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Artykuły w czasopismach na temat "Microscale damage mechanism"
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Zhaodong, Ding, i Li Jie. "A physically motivated model for fatigue damage of concrete". International Journal of Damage Mechanics 27, nr 8 (13.08.2017): 1192–212. http://dx.doi.org/10.1177/1056789517726359.
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The fatigue problem of concrete is still a challenging topic in the researches and applications of concrete engineering. This paper aims to develop a fatigue damage evolution law based model for concrete motivated by the analysis of physical mechanism. In this model, the fatigue energy dissipation process at microscale is investigated with rate process theory. The concept of self-similarity is employed to bridge the scale gap between microscale cracking and mesoscale dissipative element. With the stochastic fracture model, the crack avalanches and macro-crack nucleation processes from mesoscale to macroscale are simulated to obtain the behaviors of macroscope damage evolution of concrete. In conjunction with continuum damage mechanics framework, the fatigue damage constitutive model for concrete is then proposed. Numerical simulations are carried out to verify the model, revealing that the proposed model accommodates well with physical mechanism of fatigue damage evolution of concrete whereby the fatigue life of concrete structures under different stress ranges can be predicted.
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Zhang, Di, Lu Zheng, Ping Li, Gongnan Xie i Yonghui Xie. "A Combined Numerical and Experimental Analysis on Erythrocyte Damage Mechanism in Microscale Flow". Advances in Mechanical Engineering 5 (styczeń 2013): 962658. http://dx.doi.org/10.1155/2013/962658.
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Chandra, A., Y. Huang, Z. Q. Jiang, K. X. Hu i G. Fu. "A Model of Crack Nucleation in Layered Electronic Assemblies Under Thermal Cycling". Journal of Electronic Packaging 122, nr 3 (5.11.1999): 220–26. http://dx.doi.org/10.1115/1.1286100.
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A model for crack nucleation in layered electronic assemblies under thermal cycling is developed in this paper. The present model includes three scales: (i) at the microscale or the mechanism level, the damage mechanisms such as diffusive void growth or fatigue cracks, determine the damage growth rate; (2) at an intermediate mesoscale, the localized damage bands are modeled as variable stiffness springs connecting undamaged materials; and (iii) at the macroscale or the continuum level, the localized damage band growing in an otherwise undamaged material is modeled as an array of dislocations. The three scales are then combined together to incorporate damage mechanisms into continuum analysis. Traditional fracture mechanics provides a crack propagation model based on pre-existing cracks. The present work provides an approach for predicting crack nucleation. The proposed model is then utilized to investigate crack nucleations in three-layered electronic assemblies under thermal cycling. The damage is observed to accumulate rapidly in the weakest regions of the band. Estimates are obtained for critical time or critical number of cycles at which a macroscopic crack will nucleate in these assemblies under thermal cycling. This critical number of cycles is found to be insensitive to the size of the damage cluster, but decreases rapidly as the local excess damage increases. [S1043-7398(00)00503-X]
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Chen, Junjie, Jinhee Kim, Wenhao Shao, Stephen H. Schlecht, So Young Baek, Alexis K. Jones, Taeyong Ahn, James A. Ashton-Miller, Mark M. Banaszak Holl i Edward M. Wojtys. "An Anterior Cruciate Ligament Failure Mechanism". American Journal of Sports Medicine 47, nr 9 (lipiec 2019): 2067–76. http://dx.doi.org/10.1177/0363546519854450.
