Academic literature on the topic 'Torsional defects'
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Journal articles on the topic "Torsional defects":
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Zhan, Hai Fei, Yuan Tong Gu, Cheng Yan, and Prasad K. D. V. Yarlagadda. "Numerical Exploration of the Defect’s Effect on Mechanical Properties of Nanowires under Torsion." Advanced Materials Research 335-336 (September 2011): 498–501. http://dx.doi.org/10.4028/www.scientific.net/amr.335-336.498.
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Molecular dynamics (MD) simulations have been carried out to investigate the defect’s effect on the mechanical properties of single-crystal copper nanowire with different surface defects, under torsion deformation. The torsional rigidity is found insensitive to the surface defects and the critical angle appears an obvious decrease due to the surface defects, the largest decrease is found for the nanowire with surface horizon defect. The deformation mechanism appears different degrees of influence due to surface defects. The surface defects play a role of dislocation sources. Comparing with single intrinsic stacking faults formation for the perfect nanowire, much affluent deformation processes have been activated because of surface defects, for instance, we find the twins formation for the nanowire with a surface 45odefect.
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Kumar, Sudhir, P. Ratnakar, NV Murali Krishna Chakka, Sanjib Das, Anandamy Bagchi, and Lavanya Anumula. "Do NiTi Instruments show Defects before Separation? Defects caused by Torsional Fatigue in Hand and Rotary Nickel-Titanium (NiTi) Instruments which Lead to Failure during Clinical Use." Journal of Contemporary Dental Practice 13, no. 6 (2012): 867–72. http://dx.doi.org/10.5005/jp-journals-10024-1243.
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ABSTRACT Aims Visual and microscopic evaluation of defects caused by torsional fatigue in hand and rotary nickel titanium (NiTi) instruments. Materials and methods Ninety-six NiTi greater taper instruments which were routinely used for root canal treatment only in anterior teeth were selected for the study. The files taken include ProTaper for hand use, ProTaper Rotary files and Endowave rotary files. After every use, the files were observed visually and microscopically (Stereomicroscope at 10×) to evaluate the defects caused by torsional fatigue. Scoring was given according to a new classification formulated which gives an indication of the severity of the defect or damage. Statistical analysis Data was statistically analyzed using KruskallWallis and Mann-Whitney U test. Results Number of files showing defects were more under stereomicroscope than visual examination. But, the difference in the evaluation methods was not statistically significant. The different types of defects observed were bent instrument, straightening/stretching of twist contour and partial reverse twisting. Endowave files showed maximum number of defects followed by ProTaper for hand use and least in ProTaper Rotary. Conclusion Visible defects due to torsional fatigue do occur in NiTi instruments after clinical use. Both visual and microscopic examinations were efficient in detecting defects caused due to torsional fatigue. This study emphasizes that all files should be observed for any visible defects before and after every instrumentation cycle to minimize the risk of instrument separation and failure of endodontic therapy. How to cite this article Chakka NVMK, Ratnakar P, Das S, Bagchi A, Kumar S, Anumula L. Do NiTi Instruments show Defects before Separation? Defects caused by Torsional Fatigue in Hand and Rotary Nickel-Titanium (NiTi) Instruments which Lead to Failure during Clinical Use. J Contemp Dent Pract 2012;13(6):867-872.
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Liu, T.-Y., M. Bartnikowski, AC Wu, M. Veitch, KA Sokolowski, SM Millard, AR Pettit, V. Glatt, CH Evans, and JW Wells. "Healing of sub-critical femoral osteotomies in mice is unaffected by tacrolimus and deletion of recombination activating gene 1." European Cells and Materials 41 (March 17, 2021): 345–54. http://dx.doi.org/10.22203/ecm.v041a22.
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Clinical management of delayed healing or non-union of long bone fractures and segmental defects poses a substantial orthopaedic challenge. There are suggestions in the literature that bone healing may be enhanced by inhibiting the activities of T and B lymphocytes, but this remains controversial. To examine this matter in more detail, sub-critical-sized segmental defects were created in the femora of mice and it was assessed whether there might be a benefit from the administration of a Food and Drug Administration (FDA)-approved drug that blocks T cell activation (tacrolimus). Defects were stabilised using an internal plate. In certain groups of animals, 1 mg/kg or 10 mg/kg tacrolimus was delivered locally to the defect site for 3 or 7 d using an implanted osmotic pump with a silicon catheter directing drug delivery into the defect area. Healing was monitored by weekly X-ray and assessed at 12 weeks by mechanical testing, µCT and histology. Radiographic and histological evaluations revealed that 100 % of defects healed well regardless of tacrolimus dosage or duration. A comparison of healed C57BL/6 and Rag1−/− femora by µCT and ex vivo torsion testing showed no differences within mouse strains in terms of bone volume, tissue volume, bone volume/tissue volume ratio, shear modulus, torsional rigidity or torsional stiffness. These data failed to support an important role for tacrolimus in modulating the natural healing of segmental defects under those experimental conditions.
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HUQ, ABUL M. A., ABUHANIF K. BHUIYAN, KIN LIAO, and KHENG LIM GOH. "DEFECT–DEFECT INTERACTION IN SINGLE-WALLED CARBON NANOTUBES UNDER TORSIONAL LOADING." International Journal of Modern Physics B 24, no. 10 (April 20, 2010): 1215–26. http://dx.doi.org/10.1142/s021797921005510x.
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This paper presents an analysis of interactions between a pair of Stone–Wales (SW) defects in a single-walled carbon nanotube (SWCNT) that has been subjected to an external torque. Defect pairs, representing the different combinations of SW defect of A (SW-A) and B (SW-B) modes, were incorporated in SWCNT models of different chirality and diameter and solved using molecular mechanics. Defect–defect interaction was investigated by evaluating the C–C steric interactions in the defect that possesses the highest potential energy, E, as a function of inter-defect distance, D. This study reveals that the deformation of the C–C bond is attributed to bond stretching and bending. In the SW-B defects, there is an additional contributor arising from the dihedral angular deformation. The magnitude of E depends on the type of defect but the profile of the E versus D curve depends on the orientation of the defects. The largest indifference length, D0, beyond which two defects cease to interact, is approximately 30 Å. When the angular displacement of the tube increases two-fold, E increases, but the profile of the E versus D curve is not affected. The sense of rotation affects the magnitude of E but not the profile of the E versus D curve.
