Academic literature on the topic 'Voids and defects'
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Journal articles on the topic "Voids and defects"
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Wu, Xianlong, Xiaohua Bao, Jun Shen, Xiangsheng Chen, and Hongzhi Cui. "Evaluation of Void Defects behind Tunnel Lining through GPR forward Simulation." Sensors 22, no. 24 (2022): 9702. http://dx.doi.org/10.3390/s22249702.
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Voids, a common defect in tunnel construction, lead to the deterioration of the lining structure and reduce the safety of tunnels. In this study, ground-penetrating radar (GPR) was used in tunnel lining void detection. Based on the finite difference time domain (FDTD) method, a forward model was established to simulate the process of tunnel lining void detection. The area of the forward image and the actual void area was analyzed based on the binarization method. Both the plain concrete and reinforced concrete lining with various sizes of air-filled and water-filled voids were considered. The rationality of the model was verified by measured data. It was observed that the response mode of voids can be hyperbolic, bowl-shaped, and strip-shaped, and this depends on the void’s width. Compared with the air-filled voids, water filling increases the response range of the voids and produces a virtual image. Although the diffracted wave caused by a steel bar will bring about significant interference to the void response, the center position of the voids can be accurately located using 3D GPR.
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Ding, Zude, Jincheng Wen, Xiafei Ji, Zhihua Ren, and Sen Zhang. "Experimental Investigation of the Mechanical Behavior of NC Linings in consideration of Voids and Lining Thinning." Advances in Civil Engineering 2020 (June 25, 2020): 1–14. http://dx.doi.org/10.1155/2020/8876785.
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The presence of voids or lining thinning directly affects the mechanical behavior of linings, and these defects threaten the safety of tunnel operation. In this study, a series of 1/5-scale model tests was used to investigate the mechanical behavior of normal concrete (NC) linings in consideration of voids and combined defects. Test results showed that the void and combined defects substantially reduced the load-bearing capacity and deformation properties of the linings. The inelastic mechanical behavior of the linings was also significantly affected by the defects. The effects of lining defects located at the spandrel were slightly weaker than those of lining defects located at the crown. As the void size or degree of combined defects increased, the tensile strain at the location of the lining defects also increased. Therefore, the defect position of the linings was easily damaged. The defects considerably reduced the overall deformation of the linings but increased the local deformation. The distribution of lining cracks was concentrated at the defect position. In addition, different failure characteristics of the lining were observed due to the differences in defects.
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Hoffman, Richard T., Alexander P. Moore, and Chaitanya S. Deo. "Examination of the Effect of Vacancy Detachment Rates on Kinetic Monte Carlo Simulations of bcc Metals." MRS Advances 1, no. 35 (2016): 2489–94. http://dx.doi.org/10.1557/adv.2016.513.
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ABSTRACTA Kinetic Monte Carlo simulation, using a modified version of the SPPARKS code, of simple defects and complex vacancy clusters was run on a bcc lattice. In this simulation the complexity of void formation was varied by introducing a detachment rate for individual vacancies leaving the void and either treating this value as constant for all size voids or having this value be dependent on the size of the void. Molecular Dynamics simulations were used to determine the binding energies of vacancies for voids of varying size. The simulation was then run over long time periods to determine the number of defects in the simulation under irradiation conditions. It was found that the additional complexity of size dependent void detachment rates had little effect on the defect concentrations and thus a constant barrier should be sufficient for simulations of voids in bcc metals.
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Zheng, Wenting, Bin Xu, Zongjun Xia, et al. "A Concrete Core Void Imaging Approach and Parameter Analysis of Concrete-Filled Steel Tube Members Using Travel Time Tomography: Multi-Physics Simulations and Experimental Studies." Sensors 24, no. 8 (2024): 2503. http://dx.doi.org/10.3390/s24082503.
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Concrete-filled steel tube (CFST) members have been widely used in civil engineering due to their advanced mechanical properties. However, internal defects such as the concrete core voids and interface debonding in CFST structures are likely to weaken their load-carrying capacity and stiffness, which affects the safety and serviceability. Visualizing the inner defects of the concrete cores in CFST members is a critical requirement and a challenging task due to the obvious difference in the material mechanical parameters of the concrete core and steel tube in CFST members. In this study, a curved ray theory-based travel time tomography (TTT) with a least square iterative linear inversion algorithm is first introduced to quantitatively identify and visualize the sizes and positions of the concrete core voids in CFST members. Secondly, a numerical investigation of the influence of different parameters on the inversion algorithm for the defect imaging of CFST members, including the effects of the model weighting matrix, weighting factor and grid size on the void’s imaging quality and accuracy, is carried out. Finally, an experimental study on six CFST specimens with mimicked concrete core void defects is performed in a laboratory and the mimicked defects are visualized. The results demonstrate that TTT can identify the sizes and positions of the concrete core void defects in CFST members efficiently with the use of optimal parameters.
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Gong, Yaohua, Tao Huang, Xun’an Zhang, Yongyong Suo, Purong Jia, and Shuyi Zhao. "Multiscale Analysis of Mechanical Properties of 3D Orthogonal Woven Composites with Randomly Distributed Voids." Materials 14, no. 18 (2021): 5247. http://dx.doi.org/10.3390/ma14185247.
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Voids are common defects in 3D woven composites because of the complicated manufacturing processes of the composites. In this study, a micro–meso multiscale analysis was conducted to evaluate the influence of voids on the mechanical properties of three-dimensional orthogonal woven composites. Statistical analysis was implemented to calculate the outputs of models under the different scales. A method is proposed to generate the reasonable mechanical properties of the microscale models considering randomly distributed voids and fiber filaments. The distributions of the generated properties agree well with the calculated results. These properties were utilized as inputs for the mesoscale models, in which void defects were also considered. The effects of these defects were calculated and investigated. The results indicate that tensile and shear strengths were more sensitive to the microscale voids, while the compressive strength was more influenced by mesoscale voids. The results of this study can provide a design basis for evaluating the quality of 3D woven composites with void defects.
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Dhimole, Vivek Kumar, Pruthvi Serrao, and Chongdu Cho. "Review and Suggestion of Failure Theories in Voids Scenario for VARTM Processed Composite Materials." Polymers 13, no. 6 (2021): 969. http://dx.doi.org/10.3390/polym13060969.
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Fiber-reinforced composite structures are used in different applications due to their excellent strength to weight ratio. Due to cost and tool handling issues in conventional manufacturing processes, like resin transfer molding (RTM) and autoclave, vacuum-assisted resin transfer molding (VARTM) is the best choice among industries. VARTM is highly productive and cheap. However, the VARTM process produces complex, lightweight, and bulky structures, suitable for mass and cost-effective production, but the presence of voids and fiber misalignment in the final processed composite influences its strength. Voids are the primary defects, and they cannot be eliminated completely, so a design without considering void defects will entail unreliability. Many conventional failure theories were used for composite design but did not consider the effect of voids defects, thus creating misleading failure characteristics. Due to voids, stress and strain uncertainty affects failure mechanisms, such as microcrack, delamination, and fracture. That’s why a proper selection and understanding of failure theories is necessary. This review discusses previous conventional failure theories followed by work considering the void’s effect. Based on the review, a few prominent theories were suggested to estimate composite strength in the void scenario because they consider the effect of the voids through crack density, crack, or void modeling. These suggested theories were based on damage mechanics (discrete damage mechanics), fracture mechanics (virtual crack closure technique), and micromechanics (representative volume element). The suggested theories are well-established in finite element modeling (FEM), representing an effective time and money-saving tool in design strategy, with better early estimation to enhance current design practices’ effectiveness for composites. This paper gives an insight into choosing the failure theories for composites in the presence of voids, which are present in higher percentages in mass production and less-costly processes (VARTM).