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Background: Nearly three-quarters of anterior cruciate ligament (ACL) injuries occur as “noncontact” failures from routine athletic maneuvers. Recent in vitro studies revealed that repetitive strenuous submaximal knee loading known to especially strain the ACL can lead to its fatigue failure, often at the ACL femoral enthesis. Hypothesis: ACL failure can be caused by accumulated tissue fatigue damage: specifically, chemical and structural evidence of this fatigue process will be found at the femoral enthesis of ACLs from tested cadaveric knees, as well as in ACL explants removed from patients undergoing ACL reconstruction. Study Design: Controlled laboratory study. Methods: One knee from each of 7 pairs of adult cadaveric knees were repetitively loaded under 4 times–body weight simulated pivot landings known to strain the ACL submaximally while the contralateral, unloaded knee was used as a comparison. The chemical and structural changes associated with this repetitive loading were characterized at the ACL femoral enthesis at multiple hierarchical collagen levels by employing atomic force microscopy (AFM), AFM–infrared spectroscopy, molecular targeting with a fluorescently labeled collagen hybridizing peptide, and second harmonic imaging microscopy. Explants from ACL femoral entheses from the injured knee of 5 patients with noncontact ACL failure were also characterized via similar methods. Results: AFM–infrared spectroscopy and collagen hybridizing peptide binding indicate that the characteristic molecular damage was an unraveling of the collagen molecular triple helix. AFM detected disruption of collagen fibrils in the forms of reduced topographical surface thickness and the induction of ~30- to 100-nm voids in the collagen fibril matrix for mechanically tested samples. Second harmonic imaging microscopy detected the induction of ~10- to 100-µm regions where the noncentrosymmetric structure of collagen had been disrupted. These mechanically induced changes, ranging from molecular to microscale disruption of normal collagen structure, represent a previously unreported aspect of tissue fatigue damage in noncontact ACL failure. Confirmatory evidence came from the explants of 5 patients undergoing ACL reconstruction, which exhibited the same pattern of molecular, nanoscale, and microscale structural damage detected in the mechanically tested cadaveric samples. Conclusion: The authors found evidence of accumulated damage to collagen fibrils and fibers at the ACL femoral enthesis at the time of surgery for noncontact ACL failure. This tissue damage was similar to that found in donor knees subjected in vitro to repetitive 4 times–body weight impulsive 3-dimensional loading known to cause a fatigue failure of the ACL. Clinical Relevance: These findings suggest that some ACL injuries may be due to an exacerbation of preexisting hierarchical tissue damage from activities known to place larger-than-normal loads on the ACL. Too rapid an increase in these activities could cause ACL tissue damage to accumulate across length scales, thereby affecting ACL structural integrity before it has time to repair. Prevention necessitates an understanding of how ACL loading magnitude and frequency are anabolic, neutral, or catabolic to the ligament.
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Cao, Minghua, Konstantinos P. Baxevanakis i Vadim V. Silberschmidt. "Effect of Graphite Morphology on the Thermomechanical Performance of Compacted Graphite Iron". Metals 13, nr 3 (24.02.2023): 473. http://dx.doi.org/10.3390/met13030473.
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Compacted graphite iron (CGI) has gained significant attention in automotive industry applications thanks to its superior thermomechanical properties and competitive price. Its main fracture mechanism at the microscale—interfacial damage and debonding between graphite inclusions and a metallic matrix—can happen under high-temperature service conditions as a result of a mismatch in the coefficients of thermal expansion between the two phases of CGI. Macroscopic fracture in cast iron components can be initiated by interfacial damage at the microscale under thermomechanical load. This phenomenon was investigated in various composites but still lacks information for CGI, with its complex morphology of graphite inclusions. This research focuses on the effect of this morphology on the thermomechanical performance of CGI under high temperatures. A set of three-dimensional finite-element models was created, with a unit cell containing a single graphite inclusion embedded in a cubic domain of the metallic matrix. Elastoplastic behaviour was assumed for both phases in numerical simulations. The effect of graphite morphology on the thermomechanical performance of CGI was investigated for pure thermal loading, focusing on a high-temperature response of its constituents. The results can provide a deeper understanding of the correlation between graphite morphology and CGI fracture mechanisms under high temperatures.
