeira (Apuleia leiocarpa), Eucalipto grandis ( Eucalyptus grandis) e Pinus elliotti (Pinus elliottii). Todos os corpos-de-prova foram ensaiados com aproximadamente 12% de umidade e os ensaios foram realizados em ambiente controlado (21° C ± 1°C). Os resultados permitiram concluir que a hipótese foi verdadeira para todas as espécies estudadas quando se considera a tensão de ruptura
Abstract: Most of the exported wood in Brazil is unprocessed, without any aggregated value. To change this scenario technology for wood processing and qualification are required. One of the problems faced by the furniture industry refers to the non classification of the wood, which cause difficulties to projects elaboration and quality certification of the furniture made from this material. In this context the Brazilian Industries of furniture seek for parameters to certificate its products, and the NBR 7190/97 standard ¿Project of Structures of Wood " is, nowadays, the only instrument for the characterization of wood properties. However, for the furniture industry it is very difficult to obtaining the dimensions specified by the standard. This research had as main objective to verify if the means values of the modulus of elasticity and rupture in compression parallel to the grain can be considerate statistically equal, when smaller specimen are used, if the proportionality is maintained. For that it was adopted, as alternative to the specimen proposed by NBR 7190/97, the dimension 0.03 x 0.03 x 0.09 m. For the experiments there were used 7 different species with varied densities. The secondary objective was to evaluate the influence of the specimen size and of the transducer frequency in the speed of ultrasound wave propagation in the longitudinal direction. The adopted species were: Cerejeira (Amburana cearensis), Perobinha (Paratecoma peroba), Cabreúva vermelha (Myroxylon peruiferum), Angico-preto (Anadenanthera macrocarpa), Garapeira (Apulleia leiocarpa), Eucalyptus grandis, (Eucalyptus grandis) and Pinus ellioti (Pinus elliottii). All specimens were tested with approximately 12% moisture content and were accomplished in controlled atmosphere (21° C ± 1°C). The results allowed concluding that the hypothesis was true for all the studied species when the rupture in compression parallel to the grain was considered. For the module of elasticity this hypothesis was not confirmed for two species, from the seven evaluated (garapeira e eucalipto). Although, the mean difference between the results obtained in the tests using both specimens size was 10%, smaller then the maximum allowed variability in mechanical tests (18%). For the ultrasonic velocity propagation four species did not presents statistical variation with the modification of the size of the specimens - cerejeira, garapeira, pinus and eucalyptus while for the perobinha, angico and cabreúva the ultrasonic wave velocity propagation could not be considered statistically equal when the dimension of the specimens was modify. On average (considering all the studied species) the relationship among the ultrasonic wave velocity propagation (VLL) in normalized specimen and in proposed specimen was 0.99, being respectively the maximum and the lower relationships of 1.02 and 0.93. The velocity of wave propagation presents larger variations for values of length of wave percolation/wave length (L/?) up to 3, being more constant above that limit. It was also possible to verify, for the studied species, that the velocity of wave propagation increases with the increase of the transducer frequency. Key words: modulus of elasticity of wood; compression strength parallel to the fiber; ultrasonic wave velocity; dynamic constant
Mestrado
Construções Rurais e Ambiencia
Mestre em Engenharia Agrícola

The diploma thesis deals with different methods of determining levels of degradation of concrete due to freezing, also considering the options of freeze thaw resistance determination in structure. At first the properties of concrete and possible mechanisms of concrete degradation are described – mainly the effects of freezing water in the inner structure and of the combination of freezing water and de-icing chemicals on the surface. Principle and properties of air-entrained concrete are also mentioned. An overview of the approaches that current standards use to determine the freeze-thaw resistance of concrete is listed, followed by description of the tests that are used on air-entrained concrete specimens in the main part of the thesis. A portion of the test specimens was made in moulds while the rest was obtained from structure (concrete block). The non-destructive tests used are evaluated in several different ways and their results are compared with the destructive tests. Comparison and evaluation of different approaches used to determine the freeze-thaw resistence of concrete are the main outcome of this thesis.

Improving the quality of metal castings for serial production of automotive industry, leading to improvements in the properties of casts and their lower costs. This publication analyzes the non-metallic inclusions contained in casts of heads of internal combustion engines, molded of Nemak Czech Republic, Ltd. Tackling includes analysis of size, shape, chemical composition and hardness of the specific non-metallic inclusions. The thesis describes the purity metal holding furnaces and proposals to eliminate inclusions from metal.

On passe en revue les diverses méthodes de contrôle non destructif et on présente en particulier les techniques de générations et détection des ondes de surface sur matériaux non piézoélectriques. On discute des problèmes de conversion d'une onde plane de volume en une onde de surface. On présente la réalisation de la sonde à ondes de surface focalisées et les performances attendues à partir de modèles théoriques simples. On décrit les montages expérimentaux ayant permis la caractérisation de la sonde et on confronte les résultats obtenus à la théorie précédemment exposée. On présente l'application des ondes de surface focalisées au cas de deux matériaux non piézoélectriques: l'alumine et le carbure de silicium, dans lesquels on relève le profil de défauts non apparents.

Since their inception, building materials are constantly improving. New ways to explore and improve the material's properties are constantly investigated (especially to improve the mechanical and deformation characteristics of the materials). This thesis is focused on identifying and comparing values of the modulus of elasticity of fine-grained composites. These features are compared with respect to water cement ratio, ageing and compressive strength of the investigated materials. Afterwards, the values of the modulus of elasticity are studied in the relation to the tested materials.