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Endo, Masahiro, and Yukitaka Murakami. "Effects of an Artificial Small Defect on Torsional Fatigue Strength of Steels." Journal of Engineering Materials and Technology 109, no. 2 (April 1, 1987): 124–29. http://dx.doi.org/10.1115/1.3225951.
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In order to elucidate the effect of small defects on the torsional fatigue strength of steels, reversed torsion tests were carried out on the 0.46 percent C steel specimens containing a small hole. The hole diameter ranges from 40 to 500μm. The fatigue behaviors on the specimen surface and near the hole were observed with the aid of a microscope. The torsional fatigue strength of steels containing small holes can be predicted from the results of rotating bending fatigue test by considering the threshold condition for crack propagation.
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Amanatullah, Derek F., Joel C. Williams, David P. Fyhrie, and Robert M. Tamurian. "Torsional Properties of Distal Femoral Cortical Defects." Orthopedics 37, no. 3 (March 1, 2014): 158–62. http://dx.doi.org/10.3928/01477447-20140225-51.
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Nasr, Anouar, Yves Nadot, Chokri Bouraoui, and Raouf Fathallah. "Effect of Artificial Defect and Mean Shear Stress on Torsional Fatigue Behaviour." Applied Mechanics and Materials 146 (December 2011): 74–82. http://dx.doi.org/10.4028/www.scientific.net/amm.146.74.
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The aim of this work is to study the influence of artificial defect and mean stress on fatigue strength under torsion loading. Spherical artificial defects have been machined at the surface of gauge length of fatigue samples. Experimental investigations conducted on both defective and defect free materials. The crack initiation mechanisms have been identified based on several observations on Scanning Electron Microscope (SEM) at different stage of fatigue life. It is observed that the defect free material subjected to torsion loading allows relatively earlier initiation. Experimental results show that mean shear stress has no effect on fatigue behaviour under torsion loading. It is also concluded that defects are much more damaging in high cycle fatigue regime than in low cycle fatigue one.
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KHARRAT, M., M. N. ICHCHOU, O. BAREILLE, and W. ZHOU. "PIPELINE INSPECTION USING A TORSIONAL GUIDED-WAVES INSPECTION SYSTEM. PART 2: DEFECT SIZING BY THE WAVE FINITE ELEMENT METHOD." International Journal of Applied Mechanics 06, no. 04 (July 9, 2014): 1450035. http://dx.doi.org/10.1142/s1758825114500355.
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This paper represents the second part of the work that considers the identification and sizing of machined defects in a pipeline. This study deals with the torsional-mode reflection from defects and structural singularities in an industrial pipeline in order to perform the defect sizing. The wave finite element method (WFEM) is used to construct a numerical database of reflection coefficients from rectangular defects by varying thickness, axial and circumferential extents. Calculation is made depending on the frequency. The approximation of defects' sizes is carried out by sweeping the numerical database to find the suitable combination of dimensions for a given defect. The axial and circumferential extents are evaluated by fixed intervals for each possible thickness. Reflections from structural singularities (elbows, concrete blocks, clamps and welds) are also treated by comparing reflection coefficients obtained by the WFEM to those evaluated experimentally. Results show a good agreement for most of the structural singularities but not for the others.
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Kim, Young-Wann, and Kyung-Jo Park. "The interaction of fundamental torsional guided waves from axial and oblique defects in pipes." Insight - Non-Destructive Testing and Condition Monitoring 63, no. 6 (June 1, 2021): 334–40. http://dx.doi.org/10.1784/insi.2021.63.6.334.
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A quantitative study of the interaction of the T(0,1) torsional mode with axial and oblique defects in a pipe is presented in this paper. A mode decomposition technique employing the chirplet transform is used to separate the multimodal signals reflected from the defects. Reflection signals are obtained from experiments on a carbon steel pipe. The influence of the crack length and inclination angle on the reflection is investigated. The reflection from an axial defect is found to consist of a series of wave pulses with gradually decaying amplitude. The results show that the reflection coefficient of an axial crack initially increases with the crack length but finally reaches an oscillating regime. Furthermore, for an oblique crack, it is revealed that the reflection coefficient is linearly dependent on the equivalent circumferential extent of the defect and is independent of the axial length.
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Kharrat, M., M. N. Ichchou, O. Bareille, and W. Zhou. "Wave Diffusion Sensitivity to Angular Positions of Defects in Pipes." Journal of Computational Acoustics 23, no. 03 (June 25, 2015): 1550013. http://dx.doi.org/10.1142/s0218396x15500137.
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This paper provides a numerical investigation onto the effect of the angular position of a defect on the wave diffusion in a steel pipe. The wave finite element method (WFEM) is used to calculate reflection and transmission coefficients from defects with different angular positions as a function of frequency. The modeled defects are impinged successively by torsional T(0, 1), longitudinal L(0, 2) and flexural F(1, 2) modes. The wave diffusion in each case is examined leading to several important remarks. Results show that the choice of the incident mode as well as the studied reflected and transmitted modes play a crucial role in the circumferential localization of defects in pipes.
Dissertations / Theses on the topic "Torsional defects":
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Carandente, Rosalba. "Interaction between the fundamental torsional guided wave mode and complex defects in pipes." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9484.
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The presence of defects in pipelines is a concern especially in petrochemical applications where the service integrity of pipes is a fundamental requirement to avoid process interruptions and to fulfil safety standards. Guided wave inspection is now routinely used in industry for screening long lengths of pipe for corrosion, any suspect areas then being followed up with conventional ultrasonic thickness gauging. However, this is difficult in cases where the suspect area is inaccessible (e.g. buried pipelines or pipes passing though walls), so it would be very useful to apply guided wave techniques for sizing as well as the detection and location of defects. This target is challenging due to the complexity of the profiles encountered in practice. The present work aims to improve the understanding of the scattering of the fundamental torsional mode T(0, 1) from complex shaped discontinuities and to determine the controlling parameters of this phenomenon. The overall analysis starts with a study of the reflection from axi-symmetric tapered steps and notches in pipes. After that the scattering from three dimensional (3D) defects with different shapes has been studied. Firstly, flat-bottomed defects with different surface profiles have been analyzed, and then the study of the reflection behavior from 3D defects with varying depth profile has been carried out. All of the work presented here uses the T(0,1) mode for inspection. It is revealed that the reflection coefficient maxima from axi-symmetric tapered defects decrease with increasing frequency as the slope of the taper becomes more gradual, this effect being more pronounced when the ratio of the average defect length to the wavelength increases. Tapered defects are therefore expected to be more difficult to detect at higher inspection frequencies; this effect is more evident for shallower tapers. It is also found that at a given maximum depth of a finite discontinuity, the peak of the reflection coefficient from a defect is linearly dependent on the circumferential extent of the defect, and is independent of its shape. The results from these analyses have been used to propose a practical approach to determine the maximum depth of a complex discontinuity from the reflection coefficient behavior, provided that the external circumferential extent of the defect is known. This method has been applied to real corrosion patches and the results validated with experiments. Its main limitation is on defects with a gradual corrosion section profile, but with a sudden change of the depth over a small circumferential region. It is shown then that a possible way to diagnose sharp circumferential profile changes is to measure the reflection coefficient spectrum at frequency higher than usually used in long range guided wave inspection.