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Li, Yuxuan. "Research Progress on Concrete-Filled Steel Tubes with Defects." Academic Journal of Science and Technology 14, no. 3 (2025): 235–39. https://doi.org/10.54097/pz6tqd36.
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Concrete-filled steel tube (CFST) structures are widely used in civil engineering due to their high load-bearing capacity and construction efficiency. However, core concrete defects such as voids and interfacial gaps significantly degrade mechanical performance, posing serious threats to structural safety. This paper systematically reviews influencing factors of CFST mechanical properties, load-bearing capacity calculation methods, and defect damage mechanisms. Studies indicate that cross-sectional shape (circular > square > polygonal), steel tube thickness, and material strength significantly affect axial compression performance. Void defects reduce load-bearing capacity by 18.5%–59% by disrupting the confinement effect, with near-wall voids causing 15%–20% greater losses than central voids. Secondary grouting and CFRP reinforcement restore 85%–92% and 10%–15% of capacity, respectively, but irreversible performance losses persist. Finite element models reveal conservative deviations (up to 20%) in current codes for thin-walled high-strength CFST columns. The study highlights higher defect sensitivity in non-circular sections, necessitating defect rate–capacity reduction coefficient tables. Future research should focus on multi-defect coupling effects, smart repair technologies, and refined computational models to enhance engineering reliability.
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Xi, Guangqing, and Qinghua Geng. "Research and Application of Neutron Detection Technology in Inspection of Void Defects in Turbine Runner Chamber." Journal of Physics: Conference Series 2133, no. 1 (2021): 012027. http://dx.doi.org/10.1088/1742-6596/2133/1/012027.
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Abstract After a long-term operation of the turbine runner chamber, there may be voids between the steel lining and the concrete. If it is not discovered and treated in time, the safe and stable operation of the unit will be affected. In engineering practice, the hammering method is often used to detect hole defects, and the accuracy is low. The neutron detection technology is proposed to detect the void defects of the steel lining, quantitatively display the void location and size, and improve the accuracy of void defect detection.
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Hu, Shouying, Shan Jiang, Dong Chen, Haoran Li, and Tao Xu. "Post-Fire Mechanical Properties of Half-Grouted Sleeve Connectors with Grouting Defects." Buildings 14, no. 5 (2024): 1434. http://dx.doi.org/10.3390/buildings14051434.
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Half-grouted sleeve connectors are a primary method for connecting rebar in prefabricated concrete structures. However, due to limitations in the construction environment, all kinds of grouting defects are inevitable, especially grouting voids. Additionally, fire disasters, among the most common types of disasters, significantly threaten the structural performance and safety of these prefabricated structures. Therefore, it is imperative to determine the mechanical properties of half-grouted sleeve connectors with grouting voids after high temperatures. This study designed and prepared 48 groups of half-grouted sleeve specimens with different grouting voids and defect locations. These specimens were heated to the specified temperature (25 °C, 200 °C, 300 °C, 400 °C, 500 °C, 600 °C), followed by unidirectional tensile testing after natural cooling. The experimental results showed that rebar fracture failure and rebar pulled-out failure were the failure modes of specimens. With the increase in temperature, bearing capacity, safety factor and ductility coefficient of specimens all decreased. When the temperature was lower than 400 °C, the specimen with void length less than twice the diameter of the rebar (i.e., 2d) had sufficient connection performance. For specimens with the same total void lengths, the bearing capacity of discrete voids is lower than concentrate voids at the same temperature. The load-displacement curve, safety coefficient, ductility coefficient and grey correlation degree of half-grouted sleeve specimens with grouting voids at different temperatures are analyzed and discussed, and the bond stress slip constitutive model is given. Grouting defects have greater influence on specimens after grey correlation analysis. Findings from this study provide valuable references for the safety performance evaluation of prefabricated structures with half-grouted sleeve connectors after exposure to fire.
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Sun, Wenhui, Xuan Wu, and Cuiping Yang. "Mechanism and Control Scheme of Central Defects in Cross Wedge Rolling of Railway Vehicle Axles." Metals 13, no. 7 (2023): 1309. http://dx.doi.org/10.3390/met13071309.
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Faced with a great demand for railway axles, the cross wedge rolling (CWR) process has the advantages of high efficiency and material saving, and good forming quality of axles is significant for railway transportation safety. The stress inside the railway axle of CWR was analyzed by the finite element method. It was found that the center of the rolled piece is subjected to tensile stress in transverse and axial directions and compressive stress in radial direction, making it more prone to defects. By simulating the evolution of micro voids in the center of the CWR piece, it was found that the presence of voids makes the strain around them significantly large and concentrated and the material between the voids deforms intensely. When voids expand relative to the rolled piece and the internal necking between voids is significant, void coalescence is easy to occur, and central defects are formed. The influence of process parameters on void evolution was analyzed. The scheme of detaching die was proposed to avoid central defects of the CWR piece and the optimal parameter conditions of CWR of railway axles were determined, which proved that the quality of railway axles formed with optimized parameters meets the technical requirements of railway vehicle axles.
Dissertations / Theses on the topic "Voids and defects"
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Hyde, Alden S. "Micromechanics-Enriched Finite Element Modeling of Composites With Manufacturing or Service-Induced Defects." DigitalCommons@USU, 2019. https://digitalcommons.usu.edu/etd/7506.
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Composite materials are increasingly used in many industries due to the high strength and low weight properties that they exhibit. Since composites are becoming more popular, they are being used in applications such as aircraft, boats, wind turbine blades, and even sports equipment. Composite behavior is complicated since they are made up of two completely different materials such as strong thin fibers and a relatively weaker resin material that hold the fibers together. It is becoming more important to understand how composites behave in different situations so that equipment designers have reliable material information in order to design safe products that will not harm human life. Fabrication of composite material is not perfect and introduces defects such as the fibers being wavy and the matrix having voids. These defects decrease the strength of composites and if not accounted for in design, could be detrimental. To better understand the effects of these defects in composite materials, experimental tests can be performed to determine the material properties but it costs a lot of money and time. If the material properties of the composite do not match what is desired, different constituent materials are selected to create new composite specimens and the tests must be repeated which costs more time and more money. Computational approaches such as Finite Element Modeling (FEM) are gaining popularity as a way to predict composite behavior without the high cost of fabrication and equipment. Another advantage is the ability to test various materials and various defects by simply changing parameters in the computation. For this thesis, an FEM protocol is developed to model composites made from the material AS4/8552. First, the strength properties are extracted from a model without defects and then, defects such as waviness in the fiber and voids in the matrix are added to the model to see its effect. Knowing the effect of certain defects may help motivate composite fabricators to develop processes that eliminate detrimental defects.
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Rogers, Stuart Craig. "Defect Detection Microscopy." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2256.