El hormigón armado compuesto de cemento Portland fue inventado hace algo más de un siglo aproximadamente y se ha convertido en el material más utilizado en la construcción. La durabilidad de este hormigón es una de las consideraciones más importantes a ser tenidas en cuenta en el diseño de nuevas estructuras y en la evaluación estructural de las ya existentes. Cuando un hormigón sujeto a un ambientes o cargas que puede degradarlo, como puede ser su uso en puentes y ambientes marinos o si contiene grandes cantidades de alúmina o áridos reciclados, el conocimiento o predicción de su durabilidad es una aspecto crítico para su comportamiento en servicio. Los ensayos no destructivos se han mostrado como unos de los ensayos preceptivos con una importancia económica y social más relevante desde que se han aplicado para la auscultación de la durabilidad de las estructuras de hormigón pertenecientes a la ingeniería civil, donde estos materiales son ampliamente utilizados. En cualquier caso, el uso de las técnicas no destructivas en estos materiales no está suficientemente implementado, hecho este motivado por las características heterogéneas de su microestructura. De todos los métodos no destructivos aplicables para el hormigón, el uso de pulsos ultrasónicos es de gran interés para la caracterización de la microestructura y las propiedades de materiales heterogéneos. El objetivo del presente trabajo es obtener un procedimiento de evaluación del ciclo de vida del hormigón preparado y puesto en servicio para ambientes marinos. Además, será estudiado y analizado la incorporación de varias metodologías (destructivas y non destructivas) para caracterizar el proceso de degradación de morteros y hormigones expuestos a disolución de sulfato de sodio y a exposición en disolución de nitrato amónico. Con esta finalidad, una integración adecuada de diferentes técnicas será usada para la caracterización de propiedades y el seguimiento del proceso de degradación que afectan al hormigón. Como objetivos adicionales, destaca que fueron estudiadas las relaciones entre los parámetros destructivos y no destructivos, así como la relación entre los distintos parámetros no destructivos entre sí. Muchos de los estudios anteriores que han usado la inspección ultrasónica las cuáles fueron utilizadas para determinar la relación agua/cemento del mortero, de la pasta de cemento y del hormigón, o para monitorizar los cambios estructurales, para diferentes relaciones a/c, en el proceso de curado. En este trabajo de investigación fue analizado el efecto que tiene para diferentes relaciones a/c en los parámetros ultrasónicos durante el proceso de degradación. Para este objetivo, se utilizaron un Cemento Portland tipo II A L 42.5 (LPC), y otro sulforresistente tipo I 42.5R/SR (SRPC) que fueron usados en la fabricación de dos marcos de hormigón, los cuales fueron utilizados como hormigón en servicio (caso real). Para el estudio del efecto de la variación de a/c en los parámetros ultrasónicos durante la degradación se utilizaron muestras de mortero con deferentes relaciones agua cemento 0.525- 0.45- 0.375 and 0.30 a partir de LPC para obtener diferentes niveles de degradación. Para monitorizar el proceso de degradación se utilizó la inspección por pulso/eco (1 y 3.5 MHz) para la obtención del parámetro del área del perfil de atenuaciones (APA) el cual fue estimado por L Vergara et al., 2003 y usado por Fuente et al, 2004. Para seguir el proceso de curado de pasta de cemento y morteros, este parámetro ha demostrado una alta sensibilidad para caracterizar los cambios microestructurales de materiales derivados del cemento a lo largo de su curado. El método de transmisión se ha utilizado para la determinación de las velocidades de ondas longitudinales con la frecuencia de 1MHz y transversales con la frecuencia de 500 kHz. La velocidad ultrasónica también ha demostrado la capacidad para seguir los cambios microestructurales de un modo sencillo porque dicho parámetro está relacionado con la variación de las propiedades mecánicas, y bajo ciertas premisas, con la variación de la porosidad. El análisis con la imagen ultrasónica con 2 MHz fue también usada para la consecución de los mismos objetivos. Como métodos destructivos, los ensayos de resistencia a la compresión y flexión fueron los utilizados para determinar la pérdida de actividad resistente de morteros y hormigones, y la porosidad conectada al agua para analizar los cambios en la matriz porosa por el efecto de la difusión de elementos agresivos que penetran en el material provocando su degradación. La porosimetría de mercurio (MIP) fue usada para observar las variaciones del volumen y tamaño de poro y, por último, la microscopía electrónica de barrido (MEB) que fue utilizada para cuantificar y detectar los cambios en la microestructura por el ataque de elementos agresivos. Los resultados obtenidos muestran que, la degradación producida por exposición a sulfato de sodio, tiene dos etapas, en la primera etapa se forma la etringita que llena los poros pero que no produce microfisuración. En esta etapa se observó una variación en los parámetros obtenidos por ejemplo, incremento de la velocidad de la onda ultrasónica, de las resistencias a compresión y a la flexión o la disminución de la porosidad. Esta variación en los parámetros podría indicar una mejora en las prestaciones mecánicas del material objeto de la investigación, pero en realidad esto no es cierto porque los poros están llenos de etringita, provocando una expansión, que es la causa de la degradación en la segunda etapa. En dicha segunda etapa, se produce una microfisuración generalizada por la expansión de la etringita e incrementando su volumen dentro de los poros. Este hecho produjo un cambio en los parámetros medidos que contrastan con la evolución en la primera etapa, disminución de la velocidad de las ondas ultrasónicas, y de las resistencias mecánicas y consecuentemente un aumento de la porosidad. Por otro lado, la degradación por ataque de nitrato amonio tiene una única etapa debida al proceso de descalificación que comienza desde el principio del proceso de exposición y es lineal durante todo el periodo de exposición. Para ambos casos, la integración de las diversas técnicas se revela como satisfactoria para el seguimiento del proceso de degradación, encontrando buenas correlaciones entre los parámetros no destructivos y los parámetros destructivos de técnicas de análisis físico-químico.
Mahmoud, TI. (2013). Evaluation of the degradation process of cement-based materials exposed to aggressive environment by using ultrasonic techniques and physical characterisation [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/27550
TESIS

El objetivo de la tesis es realizar aportaciones en el campo de las estrategias de test basadas en la vigilancia del consumo quiescente de los circuitos integrados CMOS y de los sensores utilizados para dicho fin (test de corriente o test iddq). Para ello se analiza en primer lugar el estado del arte en el diseño de sensores para el test IDDQ y se extraen criterios para la evaluacion de la calidad de dichos sensores. En la tesis se propone un nuevo tipo de sensor integrado (proportional built-in current sensor) que utiliza como elemento transductor un transistor bipolar compatible con la tecnologia CMOS. Se caracteriza tambien su comportamiento estetico y dinamico y se realizan pruebas con circuitos experimentales para validar los analisis realizados.

En la tesis se proponen dos metodos originales para el test IDDQ mediante sensores externos al circuito que se este verificando (cut): el primero se basa en la desconexion de la alimentacion del cut y en la observacion del comportamiento de sus salidas. El segundo metodo se basa en el analisis de la evolucion de la tension en el nodo de alimentacion de un CUT cuando se le aplica un conjunto de vectores de test estando el circuito alimentado por un condensador. Ambos metodos propuestos requieren un interruptor para la alimentacion del CUT con unas caracteristicas especiales. Por ello, se ha diseñado un nuevo tipo de interruptor que cumple con las especificaciones de baja resistencia en estado de conduccion y baja inyeccion de carga en el paso del estado de no conduccion al de conduccion. Finalmente, los metodos propuestos se han validado experimentalmente al ser implementados en una maquina de test convencional verificandose su efectividad en la deteccion de los defectos de multiples circuitos integrados.

The Ph.D. thesis deals with one of the most important characteristics of hardened concrete; i.e. the modulus of elasticity. The thesis aims to describe and evaluate the important factors that affect the final value of concrete modulus of elasticity, especially those that can be influenced during construction. Another aim is to find ways to determine the static modulus of elasticity of concrete by non-destructive means (primarily ultrasonic pulse method, resonance method and use of electronic rebound hammers), thus to determine the possibility of creating calibration curve for NDT determination of the modulus of elasticity.

One of the goals of current research in medical ultrasound is to develop techniques to quantitatively differentiate between tissue types and tissue states on the basis of the changes in the backscattered signal caused by differences in the elastic properties of the tissues under study. In this dissertation, we proposed to classify white matter and gray matter of adult brain tissues. The first step in this investigation was to develop a linear dichotomizer for the classification of white matter and gray matter using a power spectrum eigenvector approach with Linear Discriminant Analysis (LDA). The LDA classifier is described in Chapter 4. The successful classification rates for pure white matter and pure gray matter tissues were 99% using the LDA. When the LDA was used in transition regions the successful classification rates for both type of tissues dropped to 56%. We concluded that the weakness with this classification scheme was that it did not exploit the information at different scales.
In order to overcome this weakness, two multiscale classification methods were developed in Chapter 5, a power spectrum eigenvector approach with Wavelet transform-Linear Discriminant Analysis (WLDA) and a power spectrum eigenvector approach with Wavelet transform-Artificial Neural Network (WANN). Both methods were tested on calibrated media, also known as tissue mimicking phantoms, as well as on synthetically generated media. The data from synthetically generated media were obtained by a three Dimensional Finite Difference Time Domain method (3D FDTD). Both multiscale classification methods performed as well as the LDA method in classifying pure white matter and pure gray matter but they performed better than the LDA in transition regions. The successful classification rates in transition regions were 88% for white matter and 86% for gray matter using WLDA and 89% for white matter and 88% for gray matter using WANN.