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Lian, Jun He, Xiao Xu Jia, Sebastian Münstermann i Wolfgang Bleck. "A Generalized Damage Model Accounting for Instability and Ductile Fracture for Sheet Metals". Key Engineering Materials 611-612 (maj 2014): 106–10. http://dx.doi.org/10.4028/www.scientific.net/kem.611-612.106.
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With the requirement of vehicle performance and fuel economy, dual-phase (DP) steels as one of the advanced high stress steels (AHSS) are increasingly used in the automotive industry due to the excellent combination of the tensile strength and ductility. On a microscale the ductile fracture is governed by the void nucleation, growth and coalescence mechanism. In the dual-phase steels this damage mechanism exhibits a rather complex situation: voids are generated by the debonding of the hard phase from the matrix and the inner cracking of the hard phase besides by inclusions. On a macroscale fracture of these materials is observed in the automotive industry with the absence of strain localization or minimal post-necking deformation. Consequently the failure during the forming process is caused by a competitive or combined mechanism of internal damage evolution and metal instability. In this study, the target is to develop a simple and generalized model for metal forming processes accounting for instability, damage and ductile fracture. Theoretical predictions of metal instability by the Hill–Swift necking criterion and the modified maximum force criterion are considered. The damage model is developed by the combination of the prediction of metal instability and ductile fracture of sheet metals. The model is developed in 3D triaxial stress state and the accumulation of damage is stress state dependent. Furthermore, the influence of the hardening curve effected by damage on the forming limit curve is investigated.
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González, Sergio, Gianluca Laera, Sotiris Koussios, Jaime Domínguez i Fernando A. Lasagni. "Simulation of thermal cycle aging process on fiber-reinforced polymers by extended finite element method". Journal of Composite Materials 52, nr 14 (12.10.2017): 1947–58. http://dx.doi.org/10.1177/0021998317734625.
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The simulation of long life behavior and environmental aging effects on composite materials are subjects of investigation for future aerospace applications (i.e. supersonic commercial aircrafts). Temperature variation in addition to matrix oxidation involves material degradation and loss of mechanical properties. Crack initiation and growth is the main damage mechanism. In this paper, an extended finite element analysis is proposed to simulate damage on carbon fiber reinforced polymer as a consequence of thermal fatigue between −50℃ and 150℃ under atmospheres with different oxygen content. The interphase effect on the degradation process is analyzed at a microscale level. Finally, results are correlated with the experimental data in terms of material stiffness and, hence, the most suitable model parameters are selected.
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Chen, Wei, Lei Huang, Yaoyao Liu, Yanfei Zhao, Zhe Wang i Zhiwen Xie. "Oxidative Corrosion Mechanism of Ti2AlNb-Based Alloys during Alternate High Temperature-Salt Spray Exposure". Coatings 12, nr 10 (20.09.2022): 1374. http://dx.doi.org/10.3390/coatings12101374.
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This study investigates the corrosion damage mechanisms of Ti2AlNb-based alloys under high temperature, salt spray and coupled high temperature-salt spray conditions. This alloy was analysed in detail from macroscopic to microscopic by means of microscale detection (XRD, SEM and EDS). The results indicated that Ti2AlNb-based alloy surface oxide layer is dense and complete, and the thickness is only 3 µm after oxidation at 650 °C for 400 h. Compared to the original sample, the production of the passivation film resulted in almost no damage to Ti2AlNb-based alloy after 50 cycles of salt spray testing at room temperature. The tests showed that Ti2AlNb alloy shows good erosion resistance at 650 °C and in salt spray. However, this alloy had an oxide layer thickness of up to 30 µm and obvious corrosion pits on the surface after 50 cycles of corrosion under alternating high temperature-salt spray conditions. The Cl2 produced by the mixed salt eutectic reaction acted as a catalytic carrier to accelerate the volatilisation of the chloride inside the oxide layer and the re-oxidation of the substrate. In addition, the growth of unprotected corrosion products (Na2TiO3, NaNbO3 and AlNbO4) altered the internal structure of the oxide layer, destroying the surface densification and causing severe damage to the alloy surface.