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The automotive industry's search for stronger lighter materials has been hampered in its desire to make greater use of Magnesium alloys by their poor formability below 150°C. One current challenge is to identify the complex structure and deformation mechanisms at work and determine which of these are primary contributors to the nucleation of defects. Orientation Imaging Microscopy has been the most accessible tool for microstructural analysis over the past 15 years. However, using OIM to analyze defect nucleation sites requires prior knowledge of where the defects will occur because once the defects nucleate the majority of microstructural information is destroyed. This thesis seeks to contribute to the early detection of nucleation sites via three mechanisms: 1. Detection of cracks that have already nucleated, 2. Detection of surface topography changes that may indicate imminent nucleation and 3. Beam control strategies for efficiently finding areas of interest in a scan. Successive in-situ OIM scans of a consistent sample region while strain is increased, while using the three techniques developed in this thesis, will be employed in future work to provide a powerful defect analysis tool. By analyzing retrieved EBSD patterns we are able to locate defect / crack sites via shadowing on the EBSD patterns. Furthermore, topographical features (and potentially regions of surface roughening) can be detected via changes in intensity metrics and image quality. Topographical gradients are currently only detectable in line with the beam incidence. It is therefore suggested that the tensile specimens to be examined are orientated such that the resulting shear bands occur preferentially to this direction. The ability to refine the scan around these areas of interest has been demonstrated via an off-line adaptive scan routine that is implemented via the custom scan tool. A first attempt at a defect detection framework has been outlined and coded into MATLAB. These tools offer a first step to accessing the information about defect nucleation that researchers are currently seeking.
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Hourahine, Benjamin. "A first principles study of hydrogen related defects in silicon." Thesis, University of Exeter, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324743.
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Anbarasu, Arungalai. "Characterization of defects in fiber composites using terahertz imaging." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24632.
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Adegoke, Olutayo. "Processability of Laser Powder Bed Fusion of Alloy 247LC : Influence of process parameters on microstructure and defects." Licentiate thesis, Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-16114.
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This thesis is about laser powder bed fusion (L-PBF) of the nickel-based superalloy: Alloy 247LC. Alloy 247LC is used mainly in gas turbine blades and processing the blades with L-PBF confers performance advantage over the blades manufactured with conventional methods. This is mainly because L-PBF is more suitable, than conventional methods, for manufacturing the complex cooling holes in the blades. The research was motivated by the need for academia and industry to gain knowledge about the processability of the alloy using L-PBF. The knowledge is essential in order to eventually solve the problem of cracking which is a major problem when manufacturing the alloy. In addition, dense parts with low void content should be manufactured and the parts should meet the required performance. Thus, the thesis answered some of the important questions related to process parameter-microstructure-defect relationships. The thesis presented an introduction in chapter 1. A literature review was made in chapter 2 to 4. In chapter 2, the topic of additive manufacturing was introduced followed by an overview of laser powder bed fusion. Chapter 3 focused on superalloys. Here, a review was made from the broader perspective of superalloys but was eventually narrowed down to the characteristics of nickelbased superalloys and finally Alloy 247LC. Chapter 4 reviewed the main research on L-PBF of Alloy 247LC. The methodology applied in the thesis was discussed in chapter 5. The thesis applied statistical design of experiments to show the influence of process parameters on the defects and microstructure, so a detail description of the method was warranted. This was given at the beginning of chapter 5 and followed by the description of the L-PBF manufacturing and the characterization methods. The main results and discussions, in chapter 6, included a preliminary investigation on how the process parameters influenced the amount of discontinuity in single track samples. This was followed by the results and discussions on the investigation of voids, cracks and microhardness in cube samples (detail presentation was given in the attached paper B). Finally, the thesis presented results of the microstructure obtainable in L-PBF manufactured Alloy 247LC. The initial results of the microstructure investigation were presented in paper A.
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Parvathaneni, Keerthi Krishna. "Characterization and multiscale modeling of textile reinforced composite materials considering manufacturing defects." Electronic Thesis or Diss., Ecole nationale supérieure Mines-Télécom Lille Douai, 2020. http://www.theses.fr/2020MTLD0016.
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L’influence des porosités induites par les procédés de fabrication sur les propriétés mécaniques des composites textiles a été étudiée à la fois par caractérisation expérimentale et par modélisation multi-échelle. En particulier, les porosités ont été caractérisés en termes de fraction volumique, taille, forme et distribution, et les effets de chaque caractéristique sur les propriétés mécaniques des composites textiles ont été analysés. De nombreuses plaques de composites textiles ont été fabriquées par le procédé Resin Transfer Molding (RTM). Ainsi, un renfort textile en verre interlock 3D a été imprégné par une résine époxy injectée sous une pression constante pour générer différents types de porosités. Des essais mécaniques ont été réalisés pour examiner la dépendance du module et de la résistance en traction des composites par rapport au taux de porosité total, intra-toron et inter-toron et également par rapport aux caractéristiques géométriques des porosités. Des analyses au microscope électronique ont été effectuées pour obtenir des informations locales sur les fibres (diamètre et distribution) et les porosités intra-toron (rayon, rapport d’aspect et distribution). A partir de ces résultats, un nouvel algorithme a été développé pour générer le Volume Elémentaire Représentatif (VER) qui est statistiquement équivalent au composite contenant les porosités. De plus, l’effet de la morphologie, du diamètre et de la distribution spatiale des porosités (homogène, aléatoire et concentré) sur les propriétés homogénéisées des torons a également été étudié par la méthode des éléments finis. La tomographie par rayons X a été utilisée pour extraire la géométrie méso-échelle réelle en trois dimensions et les porosités intra-toron. Ensuite, ces données ont été utilisées pour créer un modèle numérique à l’échelle mésoscopique (VER) et prédire les propriétés élastiques des composites avec porosités. Une étude paramétrique utilisant une méthode numérique multi-échelle a été effectuée pour étudier l’effet de chaque caractéristique des porosités, c.-à-d. le taux volumique, la taille, la forme, la distribution et la localisation sur les propriétés élastiques de composites. Ainsi, la méthode multi-échelle proposée permet d’établir une corrélation entre les porosités à différentes échelles et les propriétés mécaniques des composites textiles<br>The influence of void-type manufacturing defects on the mechanical properties of textile composites was investigated both by experimental characterization and by multiscale modeling. In particular, voids characteristics such as not only void volume fraction but also its size, shape, and distribution have been characterized for textile composites and their effect on the mechanical properties have been analyzed. Several textile composite plates were fabricated by the resin transfer molding (RTM) process where 3D interlock glass textile reinforcement was impregnated by epoxy resin under a constant injection pressure to generate different types of voids. A series of mechanical tests were performed to examine the dependency of tensile modulus and strength of composites on the total void volume fraction, intra & inter-yarn void volume fraction, and their geometrical characteristics. Microscopy observations were performed to obtain the local information about fibers (diameter and distribution), and intra-yarn voids (radius, aspect ratio and distribution). Based on these results, a novel algorithm was proposed to generate the statistically equivalent representative volume element (RVE) containing voids. Moreover, the effect of void morphology, diameter and spatial distribution (homogeneous, random and clustering) on the homogenized properties of the yarns was also investigated by the finite element method. X-ray micro-computed tomography was employed to extract the real meso-scale geometry and inter-yarn voids. Subsequently, this data was utilized to create a numerical model at meso-scale RVE and used to predict the elastic properties of composites containing voids. A parametric study using a multiscale numerical method was proposed to investigate the effect of each void characteristic, i.e. volume fraction, size, shape, distribution, and location on the elastic properties of composites. Thus, the proposed multiscale method allows establishing a correlation between the void defects at different scales and the mechanical properties of textile composites
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Adhikari, Dipasree. "Analysis of partial discharge activity in void defects in polymer insulation." Thesis, Glasgow Caledonian University, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627718.
