To see the other types of publications on this topic, follow the link: Voids and defects.
Journal articles on the topic 'Voids and defects'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Voids and defects.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
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.
Full textAbstract:
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.
2
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.
Full textAbstract:
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.
3
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.
Full textAbstract:
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.
4
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.
Full textAbstract:
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.
5
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.
Full textAbstract:
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.
6
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.
Full textAbstract:
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).
7
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.
Full textAbstract:
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.
8
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.
Full textAbstract:
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.
9
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.
Full textAbstract:
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.
10
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.
Full textAbstract:
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.
11
Jeong, C. S., Bum Joon Kim, and Byeong Soo Lim. "Creep Characteristics and Micro-Defects of Main Steam Pipe Steel at High Temperature." Key Engineering Materials 326-328 (December 2006): 1129–32. http://dx.doi.org/10.4028/www.scientific.net/kem.326-328.1129.
Full textAbstract:
The initiation and growth of micro-defects such as micro cracks and voids usually causes the failure of long term operated structural components at high temperature. In this study, the creep characteristics and void nucleation and growth characteristics of P92 steel which is used as main steam pipe material in power plant were investigated at several temperatures and loading conditions. The area fraction of void increased with increase of test temperature, stress, and load holding time. In case of internal defect presence, micro-voids initiated in the early stage of loading period and resulted in the increased load line displacement and crack growth rate. The microvoids were found to form along the prior austenite grain boundaries and at the martensite packet boundaries.
12
Zhang, Lei, Bing Li, Lei Chen, Zhongyu Shang, and Tongkun Liu. "Classification of internal defects of gas turbine blades based on the discrimination of linear attenuation coefficients." Insight - Non-Destructive Testing and Condition Monitoring 65, no. 6 (2023): 335–40. http://dx.doi.org/10.1784/insi.2023.65.6.335.
Full textAbstract:
In the process of manufacturing and servicing gas turbine blades, various types of defect are formed and grow rapidly due to the extremely harsh working environment, which poses a huge threat to the safe operation of the gas turbines. Given that different types of defect cause varying degrees of damage to the turbine blades, it is vital to distinguish and deal with defects differently. Considering the shape of the blade (free-form surface) and the location of the defect (inside the blade), digital radiographic imaging can be used for the non-destructive testing of turbine blades. Although some types of defect (for example porosity and cracks) can be distinguished from others (for example voids and inclusions) based on differences in morphological and textural characteristics, others (for example voids and inclusions) may be misclassified due to similarities in morphological and textural characteristics. These defects with similar morphological characteristics are composed of different materials, which can be utilised as a basis for classification. This paper presents a classification method for defects with similar morphological characteristics based on the discrimination of linear attenuation coefficients. Several typical defects, including voids and inclusions, are set into a cuboidal block and into nylon blades in this work. Their corresponding linear attenuation coefficients are obtained. A binary classification of the linear attenuation coefficient enables the categorisation of voids and inclusions. Experimental results demonstrate that the proposed method has high efficiency and the judgement for voids and inclusions is accurate.
13
Xu, Kun, and Xiaomei Qian. "An FEM Analysis with Consideration of Random Void Defects for Predicting the Mechanical Properties of 3D Braided Composites." Advances in Materials Science and Engineering 2014 (2014): 1–12. http://dx.doi.org/10.1155/2014/439819.
Full textAbstract:
Random void defects have detrimental effect on the mechanical properties of 3D braided composites. A 3D FEM based on a periodic representative unit cell is developed to appraise the mechanical properties of 3D 4-directional braided composites containing the defects. Two basic types of void defects, such as the dry patches in the reinforced yarns and the voids in the resin matrix pocket, have been taken into account. A simple method for generating the random void defect elements in FEM is presented. The FE software ABAQUS is adopted to study the elastic properties. The predicted effective elastic properties are in good agreement with the available experimental data, demonstrating the applicability of the mesomechanical FEM. By considering the random distribution of void defects, the probability statistics analysis of mechanical properties was conducted. In addition, the effect of the void volume fraction on the elastic properties was discussed in detail, and some useful conclusions were drawn herein.
14
Dong, Jiwei, and Yaohua Gong. "Influence of void defects on progressive tensile damage of three-dimensional braided composites." Journal of Composite Materials 52, no. 15 (2017): 2033–45. http://dx.doi.org/10.1177/0021998317737829.
Full textAbstract:
A meso-finite element model with random voids in matrix is developed to simulate the tensile progressive damage of three-dimensional braided composites. A stiffness degradation method for generating the random void defect element in finite element method is presented. Proper criteria are adopted as initial damage of components, and stiffness degradation is implemented for damage propagation. The tensile strengths are predicted from calculated stress–strain curves. From simulation, void defects in matrix make the redistribution of micro-stress and accelerate the damage propagation of three-dimensional braided composites. Furthermore, void defects reduce the strength and ductility of the composites, but the reduction is not obvious if the porosity is controlled within a range.
15
Maruyama, Toshio, Kojiro Akiba, Mitsutoshi Ueda, and Kenichi Kawamura. "Void Formation in Growing Oxide Scales with Schottky Defects and P-Type Conduction." Materials Science Forum 595-598 (September 2008): 1039–46. http://dx.doi.org/10.4028/www.scientific.net/msf.595-598.1039.
Full textAbstract:
A quantitative elucidation of the void formation in a growing scale with Schottky defects and p-type conduction during high temperature oxidation of metals. The evaluation of the divergence of ionic fluxes indicates that (1) Voids form in the scale preferentially in the vicinity of the metal/scale interface, (2) The volume of voids increases in a parabolic manner, (3) The volume fraction of voids and the scale is independent of time. The comparison between the calculation and the experimentally observed scale microstructure of NiO and CoO confirmed well the validity of the prediction.
16
Avitzur, B., and J. C. Choi. "Analysis of Central Bursting Defects in Plane Strain Drawing and Extrusion." Journal of Engineering for Industry 108, no. 4 (1986): 317–21. http://dx.doi.org/10.1115/1.3187082.