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Bhana, Vishal Bhooshan. "Online damage detection on shafts using torsional and undersampling measurement techniques." Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/25437.
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The presence of cracks in rotors is one of the most dangerous defects of rotating machinery. This can lead to catastrophic failure of the shaft and long out-of-service periods. The occurrence of a crack in a rotating shaft introduces changes in flexibilities which alters the dynamics during operation. This research deals with detecting damage in rotors by means of constantly monitoring the variation in the rotor’s dynamics during normal operating conditions. This project entails a computer finite element section as well as an experimental investigation. The flexibility in the region of the crack is different from an uncracked section. A finite element model of a shaft is built and investigated. The damaged model is the same except that the nodes in the location of the crack are not equivalenced in order to represent the crack. A simple constant cross-sectional shaft with semi-circular transverse surface cracks varying in size have been modelled on the Patran finite element software and a normal modes analysis was done using the Nastran solver. The results revealed a change in the natural frequencies due to the variation in the size of the crack. The experimental investigation involved creating sample shafts with damage positioned in them that would closely resemble what one may find in actual real-life situations and the dynamics during rotation with various torsional loadings are investigated and monitored using three methods. A fibre-optical sensor, Digital image correlation system and telemetry strain gauges were used. Undersampling techniques were used for the DIC system. Results showed that the fibre-optic sensor is by far the most favourable as it is able to detect damage under constant operation. The finite element model was updated by re-modelling the geometry, damage and material properties. The solution of the analysis matched the experimental results closely and model verification was achieved.Dissertation (MEng)--University of Pretoria, 2013.
Mechanical and Aeronautical Engineering
unrestricted
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Kharrat, Mohamed. "Design and development of a torsional guided-waves inspection system for the detection and sizing of defects in pipes." Thesis, Ecully, Ecole centrale de Lyon, 2012. http://www.theses.fr/2012ECDL0016/document.
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Plusieurs industries manipulent des substances liquides et gazeuses qui circulent souvent dans de longues canalisations. La technique d'ondes guidées est couramment utilisée dans ce domaine. Cette technique est en progrès continu. Dans cette thèse, un système d'inspection a été conçu et développé. Il est basé sur des transducteurs piézoélectriques qui génèrent des ondes guidées de torsion pouvant se propager le long du tube testé. Les signaux réfléchis des défauts et singularités rencontrés sont détectés aussi par des capteurs piézoélectriques. Des simulations numériques utilisantpar la méthode d'éléments finis standard et la méthode Wave Finite Element(WFEM) ont été effectuées afin de vérifier et de visualiser le phénomène de propagation des ondes dans des tubes intacts et endommagés. Un ensemble de tests a été mis en place sur des tubes droits et courbés avec deux matériaux différents: PVC et acier. L'interaction entre les ondes générées et les défauts usinés a été prouvée.Les résultats numériques et expérimentaux confirment certaines caractéristiques spécifiques concernant le coefficient de réflexion de l'onde. Par la suite, un pipeline industriel d'environ soixante mètres de long et contenant plusieurs défauts et singularités a été testé par le système d'inspection. Les signaux enregistrés ont soumis certains traitements numériques afin de les rendre exploitables. Les signaux traités sont analysés afin d'identifier et de distinguer les réflexions des défauts de celles des singularités structurés. La méthode WFEM a été employée pour construire une base de données numérique des coefficients de réflexion en variant la profondeur et les extensions axiale et circonférentielle du défaut modélisé. Le calcul a été établi en fonction de la fréquence. La corrélation des tailles des défauts est effectuée en balayant la base de données numérique pour trouver la combinaison appropriée de dimensions pour un défaut donné. Les réflexions à partir des singularités structurées (coudes, blocs de béton, colliers, et les soudures) sont traitées ainsi en comparant des coefficients de réflexion obtenus par WFEM à ceux évalués expérimentalement. Enfin, on a étudié numériquement l'effet de la position angulaire d'un défaut sur les coefficients de réflexion et de transmission tout en excitant à différents types d'ondes. La méthode WFE est aussi utilisée pour effectuer le calcul. Cette étude donne un guide à la localisation circonférentielle des défauts dans les tubesLong pipelines are widely used in several industries transporting liquid or gas. The guided wave technique is commonly used in this field and it is under continuing progress. In this thesis, an inspection system has been designed and developed. Piezoelectric transducers are employed to generate torsional guided waves that could propagate along the tested pipe; and receive reflected signals from encountered features and damages. Numerical simulations using standard FE and Wave Finite Element methods have been carried out in order to verify and visualize the wave propagation phenomenon in both intact and damaged pipes. A set of tests has been performed on straight and curved pipes with two different materials: PVC and steel. The interaction between generated waves and machined defects has been proven. Numerical and experimental results confirm some specific features in the wave reflection coefficient. Thereafter, an industrial pipeline of about sixty meters long and containing several features has been tested by the inspection system.Recorded signals had submitted some numerical treatments in order to make them interpretable. Processed signals are analyzed to identify defects reflections from structured singularities echoes. The Wave Finite Element Method (WFEM) has been used to construct a numerical database of reflection coefficients from modelled defects by varying thickness, axial and circumferential extents. Calculation was made depending on frequency. The approximation of defect sizes is carried out by sweeping the numerical database to find the suitable combination of dimensions fora given defect. Reflections from structural singularities (elbows, concrete blocks,clamps, and welds) are treated as well by comparing reflection coefficients obtained by WFEM to those evaluated experimentally. Finally, a numerical investigation deals with the effect of defect angular-position on reflection and transmission coefficients while exciting by different types of waves. The spectral method Wave Finite Element has been used to carry out calculation. This study gives guidance to circumferential localization of defects in pipes
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Tailony, Rauf. "Internal Combustion Engine Cold Test Driveline Modeling, Analysis and Development." University of Toledo / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1564765172535669.