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Polymers used as electrical insulators in high voltage (RV) plant are subjected to inherent design and fault level stresses during service. As a result of these stresses the materials degrade and deteriorate, reducing equipment life and lowering reliability of power systems. Defects in polymeric insulators will result in partial discharge (PD) activity, potentially leading to plant failure. PD is both a symptom of a fault in insulation and the source of various stress mechanisms, that cause further material degradation. It is important to understand correlations between PD signal parameters, discharge induced degradation and defect type. In this thesis PD activity and subsequent material degradation for void defects in different polymeric insulators are studied. The ability to relate identifiable specific signal characteristics at a fault would aid asset managers with assessment of the insulation degradation. This project measures and identifies differences in characteristics of PD and PD induced material degradation in different types of void defects to quantify the material physical conditions. The results of this research correlate changes in the PD patterns for single void and multiple void arrangements with induced chemical and physical changes on the surface of the void. This work also shows that PD activity in air voids in polymeric insulators is dependent on the void shape, size and sample construction. This thesis investigates the relationship between the PD characteristics and the induced material degradation in four different polymer materials, to aid development of mechanisms to enable prediction of the level of degradation of a known polymeric insulator by measuring its PD characteristics and vice-versa. The results show that there are identified differences in PD activity and subsequent chemical and morphological changes for the four different polymers due to difference in polymer structure, chemistry, morphology and ability to extract initiating electrons from the material surface. Most of the experiments conducted in past research work on PD in voids have been perfol1ned using self-contained internal voids. This work compares PD characteristics and material degradation in unvented and vented voids. This investigation enables analysis of the influence of vents on PD processes in voids. The results show that that there is a sharp increase in the PD activity and subsequent void surface changes over time for the unvented voids, whereas the PD activity for vented voids increase very slowly over time.
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Bodanezi, Augusto. "Influência da radiopacidade dos materiais obturadores sobre a sensibilidade, especificidade e confiabilidade da análise radiográfica de obturações endodônticas." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/25/25138/tde-02042009-110149/.
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Investigou-se o efeito da radiopacidade de diferentes materiais obturadores sobre a sensibilidade, especificidade e confiabilidade da análise radiográfica de obturações endodônticas. Após determinação da radiopacidade dos materiais, um total de 80 dentes caninos tiveram seus canais radiculares preparados com a técnica clássica antes de serem divididos em 5 grupos cada qual a ser obturado com um dos cimentos obturadores estudados (AH Plus, Endomèthasone®, Sealer 26, Acroseal e cimento não-radiopaco). Antes do preenchimento com a técnica de condensação lateral da guta-percha, em metade dos dentes de cada grupo, inseriu-se um fio de nylon radiolúcido (Ø 0.25 mm), ao longo do canal radicular para simular um defeito de obturação (n=8). Um total de 36 dentes molares superiores, depois de instrumentados, foram divididos em 3 grupos cada qual a ser obturado com um dos cimentos testados (AH Plus, Acroseal e cimento não-radiopaco) (n=12). Antes da obturação com a mesma técnica utilizada nos caninos, um fio de 0.08 mm de espessura foi estendido no canal disto-vestibular de cada dente. Após a utilização de artifícios para simular a sobreposição dos tecidos humanos, os dentes obturados foram radiografados e as imagens periapicais analisadas por endodontistas e radiologistas quanto à presença de defeitos de preenchimento nas obturações. Após análise estatística empregandose os testes exato de Fisher, Kappa e teste t (p<0.05). Observou-se menor sensibilidade no exame dos dentes anteriores obturados com os cimentos radiopacos, principalmente na avaliação dos radiologistas, e identificou-se maior especificidade para as obturações efetuadas com os cimentos endomethasone® e Acroseal. No julgamento dos dentes posteriores, o cimento Acroseal proporcionou menor sensibilidade do que o AH Plus e houve menores valores de especificidade na avaliação dos endodontistas, embora sem diferenças entre os grupos de cimentos estudados. A confiabilidade mostrou-se maior para as obturações dos caninos realizadas com Endomethasone® e Sealer 26 e não se detectaram diferenças entre os grupos na avaliação das obturações dos molares. Concluiu-se que a radiopacidade dos cimentos influenciou na sensibilidade, especificidade e confiabilidade da análise radiográfica de obturações endodônticas, assim como a especialidade dos examinadores.<br>The aim of this study was to investigate the effect of different radiopaque sealers in the sensitivity, specificity and realiability of radiographic root canal filling exam. After radiopacity distinction of root canal sealing materials, a total of 80 extracted single-rooted upper canines had their canals prepared with classic technique before being divided into 5 groups, each to be filled with one of the tested sealers (AH Plus, Endomèthasone®, Sealer 26, Acroseal and non-radiopaque sealer). In half specimens a radiolucent nylon monofilament string (Ø 0.25 mm) positioned inside the root canal to simulate a radiolucent void before being filled with gutta percha lateral condensation (n=8). A total of 36 maxillary molars were divide into 3 groups, each to be filled with one of the tested sealers (AH Plus, Acroseal and non-radiopaque sealer). Before being filled with lateral condensation technique, a Ø 0.08mm string was positioned alongside distobuccal root canal. After root canal filling, each tooth was strictly positioned in a device to simulate bone and soft tissue before being exposed to X rays. The resulting images were interpreted for presence of voids by radiologists and endodontists. The differences between groups were assessed using Fisher Exact, Cohens Kappa and t test (>0.05). There were less sensitivity for all radiopaque sealers, specially for radiologists, and higher specificity when Endomethasone® and Acroseal were used to fill the upper canines. Root canal fillings performed in maxillary molars with Acrosel showed lower sensibility values than AH Plus mainly to endodontists, but no difference in specificity between groups. There were lower reliability than control group for canines filled with Endomethasone® and Sealer 26. The differences of reliability between groups were not statistically significant. It was concluded that radiopacity of sealers influenced on sensitivity, specificity and reliability of radiographic root canal filling exam, as well as the speciality of examiners.
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Huang, Shaosong. "INITIAL STAGE OF DEFECT STRUCTURAL EVOLUTION IN F82H AND ITS MODEL ALLOYS BY IRRADIATION DAMAGE." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/188579.
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May, Daniel. "Transiente Methoden der Infrarot-Thermografie zur zerstörungsfreien Fehleranalytik in der mikroelektronischen Aufbau- und Verbindungstechnik." Doctoral thesis, Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-163082.