Dreiaxiale Druckprüfungen können als Einstufenversuche, als Mehrstufenversuche oder als Versuche mit kontinuierlichen Bruchzuständen ausgeführt werden. Bei der Anwendung der Mehrstufentechnik ergeben sich insbesondere Fragestellungen hinsichtlich der richtigen Wahl des Umschaltpunktes und des optimalen Verlaufs des Spannungspfades zwischen den einzelnen Versuchsstufen. Fraglich beim Versuch mit kontinuierlichen Bruchzuständen bleibt, ob im Versuchsverlauf tatsächlich Spannungszustände erfasst werden, welche die Höchstfestigkeit des untersuchten Materials repräsentieren. Die Dissertation greift diese Fragestellungen auf, ermöglicht den Einstieg in die beschriebene Thematik und schafft die Voraussetzungen, die zur Lösung der aufgeführten Problemstellungen notwendig sind. Auf der Grundlage einer umfangreichen Datenbasis gesteinsmechanischer und petrophysikalischer Kennwerte wurde ein numerisches Modell entwickelt, welches das Spannungs-Verformungs-, Festigkeits- und Bruchverhalten eines Sandsteins im direkten Zug- und im einaxialen Druckversuch sowie in dreiaxialen Druckprüfungen zufriedenstellend wiedergibt. Das Festigkeitsverhalten des entwickelten Modells wurde in Mehrstufentests mit unterschiedlichen Spannungspfaden analysiert und mit den entsprechenden Laborbefunden verglichen.

L'emploi de sondes lasers, dans la constitution d'un dispositif de contrôle non destructif par ultrasons, est une solution intéressante. De telles sondes opèrent sans contact et sur tous les types de matériaux. Ces propriétés, potentiellement, ouvrent un large champ d'applications et facilitent l'insertion d'un tel système sur une chaîne de production. L'objet de ce travail, est l'étude d'un dispositif de contrôle non destructif par ultrasons, employant ces sondes et entièrement piloté par ordinateur qui soit capable de fonctionner sur un site industriel. Dans le cadre d'un programme de recherche, ce dispositif a été utilisé pour tester des céramiques
Lasers sensors are a very interesting solution for the constitution of non destructive network using acoustical waves. Such sensors operate without contact and work on every materials. These properties open the application field and make easier the introduction of such system on a production line. The goal of this work is the study of a non destructive testing network, using laser sensors to generate and detect ultrasound, piloted by a personal computer and able to work on industrial site. For a research program, this system has been used to test ceramics

L'objet de cette thèse consiste en l'élaboration d'une chaine de traitements permettant d'extraire l'information utile de données 3d ultrasonores et de caractériser les défauts éventuellement présents dans la pièce inspectée. Cette caractérisation a été abordée pour des fissures contrôlées par un même émetteur/récepteur. Dans une première partie nous rappelons les principes du contrôle non destructif par ultrasons ainsi que les représentations classiques des données ultrasonores. La deuxième partie est consacrée à l'étude d'un modèle d'extraction de l'information d'échos présents sur les données au moyen d'une base d'ondelettes adaptée. L'utilisation d'une ondelette unique translatée dans le temps est rendue possible par un travail sur une représentation complexe des données réelles originales. Une première étape permet de détecter et de positionner les échos d'amplitude significative. Dans un deuxième temps, on effectue une régularisation spatialement cohérente des instants de détection à l'aide d'un modèle markovien. On élimine ainsi les échos dont les instants de détection ne font pas partie de surfaces d'instants régulières. Les parties suivantes traitent de la localisation et du dimensionnement des fissures. On utilise des caractéristiques extraites du faisceau ultrasonore afin de déterminer le trajet de l'onde ultrasonore du capteur à l'objet diffractant lorsque la réponse de l'écho est maximale. On met en correspondance l'instant de détection obtenu pour cet écho et le temps de parcours selon le trajet défini afin de positionner un point d'arête dans la pièce. On obtient ainsi un ensemble de points de discrétisation pour chaque arête. Dans le cadre de données 3d obtenues sur un matériau isotrope, on élimine les points d'arête extrêmes en utilisant un critère de comparaison sur les courbes échodynamiques associées aux points de détection sur les données réelles et sur des données simulées équivalentes. La localisation est abordée pour des fissures situées dans un matériau isotrope ou acier revêtu d'anisotrope.