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Deere, Matthew. "Guided wave evaluation of pipes using the first and second order torsional wave mode." Thesis, Brunel University, 2017. http://bura.brunel.ac.uk/handle/2438/15307.
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Guided wave inspection is a form of ultrasonic testing used for non-destructive testing (NDT). Guided waves are capable of propagating long distances bounded by the geometries of the specimen, such as pipes and plates. The technique is commercially used to detect defects in pipelines and is capable of a full volumetric screening many metres (often up to around 100m) from one location. Fundamental axisymmetric wave modes are used to inspect pipelines and are used to quantify defects and features. However, as the technology has progressed, a demand for improving defect sensitivity, spatial resolution and developing the technology into new fields has been recognised. Operating at medium range frequencies is one possibility that could provide the increase in defect sensitivity and spatial resolution required that may not be achieved at low range frequencies. The use of higher order wave modes could also provide additional information useful for defect sizing. Guided wave inspection is a complex ultrasonic technique due to the many wave modes that exist and testing at medium range frequencies requires some challenges to be overcome. The research presented here investigates the potential of using the second order torsional wave mode at medium range frequencies and provides a new sizing technique that for some applications is likely to offer advancement in guided wave inspection and monitoring. The approach firstly included the design and implementation of a setup for analysing the complex signal responses in order to access the higher order torsional wave mode T(0,2) for defect sizing. An efficient method of using FEA has been presented using segmented models to provide the capability of analysing defects with small increment changes that could not be achieved using a full 3D model of the pipe. Using a pipe segment to virtually represent the full pipe also allowed small changes in defect size to be investigated, which would otherwise be extremely difficult to accurately machine experimentally. The FEA modelling technique is also based on broadband signals in comparison to the conventional approach of using narrowband signals and is capable of obtaining a wide frequency spectrum from one model, which significantly reduces the number of models needed to conduct a frequency analysis. Following on from this work, a high density transducer array was developed and compared against a conventional transducer array used in guided wave inspection for the purpose of medium range frequency inspection, which can also be applied to conventional low range frequency inspection. Finally, a new defect sizing method using T(0,2) is presented, which is capable of predicting the depth using peak amplitude responses from spectral analysis and by comparing this to the cut-off frequency of the remaining wall thickness of the defect. The technique has the potential to improve defect sizing, defect sensitivity, increase spatial resolution, and increase the performance of medium range inspection.
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Netto, Anibal Livramento da Silva. "Dinâmica quântica em espaços com defeitos." Universidade Federal da Paraíba, 2010. http://tede.biblioteca.ufpb.br:8080/handle/tede/5776.
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In this work we studied the quantum dynamics of particles in a non-euclidian space. First, we studied the dynamics of a particle in a space with a linear topological defect, by confinement potential which mimics different mesoscopic systems [1, 2, 3]. By the effective mass approach [4, 5], one can apply our results to semiconductor nanostructures. Second, we studied the quantum dynamics of a particle, also in the effective mass approach, for the confinement in a spherical space. The confinement potential presented is alike the one in reference [7], but now fitted to a surface with positive curvature. We studied the dynamics for the spherical space in two situations: with and without including a topological defect. Third, we studied, both relativistic and non-relativistic, for a space with a density of defects. Some results from this thesis were published in references [8, 9].
Neste trabalho estudamos a dinâmica de partículas em um espaço não-euclidiano. Inicialmente, estudamos a dinâmica de uma partícula em um espaço com um defeito topológico linear, para um confinamento através de um potencial que consegue modelar diferentes sistemas mesoscópicos [1, 2, 3]. Através da abordagem de massa efetiva [4, 5], pode-se aplicar nossos resultados a nanoestruturas semicondutoras. Em um segundo momento, estudamos a dinâmica quântica de uma partícula, também na abordagem de massa efetiva, para o confinamento em um espaço esférico. O potencial confinante tratado é similar ao da referência [7], só que agora ajustado para uma superfície de curvatura positiva. Estudamos a dinâmica para o espaço esférico em duas situações: com e sem a inserção de um defeito topológico. Em um terceiro momento, estudamos a dinâmica, tanto relativística quanto não relativística, para um espaço com uma densidade de defeitos. Parte dos resultados desta tese foram publicados nas referências [8, 9].
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Serrano, Munoz Itziar. "Influence of casting defects on the fatigue behaviour of an A357-T6 aerospace alloy." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0117/document.