Full textAbstract:
Based on the upper-bound theorem in limit analysis, the central bursting defect in plane strain drawing and extrusion is analyzed by comparing the proportional flow with the central bursting flow for the metal with voids at the center. A criterion for the unique conditions that promote this defect has been derived. The metal with voids may flow in the identical manner to that of solid strip with no voids to form a sound flow, deterring central bursting. A solid strip, on the other hand, or a material with voids, may flow in a manner so as to produce central bursting defects. A major conclusion of the study is that, for a range of combinations of inclined angle of the die, reduction, and friction, central bursting is expected whether or not the material originally had any voids. On the other hand, central bursting can be prevented even if the original rod contains small-size voids.
17
Seon, Guillaume, Yuri Nikishkov, Andrew Makeev, and Lauren Fergusson. "Predicting Formation of Manufacturing Defects in Contoured Composites." Journal of the American Helicopter Society 64, no. 4 (2019): 1–15. http://dx.doi.org/10.4050/jahs.64.042005.
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 structures. This work seeks to fill the gaps in understanding generation of the noted defects in contoured polymer–matrix composite laminates. In particular, understanding and modeling 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 modeling (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 modeling of voids at ply interfaces to improve the accuracy of predicting their evolution during the debulking operations.
18
Lee, Kyo-Moon, Soo-Jeong Park, Tianyu Yu, Seong-Jae Park, and Yun-Hae Kim. "Experimental prediction of internal defects according to defect area on NDI via water absorption behavior." International Journal of Modern Physics B 35, no. 14n16 (2021): 2140021. http://dx.doi.org/10.1142/s021797922140021x.
Full textAbstract:
This study analyzed the relationship between the defect area identified through a C-scan and the void volume in CF-PEKK composite materials through the water absorption behavior to predict the void volume. The water absorption content varies with the defect area; however, the defect area identified through a C-scan and the water absorption content did not show a proportional relationship. This is because voids are distributed in the through-thickness. The results indicated that the absorption behavior could be used to predict the void volume. Irreversible absorption was found to be independent of the void volume. Further, no matrix degradation was seen with water immersion at [Formula: see text]C; however, some local swelling was seen.
19
Bernhard, T., S. Branagan, R. Schulz, et al. "The Formation of Nano-voids in electroless Cu Layers." MRS Advances 4, no. 41-42 (2019): 2231–40. http://dx.doi.org/10.1557/adv.2019.336.
Full textAbstract:
ABSTRACTThe electrical reliability of multilayer high density interconnection printed circuit boards (HDI-PCBs) is mainly affected by the thermo-mechanical stability of stacked micro via interconnections. Here, a critical failure mode is the stress related crack between the electrolytically filled via and the target pad, commonly known as target pad separation. The junction includes two Cu-Cu-interfaces, one between the target Cu pad and the thin electroless Cu layer and the second between electroless Cu and electrolytic Cu. In this paper we will show that state-of-the-art electroless Cu plating processes are able to provide solid, completely recrystallized and highly reliable stacked via junctions. Defect free interfaces were achieved by using ionic Pd-activators and electroless Cu baths with a cyanide based stabilizer system. Cyanide free electroless Cu baths tend more to the formation of nanometer sized defects, discovered via Transmission Electron Microscopy (TEM). In this case a precise adjustment of single stabilizer components is mandatory to achieve defect free layers. The defects are hollow and were identified as “nano voids”. A critical density of these nano voids weakens the interface, predefines the crack path and reduces the overall reliability of the junction. A precise localization of the nano voids within the junction was enabled by detecting the Ni-containing electroless Cu layer via TEM-Ni mapping. Slower volume exchange of the electroless Cu solution within the blind micro via (BMV) substantially increases the nano void density. The ability of nano voids to migrate and coalesce at elevated temperatures was investigated as well.
20
Mascher, P., S. Dannefaer, and D. Kerr. "Deformation-induced vacancy-type defects in GaAs." Canadian Journal of Physics 69, no. 3-4 (1991): 298–306. http://dx.doi.org/10.1139/p91-050.
Full textAbstract:
Semi-insulating undoped GaAs was plastically deformed and then investigated by positron-lifetime spectroscopy. Strains between 0 and 40% and temperatures of deformation of 450, 500, and 600 °C were investigated, with detailed investigations carried out for the lowest temperature of deformation. Between 0 and 4% strain, a reduction of the grown-in vacancy response takes place simultaneously with a slight increase in vacancy cluster size to two or three vacancies. Between 4 and 6% strain a very substantial increase in vacancy production occurs but nearly all of these vacancies are clustered into voids with a radius of about 50 Å (1 Å = 10−10 m) and density in the order of 1013–1014 cm−3. The total concentration of vacancies necessary to produce these voids is 1017–1018 cm−3. This clearly shows that vacancies are formed upon deformation and that they are mobile at 450 °C. Upon further deformation to 20% strain, the overall defect concentration becomes so high that all positrons become trapped for which reason no absolute defect concentrations can be deduced. The dominant defect types can nevertheless be identified as voids (of average size of 20 Å), two- or three-vacancy clusters, and shallow traps. Isothermal annealing of 40% strained samples shows that heat treatment reduces the void concentration but increases the average void size, and results only in a small decrease in shallow-trap concentration. The shallow traps are likely the dislocation lines themselves and the small vacancy clusters appear to be associated with the dislocation lines.
21
Her, Shiuh Chuan, and Ming Chih Chang. "Identification of Voids and Cracks by Ultrasonic Technique." Key Engineering Materials 326-328 (December 2006): 665–68. http://dx.doi.org/10.4028/www.scientific.net/kem.326-328.665.
Full textAbstract:
Ultrasonic is one of the most wide use of nondestructive evaluation technique. Voids and cracks are the most common defects in a solid. In this investigation, the ultrasonic technique is used to distinguish the defects between the void and crack. As an incident wave impinges on the crack tip, the diffractive wave can be detected from various angles. The amplitude of the diffraction is dependent on the receiving angle. For a void, the incident wave is scattered, the amplitude of the scattering wave is also dependent on the receiving angle. By comparing the amplitudes between the diffractive wave and the scattering wave, one is able to identify the defect of a void or a crack from the other. In this work, 5MHz of longitudinal and shear transducers are used and placed in a variety of incident and receiving angles to examine the difference between the void and crack. The experimental results are validated by the theoretical calculation. In order to identify the void and crack, it is required to have significant difference between the diffractive and scattering waves. The range of the detecting angle, which possesses a meaningful difference between the diffractive and scattering waves, is proposed through the numerical and experimental study to help the identification of the void and crack.