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Falk, Martin, i Michael Hausmann. "A Paradigm Revolution or Just Better Resolution—Will Newly Emerging Superresolution Techniques Identify Chromatin Architecture as a Key Factor in Radiation-Induced DNA Damage and Repair Regulation?" Cancers 13, nr 1 (23.12.2020): 18. http://dx.doi.org/10.3390/cancers13010018.
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DNA double-strand breaks (DSBs) have been recognized as the most serious lesions in irradiated cells. While several biochemical pathways capable of repairing these lesions have been identified, the mechanisms by which cells select a specific pathway for activation at a given DSB site remain poorly understood. Our knowledge of DSB induction and repair has increased dramatically since the discovery of ionizing radiation-induced foci (IRIFs), initiating the possibility of spatiotemporally monitoring the assembly and disassembly of repair complexes in single cells. IRIF exploration revealed that all post-irradiation processes—DSB formation, repair and misrepair—are strongly dependent on the characteristics of DSB damage and the microarchitecture of the whole affected chromatin domain in addition to the cell status. The microscale features of IRIFs, such as their morphology, mobility, spatiotemporal distribution, and persistence kinetics, have been linked to repair mechanisms. However, the influence of various biochemical and structural factors and their specific combinations on IRIF architecture remains unknown, as does the hierarchy of these factors in the decision-making process for a particular repair mechanism at each individual DSB site. New insights into the relationship between the physical properties of the incident radiation, chromatin architecture, IRIF architecture, and DSB repair mechanisms and repair efficiency are expected from recent developments in optical superresolution microscopy (nanoscopy) techniques that have shifted our ability to analyze chromatin and IRIF architectures towards the nanoscale. In the present review, we discuss this relationship, attempt to correlate still rather isolated nanoscale studies with already better-understood aspects of DSB repair at the microscale, and consider whether newly emerging “correlated multiscale structuromics” can revolutionarily enhance our knowledge in this field.
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Xu, Zhi-Hui, Young-Bae Park i Xiaodong Li. "Nano/micro-mechanical and tribological characterization of Ar, C, N, and Ne ion-implanted Si". Journal of Materials Research 25, nr 5 (maj 2010): 880–89. http://dx.doi.org/10.1557/jmr.2010.0117.
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Ion implantation has been widely used to improve the mechanical and tribological properties of single crystalline silicon, an essential material for the semiconductor industry. In this study, the effects of four different ion implantations, Ar, C, N, and Ne ions, on the mechanical and tribological properties of single crystal Si were investigated at both the nanoscale and the microscale. Nanoindentation and microindentation were used to measure the mechanical properties and fracture toughness of ion-implanted Si. Nano and micro scratch and wear tests were performed to study the tribological behaviors of different ion-implanted Si. The relationship between the mechanical properties and tribological behavior and the damage mechanism of scratch and wear were also discussed.
Rozprawy doktorskie na temat "Microscale damage mechanism"
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Damaghi, Mehdi Verfasser], Daniel [Akademischer Betreuer] Mueller, Stefan [Akademischer Betreuer] Diez i Petra [Akademischer Betreuer] [Schwille. "Characterizing the Functional and Folding Mechanism of β-barrel Transmembrane Proteins Using Atomic Force Microscope / Mehdi Damaghi. Gutachter: Stefan Diez ; Petra Schwille. Betreuer: Daniel Mueller". Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://d-nb.info/1068152710/34.
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Abhilash, M. N. "Microscale mechanical behaviour of ceramic matrix composites considering processing e ects". Thesis, 2022. https://etd.iisc.ac.in/handle/2005/5985.