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In dieser Arbeit wurde eine neue fehleranalytische Methode zur industriellen Anwendung an neuen Technologien der Aufbau- und Verbindungstechnik entwickelt. Das Verfahren basiert auf der Wechselwirkung von thermischen Wellen und Defekten. Die Besonderheit ist dabei die Zerstörungsfreiheit, die Geschwindigkeit, das Auflösungsvermögen und die durch neueste IR-Detektoren erreichte Temperaturempfindlichkeit. Es wurden grundlegende Studien bezüglich Auflösung und parasitären Effekten bei der Anwendung unter industriellen Randbedingungen durchgeführt. Dabei wurde eine systematische Vorgehensweise bezüglich der Komplexität gewählt. Dies ermöglicht nun u.a. eine Vorhersage der zu erwartenden Prüfdauer zur Auflösung vergrabener Defekte, der Begrenzung der maximalen Anregungsimpulsbreite (bei gegebener Defekttiefe) und die quantitative Ermittlung des Einflusses einer Lackschicht. Methodisch kamen grundsätzlich Simulationen und vergleichende Experimente zum Einsatz. Es wurden spezielle Proben zur Isolierung und Klärung parasitärer Effekte verwendet. Letztlich konnte das Messsystem erfolgreich an industriellen Problemstellung demonstriert werden. Das entwickelte Messsystem zeichnet sich durch hohe Flexibilität aus. Verschiedene problemangepasste Anregungsquellen (interne und externe Anregung durch zahlreiche physikalische Effekte) kommen zum Einsatz. Das Messsystem besteht aus vier Hauptmodulen, der Differenzbild-Methode, der Impulsthermografie, und zwei Varianten der LockIn-Thermografie. Zusammen ist das System in der Lage, Voids, Delaminationen und Risse in verschiedenen Bereichen auch der modernen AVT sicher zu erkennen. Es werden dabei Temperaturauflösugnen bis zu 5 mK und laterale Auflösungen bis 17 µm erreicht. Diese Arbeit legt einen Grundstein für die Anwendung der thermischen Fehleranalytik in der Industrie, indem hier die Grenzen der IR-Messtechnik aufgezeigt und charakterisiert werden<br>In this work a new failure analytical method for the industrial application of new technologies in electronic packaging has been developed. The developed method is based on the interaction of the thermal waves and defects. The special fature is non-destructive, speed, resolution and high temperature sensitivity due to latest IR-detectors. It fundamental studies regarding resolution and parasitic effects in the application were carried out cinsidering industrial conditions. Here, a systematic approach regarding the complexity has been selected. This now enables a prediction of the expected test period for detecting buried defects, limits for excitation pulse width (for a given defect depth) and the quantitative determination of the influence of parasitic paints. Methodically always simulations and comparative experiments were used. Simple samples for the isolation and purification of parasitic effects has been used. Finally, the measurement system has been successfully demonstrated on an industrial applications. The developed measurement system is characterized by high flexibility. Different problem-adapted excitation sources (internal and external excitation by numerous physical effects) are used. The measurement system currently consists of four main modules, the difference image method, the pulse thermography, and two variants of LockIn-thermography. Together, the system is capable of detecting voids, delaminations and cracks in various fields of electronic packageing. It will reach temperature resolutions up to 5 mK and lateral resolutions down to 17 µm. This work stes a foundation for the application of thermal failure analysis for industry by showing and charcterization the limits of IR imaging
Books on the topic "Voids and defects"
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Wimsatt, Andrew, Joshua White, Chin Leung, et al. Mapping Voids, Debonding, Delaminations, Moisture, and Other Defects Behind or Within Tunnel Linings. Transportation Research Board, 2013. http://dx.doi.org/10.17226/22609.
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Chawla, Krishan K., and Gary M. Gladysz. Voids in Materials: From Unavoidable Defects to Designed Cellular Materials. Elsevier, 2020.
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Chawla, Krishan K., and Gary M. Gladysz. Voids in Materials: From Unavoidable Defects to Designed Cellular Materials. Elsevier Science & Technology Books, 2014.
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Chawla, Krishan K., and Gary M. Gladysz. Voids in Materials: From Unavoidable Defects to Designed Cellular Materials. Elsevier, 2021.
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Chawla, Krishan K., and Gary M. Gladysz. Voids in Materials: From Unavoidable Defects to Designed Cellular Materials. Elsevier, 2018.
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Analytical Models of Thermal and Phase-Transformation-Induced Stresses in Materials with Void Defects II. Nova Science Publishers, Incorporated, 2019.
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Ceniga, Ladislav, and Slovakia Kosice. Analytical Models of Thermal and Phase-Transformation Induced Stresses in Materials with Void Defects I. Nova Science Publishers, Incorporated, 2018.
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Forrest, Alan. Military Trauma. Edited by David Andress. Oxford University Press, 2013. http://dx.doi.org/10.1093/oxfordhb/9780199639748.013.022.
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The Old Regime army had been battered by serial defeats during the eighteenth century, and was open to proposals for reform. When 1789 came it was not army reforms that spread despair and trauma but the political situation created in the early years of the French Revolution: the assault on privilege, the ambivalent attitude of the king, the crisis of loyalty which this created for the officers, and the gaping void in the army’s ranks caused by desertion, emigration and the ideology of the Rights of Man. The defeats that followed the declaration of war added to despair, and it was only by resort to further traumatic measures—radicalizing recruitment, promoting officers from the ranks, and amalgamating the line army with the new volunteers, and ultimately the resort to Terror—that the fortunes of the army were turned around.
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High-Voltage Electrical Inspection of Pipeline Coatings. AMPP, 1998. https://doi.org/10.5006/nace_rp0274-1998.
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Scope Electrical inspection (holiday detection) is a test of the continuity of a protective coating. This type of inspection does not provide information concerning coating resistance, bond, physical characteristics, or the overall quality of the coating, nor is it intended to do so. It will detect bubble or blister type voids, cracks, thin spots, and foreign inclusions or contaminants in the coating that are of such size, number, or conductivity as to significantly lower the electrical resistance or dielectric strength of the coating. Electrical holiday detector: A device for locating discontinuities in the coating. Use of a holiday detector should be at the discretion of the coating inspector. An initial holiday inspection, performed as soon after the application of the coating as practicable, serves to check the materials and the application procedures. A final coating inspection, before the coated pipe is placed in the ditch, will disclose any defect or damage to the coating, except disbanding, which has occurred during the construction period. This recommended practice presents acknowledged techniques in the use of holiday detector equipment currently used on pipeline coatings prior to lowering-in operations and presents a table of recommended voltages for various coating thicknesses.
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Francesca, Mazza. Ch.9 Assignment of rights, transfer of obligations, assignment of contracts, s.1: Assignment of rights, Art.9.1.15. Oxford University Press, 2015. http://dx.doi.org/10.1093/law/9780198702627.003.0184.
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This commentary analyses Article 9.1.15 of the UNIDROIT Principles of International Commercial Contracts (PICC) concerning the undertakings of the assignor with respect to the assignee. According to Art 9.1.15, the assignor undertakes that the assigned right exists at the time of the assignment. This is not the case if, for instance, the contract from which the purported right arises had never been concluded or was void, or had previously been avoided. Similarly, if the obligor had already performed its obligation, the right would no longer exist. If a future right is assigned, no such undertaking exists. Rather, the assignee takes the risk that the future right never comes into existence. This commentary discusses the rule which entitles the assignor to assign the right, assert against the assignee all the defences that the obligor would have been able to assert against the assignor, the right of set-off against the assignee if it was available to the obligor before the notice of assignment of a right was received, and reimbursement of payment by the obligor.
Book chapters on the topic "Voids and defects"
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Hu, Wei, Qian Liu, and Bin Xu. "Experimental Study on a Void Imagination Approach for a Full-Scale Concrete-Filled Steel Tube Specimen in Long-Span Suspension Bridge Tower with Electromechanical Impedance." In Novel Technology and Whole-Process Management in Prefabricated Building. Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-97-5108-2_22.
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AbstractDue to complex internal structure details and insufficient quality control methodologies during concrete pouring, defects such as void in large-scale concrete-filled steel tube (CFST) components possibly occur. In this paper, an internal void defects imagination approach using electromechanical impedance (EMI) measurement with surface-fixed Piezoelectric Lead Zirconate Titanate (PZT) sensors is proposed for a full-scale CFST specimen with a diameter of 3.6m that is employed in a tower with a height of 350 m of a long-span suspension bridge. A variety of voids are mimicked by placing empty boxes of various sizes at various locations under the inner horizontal diaphragm of CFST specimen to test the viability of the proposed method. To detect the existence of the voids, numerous PZT sensors are mounted on the outer surface of the specimen and Electromechanical impedance (EMI) measurement of the PZT sensors at selected certain frequency band are made. Based on the analysis on the impedance curves and the root mean square deviation (RMSD) of each EMI measurement, the localization of each artificially mimicked void defect is detected successfully. Moreover, the distribution of all mimicked voids is visualized with an imagination method based on RMSD values of PZT sensors at different locations. The visualization result meets the actual locations of the artificially mimicked void defects inside the CFST specimen.