22
Mohseni, Yasaman, Sinduja Suresh, Marie-Luise Wille, Prasad K. D. V. Yarlagadda, and J. Paige Little. "Quantitative Assessment of Voids’ Impact on Mechanical Properties of Standard Dogbone Model Versus End-User Component in Non-Linear Geometry." Polymers 17, no. 7 (2025): 956. https://doi.org/10.3390/polym17070956.
Full textAbstract:
Additive manufacturing (AM) offers advantages such as design flexibility and reduced production times, but defects like voids impact mechanical performance and limit its broader adoption. This study quantitatively examines the relationship between void characteristics (volume fraction, distribution, and size) and mechanical properties in both linear and non-linear geometries, represented by a dogbone model and an end-use component, respectively. Samples were produced using Fused Filament Fabrication (FFF) with varying overlap levels to control void content. As the overlap increased from 0% to 99%, voids transitioned from large linear gaps to smaller point-shaped voids. In non-linear geometry, void reduction from 12% to 2% led to a threefold improvement in mechanical response, while in dogbone samples, voids decreased from 12% to nearly 0%, improving the elastic modulus by only 1.5 times. This disparity is due to differences in void distribution, as voids in non-linear geometries affect both margins and internal layers, significantly influencing structural integrity. The findings highlight the importance of the void location in determining mechanical performance and emphasize the limitations of using linear dogbone models to assess void–property relationships in complex 3D-printed structures.
23
Hamidi, Youssef K., Levent Aktas, and M. Cengiz Altan. "Formation of Microscopic Voids in Resin Transfer Molded Composites." Journal of Engineering Materials and Technology 126, no. 4 (2004): 420–26. http://dx.doi.org/10.1115/1.1789958.
Full textAbstract:
Performance of composite materials usually suffers from process-induced defects such as dry spots and microscopic voids. While effects of void content in molded composites have been studied extensively, knowledge of void morphology and spatial distribution of voids in composites manufactured by resin transfer molding (RTM) remains limited. In this study, through-the-thickness void distribution for a disk-shaped, E-glass/epoxy composite part manufactured by resin transfer molding is investigated. Microscopic image analysis is conducted through-the-thickness of a radial sample obtained from the molded composite disk. Voids are found to concentrate primarily within or adjacent to the fiber preforms. More than 93% of the voids are observed within the preform or in a so-called transition zone, next to a fibrous region. In addition, void content was found to fluctuate through-the-thickness of the composite. Variation up to 17% of the average void content of 2.15% is observed through-the-thicknesses of the eight layers studied. Microscopic analysis revealed that average size of voids near the mold surfaces is slightly larger than those located at the interior of the composite. In addition, average size of voids that are located within the fiber preform is observed to be smaller than those located in other regions of the composite. Finally, proximity to the surface is found to have no apparent effect on shape of voids within the composite.
24
Liu, Yifang, Junyu Chen, Jiaxin Jiang, and Gaofeng Zheng. "Void Suppression in Glass Frit Bonding Via Three-Step Annealing Process." Micromachines 13, no. 12 (2022): 2104. http://dx.doi.org/10.3390/mi13122104.
Full textAbstract:
In this work, void formation was systematically observed for the glass frit bonding technique as a function of the annealing temperature, annealing time, and annealing ambient. High annealing temperature and long annealing time were adopted to reach the maximum heat flux to avoid voids/bubbles. As demonstrated in the experiments, the voids appearing during glass frit bonding are related to the quantity of byproducts from the combustion of organic matter. The experimental results indicate that solely in air, under vacuum, or annealed for short time, the combustion products cannot be fully degassed, and voids occur. It was shown that the alternating three-step conditioning process including glass liquid forming in air, bubble removal under vacuum, and void filling-up in air can lead to void-free and uniform wafer bonding. The glass frit bonding samples with lots of voids/bubbles were compared to the ones without any defects.
25
Zhou, Bo, Fangai Yu, He Li, and Wen Xin. "A Quantitative Study on the Void Defects Evolving into Damage in Wind Turbine Blade Based on Internal Energy Storage." Applied Sciences 10, no. 2 (2020): 491. http://dx.doi.org/10.3390/app10020491.
Full textAbstract:
As manufacturing defects, voids in wind turbine blades may cause damage under fatigue loads. In this paper, the internal energy storage is used as an indicator to identify the critical moment when a defect evolves into damage. The heat transfer equation of composites material containing void defects is derived based upon the theory of the thermodynamics of irreversible processes. In order to obtain the numerical calculation model of the internal energy storage of the evolving process, the thermal conductivity along the transverse direction is homogenized as the temperature date along this direction is acquired by a thermal camera. Specimens with different void fractions are tested with infrared thermal imaging under fatigue load, during which the stress, strain and temperature data are acquired to establish the curve of internal energy storage against the fatigue cycle. This relationship curve can be used to identify the critical moment when void defects evolve into damage. The feasibility of this method is proven by microscopic observation.
26
Vanfleet, R. R., M. Shverdin, Z. H. Zhu, Y. H. Lo, and J. Silcox. "Interface Voids and Precipitates in GaAs Wafer Bonding." Microscopy and Microanalysis 5, S2 (1999): 748–49. http://dx.doi.org/10.1017/s1431927600017062.
Full textAbstract:
Wafer bonding allows the production of Compliant Universal substrates that are made by bonding a thin (< 10 nm) layer twisted ∼45 degrees to the underlying substrate. Subsequent growth on this twisted layer results in defect free films even when the growth material has a significant lattice mismatch with the substrate. Defects on the bonding interface are a common observation when bonding GaAs to many substrates, but the exact nature of these defects has not been clear. We have studied this bonding layer in GaAs-GaAs twist bonded structures by Scanning Transmission Electron Microscopy and Electron Energy Loss Spectroscopy and established that the defects are voids with a portion being partially filled with gallium. Two general sizes of voids are seen. The larger voids are approximately 45 nm in diameter and 22 nm in the wafer normal direction and are distributed in an approximately linear relationship.
27
Chang, Ching-Ray, and Jyh-Shinn Yang. "Magnetization Configurations and Magnetization Reversal of Thin Submicron Permalloy Ellipses with Structural Defects." Journal of Nanoscience and Nanotechnology 8, no. 6 (2008): 2901–4. http://dx.doi.org/10.1166/jnn.2008.18316.