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L’excellente coulabilité, les coûts de production relativement bas, et ratio poids/résistance mécanique élevé des alliages de fonderie Al-Si-Mg en font une des solutions les plus intéressantes dans le secteur automobile ainsi que dans le domaine aérospatial. Toutefois, il est bien connu que la durée de vie de ces composants moulés à grand nombre de cycles (105 < Nf < 107 cycles) est sévèrement réduite lorsque des défauts de fonderie (notamment pores et oxydes) sont débouchants et/ou subsurfaciques sont présents. Ces défauts concentrent les contraintes et peuvent considérablement réduire la période d’amorçage des fissures de fatigue en fonction de leur taille, forme et des caractéristiques microstructurales du matériau. Les défauts internes (à partir desquels les fissures peuvent amorcer et propager sans interaction avec l’air ambiant) ainsi que les défauts de surface (ceux qui sont placés à la surface et en contact direct avec l’air ambiant) vont également nuire la durée de vie des composants moulés. Toutefois, dans le cas des défauts internes, les coefficients de sécurité préconisés par les règles de conception ne font pas intervenir la distance de défaut par rapport à la surface. Le suivi de fissures de fatigue effectué à la surface d’éprouvettes macroscopiques de traction indique que la présence d’un défaut avec une taille supérieure à celle des fissures microstructuralement courtes (√A ≈ 500 μm, taille contrôlée par la SDAS) produit une remarquable réduction de la durée vie. En revanche, la durée de vie n’est pas affectée lorsqu’un défaut plus petit (√A ≈ 300 μm) est présent à la surface car l’amorçage et les premiers stades de propagation sont encore influencés par la SDAS. Les essais de fatigue en torsion pure montrent que la morphologie des surfaces de rupture est fortement influencée par le niveau de contrainte. De plus, le nombre de cycles à l’amorçage est réduit par rapport à la traction. Cet amorçage est multi-site et plusieurs fissures peuvent croitre simultanément au cours de la durée de vie d’une éprouvette, la rupture finale se produisant lors de la jonction de certaines de ces fissures. La propagation des fissures en torsion est largement influencée par la cristallographie locale et les retassures ne semblent pas être des sites de nucléation préférentiels. Les durées de vie odes échantillons macroscopiques contenant défauts artificiel internes (Øeq ≈ 2 mm) sont pratiquement similaires à celles obtenues avec un matériau de référence. L’amorçage et la propagation de fissures internes a été rarement observé lors des expériences de tomographie synchrotron. Dans les rares cas où de telles fissures ont pu être observées, le chemin de fissuration semble fortement influencé par la cristallographie alors que les fissures amorcées depuis la surface se propagent globalement en mode I. La vitesse de propagation des fissures internes est très inférieure à celle des fissures se propageant à partir de la surfaceThe excellent castability, relatively low production costs, and high strength to weight ratios make Al-Si-Mg cast alloys an attractive choice for use in cheaper and lighter engineering components, in both automotive and aerospace industries. However, it is well known that High Cycle Fatigue (HCF) lives (105 < Nf < 107 cycles) of cast components are severely reduced when casting defects (notably pores and oxides) are present at the free surface or subsurface. They act as stress raisers which can considerably reduce the crack incubation period depending on their size, shape and the microstructural features of the surrounding material. Internal casting defects are of special interest to this work. The application of safety coefficients considers that all casting defects present in a component have the same deleterious effect and no attention is paid, for example, to their distance to the free surface. In other words, internal defects (corresponding to the case where the depth of the defect allows crack nucleation and propagation to essentially occur without interaction with the air environment) are considered as damaging to fatigue life as surface defects (those placed at the free surface and in contact with the air environment). Surface crack monitoring performed on uniaxial fatigue specimens indicates that the presence of a surface microshrinkage exceeding the size of microstructurally small cracks (√A ≈ 500 μm, controlled by the SDAS) readily nucleates a fatigue cracks producing steady crack propagation and remarkable reduction in the expected fatigue life. A smaller surface defect (√A ≈ 300 μm) nucleated a crack that did not reduced the expected fatigue life as in this case early stages of propagation are still nfluenced by the SDAS. Pure torsional cycling reveals that the morphology of fracture surfaces is highly influenced by the stress level. In general, torsional fatigue behaviour is described by having reduced (with respect to uniaxial testing) and multisite crack nucleation periods. Several dominant cracks can evolve simultaneously and the final failure occurs by the linkage of some of those cracks. Crack propagation is controlled by the crystallography and pores do not appear to be preferential nucleation sites. S-N curves show that macroscopic specimens containing Øeq ≈ 2 mm internal artificial defect produce similar fatigue lives to those obtained with a defect-free material. Internal crack nucleation was rarely observed during synchrotron tomography experiments; instead the fatal cracks initiated from much smaller surface defects. Tomographic images show that, in the case of internal propagation, crystallographic paths are formed while surface cracks propagate in mode I. The crack growth rate of internal cracks is much smaller than that of cracks propagating from the free surface
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Bakke, Filho Knut. "Fases geométricas, quantização de Landau e computação quâantica holonômica para partículas neutras na presença de defeitos topológicos." Universidade Federal da Paraíba, 2009. http://tede.biblioteca.ufpb.br:8080/handle/tede/5724.
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Previous issue date: 2009-08-06Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
We start this work studying the appearance of geometric quantum phases as in the relativistic as in the non-relativistic quantum dynamics of a neutral particle with permanent magnetic and electric dipole moment which interacts with external electric and magnetic fields in the presence of linear topological defects. We describe the linear topological defects using the approach proposed by Katanaev and Volovich, where the topological defects in solids are described by line elements which are solutions of the Einstein's equations in the context of general relativity. We also analyze the in uence of non-inertial effects in the quantum dynamics of a neutral particle using two distinct reference frames for the observers: one is the Fermi-Walker reference frame and another is a rotating frame. As a result, we shall see that the difference between these two reference frames is in the presence/absence of dragging effects of the spacetime which makes its in uence on the phase shift of the wave function of the neutral particle. In the following, we shall use our study of geometric quantum phases to make an application on the Holonomic Quantum Computation, where we shall show a new approach to implement the Holonomic Quantum Computation via the interaction between the dipole moments of the neutral particle and external fields and the presence of linear topological defects. Another applications for the Holonomic Quantum Computation is based in the structure of the topological defects in graphene layers. In the presence of topological defects, a graphene layer shows two distinct phase shifts: one comes from the mix of Fermi points while the other phase shift comes from the topology of the defect. To provide a geometric description for each phase shift in the graphene layer, we use the Kaluza-Klein theory where we establish that the extra dimension describes the Fermi points in the graphene layer. Hence, we can implement the Holonomic Quantum Computation through the possibility to build cones and anticones of graphite in such way we can control the quantum uxes in graphene layers. In the last part of this work, we study the Landau quantization for neutral particles as in the relativistic dynamics and non-relativistic dynamics. In the non-relativistic dynamics, we study the Landau quantization in the presence of topological defects as in an inertial as in a non-inertial reference frame. In the relativistic quantum dynamics, we start our study with the Landau quantization in the Minkowisky considering two different gauge fields. At the end, we study the relativistic Landau quantization for neutral particles in the Cosmic Dislocation spacetime.