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Wei, Zheng, Jianqiang Zhou, Kexin Wang, and Xiaowen Hu. "Deep Migration Learning-Based Detection of Structural Diseases in Railway Tunnel Lining Structures." In Lecture Notes in Civil Engineering. Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-97-2417-8_11.
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AbstractIt is difficult to quickly and accurately detect defects such as voids, voids, and non compactness in the lining structure of formed railway tunnels. We have conducted in-depth research on the propagation law of ground penetrating radar electromagnetic waves in tunnel lining structures and intelligent detection methods based on deep learning. The finite difference method was applied to numerically simulate the propagation process of electromagnetic waves in tunnel lining structures with different diseases. B-scan radar images were obtained, and the characteristics of voids, voids, and non dense images were summarized. On this basis, a sample library composed of numerical simulation and real radar images was established, and a deep migration method for detecting railway tunnel lining structural defects was proposed. Automatically learning complex disease features and updating network model parameters overcomes the limitations of limited real disease sample sets for tunnel lining structures. The experimental results show that the network after transfer learning can accurately detect defect bodies in actual tunnel lining structures, verifying the effectiveness and feasibility of the proposed method.
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Méndez, David, A. Aouni, Daniel Araújo, Gabriel Ferro, Yves Monteil, and Etienne Bustarret. "Planar Defects, Voids and their Relationship in 3C-SiC Layers." In Materials Science Forum. Trans Tech Publications Ltd., 2005. http://dx.doi.org/10.4028/0-87849-963-6.189.
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Hähner, P., and W. Frank. "A Mesoscopic Theory of Irradiation-Induced Void-Lattice Formation." In Patterns, Defects and Materials Instabilities. Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-009-0593-1_25.
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Hu, Jinqiu, Xuefeng Yan, and Cong Zeng. "Study on the Circumferential Mechanical Properties of Buried PE Pipes with Soil Erosion Void." In Lecture Notes in Civil Engineering. Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-97-5814-2_8.
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AbstractSoil erosion void is a common pipeline defect, which has a great impact on the stability and safety of pipeline operation, but the force characteristics for eroded pipes are still unclear. Buried PE pipes in municipal engineering are taken as the research object, and the calculation method of soil pressure at the bottom of the pipe with soil erosion void is proposed, and the influence of factors such as size and location of the void on the stress characteristics of buried PE pipes with soil erosion void is studied by using the numerical model. The results of the study show that the void will affect the structural stress of PE pipes, the size of the void is positively correlated with the influence degree and influence range of the pipe; the location of the void determines the influence location of the pipe.
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Yang, Xiaoliang, Xuequan Wang, Zhe Pan, Jie Liu, and Jiandong Luo. "Preliminary Application of CT Technology in Non-destructive Testing of Nuclear Fuel Elements." In Springer Proceedings in Physics. Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-1023-6_10.
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AbstractWith the emergence of various novel fuel elements, traditional X-ray test technologies refer to national standards that have gradually been unable to meet the non-destructive testing (NDT) requirements for these novel fuel elements. As a new NDT technology, industrial computed tomography (CT) has great potential for NDT of nuclear fuel elements. In this paper, through a personalized transformation of self-developed X-ray equipment, we carried out CT scanning imaging experiments up to more than 400 kV on pellet-shell gap in rod-shaped fuel elements, a high-density annular component, and a tungsten-based workpiece. Not only that, after three-dimensional reconstruction and image analysis, it was found that sub-millimeter internal void defects could be detected. Furthermore, size measurements were carried out through image analysis which achieved a relative error of 5%. A conservative conclusion can be drawn from this research: industrial CT, including but not limited to micro-CT, high-energy X-ray CT, etc., has an optimistic future in testing internal defects and measuring internal dimensions of novel fuel elements.
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Satar, Siti Faridah, N. A. Muhamad, and Nurun Najah Abdul Rahim. "Temperature Distribution Pattern in PILC Cable with Void Defect by Using COMSOL Multiphysics." In 10th International Conference on Robotics, Vision, Signal Processing and Power Applications. Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-13-6447-1_30.
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Du, Xiaosong, Praveen Gurrala, Leifur Leifsson, et al. "Stochastic-Expansions-Based Model-Assisted Probability of Detection Analysis of the Spherically-Void-Defect Benchmark Problem." In Lecture Notes in Computer Science. Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-93701-4_47.
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Zhang, Wei, Yin Yu, Yile Hu, Haomin Li, and Zekai Zhao. "A Finite Element Method of Research on Transverse Mechanical Properties of Fiber-Reinforced Composites with Random Matrix Void Defects." In Lecture Notes in Electrical Engineering. Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-97-0550-4_12.
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Yang, Fei-fei, Zhan-peng Yin, Yan-zhao Luo, Xin Li, and Guo-biao Di. "Study on Banded Segregation of High-Strength Hot-Rolled Grade Steel and the “Void” Defect in Casting Slabs." In The Minerals, Metals & Materials Series. Springer Nature Switzerland, 2025. https://doi.org/10.1007/978-3-031-80748-0_127.
Full textConference papers on the topic "Voids and defects"
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Seon, Guillaume, Yuri Nikishkov, Lauren Fergusson, and Andrew Makeev. "Predicting Formation of Manufacturing Defects in Contoured Composites." In Vertical Flight Society 74th Annual Forum & Technology Display. The Vertical Flight Society, 2018. http://dx.doi.org/10.4050/f-0074-2018-12815.
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Composite helicopter rotor components are typically thick and often have areas with a tight radius of curvature, which make them especially prone to process-induced defects, including wrinkles and voids at ply interfaces. Such flaws cause high rejection rates in production of flight-critical components and structure. This work seeks to fill the gaps in understanding generation of the noted defects in contoured polymer-matrix composite (PMC) laminates. In particular, understanding and modelling defect formation at the early stages of the manufacturing process might be the missing link to enable the development of practical engineering solutions allowing for better control of the manufacturing process of contoured composite parts. In this work, an approach based on a continuum description of the uncured prepreg material, including the initial bulk or void content, and finite element modelling (FEM) is used to simulate the consolidation process at the early stages of manufacturing of contoured laminates. The simulation predicts instabilities leading to formation of both wrinkles and voids at ply interfaces during laminate debulking or vacuum consolidation. Applicability of the method to consolidation in both closed-cavity and open-face tooling is also demonstrated. FEM results show good correlation with X-ray Computed Tomography data. This work also introduces a new simulation concept based on finite element and discrete modelling of voids at ply interfaces to improve accuracy of predicting their evolution during the debulking operations.
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Seon, Guillaume, Yuri Nikishkov, Lauren Fergusson, and Andrew Makeev. "Predicting Formation of Manufacturing Defects in Contoured Composites." In Vertical Flight Society 74th Annual Forum & Technology Display. The Vertical Flight Society, 2018. http://dx.doi.org/10.4050/f-0074-2018-12822.