Full textAbstract:
We have studied the magnetic switching behavior of thin elliptical permalloy films with structural defects by micromagnetic simulations. The nonmagnetic void was found to tend to pin the adjacent magnetic moment, which alters the local equilibrium magnetization patterns and modifies the switching behavior of magnetization. In particular, for the case of voids close to the edge, the curling effect of voids is significant, and induces the occurrence of the multiple-stage modes of magnetization reversal, resulting in a high switching field.
28
Méndez, David, A. Aouni, Daniel Araújo, Gabriel Ferro, Yves Monteil, and Etienne Bustarret. "Planar Defects, Voids and their Relationship in 3C-SiC Layers." Materials Science Forum 483-485 (May 2005): 189–92. http://dx.doi.org/10.4028/www.scientific.net/msf.483-485.189.
Full textAbstract:
One of the problems with Si(001)/3C-SiC templates is that they involve highly defective interfaces due to the presence of misfit dislocations, voids and planar defects that degrade the SiC layer quality. A way to accommodate the high lattice mismatch between these materials and reduce the voids density is to carbonize the Si substrate before the epitaxial growth. In this contribution an alternative way to reduce planar defects density is presented by analyzing the relationship between planar defects and voids. Planar view and cross section transmission electron microscopy micrographs show a diminution of planar defects in the regions surrounding the voids. Due to the lower elastic energy over the voids and/or to a lateral growth in these regions, the generation of planar defects is partially deactivated, improving locally the crystalline quality of the SiC layer. The introduction of such cavities can be thus seen as a new parameter of Si/SiC templates design.
29
Chen, Guo, Wei, Xie, and Long. "Effect of Strengthening Methods on the Defect Evolution under Irradiations Investigated with Rate Theory Simulations." Metals 9, no. 7 (2019): 735. http://dx.doi.org/10.3390/met9070735.
Full textAbstract:
Under irradiations, mechanical performance of nuclear alloys would degrade due to irradiation induced defects. Different strengthening methods can play a different role in the evolution of the defects. In this study, the effect of four typical strengthening methods including fine grain strengthening, dislocation strengthening, second phase strengthening and solid solutions strengthening on the defect evolutions in bcc iron-based alloys are investigated with rate theory simulations, a technique capable of simulating a long-term evolution of defects caused by irradiations. Simulations show that at high dose, irradiation induced voids become the dominating factor that affect irradiation hardening. Strengthening methods with the enhancement of sink strength (fine grain strengthening, dislocation strengthening and second phase strengthening) have little effects on the evolution of voids, while strengthening method with impediment of migration of defects (solid solutions strengthening) can effectively inhibit the nucleation and growth of voids. For fine grain strengthening and dislocation strengthening, the irradiation hardening is almost kept unchanged when changing grain size and initial dislocation density. For second phase strengthening, the irradiation hardening can be inhibited to some extent by increasing mainly the number density of precipitates. The solid solutions strengthening is the most proper method to inhibit irradiation hardening of bcc iron-based alloy because it can inhibit the development of voids, especially at high dose.
30
Yang, Longlong, Kun Sun, and Huaying Wu. "Effect of Void Defects on the Indentation Behavior of Ni/Ni3Al Crystal." Nanomaterials 13, no. 13 (2023): 1969. http://dx.doi.org/10.3390/nano13131969.
Full textAbstract:
Inconel 718 (IN 718) superalloys are widely used as engineering materials owing to their superior mechanical performance. And voids are unavoidable defects in IN 718 superalloy preparation, which dramatically affect the mechanical properties of IN 718 superalloys. In this work, the effects of void radius, distance from the top of the void to the substrate surface, and substrate temperature on the mechanical properties of the Ni/Ni3Al crystal are systematically investigated. It is shown that voids affect the formation of stair-rod dislocations and Shockley dislocations in the substrate, which in turn determines the mechanical properties. Thus, with the increase in void radius, Young’s modulus and hardness gradually decrease. With the increase in void distance, Young’s modulus and hardness increase and finally tend to be stable. In addition, the increase in substrate temperature leads to the interphase boundary becoming irregular and increases the defects in the γ and γ″ phases. As a result, Young’s modulus and hardness of the substrate decrease. This work aims to provide a guideline for investigating the indentation properties of Ni-based superalloys using MD.
31
Mehdikhani, Mahoor, Larissa Gorbatikh, Ignaas Verpoest, and Stepan V. Lomov. "Voids in fiber-reinforced polymer composites: A review on their formation, characteristics, and effects on mechanical performance." Journal of Composite Materials 53, no. 12 (2018): 1579–669. http://dx.doi.org/10.1177/0021998318772152.
Full textAbstract:
Voids, the most studied type of manufacturing defects, form very often in processing of fiber-reinforced composites. Due to their considerable influence on physical and thermomechanical properties of composites, they have been extensively studied, with the focus on three research tracks: void formation, characteristics, and mechanical effects. Investigation of voids in composites started around half a century ago and is still an active research field in composites community. This is because of remaining unknowns and uncertainties about voids as well as difficulties in their suppression in modern manufacturing techniques like out-of-autoclave curing and parts with high complexity, further complicated by increased viscosity of modified resins. Finally, this is because of the increasing interest in realization of more accurate void rejection limits that would tolerate some voidage. The current study reviews the research on formation, characterization, and mechanical effects of voids, which has been conducted over the past five decades. Investigation and control of void formation, using experimental and modeling approaches, in liquid composite molding as well as in prepreg composite processing are surveyed. Techniques for void characterization with their advantages and disadvantages are described. Finally, the effect of voids on a broad range of mechanical properties, including inter-laminar shear, tensile, compressive, and flexural strength as well as fracture toughness and fatigue life, is appraised. Both experimental and simulation approaches and results, concerning voids' effects, are reviewed.
32
Tavaf, Vahid, and Sourav Banerjee. "Effect of Defects Part I: Degradation of Constitutive Coefficients as an Input to the Composite Failure Model with Microvoids and Porosity." Journal of Composites Science 6, no. 2 (2022): 37. http://dx.doi.org/10.3390/jcs6020037.