La enfermedad tiroidea autoinmune se ha asociado a baja reserva ovárica, la cual puede ser causada por muchos otros factores incluyendo iatrogénica, quimioterapia, genética, infecciosa, autoinmune e idiopática. Gerard en el 2000, describió las principales etiologías de el fallo ovárico prematuro, siendo la etiología idiopática y autoinmune las más frecuentes, seguido del Síndrome de Turner y quimioterapia entre otras. Ejemplos de autoinmunidad endocrina auto inmunitaria asociada al fallo ovárico o baja reserva es el hipotiroidismo, falla adrenal (enfermedad de Addison) y diabetes tipo 1. De éstas la más frecuente es el hipotiroidismo y probablemente en algunas circunstancias, el ovario podría ser dañado por los anticuerpos mismos que dañan la glándula tiroides. Por analogía, el ovario podría también incurrir en daño autoinmune aunque otras glándulas no se vean afectadas. Desafortunadamente los exámenes actuales no son lo suficientemente sensibles para determinar cuándo este es el caso. En numerosas publicaciones se ha relacionado el fallo ovárico prematuro con el antecedente de hipotiroidismo primario autoinmune. Sin embargo, el fallo ovárico es probablemente un posible efecto radical y último de este evento autoinmune, y que cuando se hace el diagnóstico, desgraciadamente es irreversible. Consideramos que si el daño al ovario forma parte de un proceso progresivo que termina finalmente con la falla precoz gonadal, podríamos detectar etapas más tempranas de este proceso deteriorante del ovario en pacientes con hipotiroidismo primario autoinmune. El interés de este campo es de encontrar un marcador autoinmune capaz de predecir el fallo ovárico. Tal marcador podría prevenir el fallo ovárico antes de que sea completa o cuando el fallo ovárico aun se encuentre en etapas tempranas. Estas alteraciones pueden afectar el ovario en cualquier etapa de la vida, incluyendo prepuberal, puberal y reproductiva. Desde la década pasada se ha investigado más acerca del posible papel de autoinmunidad en el contexto de la disminución de la reserva ovárica. Debido a sus antecedentes, el hipotiroidismo autoinmune puede ser uno de los trastornos endocrinológicos asociados con la reserva ovárica disminuida por lo que es importante determinar su probable participación en etapas tempranas, antes de que sucediera la falla ovárica como proceso final. OBJETIVO. Comparar la reserva ovárica en pacientes con hipotiroidismo primario autoinmune eutiroideas versus pacientes control, mediante test de clomifeno, carga folicular antral por Ultrasonido vaginal basal y determinación de hormona Antimulleriana. MATERIAL Y METODOS. Estudio prospectivo, longitudinal y comparativo, realizado de Julio del 2007 a junio del 2008 en la Unidad de Biología de la Reproducción del departamento de Ginecología y Obstetricia del Hospital Universitario “Dr. José Eleuterio González” de la Universidad Autónoma de Nuevo León, en conjunto con el servicio de Endocrinología y autorizado por el comité de Etica. Se enrolaron 52 pacientes, 27 de las cuales tenían el diagnóstico de Hipotiroidismo Primario Autoinmune y 25 pacientes sanas (del programa de donación de óvulos) formaron el grupo control. Se les realizaron mediciones de Test de Clomifeno, carga folicular antral (CFA) por utrasonido vaginal y medición de hormona Antimulleriana. Para la comparación de ambos grupos se utilizó la prueba t de student. Todos los análisis estadísticos se realizaron a 2 colas. Se estableció por convenio como estadísticamente significativo la presencia de un valor de p < 0.5. RESULTADOS. Las pacientes controles (n= 25 pacientes) presentaron una edad promedio de 26.2 años. En el grupo de casos con hipotiroidismo primario autoinmune, se observó una edad promedio de 27.7 años (NS). Las pacientes con hipotiroidismo primario tuvieron una carga folicular antral (CFA) promedio de 14.5 mientras que en las pacientes control, la media fue de 16. No hubo una diferencia estadísticamente significativa entre ambos grupos. En el grupo control el valor más bajo detectable de la AMH fue 0.5ng/ml y el más alto fue de 7.34 ng/ml teniendo una media de 2.77 esto con una variación de los datos con respecto al promedio de 2.50. En las pacientes con Hipotiroidismo primario autoinmune el nivel más bajo detectado fue 0.5 ng/ml y el más alto de 10.0 ng/ml teniendo una media de 2.42 esto con una variación de los datos con respecto al promedio de 1.86, sin tener diferencia estadísticamente significativa (p= 0.853). En cuanto a la prueba de citrato de clomifeno, en el grupo de pacientes con hipotiroidismo se observó una FSH basal (día 3) promedio de 4.5 UI/ml, con una variación de 2.59 UI/ml y una FSH posterior a la administración del citrato de clomifeno (día 10), de 6.34 UI/ml con una variación de 1.27 UI/ml. En el caso del grupo control, la media observada de la FSH en el día 3 fue de 4.37 UI/ml, con una variación de 1.96 UI/ml, mientras que la media de la FSH realizada en el día de 10, fue de 5.97 UI/ml, con una variación de 2.18 UI/ml, sin tener una diferencia estadísticamente significativa entre ambos grupos, en ambos valores de FSH. CONCLUSIONES. Las pacientes con hipotiroidismo primario autoinmune forman un grupo especial que ha sido poco estudiado aún y cuando representa un porcentaje importante de la consulta de la biología reproductiva. La atención médica prácticamente se limita a la confirmación del diagnóstico y administración de terapia de reemplazo con hormonas tiroideas. Este estudio representa el primer análisis que consideró la reserva folicular antral y el volumen ovárico, además de la medición de la Hormona Antimulleriana y el Test de Clomifeno como parámetros para medir reserva ovárica en pacientes con hipotiroidismo primario autoinmune, controladas con levotiroxina. Aunque en un inicio del estudio se sospechaba que las pacientes con esta patología pudieran haber perdido parte de su reserva ovárica, debido a la naturaleza autoinmune de la misma, en base a los resultados es posible afirmar que esto no ocurrió Los resultados de este estudio denotan que la reserva ovárica se encuentra conservada en pacientes hipotiroideas controladas (eutiroideas), lo que mejora su pronóstico reproductivo en comparación con pacientes con escaso o nulo control endocrinológico.
Primary autoinmune hypothyroidism has been associated with low ovarian reserve, which can be due to many other factors including iatrogenic, chemotherapy, genetic, infectious and idiopathic. Gerard in 2000, described the most frequent ethiologies for low ovarian reserve, being the idiopathic and the autoinmune the most frequent, followed by Turner’s syndrome and chemotherapy. Some of autoinmune endocrine pathology associated with low ovarian reserve include hypothyroidism, adrenal failure (Addison’s disease) and type 1 Diabetes Mellitus. Of these, hypothyroidism is considered the most frecuent etiology and in some circumstances the ovary can be affected by the same antibodies as the thyroid gland. Unfortunately, laboratory analysis are not sensitive enough to determine in which is the case. In several publications, premature ovarian failure has been related with a history of primary autoinmune hypothyroidism. Nevertheless, ovarian failure is probably a radical effect of this pathology and unfortunately when the diagnosis is made, ovarian failure is irreversible. We consider that if ovarian damage forms part of a progressive process that ends with premature ovarian failure, we can detect early stages of this process. The interest in this field es to find a marker which can predict ovarian failure. This marker can prevent ovarian failure before it is complete or when it is still in early stages. This alterations can affect the ovary in any stage of a woman’s reproductive lifespan. Since last decade, much has been investigated regarding a possible role of autoinmunity in premature ovarian failure. Due to the history, autoinmune hypothyroidism can be one of the endocrine pathologies associated with low ovarian reserve. For this reason it is considered very important to determine its possible participation in early stages, before ovarian failure establishes as a final process OBJECTIVE. To compare ovarian reserve in euthyroid patients with autoimmune primary hypothyroidism versus control patients, using clomiphene test, antral follicle count by transvaginal ultrasound and antimüllerian hormone determination MATERIALS AND METHODS. Prospective, longitudinal and comparative trial. From July 2007 to June 2008 at Unidad de Biología de la Reproducción at the Obstetrics and Gynecology Centre of Hospital Universitario ‘Dr. José Eleuterio González’ from the Universidad Autónoma de Nuevo León, together with the Endocrinology department and authorized by the Ethics Committee Fifty two patients were recluted, 27 of them with primary autoimmune hypothyroidism and 25 healthy patients (from the oocyte donation program) as the control group Clomiphene test, antral follicle count by transvaginal ultrasound and antimüllerian hormone determination were made. T student test was made to compare both groups. Any value of p < 0.05 was considered statistically significative. RESULTS. Patients in the control group (n= 25) presented an average age of 26.2. In the study group, the average age was 27.7. Average antral follicle count in patients with primary autoimmune hypothyroidism was 14.5, while in patients in the control group the average antral follicle count was 16, without this being statistically significant. In the control group the median antimüllerian value was 2.77 ng/mL (0.50-7.34 ng/mL). In the study group the median antimüllerian value was 2.42 ng/mL (0.50-10.0 ng/mL), without being statistically significant (p=0.853). With respect to the clomiphene test, in the group with hypothyroidism the average FSH value on day 3 was 4.5 IU/mL, with a variation of 2.59 IU/mL, and a FSH on day 10 (after the administration of clomiphene citrate) of 6.34 IU/mL, with a variation of 1.27 IU/mL. In the control group the average FSH value on day 3 was 4.37 IU/mL, with a variation of 1.96 IU/mL, and a FSH on day 10 (after the administration of clomiphene citrate) of 5.97 IU/mL, with a variation of 2.18 IU/mL. No statistically difference was seen in neither groups, in both FSH values. CONCLUSIONS. Patients in the study group form a special group that has been poorly studied even though it represents an important number of patients seeking for fertility. Medical attention limits to the confirmation of the diagnosis and replacement with thyroid hormones. This study represents the first analysis that considers antral follicle count and ovarian volumen, besides the determination of antimüllerian hormone and clomiphene test as parameters to measure ovarian reserve in patients with primary autoimmune hypothyroidism, controled with levothyroxine. Although in the beginning of the study it was suspected that patients with this pathology might have lost part of their ovarian reserve, due to the autoimmune etiology, this could not be confirmed with the results The results of this study denote that ovarian reserve is maintained in euthyroid patients with primary autoimmune hypothyroidism, which improves their reproductive prognosis in comparison with patients with poor or no endocrine control.