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The current work explores the phenomenon of microscale damage mechanism driven quasi-
ductile behaviour of C/BN/SiC ceramic matrix composite (CMC) at the microscale focusing
on process-microstructure-property correlations. C/BN/SiC minicomposites have been fabri-
cated by chemical vapour infiltration (CVI) with varying interphase thicknesses and constituent
volume fractions by varying the interphase (BN) and matrix (SiC) in filtration durations. The
effect of processing durations on the resulting microstructure, tensile response and damage
mechanisms up to and during ultimate failure of CMC minicomposites have been obtained ex-
perimentally that highlight the significant infuence of processing duration on the tensile and
failure behaviour of CMC minicomposites.
Processing induced micro-scale matrix porosity in the fabricated minicomposites has been
characterized by X-ray micro-computed tomography. Effective elastic properties in the presence
of matrix micro-pores have been obtained by a two-step numerical homogenization approach
that includes the statistical distributions of pore parameters obtained from experimental char-
acterization. A variation of the approach has been utilized to investigate the severity of pores
with respect to their location and orientation relative to the fiber reinforcement.
A probabilistic progressive damage modeling approach has been proposed to predict the
tensile response of CMC minicomposites considering the microstructural information from fab-
ricated minicomposites. The highlight of the proposed numerical approach is the development
of a 3 phase shear lag model to better approximate matrix crack driven stress transfer in the
presence of an interphase between the ber and the matrix. The in
uence of volume frac-
tions, constituent properties and interfacial properties on the mechanical behavior of CMC
minicomposites have been presented.
The presented approaches and results provide an insight into the processing-microstructure-
tensile response relationship and the e ect of processes induced defects on the tensile response
in CMCs. Additionally, modeling approaches have been proposed for predicting the tensile
response of CMCs at the microscale considering processing induced defects.
Książki na temat "Microscale damage mechanism"
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Lee, H. K., B. R. Kim i S. Na. Microscale damage analysis for microcrack propagation of brittle composite materials. Hauppauge, N.Y: Nova Science, 2010.
Znajdź pełny tekst źródłaCzęści książek na temat "Microscale damage mechanism"
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Ge, Jia, Wei Tan, Giuseppe Catalanotti, Brian G. Falzon, John McClelland, Colm Higgins, Yan Jin i Dan Sun. "Understanding Chip Formation in Orthogonal Cutting of Aeronautical Thermoplastic CF/PEKK Composites Based on Finite Element Method". W Advances in Transdisciplinary Engineering. IOS Press, 2022. http://dx.doi.org/10.3233/atde220584.
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There has been an enormous increase in using of carbon fiber reinforced thermoplastic (CFRTP) especially carbon fiber reinforce polyetherketoneketone (CF/PEKK) in automotive and aeronautical industries. However, fundamental material removal mechanism of such material has never been elucidated in the literature. In this work, finite-element (FE) method is deployed and microscale numerical model considering fiber, matrix and interface has been established to understand the mechanisms of chip formation in orthogonal cutting of unidirectional (UD) thermoplastic CF/PEKK composites. Chip formation and subsequent surface / subsurface damage with different fiber orientations (0°, 45°, 90°, 135°) are modelled and compared. Results suggest that, for CF/PEKK, the chip formation mechanism is significantly affected by the fiber orientation and the most severe subsurface damage can be seen at fiber orientation 135°, as a result of bending fracture below the ideal machined surface.
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Chen, Fei, Chaohui Yan i Bo Zhou. "Study on Damage Mechanism of Fracturing Fluid Reservoir and RBF Neural Network Prediction". W Advances in Transdisciplinary Engineering. IOS Press, 2022. http://dx.doi.org/10.3233/atde221097.