Full textAbstract:
Composite helicopter rotor components are typically thick and often have areas with a tight radius of curvature, which make them especially prone to process-induced defects, including wrinkles and voids at ply interfaces. Such flaws cause high rejection rates in production of flight-critical components and structure. This work seeks to fill the gaps in understanding generation of the noted defects in contoured polymer-matrix composite (PMC) laminates. In particular, understanding and modelling defect formation at the early stages of the manufacturing process might be the missing link to enable the development of practical engineering solutions allowing for better control of the manufacturing process of contoured composite parts. In this work, an approach based on a continuum description of the uncured prepreg material, including the initial bulk or void content, and finite element modelling (FEM) is used to simulate the consolidation process at the early stages of manufacturing of contoured laminates. The simulation predicts instabilities leading to formation of both wrinkles and voids at ply interfaces during laminate debulking or vacuum consolidation. Applicability of the method to consolidation in both closed-cavity and open-face tooling is also demonstrated. FEM results show good correlation with X-ray Computed Tomography data. This work also introduces a new simulation concept based on finite element and discrete modelling of voids at ply interfaces to improve accuracy of predicting their evolution during the debulking operations.
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Lua, Jim, Waruna Seneviratne, Nam Phan, et al. "Characterization of Fabrication Induced Defects and Assessment of Their Effects on Integrity of Composite Structures." In Vertical Flight Society 74th Annual Forum & Technology Display. The Vertical Flight Society, 2018. http://dx.doi.org/10.4050/f-0074-2018-12823.
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Voids and ply waviness are the most common types of fabrication process induced defects in composite structures that can have detrimental effects on their load bearing capacity. To date, extensive works have been done on the characterization of fabrication induced defects on the mechanical properties of composites but less study has been performed to determine the effects of defects on the failure progression. Given the durability and damage tolerance requirements for certification and design of composite structures, it is important to evaluate the effects of these defects on the damage initiation and failure progression of a loaded composite structure. In this study, void and ply waviness information are extracted from X-ray computed tomography (CT) and optical microscopy and an efficient image-to-numerical solution is developed to map the detected voids and ply waviness into a finite element based progressive failure analysis model. An interlaminar tensile (ILT) test specimen under four point bending is used to demonstrate the capability of our response and progressive damage prediction.
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Lua, Jim, Waruna Seneviratne, Nam Phan, et al. "Characterization of Fabrication Induced Defects and Assessment of Their Effects on Integrity of Composite Structures." In Vertical Flight Society 74th Annual Forum & Technology Display. The Vertical Flight Society, 2018. http://dx.doi.org/10.4050/f-0074-2018-12816.
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Voids and ply waviness are the most common types of fabrication process induced defects in composite structures that can have detrimental effects on their load bearing capacity. To date, extensive works have been done on the characterization of fabrication induced defects on the mechanical properties of composites but less study has been performed to determine the effects of defects on the failure progression. Given the durability and damage tolerance requirements for certification and design of composite structures, it is important to evaluate the effects of these defects on the damage initiation and failure progression of a loaded composite structure. In this study, void and ply waviness information are extracted from X-ray computed tomography (CT) and optical microscopy and an efficient image-to-numerical solution is developed to map the detected voids and ply waviness into a finite element based progressive failure analysis model. An interlaminar tensile (ILT) test specimen under four point bending is used to demonstrate the capability of our response and progressive damage prediction.
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Fang, Eugene, Jessica Zhang, Anisur Rahman, Jim Lua, and Nam Phan. "A Multiscale Bondline Damage Characterization and Hybrid Analysis Approach for Adhesively Bonded Composite Structures." In Vertical Flight Society 71st Annual Forum & Technology Display. The Vertical Flight Society, 2015. http://dx.doi.org/10.4050/f-0071-2015-10261.
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Adhesively bonded composite structures have been used extensively in both DoD and commercial industries. Despite many attractive features of a bonded composite structure, integrity and durability of adhesively bonded composite structures are the primary concerns due to their known sensitivity to environmental conditions and the presence of bondline defects associated with the fabrication and processing of a bonded composite structure. In order to reduce the testing matrix in characterization of properties of a bondline for the residual strength and life prediction of its bonded composite structure, a multiscale approach is developed based on an automatic generation of a representative unit cell of a heterogeneous bondline interface including voids and inclusions. Equivalent cohesive properties are extracted from a nonlinear finite element analysis for a unit cell with variations in size and geometric distribution of voids and inclusions within the bondline. The impact of a bondline quality on a global structural response is explored using a bonded I-beam with an initial delamination flaw subject to 4-point bending.
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Janoff, Dwight, Sai Prasanth Venkateswaran, and Donald McNicol. "Non-Destructive Evaluation of Subsea Thermal Insulation Using Microwave Imaging." In CORROSION 2014. NACE International, 2014. https://doi.org/10.5006/c2014-3823.
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Abstract As subsea wells are being drilled in over 5000 feet water depth, hydrate formation in the production systems has become a major concern. In subsea trees and production equipment hydrates (ice precipitation) can occur in the event of an interruption in flow caused by a temporary well shut down. During a shut down, hot produced fluids become stagnant and are cooled by the surrounding cold water. In long subsea tie backs, thermal insulation is required to keep the produced fluids above hydrate formations temperatures until they reach the processing location. Hydrates can form as high as 70 °F (21 °C) under subsea production conditions. Thermal insulation is used to extend cool down time and prevent hydrate formation until the production flow, hydrate inhibitor injection can be restored or fluids reach their processing location/facility. Subsea thermal insulation materials are usually composed of polymeric materials that can be cast or molded on to piping and complex shapes, such as subsea trees, and manifolds. These materials typically consist of a polymeric resin matrix, and hollow glass beads, that form a syntactic foam material. Polymer bases can be thermoset materials, such as silicone elastomers, urethanes, or epoxies. Thermoplastic materials are also used, particularly for long subsea tie backs, such as flow lines. Application defects, such as thermal cracking during curing, voids, and lack of bonding in field joints, can affect the long term performance of the insulation by reducing thermal resistance due to water ingress, and cold spots A non-destructive evaluation technique used for dielectric materials can be used to detect cracking, voids, and other defects in the installed insulation systems that may cause a degradation in performance. This technique was developed in the early 1990s for use on fiberglass reinforced piping and rubber expansion joints. The application of this technique on subsea thermal insulation installed on piping and other subsea equipment will be presented. Evaluations will include soundness of field joint bonding in polypropylene and polyurethanes, cracking and disbondment in epoxy syntactic insulation, and detection of voids and laps in cast glass syntactic polyurethane (GPSU).
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Whitmore, David, and Ivan Lasa. "Investigation and Mitigation of Corroded Bonded Post-Tension Tendons." In CORROSION 2018. NACE International, 2018. https://doi.org/10.5006/c2018-10557.
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Abstract There has been a long history of bonded post-tensioning (PT) in reinforced concrete structures. Generally, these structures have performed well except when bonded PT tendons have suffered from corrosion as a result of grout deficiencies. For many years cement – water grout was used for grouting PT tendons. Cement – water grouted tendons are likely to have voids in the grout due to the propensity of cement – water grouts to bleed. Prepackaged grouts are generally more robust but they may segregate in certain circumstances. Segregated prepackaged grouts have also contributed to PT strand corrosion. Evaluation of existing post-tensioned structures is important to determine if defects exist in the grout. If grouting defects are identified an impregnation system can be used to mitigate corrosion and extend the service life of PT tendons installed in deficient grout. This paper discusses the evaluation of PT structures and the PT impregnation technique which has been developed to mitigate corrosion of grouted PT tendons. Project case studies and laboratory research will be presented to demonstrate the technique and its effectiveness.