La grande fréquence des nodules thyroïdiens et la relative agressivité des traitements conventionnels ont motivé l'étude d'une méthode non invasive utilisant des Ultrasons Focalisés (HIFU). Matériel et méthodes : Les HIFU ont été testés initialement sur un modèle de brebis afin de réaliser une lésion thyroïdienne. Ces études animales ont été suivies de trois études cliniques sur des patients porteurs de nodules thyroïdiens. L'appareil utilisé associe un système d'imagerie échographique et un système de tir. Résultats : Le réglage des paramètres de tir et la mise au point de plusieurs prototypes chez l'animal a permis d'obtenir l'autorisation du comité d'éthique pour les expérimentations humaines. Ces essais ont démontré la capacité des HIFU à détruire des nodules thyroïdiens. Le dernier appareil mis au point a obtenu le marquage CE. Conclusion : Cette technique permet de réaliser une nécrose localisée dans un lobe thyroïdien et de détruire des nodules. Ces résultats doivent être confirmés par des études plus larges, mais ont été assez encourageants pour justifier la création d'une entreprise dédiée à la mise au point d'un appareil spécifique en collaboration avec l'INSERM
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The thesis deals with the measurement of the elastic modulus of concrete in existing structures and possibilities of applicability of equations for the calculation of characteristic values of concrete compressive strength on the modulus of elasticity. The modulus of elasticity is determined by dynamic and static methods on specimens taken from the concrete blocks, whose composition varies by a water cement ratio and varying amounts of admixtures. In conclusion, the results of the measurements are compared and the characteristic values of the modulus of elasticity is determined.

Os ensaios não destrutivos visam avaliar um elemento sem gerar danos a ele com a técnica empregada. Um tipo de ensaio não destrutivo é o método da velocidade do pulso de ondas ultrassônicas. Este método é comumente utilizado para determinar propriedades elásticas de um dado material e verificar danos no interior dos elementos estudados. Outra aplicação do ultrassom é a medição do nível de tensão num material por meio da propagação das ondas ultrassônicas, tendo como base a teoria da acustoelasticidade. Entretanto, o uso do ultrassom para esta finalidade ainda é pouco difundido, principalmente na aplicação em estruturas de concreto. Este trabalho teve como objetivo estudar a possibilidade de medir tensões em estruturas de concreto com o uso do ultrassom. Para tanto, foram realizados ensaios de compressão uniaxial em prismas de concreto. Durante os ensaios, foram emitidas ondas ultrassônicas nos elementos para cada nível de tensão aplicada no material. A partir destes ensaios, foi feito um estudo do comportamento acustoelástico do concreto. Verificou-se que as velocidades das ondas ultrassônicas variaram em função da intensidade das tensões normais de compressão existentes nos corpos de prova. Com base na variação das velocidades, os coeficientes acustoelásticos do concreto de cada prisma foram determinados e relacionados com propriedades do concreto. Verificou-se a possibilidade de se estimar o nível mínimo de tensão em determinadas estruturas de concreto a partir do conhecimento de seus coeficientes acustoelásticos. Concluiu-se que é possível estimar tensões em estruturas de concreto utilizando o ultrassom.
Nondestructive tests aim to analyze an element generating no damages. The pulse velocity of ultrasonic waves method is a type of nondestructive test. This method is commonly used to determine elastic properties of materials and to verify damages inside studied elements. Another application for ultrasound is the measurement of stress level in a material by means of propagation of ultrasonic waves. This application is based on the theory of acoustoelasticity. However, the use of ultrasound is still unusual for this purpose, mainly in application in concrete structures. This work intended to study the possibility of measuring stresses in concrete structures with the use of ultrasound. Uniaxial compression tests were performed on concrete prisms. During tests, ultrasonic waves were propagated in elements for each level of applied stress in the material. Then, a study about acoustoelastic behavior of concrete was performed. It was verified that the velocities of ultrasonic waves changed according to the intensity of normal compressive stresses there were in the specimens. Based on the variation of velocities, the acoustoelastic coefficients of concrete were determined for each prism. The coefficients were related with properties of concrete. The possibility of estimating the minimum level of stress in certain structures of concrete from their acoustoelastic coefficients was verified. It was concluded it is possible to estimate stresses in concrete structures using ultrasound.

A aplicação de Ensaios Não Destrutivos (END) é considerada uma alternativa para monitorar o estado das estruturas de concreto armado, principalmente quando ocorrem falhas de projeto, erros de dosagem, problemas na mistura, transporte ou lançamento do concreto. A medida da Velocidade de Pulso Ultrassônico (VPU) é um END que vem sendo usado comumente em diversas áreas da engenharia civil, devido à facilidade da operação, ao seu baixo custo, à rapidez na execução dos testes e à ausência de danos ao material analisado. O objetivo deste trabalho consiste em apresentar o resultado de uma pesquisa experimental, que visou estudar a influência que determinadas variáveis operacionais exercem sobre os resultados obtidos nos ensaios de VPU e qual a real capacidade de penetração e detecção de defeitos de diversas magnitudes. As medições foram realizadas utilizando o ultrassom pelo modo de transmissão indireta, pois esta é a alternativa que mais se adapta às condições verificadas no exame de estruturas reais de concreto armado. Primeiramente, foram moldados em laboratório dois blocos de concreto, com dimensões próximas às encontradas em estruturas reais de grande porte: um com armadura nas duas faces e outro sem armadura. Em ambos os elementos foram introduzidos objetos para simular possíveis falhas de concretagem. Em uma segunda etapa, foram realizadas perfurações visando identificar a capacidade de detecção de vazios da técnica de VPU para diferentes profundidades. Os resultados são apresentados na forma de imagens geradas através de software e por meio de analises estatísticas. Este estudo verificou que a escolha dos parâmetros de ensaio é um fator determinante para permitir a interpretação correta dos resultados, salientando-se que a experiência do operador e as dimensões de grid são os parâmetros que mais interferem na interpretação dos dados.
The use of Non-destructive Testing (NDT) methods is considered an alternative to monitor the behaviour of reinforced concrete structures, especially when there are design problems or errors related to concrete mixing, transport, placement and casting errors. The Ultrasonic Pulse Velocity (UPV) method is a Non-Destructive Test that is gaining acceptance. The test has been commonly used in various civil engineering areas due to the fact that it is easy to operate and rapid to perform, and to the low cost and lack of damage to the tested material. The objective of this work is to present the results of an experimental research that aimed to study the influence of certain technological variables on the measurements obtained from UPV tests. The work also aims to gather data to assess the penetration capacity of the US waves and their ability to detect defects of various dimensions. The measurements were performed using the indirect transmission mode, to simulate real work conditions on large structures. Firstly, two massive concrete blocks were cast in the laboratory, with dimensions close to real life structures: one with steel reinforcement on both sides and the other without reinforcement. Objects were introduced in both elements to simulate possible defects due to casting. In a second stage, perforations were conducted in the concrete elements to identify the void detection capability of the UPV technique for different depths. The results are presented by images generated by specific software and by using statistical analysis. This study found that the test parameters influence significantly the correct interpretation of the results. The operator experience and the grid dimensions are the parameters that most influence UPV data analysis.