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At present, tight oil and gas reservoirs must adopt fracturing technology to obtain productivity, which will not only transform the reservoir, but also bring reservoir damage. Taking Chang-7 member of Ordos Basin as the research object, the relationship between physical properties of tight oil reservoir and fracturing fluid damage is analyzed based on experimental analysis of reservoir physical properties, cast thin sections, electron microscope scanning, X-ray diffraction and sensitivity test. Using the traditional damage evaluation method requires a large number of cores, and core resources, as a nonrenewable precious resource, have been paid more and more attention. Therefore, the use of prediction is conducive to protecting core resources, reducing experimental costs, and improving work efficiency. Therefore, a mathematical prediction model of RBF neural network is proposed, which establishes the complex nonlinear relationship between the physical properties of Chang 7 reservoir and fracturing fluid damage in Ordos Basin. Taking 22 groups of data of Chang 7 reservoir as training data, the fitting rate of training data is 90%. Taking the other two groups of data as detection data, the error between prediction and actual experiment is less than 10%. The prediction shows that the error inside and outside the sample predicted by RBF neural network is small, the prediction accuracy of the model is high, the generalization ability is strong, and the prediction value is closer to the value obtained by laboratory experiments than BP neural network, which can provide a good theoretical basis for fracturing fluid optimization.
Streszczenia konferencji na temat "Microscale damage mechanism"
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Chandra, A., Y. Huang, Z. Q. Jiang i K. X. Hu. "A Model of Crack Nucleation in Layered Electronic Assemblies Under Thermal Cycling". W ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-0926.
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Abstract A model for crack nucleation in layered electronic assemblies under thermal cycling is developed in this paper. The present model includes three scales: (i) at the microscale or the mechanism level, the damage mechanisms such as diffusive void growth or fatigue cracks, determine the damage growth rate; (2) at an intermediate mesoscale, the localized damage bands are modeled as variable stiffness springs connecting undamaged materials; and (iii) at the macroscale or the continuum level, the localized damage band growing in an otherwise undamaged material is modeled as an array of dislocations. The three scales are then combined together to incorporate damage mechanisms into continuum analysis. Traditional fracture mechanics provides a crack propagation model based on pre-existing cracks. The present work provides an approach for predicting crack nucleation. The proposed model is then utilized to investigate crack nucleations in three-layered electronic assemblies under thermal cycling. The damage is observed to accumulate rapidly in the weakest regions of the band. Estimates are obtained for critical time or critical number of cycles at which a macroscopic crack will nucleate in these assemblies under thermal cycling. This critical number of cycles is found to be insensitive to the size of the damage cluster, but decreases rapidly as the local excess damage increases.
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Luo, Chuntao, Jun Wei, Aditi Chattopadhyay i Hanqing Jiang. "A Void Growth and a Cyclic Model in Ductile Material Using Mechanism-Based Strain Gradient Crystal Plasticity Theory". W ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-42612.
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This paper addresses the problem of theoretically predicting the evolution of void for a single crystal in ductile material accounting to the size and orientation effects. In this paper, a new damage model is derived based on the theory of mechanism-based strain gradient crystal plasticity (MSG-CP). By imposing the Taylor dislocation model into a widely used Gurson model (1), we extend the Gurson model to account for the void size effect. Meanwhile, we consider the crystal orientation effect by using MSG-CP to describe the behavior of matrix. Numerical simulation has been conducted under axisymmetric loading condition for cylindrical void and under spherical symmetric tension for spherical void. It reveals that the damage of a ductile porous material has strong orientation-dependence and size-dependence on microscale level. The traditional conclusion that the larger the void size is the faster it grows is also verified by the new model. Additionally, we add a kinematic hardening law to the MSG-CP theory, and have analyzed a hysteresic response of a single crystal under cyclic loading.
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Hagengruber, Tyler L. "Strength effects of microfracture on granular microstructures evaluated by FDEM direct numerical simulation". W 56TH US ROCK MECHANICS / GEOMECHANICS SYMPOSIUM. OnePetro, 2022. http://dx.doi.org/10.56952/arma-2022-2209.