Neste trabalho estudamos inicialmente o surgimento de fases geometricas nas dinâmicas quânticas relativística e não-relativística de uma partícula neutra que possui momento de dipolo magnético e elétrico permanente interagindo com campos elétricos e magnéticos externos na presença de defeitos topológicos lineares. Para descrevermos defeitos topológicos lineares usamos a aproximação proposta por Katanaev e Volovich, onde defeitos lineares em sólidos são descritos por elementos de linha que são soluções das equações de Einstein no contexto da relatividade geral. Analisamos também a inuência de efeitos não-inerciais na dinâmica quântica de uma partícula neutra em dois tipos distintos de referenciais para os observadores: um é o referencial de Fermi-Walker e outro é um referencial girante. Vemos que a diferença entre dois referenciais está na presença/ausência de efeitos de arrasto do espaço-tempo que irá influenciar diretamente na mudança de fase na funçãao de onda da partícula neutra. Em seguida, usamos nosso estudo de fases geométricas para fazer aplicações na Computação Quântica Holonômica onde mostramos uma nova maneira de implementar a Computação Quântica Holonômica através da interação entre momentos de dipolo e campos externos e pela presença de defeitos topológicos lineares. Outra aplicação para a Computação Quântica Holonômica está baseada na estrutura de defeitos topológicos em um material chamado grafeno. Na presença de defeitos topológicos lineares, esse material apresenta duas fases quânticas de origens distintas: uma da mistura dos pontos de Fermi e outra da topologia do defeito. Para dar uma descrição geométrica para a origem de cada fase no grafeno usamos a Teoria de Kaluza-Klein, onde a dimensão extra sugerida por esta teoria descreve os pontos de Fermi no grafeno. Portanto, a implementação da Computação Quântica Holonômica no grafeno está baseada na possibilidade de construir cones e anticones de grafite de tal maneira que se possa controlar os fluxos quânticos no grafeno. Na última parte deste trabalho estudamos a quantização de Landau para partículas neutras tanto na dinâmica não-relativística quanto na dinâmica relativística. Na dinâmica não-relativítica, estudamos a quantização de Landau na presença de defeitos em um referecial inercial e, em seguida, em um referencial nãoo-inercial. Na dinâmica relativística, estudamos inicialmente a quantização de Landau no espaço-tempo plano em duas configurações de campos diferentes. Por fim, estudamos a quantização de Landau relativística para partículas neutras no espaço-tempo da deslocação cósmica.
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Hsu, Wen-Chieh, and 許聞傑. "Focused Torsional Guided Wave for Defects Inspection on Elbow Using Time Reversal Method." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/796cdp.
Abstract:
碩士國立中山大學
機械與機電工程學系研究所
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Among the non-destructive testing techniques, guided waves has the characteristics of propagating long distance and being hard to attenuate, and it can also detect quickly and widely for the entire pipelines. However, identifying the signals of defects during the test is frequently difficult as a result of its multimodal and dispersive characteristics. Pipelines system is widespread use in petrochemical industry to transport gas or fluid. In virtue of restriction of space and pipelines planning, elbow parts will certainly provide to connect pipes, and this kind of complex pipe feature will bring about not only difficult to recognize signals but change direction of wave energy, that is, the energy will gather together outside of the elbow because of its geometry, then rest of the elbow will be blind area for the testing. In order to reduce error probability on recognizing signals, this study applied finite element method to simulate the propagation of T(0,1) torsional guided wave through the defect on the elbow, proposing time reversal method to analyze in accordance with defects signals, comparing difference of defect echo with and without this method so as to evaluate the feasibility of focusing ability of time reversal method on the elbow and also observing the influence of multiple defects exist in pipes on the focusing results. Time reversal method, a self-focusing technique, it can effectively focus on the spatial and temporal domain. The study results showed that it is beneficial to apply time reversal method to the improvement of signal-to-noise ratio on defect inspection for guided wave system. For instance, if defect exists at the end of elbow, and by comparing with defect reflective amplitude without and with time reversal method, it is clearly to show that the defect reflective amplitude with time reversal method is enhanced compared with that of without time reversal method. In addition to improving the signal-to-noise ratio and making defect easier to identify, it also showed that the wave energy will not be affected by the elbow, and can focus to the defect instead. Besides, when multiple defects exist in pipes, it will not make focusing behavior off the work either. For example, when there are three defects on the elbow pipeline, by using finite element method, the results showed that the focusing ability of wave energy will not be influenced even if it transmit through multiple defects on the pipe of straight part in advance, and can focus to the defect on the elbow part. The thesis also bring up the focusing oriented illustration which can easily to display the wave energy with time reversal method focus on elbow defects direction.
Books on the topic "Torsional defects":
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Özmen, Günay. Çok katlı yapılarda burulma düzensizligi =: Torsional irregularity in multi-storey structures. Maslak, İstanbul: Türkiye Deprem Vakfı, 2001.
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Gardiner, Matthew D., and Neil R. Borley. Paediatric surgery. Oxford University Press, 2012. http://dx.doi.org/10.1093/med/9780199204755.003.0013.
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This chapter begins by discussing the basic principles of paediatric anatomy and physiology and paediatric abdominal pain before focusing on the key areas of knowledge, namely congenital abdominal wall defects, anorectal malformations, miscellaneous neonatal conditions, infantile hypertrophic pyloric stenosis, intussusception, penile conditions, testicular torsion, epididymitis and orchitis, infantile inguinal hernia and hydrocele, and testicular maldescent. The chapter concludes with relevant case-based discussions.
Book chapters on the topic "Torsional defects":
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Nasedkina, A. A., A. Alexiev, and J. Malachowski. "Numerical Simulation of Ultrasonic Torsional Guided Wave Propagation for Pipes with Defects." In Springer Proceedings in Physics, 475–88. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-26324-3_33.
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Kiehn, R. M. "Coherent Structures in Fluids are Topological Torsion Defects." In Fluid Mechanics and Its Applications, 239–48. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-011-4601-2_21.
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Mazilkin, A. A., B. Baretzky, S. Enders, Olga A. Kogtenkova, Boris Straumal, Eugen Rabkin, and Ruslan Z. Valiev. "Hardness of Nanostructured Al-Zn, Al-Mg and Al-Zn-Mg Alloys Obtained by High-Pressure Torsion." In Defect and Diffusion Forum, 155–60. Stafa: Trans Tech Publications Ltd., 2006. http://dx.doi.org/10.4028/3-908451-17-5.155.
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Kleinert, H. "Theory of Fluctuating Nonholonomic Fields and Applications: Statistical Mechanics of Vortices and Defects and New Physical Laws in Spaces with Curvature and Torsion." In Formation and Interactions of Topological Defects, 201–32. Boston, MA: Springer US, 1995. http://dx.doi.org/10.1007/978-1-4615-1883-9_8.
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Liu, Xiaoyi. "Defect-Induced Discontinuous Effects in Graphene Nanoribbon Under Torsion Loading." In Springer Theses, 55–69. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-13-8703-6_5.