La thérapie photodynamique est une technique de traitement de certains cancers basée sur l'action de la lumière sur une substance sensibilisante qui, en présence d'oxygène, va induire une réaction photochimique détruisant la cellule cancéreuse dans laquelle elle s'est accumulée. La lumière pénétrant peu profondément dans les tissus, certains auteurs ont utilisé ces substances sensibisantes avec des ultrasons dont la pénétration peut atteindre plusieurs centimètres dans l'organisme : c'est la sonothérapie. Après une revue de la littérature rappelant les bases de la thérapie photodynamique et les travaux publiés en thérapie sonodynamique, notre première partie présente un rappel physique sur les ultrasons et leurs effets sur les tissus. Notre seconde partie aborde la conception de notre dispositif de traitement ultrasonore et les techniques de mesure d'intensité du faisceau ultrasonore : la méthode optique, mais aussi méthode calorimétrique et mesure par la technique de l'hydrophone, enfin l'intensité ultrasonore développée et un asservissement thermique rigoureux. Une simplification des manipulations a été étudiée afin de rendre notre dispositif plus convivial permettant l'emploi par un utilisateur non spécialiste. Notre troisième partie, rapporte l'ensemble des essais biologiques effectués à l'aide de notre dispositif ultrasonore : essais cellulaires avec cellules fixées en monocouche dans des boites de pétri ou en suspension dans le milieu de culture. La cytotoxicité des ultrasons couplés à une substance sensibilisante est aussi évaluée en association avec la thérapie photodynamique. Enfin, une étude des spectres de fluorescence des substances sensibilisantes après traitement par ultrasons a été étudiée. L’ensemble des résultats obtenus étant différents de ceux rapportés dans la littérature, notre quatrième partie discuté les différentes hypothèses pouvant expliquer une discordance de nos résultats.

Les pratiques d’agriculture et de production alimentaire évoluent de façon profonde afin de proposer une offre alimentaire permettant de répondre aux enjeux de la croissance démographique, et de satisfaire des critères de santé et de durabilité. Cependant, le succès des produits alimentaires qui découlent de ces mutations repose avant tout sur leur appréciation sensorielle par le consommateur. En particulier, les perceptions de texture jouent un rôle majeur dans les choix et préférences des consommateurs.Ces travaux de thèse s’insèrent dans la problématique générale de la compréhension des mécanismes de perception de texture qui découlent des interactions mécaniques entre la langue, l’aliment et le palais durant le processus oral. L’objectif de la thèse réside dans le développement d’une méthode nouvelle et originale, basée sur les ultrasons quantitatifs, pour l’évaluation non-destructive, non-invasive et en temps réel des propriétés mécaniques du système langue-aliment-palais.Un montage bio-mimétique a été développé au laboratoire afin de reproduire en conditions contrôlées, in vitro, le comportement du système langue-palais durant la compression d’un aliment. Ce système a permis de progressivement prendre en compte la complexité de l’environnement physiologique, en intégrant notamment les caractéristiques liées à la rugosité, à la lubrification et à la déformabilité de la langue. Un ensemble de gels modèles d’agar et de gélatine a été développé, permettant d’obtenir une gamme de produits alimentaires avec des caractéristiques physiques et sensorielles contrastées. Un dispositif expérimental à ultrasons quantitatifs a ensuite été conçu afin de mesurer la réponse échographique du système langue-aliment-palais au cours de compressions uni-axiales imposées par le système biomimétique sur les aliments modèles. Des techniques de traitement du signal et des outils de simulation de propagation d’ondes ont permis de développer des indicateurs quantitatifs fournissant des informations sur les mécanismes physiques observés aux interfaces du système langue-aliment-palais. Deux paramètres ultrasonores ont alors été identifiés : i) la réflectivité de l’interface entre la langue et l’aliment, qui permet de caractériser le contact intime entre l’aliment et les aspérités de la surface de la langue, et ii) le temps de vol des ondes ultrasonores dans l’aliment, qui traduit l’état de déformation subi par ce dernier. Ces propriétés issues des signaux ultrasonores ont été confrontées à des données d’analyse sensorielle évaluées grâce à un panel de juges entraînés sur les aliments modèles sélectionnés. Les attributs sensoriels « humide » et « glissant » ont par exemple pu être mis en relation avec les mesures de réflectivité ultrasonore à l’interface langue-aliment, elles-mêmes liées à l’état de lubrification de l’interface.Ces travaux de thèse ont ainsi permis de montrer le potentiel des méthodes ultrasonores pour mieux comprendre et caractériser, en conditions in vitro contrôlées, des phénomènes physiques qui peuvent jouer un rôle important dans les mécanismes de perception de texture de l’aliment. Ils permettront d’ouvrir la voie aux perspectives de transfert de la technologie en conditions in vivo, directement sur le consommateur
Agriculture and agri-food industry practices evolve in a deep way to supply a new food offer allowing to address population growth issues, and to meet health and sustainability criteria. However, the success of commercial products emerging from these transformations highly depends on sensory appreciation by the consumer. In particular, texture perceptions have been shown to play a major role in the choices and preferences of consumers.This thesis work fits within the general issue of understanding the mechanisms of texture perception resulting from the mechanical interactions between tongue, food and palate during oral processing. The aim of this thesis lies in the development of a new and original method, based on quantitative ultrasounds, for the non-destructive, non-invasive and real time evaluation of the mechanical properties of the tongue-food-palate system.A bio-mimicking system was developed in the laboratory to reproduce in controlled in vitro conditions, the behavior of tongue-palate system during the compression of a food sample. This system allowed to consider gradually the complexity of the physiological environment, by integrating characteristics related to tongue roughness, lubrication and deformability. A set of model gels of agar and gelatin was developed to obtain a range of food products with contrasting physical and sensory characteristics. Then, a quantitative ultrasound device was designed to measure the ultrasound pulse-echo response of the tongue-food-palate system throughout a uniaxial compression achieved by the bio-mimicking apparatus on the products. Signal processing methods and wave propagation simulation tools were used to develop quantitative indicators related to physical mechanisms occurring in tongue-food system interfaces. Two ultrasonic parameters were then identified: i) the reflectivity of tongue-food interface, which makes it possible to characterize the intimate contact between food and the asperities of tongue surface, and ii) the time of flight of ultrasonic waves through the food sample, which is related to the level of deformation undergone by the sample. Finally, the properties stemming from ultrasonic signals were compared with sensory data estimated on the set of food samples, thanks to a panel of trained judges. “Moist” and “slippery” sensory attributes were for instance shown to correlate with ultrasound reflectivity measurements, which are themselves related to lubrication conditions at tongue-food interface.This thesis work allowed to show the potential of ultrasonic methods to better understand and characterize, in controlled in vitro conditions, physical phenomena which may play an important role in the mechanisms of food texture perception. This work must pave the way for future investigations on the transfer of the technology to in vivo conditions, directly on the consumer