Full textAbstract:
It is always challenging to provide appropriate material properties for a composite progressive failure model. The nonstandard percentage reduction method that is commonly used to degrade the material constants with micro-scale defects generates tremendous uncertainty in failure prediction. The constitutive matrix is composed of multiple material constants. It is not necessary that all constants degrade either equally or linearly due to a certain state of material defects. With this very concern in mind, this article presents a guideline for using a quantified perturbation for each coefficient appropriately. It also presents distribution of effective material properties (EMPs) in unidirectional composite materials with different states of defects such as voids. Irrespective of resin transfer molding (RTM) or chemical vapor infiltration (CVI) processes, manufacturers’ defects such as voids of different shapes and sizes are the most common that occur in composite materials. Hence, it is important to quantify the ‘effects of defects’ void content herein on each material coefficient and EMP. In this article, stochastically distributed void parameters such as the void content by percent, size, shape, and location are considered. Void diameters and shapes were extracted from scanning acoustic microscope (SAM) images of 300,000 cycles of a fatigued composite. The EMPs were calculated by considering unit cells, homogenization techniques, and micromechanical concepts. The periodic boundary conditions were applied to unit cells to calculate the EMPs. The result showed that EMPs were degraded even when there was a small percentage of the void content. More importantly, the constitutive coefficients did not degrade equally but had a definitive pattern.
33
Tian, Fangyuan, Yanpeng Hao, Zhouyiao Zou, et al. "An Ultrasonic Pulse-Echo Method to Detect Internal Defects in Epoxy Composite Insulation." Energies 12, no. 24 (2019): 4804. http://dx.doi.org/10.3390/en12244804.
Full textAbstract:
Voids or cracks in basin insulators inside a GIS (gas-insulated metal-enclosed switchgear) could trigger partial discharges or surface flashover under electrical stresses, threatening safe GIS operation. For this paper, some epoxy composite specimens were made from similar materials and manufacturing processes to make 252 kV GIS basin insulators. Some voids with different diameters or cracks with different diameters and orientations were artificially made in the specimens with different thicknesses. An ultrasonic pulse-echo system was set up, and ultrasonic tests were carried out on the specimens with voids or cracks. A method to calculate the depth of a defect was proposed by the propagation time of defect reflected waves. The results showed that a depth of 50 mm, a diameter φ of 2 mm void, and a diameter φ of 1 mm crack in epoxy composite insulation were detected by the ultrasonic system using a 1 MHz transducer.
34
Liu, Zhu, Yongpeng Lei, Xiangyang Zhang, Zhenhang Kang, and Jifeng Zhang. "Effect Mechanism and Simulation of Voids on Hygrothermal Performances of Composites." Polymers 14, no. 5 (2022): 901. http://dx.doi.org/10.3390/polym14050901.
Full textAbstract:
Voids are comment defects generated during the manufacturing process and highly sensitive to moisture in the hygrothermal environment, which has deleterious effects on the mechanical performances. However, the combined impact of void content and water-absorbed content on mechanical properties is not clear. Based on the random sequential adsorption algorithm, a microscale unit cell with random distribution of fibers, interfaces and voids was established. The quantitative effects of voids content on strength and modulus under the loading of transverse tension, compression and shear were investigated by introducing a degradation factor dependent on water content into the constitutive model, and the different failure mechanisms before and after hygrothermal aging were revealed. Conclusively, before hygrothermal aging, voids induce the decrease in mechanical properties due to stress concentration, and every 1% increase in the void content results in a 6.4% decrease in transverse tensile strength. However, matrix degradation due to the absorbed water content after hygrothermal aging is the dominant factor, and the corresponding rate is 3.86%.
35
Oh, Minseong, Jinkuk Kim, Juhyun Cho, Mincheol Kim, Mansoo Joun, and Seokmoo Hong. "Reliability-Based Design Optimization of Bearing Hub Preform for Minimizing Defects Considering Manufacturing Tolerance in Hot Forging Process." Applied Sciences 14, no. 23 (2024): 11316. https://doi.org/10.3390/app142311316.
Full textAbstract:
A study on the optimal design of preforms has previously been actively conducted as a method to solve defects such as voids and flash in forged products. However, previous research has generally been performed through deterministic optimization for ideal cases that do not take manufacturing tolerances into account. As a result, the application of such optimal designs in actual processes may be limited due to various factors such as material manufacturing tolerances and the machining environment of preforms. Therefore, this study conducted reliability-based optimization considering tolerances in billets and preforms. The objective of the study was to optimize the design of a bearing hub and minimize defects in the final product. When comparing deterministic optimization and reliability-based optimization, the former showed relatively superior results in terms of defect indicators but had a higher occurrence of voids and lower forming loads, increasing the probability of void occurrence. On the other hand, the reliability-based optimization showed relatively lower performance in quality improvement indicators, but it successfully met the target reliability of 99% by reducing the probability of defect occurrence. These results were derived using an approximate model based on the Kriging method, providing an optimal design that is practical and effective in actual manufacturing processes.
36
Zhou, Siyi, Shunhua Yao, Tao Shen, and Qingwang Wang. "A Novel End-to-End Deep Learning Framework for Chip Packaging Defect Detection." Sensors 24, no. 17 (2024): 5837. http://dx.doi.org/10.3390/s24175837.
Full textAbstract:
As semiconductor chip manufacturing technology advances, chip structures are becoming more complex, leading to an increased likelihood of void defects in the solder layer during packaging. However, identifying void defects in packaged chips remains a significant challenge due to the complex chip background, varying defect sizes and shapes, and blurred boundaries between voids and their surroundings. To address these challenges, we present a deep-learning-based framework for void defect segmentation in chip packaging. The framework consists of two main components: a solder region extraction method and a void defect segmentation network. The solder region extraction method includes a lightweight segmentation network and a rotation correction algorithm that eliminates background noise and accurately captures the solder region of the chip. The void defect segmentation network is designed for efficient and accurate defect segmentation. To cope with the variability of void defect shapes and sizes, we propose a Mamba model-based encoder that uses a visual state space module for multi-scale information extraction. In addition, we propose an interactive dual-stream decoder that uses a feature correlation cross gate module to fuse the streams’ features to improve their correlation and produce more accurate void defect segmentation maps. The effectiveness of the framework is evaluated through quantitative and qualitative experiments on our custom X-ray chip dataset. Furthermore, the proposed void defect segmentation framework for chip packaging has been applied to a real factory inspection line, achieving an accuracy of 93.3% in chip qualification.