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Cizek, J., I. Prochazka, G. Brauer, W. Anwand, R. Kuzel, M. Cieslar, and R. K. Islamgaliev. "Ultra Fine Grained Copper Prepared by High Pressure Torsion: Spatial Distribution of Defects from Positron Annihilation Spectroscopy." In Nanomaterials by Severe Plastic Deformation, 407–12. Weinheim, FRG: Wiley-VCH Verlag GmbH & Co. KGaA, 2005. http://dx.doi.org/10.1002/3527602461.ch7b.
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Endo, M. "Effects of small defects on the fatigue strength of steel and ductile iron under combined axial/torsional loading." In Small Fatigue Cracks, 375–87. Elsevier, 1999. http://dx.doi.org/10.1016/b978-008043011-9/50035-1.
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"Torsion and Curvature from Defects." In Multivalued Fields, 342–73. WORLD SCIENTIFIC, 2008. http://dx.doi.org/10.1142/9789812791726_0012.
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SHIBATA, M., M. YAMASHITA, H.-W. GAO, H. NAKAYAMA, H. NOSE, and I. SAKAMOTO. "FRACTURE BEHAVIORS OF HIGH STRENGTH BEARING STEEL IN IMPACT TORSIONAL FATIGUE AND ITS DEFECT SENSITIVITY." In Mechanical Behaviour of Materials VI, 525–30. Elsevier, 1992. http://dx.doi.org/10.1016/b978-0-08-037890-9.50090-9.
Conference papers on the topic "Torsional defects":
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Sun, Zongqi, Li Zhang, Brian Gavigan, Takahiro Hayashi, and Joseph L. Rose. "Ultrasonic Flexural Torsional Guided Wave Pipe Inspection Potential." In ASME 2003 Pressure Vessels and Piping Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/pvp2003-1849.
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The excitation and propagation characteristics of guided wave torsional flexural mode are exploited in this paper. Theoretical computations and experiments are carried out to show the angular profiles of the torsional flexural modes propagation characteristics and the subsequent natural focusing effects. Because of such inherent advantages as less mode conversion and high sensitivity to axial defects, torsional modes and focusing possibilities have great potential in pipe inspection. By combining longitudinal and torsional modes, defect characterizations including defect size, shape etc. can be determined by truly three-dimensional guided wave pipe inspection.
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Lo̸vstad, A., P. Cawley, Donald O. Thompson, and Dale E. Chimenti. "THE REFLECTION OF THE FUNDAMENTAL TORSIONAL MODE FROM MULTIPLE SMALL DEFECTS IN PIPES." In REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION: Volume 30A; Volume 30B. AIP, 2011. http://dx.doi.org/10.1063/1.3591848.
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Zuo, Yantian, Xiaoying Tang, Houde Yu, Yaozhou Qian, and Jifeng Wang. "Application of Torsional Mode of Ultrasonic Guided Wave in Pressure Pipeline." In ASME 2012 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/pvp2012-78257.
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Ultrasonic guided wave technology is presented as a new non-destructive pipeline inspection method for its rapid, long distance inspection and applied to special pipelines which are inaccessible by other conventional NDT methods. It can be widely used in the field of long range pipeline inspection. Dispersion and attenuation characteristics of torsional modes of ultrasonic guided wave in pipeline are presented. Propagation characteristics of T (0, 1) mode at different frequencies are studied. T (0, 1) mode excited by utilizing the magnetostrictive ultrasonic guided wave detection system is applied to detect the defects of pipeline. It can be concluded that the surface condition of the pipeline, the T (0, 1) mode excitation of different patterns and frequency have great effects on defect detection and the distance of guided wave propagation. Multiple factors should be considered to select the optimal frequency and excitation patterns as pipeline inspection in field.
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Rose, Joseph L., Michael J. Avioli, and Peter J. Mudge. "Natural Focusing for the Detection of Defects Beyond Elbows." In ASME 2003 Pressure Vessels and Piping Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/pvp2003-1845.
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Long range ultrasonic guided wave inspection is advancing rapidly and is commonplace today. Benefits of using longitudinal or torsional modes are being established in special circumstances of improved sensitivity, resolution, or penetration power. The possibility of inspection under insulation, coatings, or with water filled pipes or around elbows is possible. Detection of defects beyond a pipe elbow is difficult for axisymmetric wave impingement onto the elbow. For non-axisymmetric input to the elbow region, however, via partial loading around the circumference, allows natural focusing to occur because of angular profile variation around the circumference of the pipe. An experiment is reported here to demonstrate this process.
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Carandente, R., J. Ma, P. Cawley, Donald O. Thompson, and Dale E. Chimenti. "THE REFLECTION OF THE FUNDAMENTAL TORSIONAL MODE FROM AXI-SYMMETRIC DEFECTS WITH VARYING PROFILE IN PIPES." In REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION VOLUME 29. AIP, 2010. http://dx.doi.org/10.1063/1.3362272.
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Gul, Kamran A., and Douglas E. Adams. "Modeling and Torsional Vibration Analysis of Engine Cold-Test Stand Drivelines." In ASME 2007 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/detc2007-35647.
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Many large-scale engine manufacturers use cold-testing techniques to test engine assemblies for measuring transmission noise and diagnosing cylinder faults, valve-train and oil pump defects, which cannot be detected easily using traditional hot testing. Cold-testing is done by rotating the unfired engines by an external electrical drive and a driveline and analyzing the measured torque signal characteristics at various engine speeds. In this work, two different cold-test stands, which experience large torsional oscillations excited by various engine harmonics, are modeled. The excessive vibratory response of these stands not only makes the engine fault detection process difficult by degrading the measured torque signal, but can also cause structural failure. An appropriate driveline design is required to decrease the torsional vibration and noise levels and preserve the integrity of diagnostic signals. In an effort to prevent undesirable noise and vibration problems, models of engine cold-test stands are developed that involve modeling of driveline components, engine excitation model for cold-testing, and estimation of torsional vibratory response. The developed models are validated by comparing the model predictions with experimental responses. Model parameters that can help suppress the torsional resonances are determined using embedded sensitivity functions. It is shown that using a smaller-sized motor and a softer rubber coupling, the driveline torsional resonant frequencies excited during the speed sweep can be shifted out of the test range and the amplitudes can be decreased. The developed model is, therefore, used to help redesign the cold-test stand drivelines.