Ce projet de doctorat est aux prises avec un problème de ruptures en fatigue de un alliage de titane aéronautique en raison de haute fréquence chargement. Matériel pour cette enquête a été prise de compresseur du moteur disque de l'avion réel. Essais de fatigue à ultrasons ont été réalisées jusqu'à dépasser la limite de 1010 cycles. Cette région de la durée de vie est connu comme Gigacycle ou fatigue très grand nombre de cycles. Ce projet de thèse montre pour la première fois les résultats des tests de fatigue sur l'lliage de titane aéronautique VT3-1 dans la région Gigacycle. Les propriétés de fatigue de l'alliage de titane ont été déterminées à 109 cycles pour les conditions de chargement différentes: traction-compression, tension-tension et de torsion. Mécanismes d'initiation des fissures typiques ont été identifiés et des défauts critiques de microstructure ont été trouvés. L'effet de l'anisotropie en raison de processus de fabrication sur les propriétés de fatigue de l'alliage de titane VT3-1 forgé a été étudiée. Une influence du processus de fabrication sur les propriétés de fatigue a également été étudiée par comparaison les résultats sur extrudé et forgé VT3-1 alliage de titane. La nouvelle machine de torsion à ultrasons a été conçu et installé pour la longue durée de vie (jusqu'à 1010 cycles) de tests de fatigue en rotation. Les premiers résultats sous la chargement en torsion ultrasons ont été obtenues pour l'alliage de titane réalisé par extrusion et technologies forgés
This PhD project is dealing with a problem of fatigue failures of aeronautical titanium alloy due to high frequency loading. The material for investigation was taken from the real aircraft engine compressor disk. Ultrasonic fatigue tests were carried out up to outrun limit of 1010 cycles. This region of lifetime is known as Gigacycle or very high cycle fatigue. This PhD project shows for the first time the results of fatigue tests on the VT3-1 aeronautical titanium alloy in the Gigacycle region. The fatigue properties of the titanium alloy were determined at 109 cycles for different loading conditions: tension-compression, tension-tension and torsion loading. Typical crack initiation mechanisms were identified and critical defects of microstructure were found. The effect of anisotropy due to fabrication process on the fatigue properties of the forged VT3-1 titanium alloy was studied. An influence of technological process on fatigue properties was also studied by comparison the results on extruded and forged VT3-1 titanium alloy.The new ultrasonic torsion machine was designed and installed for the long life (up to 1010 cycles) fatigue tests under rotation. The first results under ultrasonic torsion loading were obtained for the titanium alloy made by extrusion and forged technologies

This thesis is about assessment of a bridge construction influenced by fire accident. The bridge is situated at the highway D46 beyond the town Držovice. Within this construction research, there will be mentioned diagnostic methods – A non- destructive method (Ultrasonic pulse method and hardness tests) and destructive methods (borehole and tear off tests). For find out in which way was the concrete of the bridge damaged and hurt while facing a high temperature of fire, there were taken samples, which were analyzed by physical and chemical test. We can analyze composition and microstructure of the concrete. The result of this tests will be evaluated, and the actions of a remediation will be suggested.

Pour évaluer la résistance mécanique du béton dans un ouvrage existant, la méthodologie courante combine des mesures non destructives (CND) comme le rebond ou/et la vitesse des ondes ultrasoniques avec la technique destructive (carottes) afin de produire une relation‘‘modèle de conversion” entre la résistance mécanique et les mesures CND. Le modèle de conversion est utilisé pour estimer la valeur locale de résistance mécanique à chaque emplacement de test en utilisant la valeur CND correspondante. Ensuite, on calcule les estimations de la résistance moyenne et/ou de l’écart-type de la résistance (variabilité de la résistance du béton). Cependant, la fiabilité d’estimation est toujours discutable en raison des incertitudes associées à l’évaluation de la résistance basée sur les mesures CND. Pour améliorer la fiabilité, les incertitudes doivent être réduites en spécifiant et en contrôlant leurs facteurs d’influence. Par conséquent, l’objectif de cette thèse est d’analyser la méthodologie d’évaluation courante afin de fournir des recommandations pratiques qui peuvent améliorer la fiabilité de l’évaluation de la résistance in-situ du béton dans les ouvrages existantes par des tests non destructifs et des carottes.Pour ce but, un simulateur a été construit afin d’analyser les effets des facteurs les plus influents en utilisant une vaste campagne de données provenant de sources différentes (études in situ ou en laboratoire et données synthétiques générées). La première contribution de ce travail est le développement d’une nouvelle approche d’identification du modèle ‘‘bi-objectif” qui peut efficacement capturer la variabilité de la résistance mécanique en plus de la moyenne. Après avoir étudié l’effet du mode de sélection des emplacements pour les carottes, une méthode a été proposée pour sélectionner ces emplacements en fonction des mesures CND ‘‘sélection conditionnelle” qui améliore la qualité de l’évaluation sans coût supplémentaire. Une dernière innovation est l’établissement de courbes de risque qui quantifient la relation entre le nombre de carottes et la précision de l’estimation. Enfin, des recommandations ont été formulées afin de fournir des estimations plus fiables
To assess concrete strength in an existing structure, the current methodology combines nondestructive measurements (NDT) like rebound hammer or/and pulse velocity with destructive technique (cores) in order to implement a relationship ‘‘conversion model” between the compressive strength and NDT measurements. The conversion model is used to estimate the local strength value at each test location using the corresponding NDT value.Then the estimated mean strength and/or estimated strength standard deviation (concrete strength variability) values are calculated. However, the reliability of these estimated values isalways a questionable issue because of the uncertainties associated with the strength assessment based upon NDT measurements. To improve the reliability, the uncertainties must be reduced by specifying and controlling their influencing factors. Therefore, the objective of this thesis is to analyze the current assessment methodology in order to provide practical recommendations that can improve the reliability of assessing the in-situ strength in existing concrete structures by nondestructive tests and cores.To this end, a simulator was built in order to analyze the effects of the most influencing factors using a large campaign of datasets from different sources (in-situ or laboratory studies,and generated synthetic data).The first contribution of this work is the development of a new model identification approach“bi-objective” that can efficiently capture the strength variability in addition to the mean strength. After studying the effect of the way of selection the core locations, a method was proposed to select these locations depending on the NDT measurements “conditional selection” that improves the quality of assessment without additional cost. A third innovation was the development of a procedure to identify the relation between the number of cores and the accuracy of the estimation. Finally recommendations were derived in order to providemore reliable estimated values

The master‘s thesis focuses on testing the shotcrete prepared in laboratory conditions. The main observed properties are compresive strenght of shotcrete and modulus of elasticity. The aim is assessment of methods for measuring those parameters. The calibrating correlations for strenght characteristics of shotcrete are given by obtaining the results of used methods. The shotcrete composition, amount and type of accelerating additive as well as economic aspect of using shotcrete is also assessed.