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Wang, Yea-Jeng, and Ge-Ping Yu. "Effects of Proton Irradiation on Pitting Corrosion Resistance of Inconel 600 in Chloride Medium at Low Temperature." In CORROSION 1993. NACE International, 1993. https://doi.org/10.5006/c1993-93613.
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Abstract Inconel 600 specimens were irradiated with 1 Mev proton produced from Van de Graaf accelerator. Penetration curves of the irradiated specimens were calculated. The potentiodynamic cyclic polarization method and AC impedence analysis were applied to study the effects of proton irradiation on the pitting corrosion resistance of Inconel 600 in the chloride medium at room temperature. Irradiation may induce a more homogeneous distribution of alloy elements which could reduce corrosion. But radiation induced defects (voids and dislocations etc) may increase corrosion. The effects of radiation on the pitting of Inconel 600 are discussed along with the evolution of the microstructure during irradiation. The test results indicate that 0.05 dpa proton irradiated Inconel 600 specimens shows a better oxide film than those of other irradiated dose. Specimens with higher proton irradiation dose (0.2-2.0 dpa) usually show lower corrosion resistance.
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Shaheen, Samaher, David J. Nguiffo, Elizabeth E. Rodriguez, Forest G. Siewert, and Dennis M. O’Connor. "Investigating the Influence of a Laterally Placed Void on Natural Frequency Shifts Using Timoshenko Beam Theory." In ASME 2025 Aerospace Structures, Structural Dynamics, and Materials Conference. American Society of Mechanical Engineers, 2025. https://doi.org/10.1115/ssdm2025-152233.
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Abstract Additive Manufacturing (AM), particularly metal 3D printing, has revolutionized the production of complex and highly customized components across various industries. Metal AM facilitates the creation of intricate geometries; however, it introduces risks of internal defects such as voids, which can significantly impact the structural integrity of the final product. This study investigates the vibrational behavior of a 3D-printed metal beam with a lateral void defect, comparing the analytical predictions of Euler-Bernoulli and Timoshenko beam theories. The presence of a lateral void disrupts beam stiffness, affecting vibrational characteristics. The orientation and location of the void significantly influence bending stiffness, shear deformation, and natural frequencies, critical for understanding the dynamic response under operational conditions. Timoshenko theory, which accounts for shear deformation and rotary inertia, is used to model these effects more accurately than Euler-Bernoulli theory. An algorithmic approach models the void’s effects on deflection and natural frequency, with results validated through the Finite Element Method (FEM) in Ansys. The analysis highlights the superior accuracy of Timoshenko theory in predicting frequency shifts caused by void defects. A key aspect of the study is the use of the Relative Frequency Shift (RFS) method, which examines variations in natural frequencies to locate and evaluate the void’s impact. This research provides a comprehensive methodology for detecting internal voids using Timoshenko theory, ensuring structural integrity and enhancing quality assurance of 3D-printed metal components. The findings offer valuable insights for industries relying on metal AM, emphasizing the importance of early defect detection for reliable and efficient components.
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Rendon, Nathan, and William LePage. "Observations of Damage and Crack Formation in Nitinol at Inclusions Smaller Than the Critical Flaw Size." In SMST 2024. ASM International, 2024. http://dx.doi.org/10.31399/asm.cp.smst2024p0058.
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Abstract Inclusions and surface defects are the primary drivers of fatigue fractures for Nitinol. Surface defects can take the form of die marks, surface roughness, or scratches, and when present, these will typically be the sites for fatigue fractures. When such surface defects are not present, however, surface-exposed inclusions become the primary sites of fatigue fractures. Surface-exposed inclusions are either fully embedded (no surrounding voids) or particle-void assemblies (PVAs). PVAs are up to 600 times more likely to be the sites of crack nucleation compared to fully embedded particles, so they are of primary interest. PVAs typically take the form of a single, small, and unbroken inclusion with one or two associated voids (coined a "teardrop"), or a longer, drawn-out, and broken-up inclusion with many voids (coined a "stringer").
Reports on the topic "Voids and defects"
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Chen, Pictiaw, Boaz Zion, and Michael J. McCarthy. Utilization of NMR Technology for Internal Nondestructive Quality Evaluation of Fruits and Vegetables. United States Department of Agriculture, 1994. http://dx.doi.org/10.32747/1994.7568778.bard.
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Objective: The objective of this research was to investigate the potential use of NMR for evaluating various internal quality factors of fruits and vegetables, leading to the eventual development of practical techniques that are useful for future development of NMR sensors. Summary: Investigation on NMR imaging, one-dimension NMR projection, and single-pulse free-induction-decay (FID) spectrum led to the development of high-speed NMR techniques for real-time sensing of internal quality of selected fruits. NMR imaging can be used for detecting internal defects and various quality factors such as bruises, dry regions, worm damage, stage of ripeness, tissue breakdown, and the presence of voids, seeds, sprouts, and pits. The one-dimension (1-D) image profile technique, in which the 1-D projection of the NMR signal of a selected slice of the intact fruit is recorded, is suitable for detecting tissue breakdown regions, presence of pits, and other defects in fruits. The oil and sugar content of fruits can be determined from the single-pulse FID spectrum measurement, in which a surface coil is used to acquire the FID spectrum and the ratio of the resonance peaks is used as the quality index. The latter two techniques are suitable for high-speed sorting of fruits. The most important accomplishment is the successful development of high-speed NMR techniques for determining internal quality of fruits while they are moving at speed up to 30 cm/s. This accomplishment is an important step toward the development of NMR techniques for on-line sorting of fruits and vegetables.
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L51634 Significance of Changes in Residual Stresses and Mechanical Properties due to SMAW Repair. Pipeline Research Council International, Inc. (PRCI), 1990. http://dx.doi.org/10.55274/r0010104.
Full textAbstract:
There is a periodic requirement for immediate weld repairs during all pipe-laying operations. This need arises due to the occasional occurrence of girth weld flaws, which exceed specified defect tolerance levels. These defects are most commonly discovered by on-site radiographic inspection techniques and may be voids, inclusions and geometric irregularities. Repair welding may be required only over a limited portion of the pipe circumference and access for carrying out the repair may be restricted. Due to the range of types of repairs carried out and the limited time scales available, it is common for the weld repair procedures to be less well documented than the girth weld procedures. In particular, the welding procedure may not have been qualified with the same thoroughness and attention to detail as was the girth welding procedure.Weldments typically contain high residual stresses. The primary source of these residual stresses is the differential contraction, which occurs as a weldment cools. This contraction is restrained by the surrounding cooler material resulting in the weld metal being placed in tension with balancing areas of compression in the surrounding material. The input of additional thermal energy due to a repair in a highly restrained region may create a new residual stress pattern around the repair. Mechanical properties, especially toughness, may be adversely affected in the region near the repair. This program assessed the effects of SMAW repair welding on changes in surface residual stress distribution; fracture toughness and hardness around girth weld joints in line pipe. The following types of repair welds were studied: a part wall repair, a multiple part wall repair and full wall repair. The results were compared with a non-repaired weld sample. It was found that for the weld samples studied in this program, the full wall repair produced the most severe residual stress distribution followed by the multiple and single part wall repairs. The single repair only slightly increased the residual stress distribution when compared to the as-welded condition. Dramatic reductions in toughness were found in the multiple and full wall repairs due to coarse-grained regions produced during the repair operations. The single part wall repair exhibited an increase in toughness as a result of the addition of a cosmetic capping pass that resulted in greater grain refinement. This suggests that repair procedures utilizing a stringer or temper bead technique may reduce the effect of weld repairs on toughness.