37
Zhou, Tingting, Qian Zhang, Jianwei Yin, Anmin He, and Pei Wang. "Atomistic understanding of the influences of defects on the spall damage of aluminum under multiple shock loadings." Journal of Applied Physics 133, no. 1 (2023): 015901. http://dx.doi.org/10.1063/5.0130483.
Full textAbstract:
The spall damage of solid single crystal Al with initial defects such as voids or He bubbles under multiple decaying shock loadings is studied by molecular dynamics simulations. After the first shock compression and release, plenty of sparse defects in the void collapsed regions and a few disordered atoms surrounding He bubbles are formed in the Al-void and Al–He samples, respectively. The spall mechanism for the Al-void sample is the nucleation–growth–coalescence of voids originated from the defects at the early stage of damage and from the regions without defects at the late stage. Under second shock loading, the first spall region is compressed and the compression extent is dependent on the shock intensity; however, the density after complete compression is lower than the initial value. Meanwhile, a new spall region is formed due to the interaction of the second incident rarefaction wave with the one reflected from the surface of the first spall region into the sample, when the shock intensity is relatively strong. The new spall region exhibits lower spall strength for the samples with initial defects than that for the perfect sample. Additionally, respallation occurs in the first spall region after compression under the strong second shock, its damage evolution is strongly influenced by the defects formed after compression, and the spall strength is much lower than that of first spallation. For the Al–He sample, the spall mechanism is always dominated by the expansion-merging of He bubbles, with the fastest damage development and the lowest spall strength.
38
Okolie, Obinna, Nadimul Haque Faisal, Harvey Jamieson, Arindam Mukherji, and James Njuguna. "Integrated Non-Destructive Testing for Assessing Manufacturing Defects in Melt-Fusion Bonded Thermoplastic Composite Pipes." NDT 3, no. 1 (2025): 6. https://doi.org/10.3390/ndt3010006.
Full textAbstract:
The thermoplastic composite pipe (TCP) manufacturing process introduces defects that impact performance, such as voids, misalignment, and delamination. Consequently, there is an increasing demand for effective non-destructive testing (NDT) techniques to assess the influence of these manufacturing defects on TCP. The objective is to identify and quantify internal defects at a microscale, thereby improving quality control. A combination of methods, including NDT, has been employed to achieve this goal. The density method is used to determine the void volume fraction. Microscopy and void analysis are performed on pristine samples using optical micrography and scanning electron microscopy (SEM), while advanced techniques like X-ray computer tomography (XCT) and ultrasonic inspections are also applied. The interlayer between the reinforced and inner layers showed good consolidation, though a discontinuity was noted. Microscopy results confirmed solid wall construction, with SEM aligning with the XY axis slice, showing predominant fibre orientation around ±45° and ±90°, and deducing the placement orientation to be ±60°. Comparing immersion, 2D microscopy, and XCT methods provided a comparative approach, even though they could not yield precise void content values. The analysis revealed a void content range of 0–2.2%, with good agreement between microscopy and Archimedes’ methods. Based on XCT and microscopy results, an increase in void diameter at constant volume increases elongation and reduces sphericity. Both methods also indicated that most voids constitute a minority of the total void fraction. To mitigate manufacturing defects, understanding the material’s processing window is essential, which can be achieved through comprehensive material characterization of TCP materials.
39
Gleixner, R. J., B. M. Clemens, and W. D. Nix. "Void Nucleation in Passivated Interconnect Lines: Effects of Site Geometries, Interfaces, and Interface Flaws." Journal of Materials Research 12, no. 8 (1997): 2081–90. http://dx.doi.org/10.1557/jmr.1997.0279.
Full textAbstract:
Stress driven nucleation of voids in passivated aluminum interconnect lines is analyzed within the context of classical nucleation theory. A discussion of sources of tensile stress in such lines leads to an upper limit of 2 GPa. Calculations suggest that even at this high stress, nucleation rates are far too low to account for observed rates of voiding. Void formation at a circular defect at the line/passivation interface is then considered. In this case, a flaw on the order of nanometers in size may develop into a void under the imposed stress. These results strongly suggest that void nucleation in aluminum interconnect lines can be controlled by eliminating defects in the line/passivation interface.
40
Zhang, Sen, Zhihua Ren, Zude Ding, Jincheng Wen, and Zhixin Yan. "Influence of Existing Defects on Mechanical Properties of NC Lining." Advances in Materials Science and Engineering 2019 (December 19, 2019): 1–15. http://dx.doi.org/10.1155/2019/8571297.
Full textAbstract:
The mechanical properties of the lining are directly affected by defects such as voids behind the lining and insufficient thickness of the lining. In order to quantitatively evaluate this effect, the mechanical behavior of the lining under the influence of the void behind the lining, the insufficient thickness of the lining, and the combination of the two kinds of defects are adopted by the 1/5 scale model test. Based on the experimental research, numerical calculation models based on the CDP model for defect lining are established, with the effects of load direction, stratum stiffness, defect location, defect type, and degree on the mechanical behavior of the lining analyzed by the numerical simulation. The experimental and numerical results show that the void weakens the stiffness of the lining. As the void range increases, the lining becomes more deformable and its bearing capacity decreases with the “S” curve. Thinning significantly reduces the deformation properties of the lining and the bearing capacity and stiffness of the thinned section. The lining bearing capacity decreases linearly with the increase of the thinning ratio, when the load is applied at the thinning. With the influence of combined defects on the load-displacement curve of the lining fluctuating drastically, the mechanical properties of the lining are significantly reduced. The bearing capacity of lining decreases with the increase of composite defects in a “S” shape. The effect of void and lining thinning on the lining bearing capacity increases with the increase of the stiffness of the formation. The loss rate equation of the concrete lining bearing capacity under the influence of existing defects is established by using the L-M nonlinear regression analysis, a provision of scientific guidance for the safety evaluation of the defect lining.
41
Wallner, Anton S., and William M. Ritchey. "Void distribution and susceptibility differences in ceramic materials using MRI." Journal of Materials Research 8, no. 3 (1993): 655–61. http://dx.doi.org/10.1557/jmr.1993.0655.