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El Badaoui, M., V. Cahouet, F. Guillet, J. Daniere, and P. Velex. "Modeling and Detection of Localized Tooth Defects in Geared Systems." In ASME 1999 Design Engineering Technical Conferences. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/detc99/vib-8108.
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Abstract The early detection of failures in geared systems is an important industrial problem which has still to be addressed from both an experimental and theoretical viewpoint. The proposed paper combines some extensive numerical simulations of a single stage geared unit with localized tooth faults and the use of several detection techniques whose performances are compared and critically assessed. A model aimed at simulating the contributions of local tooth defects such as spalling to the gear dynamic behavior is set up. The pinion and the gear of a pair are modeled as to two rigid cylinders with all six degrees of freedom connected by a series of springs which represent gear body and gear tooth compliances on the base plane. Classical shaft finite elements including torsional, flexural and axial displacements can be superimposed on the gear element together with some lumped stiffnesses, masses, inertias, ... which account for the load machines, bearings and couplings. Tooth defects are modeled by a distribution of normal deviations over a zone which can be located anywhere on the active tooth flanks. Among the numerous available signal processing techniques used in vibration monitoring, cepstrum analysis is sensitive, reliable and it can be adapted to a complex geared system with several meshes. From an analytical analysis of the equations of motion, two complementary detection techniques based upon the acceleration power cesptrum are proposed. The equations of motion and the contact problem between mating flanks are simultaneously solved by coupling an implicit time-step integration scheme and a unilateral normal contact algorithm. The results of the numerical simulations are used as a data base for the proposed detection techniques. The combined influence of the defect location, depth and extent is analyzed for two examples of spur and helical gears with various profile modifications and the effectiveness of the two complementary detection methods is discussed before some conclusions are drawn.
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Vaziri, A., and H. Nayeb-Hashemi. "Axial and Torsional Dynamic Responses of Tubular Joints With an Annular Void." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-32381.
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Dynamic responses of adhesively bonded tubular joints subjected to a harmonic axial and torsional load are investigated. Adherents are assumed elastic and the adhesive is taken to be a linear viscoelastic material. The effects of adherents and adhesive properties on the joint response as well as on the shear stress amplitude distribution along the overlap are investigated for each case of harmonic loading. Furthermore, the effects of defects such as an annular void in the bond area on the axial and torsional dynamic responses and shear stress amplitude distributions in the bond area are studied. The results indicate that for tubular joint geometries and properties investigated the axial and torsional resonant frequencies of the joint are little affected with the adhesive loss factor. These resonant frequencies initially increase rapidly with increasing adhesive shear modulus. However, the resonant frequencies asymptotically approach a constant value with further increase in adhesive shear modulus. The results further show that the resonant frequencies of the joint may not get affected with the presence of a central void in the bond area. The distribution of shear stress amplitude in the joint area is obtained. The maximum shear stress is confined to the edge of the overlap for all applied loading frequencies. For the adhesive and adherents’ properties and geometries investigated, the maximum shear stress amplitude in the joint area is little affected by the presence of a central annular void covering up to 40% of the overlap length. However, a central void larger than 40% of the overlap length may be detrimental or beneficial to the joint strength. This depends on the applied loading frequency. A central void reduces the system axial and torsional resonant frequencies. This may depart the system further away from the applied loading frequency or may bring it closer. A system excited closer or further from to its resonant frequency will develop higher or lower shear stress amplitude in the bond area.
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Dewan, M. W., Gustavo González, and M. A. Wahab. "Effects of Rotating-Bending and Torsional Fatigue Loads on Gas Tungsten Arc (GTA) Welded AISI 1018 Low Carbon Steel Joints." In ASME 2015 International Manufacturing Science and Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/msec2015-9326.
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Most welded structures are subjected to multiaxial fatigue load and majority of the fatigue failure initiated from weld joints. Therefore, it is important to evaluate multiaxial fatigue behavior of commonly used welded materials. In the current investigations, the influence of rotating bending fatigue load along with torsional pulsed load was appraised for most commonly used AISI 1018 low carbon steel. A rotating-bending-torsional fatigue testing unit was designed and manufactured for biaxial fatigue test of welded and un-welded specimens. For welded specimens, Gas Tungsten Arc welding (also known as Tungsten-Inert-Gas (TIG) welding) was carried out on 19.05 mm diameter round bar of AISI 1018 steel using ER70-S2 filler metal. For rational comparison, only defects-free specimens were carefully chosen and tested. After welding, uniaxial tensile test was conducted to understand the fatigue loading criteria during rotating-bending fatigue test. Due to TIG welding, tensile strength was decreased considerably about 18% as compared to base metal. Rotating-bending (RB) and rotating-bending-torsional (RBT) fatigue tests were conducted to obtain a systematic understanding of biaxial fatigue behavior. RB fatigue life of welded specimens reduced compared to base metal as a result of complex thermal cycle during welding process and microstructural changes. Under combined loading conditions (RBT), base metal specimens did not exhibit significant difference on the fatigue behavior. However, for the welded specimens, the fatigue strength was reduced by about 12.8%. Moreover microstructural characterization and fracture surface analysis were performed to understand the fracture behavior of the tested specimens.
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Heckmann, Benjamin, Lucas Ginzinger, and Heinz Ulbrich. "Test Rig and Simulation Environment for Model-Based Monitoring." In ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-60187.
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With the aim to provide the basis for model-based monitoring of rotor systems a test rig and an appropriate simulation environment has been developed. Therewith several damages shall be replicated and investigated. In a first approach an unbalanced rotor system and an increasing clearance in a journal bearing are analysed. Therefore extensive experiments with the rotor test rig have been conducted. The implemented test system is modelled with a simulation environment called MBSim (http://mbsim.berlios.de). This simulation environment, developed at the Institute of Applied Mechanics, is based on a framework for the efficient simulation of multi-body-systems with unilateral contacts and elastic elements. Therewith typical defects in rotating machinery can be replicated and critical effects can be investigated. The simulation includes a spatial bending-torsional beam and unilateral contacts with friction and impacts. So it’s possible for instance to model unilateral contacts in journal bearings with clearance between shaft and bearing. Experiment and simulation are consistent with each other in a very wide range, so the basis for the higher aim of a model-based fault detection and identification is provided.