La surface des pièces mécaniques est une zone sensible soumise à des conditions de sollicitations particulières, tant mécaniquement (frottement, contrainte maximale) que chimiquement (atmosphère ambiante, corrosion). Ainsi, la ruine des pièces de service est généralement initiée en surface ; les grands secteurs industriels sont donc à la recherche de solutions technologiques permettant une amélioration des propriétés mécaniques globales par une modification des propriétés de surface. De nombreuses techniques ont été développées dans ce but, notamment les traitements de surface mécaniques. Parmi ceux-ci, le grenaillage ultrasonique permet de déformer sévèrement et superficiellement les pièces par de nombreux impacts de billes ayant des trajectoires aléatoires au sein de la chambre de traitement. Le propos de cette étude repose sur l'analyse et la compréhension des microstructures de déformation induites par un traitement de grenaillage ultrasonique, particulièrement sous conditions cryogéniques ; sujet très peu exploré à ce jour voir nouveau concernant i) des métaux susceptibles de subir une transformation martensitique et ii) l'influence d'un tel traitement sur la tenue en fatigue cyclique. Pour ce faire, plusieurs nuances d'aciers inoxydables austénitiques présentant des stabilités différentes vis-à-vis de la transformation de phase ont été traitées à très basses températures et les propriétés obtenues ont été comparées à celles mesurées sur les échantillons traités à température ambiante. Les premières observations ont montré que, suite à un traitement sous condition cryogénique (-130 °C), une baisse de dureté intervient en sous-couche de l'alliage 310S stable, associée à une hausse des propriétés mécaniques sous basse température rendant le matériau plus difficile à écrouir. Ce phénomène est complètement supprimé au sein de l'alliage métastable 304L par une transformation martensitique facilitée, intervenant plus profondément qu'à température ambiante et entrainant une augmentation de la dureté de sous-couche. Deux alliages métastables (304L et 316L) ont donc été sélectionnés afin de détailler l'influence des paramètres de traitement sur le durcissement de sous-couche par une étude paramétrique comprenant l'amplitude de vibration (40 et 60 µm), la durée (3 et 20 min) ainsi que la température de traitement (ambiante, -80 et -130 °C). Il en ressort qu'augmenter l'énergie de traitent par une hausse de l'amplitude et/ou de la durée de grenaillage entraine une augmentation des duretés de surface et de sous-couche, accompagnée par la production de couches durcies plus épaisses. L'utilisation de températures cryogéniques permet une augmentation du potentiel de durcissement, et ce principalement en sous-couche. En associant les gradients de dureté aux distributions de martensite le long des épaisseurs affectées, il a été montré que la fraction de martensite était directement liée au potentielle de durcissement en profondeur. La fraction de martensite produite étant dépendante de la température de déformation et, afin de prendre en compte la stabilité initiale de l'alliage comme paramètre additionnel, des mesures complémentaires ont été faites sur l'alliage 316L plus stable. Les résultats ont alors montré qu'il est primordial d'adapter la température de traitement à la stabilité de l'échantillon afin d'optimiser l'efficacité du durcissement de sous-couche et éviter ainsi une baisse de la dureté en profondeur. Finalement, les structures de déformation obtenues sous condition cryogénique ont été reliées à la tenue mécanique sous sollicitations cycliques en flexion rotative. Comparé à un traitement réalisé à température ambiante, un grenaillage cryogénique permet une baisse la rugosité de surface et la production de contraintes résiduelles de compression plus élevées par la présence de martensite. Cependant, une plus grande relaxation de ces dernières associée à une réduction de l'épaisseur [...]
The surface of mechanical components is a sensitive zone subjected to particular mechanical (friction, maximum stress) and chemical (ambient atmosphere, corrosion) interactions. Hence, the rupture is generally initiated on the surface. In order to increase the global integrity of the working parts, the industrial groups are still seeking technological solutions allowing the modifications of the surface properties. Nodaway, plenty of surface modification techniques have been developed like the mechanical surface treatments. Among them, the ultrasonic shot peening (or surface mechanical attrition treatment) focus on superficially deform the mechanical parts through numerous collisions of peening medias having random trajectories inside a confined chamber. The purpose of this study is based on the analysis and the comprehension of the deformed microstructures induced by the ultrasonic shot peening treatment, especially under cryogenic temperatures. To do so, several austenitic stainless steel grades having different stabilities regarding the martensitic transformation have been treated under cryogenic conditions and compared to the properties obtained under room temperature. The first observations have shown that, after a cryogenic peening, a decrease of the subsurface hardness takes place in the stable 310S alloy which was attributed to an increase of the mechanical properties under cryogenic temperature. This phenomenon is suppressed in the metastable 304L by triggering a martensitic phase transformation promoted under low temperature and happening deeper compared to room temperature, increasing substantially the subsurface hardness. Two metastable alloys (304L and 316L) were then selected to conduct an ultrasonic shot peening parametric study including the vibration amplitude (40 and 60 µm), the treatment duration (3 and 20 min) and temperature (room temperature, -80 and -130 °C). It has been shown that increasing the treatment energy by raising the vibration amplitude and/or the duration leads to an increase of the surface and subsurface hardnesses as well as the affected layer thickness. The use of cryogenic temperatures allows an additional increase of the hardness, especially in subsurface. By comparing the different hardness gradients with the martensite distributions along the hardened layers, a direct correlation with the hardening rate and the martensite fraction was observed. The initial stability of the treated material was also taken in account by carried out additional observations on the 316L having a higher stability. The results have indicated that the deformation temperature needs to be wisely chosen regarding the stability of the processed material in order to avoid a decrease of the subsurface hardness. Finally, the deformed microstructures generated under cryogenic ultrasonic shot peening were associated to the mechanical behaviors of cylindrical specimens using rotating bending fatigue tests. Compared to a room temperature treatment, a cryogenic peening allows a decrease of the surface roughness and the generation of higher surface compressive residual stresses by the formation of martensite. However, compared to a room temperature treatment, the fatigue behavior was not increased after a cryogenic peening because of a more pronounced surface residual stress relaxation and a reduction of the affected layer. However, the potential increase of the fatigue life after a cryogenic surface deformation was depicted by the study of the rupture surfaces. It was observed that, if the involvement of the surface defects introduced by the high surface roughness can be lowered, a single subsurface crack initiation can be produced increasing considerably the fatigue behavior of the processed material

The diploma thesis deals with the evaluation of the lifetimes of smooth and notched specimens. The comparison of their lifetimes is focused on the case of high-frequency cyclic loading in the area of high-cycle and gigacycle fatigue of materials. The theory of critical distances is used to evaluate and recalculate the life curves of the notched specimens. The effect of the notch is quantified using the Line method. The critical length parameter is determined so that the life curve of the notched specimens corresponds to the curve measured on smooth specimens. The result is the dependence of the critical length parameter on the number of cycles to fracture. Knowledge of critical length parameters can be used to determine the lifetime of notched specimens as well as real notched components using the results of fatigue tests of smooth specimens.