Full textAbstract:
Magnetic Resonance Imaging (MRI) is applied to porous ceramic materials to study structural properties. In ceramics, processing differences create inhomogeneous binder distribution in the materials which can cause the formation of regions with differing densities and voids. These defects can be observed with MRI using solvent permeation. Fractional porosity obtained by using image intensity measurements and weight gain due to solvent permeation can be correlated. Dark regions in the image are due to defects such as closed voids, pockets of binder, or agglomerates. Defects such as voids or agglomerates usually have different magnetic susceptibilities. This difference causes artifacts in the image. By exploiting the increase in signal loss using a gradient-echo sequence, apparent enhancement of voids in ceramics is achieved.
42
Chen, Qiu Nan, Xiao Cheng Huang, and Jian Xin Li. "Application of Ground Penetrating Radar in Detection of Tunnel Lining Structure Fracture and Processing Measures." Applied Mechanics and Materials 204-208 (October 2012): 1318–22. http://dx.doi.org/10.4028/www.scientific.net/amm.204-208.1318.
Full textAbstract:
Based on electromagnetic propagation theory, and used reflected wave detection method of Ground Penetrating Radar. To detect the tunnel with empty areas, void areas, non-dense areas, voids and other defects by the GPR. According to Jianshan Tunnel on-site detection, combined with practical examples to illustrate the GPR as a mean of nondestructive testing. The existence of tunnel defects and their reasons are analyzed comprehensively, and a series of processing measures are proposed.
43
Nguyen, Yen T., Pradeep K. Seshadri, Oishik Sen, David B. Hardin, Christopher D. Molek, and H. S. Udaykumar. "Multi-scale modeling of shock initiation of a pressed energetic material. II. Effect of void–void interactions on energy localization." Journal of Applied Physics 131, no. 21 (2022): 215903. http://dx.doi.org/10.1063/5.0090225.
Full textAbstract:
Heterogeneous energetic materials (EMs) contain microstructural defects such as voids, cracks, interfaces, and delaminated zones. Under shock loading, these defects offer potential sites for energy localization, i.e., hotspot formation. In a porous EM, the collapse of one void can generate propagating blast waves and hotspots that can influence the hotspot phenomena at neighboring voids. Such void–void interactions must be accounted for in predictive multi-scale models for the reactive response of a porous EM. To infuse such meso-scale phenomena into a multi-scale framework, a meso-informed ignition and growth model (MES-IG) has been developed, where the influence of void–void interactions is incorporated into the overall reaction rate through a function, [Formula: see text]. Previously, MES-IG was applied to predict the sensitivity and reactive response of EM, where [Formula: see text] was assumed to be a function of the overall sample porosity alone. This paper performs a deeper analysis to model the strong dependency of [Formula: see text] on other factors, such as void size and shock strength. The improved model for void–void interactions produces good agreement with direct numerical simulations of the HE microstructures and, thus, advances the predictive capability of multi-scale models of the shock response and sensitivity of EM.
44
Dvorzhinskiy, Aleksey, Giorgio Perino, Robert Chojnowski, Marjolein C. H. van der Meulen, Mathias P. G. Bostrom, and Xu Yang. "Ceramic composite with gentamicin decreases persistent infection and increases bone formation in a rat model of debrided osteomyelitis." Journal of Bone and Joint Infection 6, no. 7 (2021): 283–93. http://dx.doi.org/10.5194/jbji-6-283-2021.
Full textAbstract:
Abstract. Introduction: Current methods of managing osteomyelitic voids after debridement are inadequate and result in significant morbidity to patients. Synthetic ceramic void fillers are appropriate for non-infected bone defects but serve as a nidus of re-infection in osteomyelitis after debridement. CERAMENT G (CG) is an injectable ceramic bone void filler which contains gentamicin and is currently being evaluated for use in osteomyelitic environments after debridement due to its theoretical ability to serve as a scaffold for healing while eliminating residual bacteria after debridement through the elution of antibiotics. The goal of this study was to evaluate (1) the rate of persistent infection and (2) new bone growth of a debrided osteomyelitic defect in a rat model which has been treated with either gentamicin-impregnated ceramic cement (CERAMENT G) or the same void filler without antibiotics (CERAMENT, CBVF). Methods: Osteomyelitis was generated in the proximal tibia of Sprague Dawley rats, subsequently debrided, and the defect filled with either (1) CG (n=20), (2) CBVF (n=20), or (3) nothing (n=20). Each group was euthanized after 6 weeks. Infection was detected through bacterial culture and histology. Bone growth was quantified using microCT. Results: Infection was not detected in defects treated with CG as compared with 35 % of defects (7/20) treated with CBVF and 50 % (10/20) of empty defects (p=0.001). Bone volume in the defect of CG-treated rats was greater than the CBVF (0.21 vs. 0.17, p=0.021) and empty groups (0.21 vs. 0.11, p<0.001) at 6 weeks after implantation. Conclusions: Ceramic void filler with gentamicin (CERAMENT G) decreased the rate of persistent infection and increased new bone growth as compared to the same void filler without antibiotics (CERAMENT) and an empty defect in a rat model of debrided osteomyelitis.
45
Wan, Ya-Ting, Jian-Li Shao, Guang-Ze Yu, Er-Fu Guo, Hua Shu, and Xiu-Guang Huang. "Evolution of Preset Void and Damage Characteristics in Aluminum during Shock Compression and Release." Nanomaterials 12, no. 11 (2022): 1853. http://dx.doi.org/10.3390/nano12111853.
Full textAbstract:
It is well known that initial defects play an essential role in the dynamic failure of materials. In practice, dynamic tension is often realized by release of compression waves. In this work, we consider void-included single-crystal aluminum and investigate the damage characteristics under different shock compression and release based on direct atomistic simulations. Elastic deformation, limited growth and closure of voids, and the typical spall and new nucleation of voids were all observed. In the case of elastic deformation, we observed the oscillatory change of void volume under multiple compression and tension. With the increase of impact velocity, the void volume reduced oscillations to the point of disappearance with apparent strain localization and local plastic deformation. The incomplete or complete collapsed void became the priority of damage growth under tension. An increase in sample length promoted the continuous growth of preset void and the occurrence of fracture. Of course, on the release of strong shock, homogeneous nucleation of voids covered the initial void, leading to a wider range of damaged zones. Finally, the effect of the preset void on the spall strength was presented for different shock pressures and strain rates.
46
Burcham, Daniel, Subhadip Ghosh, Leong Eng Choon, and Fong Yok King. "Evaluation of an Infrared Camera Technique for Detecting Mechanically Induced Internal Voids in Syzygium grande." Arboriculture & Urban Forestry 37, no. 3 (2011): 93–98. http://dx.doi.org/10.48044/jauf.2011.013.
Full textAbstract:
In order to evaluate a proposed tree diagnostic technique employing infrared cameras, research was conducted to evaluate the effect of internal voids on surface temperature using a thermal photographic instrument. Three axial cylindrical voids of increasing size (Void A, 327 cm3; Void B, 745 cm3; Void C, 1159 cm3) were introduced mechanically in 45 cm long stem sections and exposed to direct sunlight. Subsequently, infrared images were collected from two diametrically opposed sides of the stem sections at regular 30-minute intervals over 150 minutes. The collected images were evaluated visually to compare stem features with observed temperature anomalies, and temperature data was extracted from a vertical transect in the infrared images. The data extracted were compared against a control stem section without defects to determine the independent and combined effects of void size and internal position on surface temperature. Mean relative temperature revealed a significant temperature change in the stems containing mechanical voids compared to the control stem. Significant increases in mean relative temperature were recorded on the stems containing Void A and Void B compared to the control. However, there was no significant change in mean relative temperature on the stem section containing Void C.
47
Xing, Liyun, Hong-Liang Cui, Changcheng Shi, et al. "Void and crack detection of polymethacrylimide foams based on terahertz time-domain spectroscopic imaging." Journal of Sandwich Structures & Materials 19, no. 3 (2016): 348–63. http://dx.doi.org/10.1177/1099636216680165.
Full textAbstract:
Terahertz reflection imaging is considered as a potential diagnostic tool for the investigation of polymethacrylimide foam defects. Using terahertz time-domain spectroscopy (TDS) and detection methods based on terahertz spectroscopic analysis, the reflection imaging results of different thicknesses of polymethacrylimide foam with two kinds of detections (cracks and voids) are studied. The samples (Degussa Rohacell WF71) are planar slabs of polymethacrylimide foams with thicknesses of 35 mm, 60.5 mm and 10 mm. It is found that the same kinds of polymethacrylimide foam defects with different foam thicknesses have similar spectral characteristics, with marked differences only in the amplitude and phase of the reflected wave. In view of this, we focus our study on the defective spectral characteristics of one of the foams (35 mm thickness). The characteristics of void and crack defects are analyzed in the time domain, which is based mainly on the variation of the reflected waveform. In particular, the imaging and clear identification of voids of less than 2.4 mm in diameter, fine cracks (0.3 mm wide), and the quantification of defects can be readily achieved using the terahertz non-destructive testing technique described here.
48
Molendowska, Agnieszka, Jerzy Wawrzeńczyk, and Henryk Kowalczyk. "Development of the Measuring Techniques for Estimating the Air Void System Parameters in Concrete Using 2D Analysis Method." Materials 13, no. 2 (2020): 428. http://dx.doi.org/10.3390/ma13020428.
Full textAbstract:
The purpose of the present study was to determine the impact of image quality on the results of air void system parameters determination in air-entrained concretes. The focus was on technical aspects related to the preparation of the scanned image of the concrete surface, which was then subjected to 2D surface analysis. Image processing aimed at separating joined voids and removing various types of defects in aggregate and cement mortar. The specific surface of the voids was determined with the air void equivalent diameter or perimeter as the calculation basis. Applying the Schwartz–Saltykov method, the 3D distribution of the air voids was reconstructed based on 2D measurements. On this basis, the micro-air content A300 was determined. The results of the 2D method were compared with the results of determinations carried out using the linear traverse (1D) method according to EN 480-11. The tests confirm the need to correct the image prior to measurements. Comparative tests showed good agreement between the air void system parameters determined using the 2D analysis and the EN 480-11 chord length counting method.
49
Wang, Feng, Wenbo Luo, Jiling Bu, Bo Zou, and Xingwu Ding. "Mitigation of Sink Voids in Thick-Walled Thermoplastic Components via Integrated Taguchi DOE and CAE Simulations." Polymers 17, no. 8 (2025): 1126. https://doi.org/10.3390/polym17081126.
Full textAbstract:
A gauge plate is a typical thick-walled injection-molded component featuring a complex construction used in high-speed railways, and it is prone to sink voids during the injection process. It is difficult to obtain a void-free injection molded part due to uneven cooling-induced localized thermal gradients, crystallization shrinkage of semicrystalline thermoplastics, fiber orientation-induced anisotropic shrinkage, injection parameter-dependent fountain flow, and inconsistent core compensation. This work employed design of experiment (DOE) and computer-aided engineering (CAE) simulations to analyze the influence of injection parameters on the volumetric shrinkage of the gauge plate and to identify the optimal injection process. A Taguchi orthogonal array L9 was applied, in which four injection molding process parameters were varied at three different levels. The fundamental causes of sink void defects in the gauge plate were then examined via MoldFlow analysis on the basis of the optimized injection parameters. The MoldFlow study indicates a high probability of the presence of sink void defects in the injection-molded gauge plate. To minimize sink void defects, a structural optimization design of the gauge plate was implemented to achieve a more uniform wall thickness, and the advantages of this optimization were demonstrated via comparative analysis. The small batch production of the injection-molded gauge plates demonstrates that the optimized gauge plate shows no sink voids, ensuring consistent quality that adheres to the engineering process and technical specifications.
50
Miller, S. C., and V. N. Goncharov. "Instability seeding mechanisms due to internal defects in inertial confinement fusion targets." Physics of Plasmas 29, no. 8 (2022): 082701. http://dx.doi.org/10.1063/5.0091949.
Full textAbstract:
Performance degradation in laser-driven inertial confinement fusion (ICF) implosions is caused by several effects, one of which is Rayleigh–Taylor instability growth. Defects in ICF targets, such as internal voids and surface roughness, create instability seeds in the shell as shocks propagate through the target. A comprehensive understanding of seeding mechanisms is essential to characterize the impact of target defects on inflight shell integrity and mass injection into the central, lower-density vapor region. An analysis of early-time behavior of both single-mode shell mass modulations and isolated voids is performed by examining the evolution of the acoustic waves launched by these target imperfections. A systematic study of localized perturbation growth as a function of defect placement and size is presented. The use of low-density ablator materials (such as foams) is suggested as a potential mitigation strategy to improve target robustness against the impact of defect-initiated growth.