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We present results of an investigation into the mechanisms of damage in granular microstructures conducted through direct numerical simulation with the combined Finite-Discrete Element Method (FDEM). Scanning Electron Microscope (SEM) images of a pressed crystalline powder are directly meshed, resolving grain-grain interfaces. Semi-ductile microfracture is simulated by prescribing a combination of inter-granular brittle fracture and intra-granular grain plasticity. Pristine (undamaged) and damaged microstructures are simulated in uniaxial compression tests and compared to experimental uniaxial compression measurements from literature. The simulation results show that the observed microscale mechanisms of damage (microfracture predominantly around and sometimes through grains and crack associated pore-growth) can well explain degradation of strength observed in the laboratory measurements. A method of tracing grain boundaries from SEM images is described and applied to meshing of a microstructure damaged through cyclic thermal loading. By calibrating the simulations to the damaged and undamaged experimental measurements, micro-mechanical/structural insight is gained into the mechanisms of damage for the material. The results show that the SEM-based micro-characterization of damage can explain the degradation in effective strength observed in the testing and can be accurately modeled using the presented methods.
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Nguyen, Ba Nghiep, Brian J. Tucker i Mohammad A. Khaleel. "Damage in Short-Fiber Composites: From the Microscale to the Continuum Solid". W ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-59129.
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This paper proposes a multiscale mechanistic approach to damage in short-fiber polymer composites (SFPC). At the microscale, the damage mechanisms are analyzed using micromechanical modeling, and the associated damage variables are defined. The stiffness reduction law dependent on these variables is then established. The macroscopic response is determined using thermodynamics of continuous media, continuum damage mechanics and finite element analysis. Final failure resulting from saturation of matrix microcracks, fiber/matrix debonding, fiber pull-out and breakage is modeled by a vanishing element technique. The model was validated using the experimental data and results from literature, as well as those obtained from a random glass/vinyl ester system.
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Yang, N. H., i H. Nayeb-Hashemi. "Evaluation of Solid Particle Erosion Damage on E-Glass/Epoxy Composites Using Acoustic Emission Activity". W ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-79278.
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The effect of solid particle erosion on the strength properties of E-glass/epoxy composite was investigated. Solid particle erosion with SiC particles 400 μm to 500 μm in diameter was simulated on 12 ply [45°/−45°/0°/45°/−45°/0°]s E-glass/epoxy composites with constant particle velocity of 42.5 m/s at impact angles of 90°, 60°, and 30° for 30, 60, 90 and 120 seconds. Damaged and undamaged specimens were subjected to tensile tests while monitoring their acoustic emission (AE) activity. An erosion damage parameter was defined as a function of the particle impact angle and erosion duration to determine the residual tensile strength of the composite. Scanning electron microscope (SEM) images of the erosion damaged specimens revealed the same damage mechanism occurred at different impact angles. The distribution of AE events by event duration, ring down counts and energy distribution were used to characterize the different damage mechanisms that occurred during tensile loading of damaged and undamaged specimens. The results showed AE activity could be used to distinguish between different damage mechanisms within the composite, such as fiber/matrix debonding, delamination and fiber fracture. The Weibull probability distribution model and the AE stress delay parameter model were developed to relate the AE activity to the erosion damage and residual strength. The results showed both the Weibull probability model and the stress delay model could be used to predict residual strength of the composites.
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Konuma, Keitaro, Masahiro Toyosada i Koji Gotoh. "Fatigue Damage at the Root of the Gate Lip of the Water Gate Under Variable Water Pressure Due to Tide and Ocean Wave". W 25th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/omae2006-92129.
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The steel water gate, which received variable water pressure due to gap of water level between sea and balancing reservoir, damaged in its gate lip by fatigue crack. In order to find the cause of this damage, various investigate programs, including observation with microscope and measurement of stress and water level, were performed. By the comprehensive analysis of the results of these investigation programs, it was concluded that this damage was caused by the cyclic loading on the gate lip from the ground surface, and found out the relation between sea water level and stress occur at damaged point. After then, the damaged part was replaced with new reinforced element. In addition, for checking the effect of this measure, the crack growth estimation was executed with FLARP, the numerical simulation code which was developed by the authors. As the result of the numerical simulation, the crack growth curve became visible quantitatively, and it was confirmed that the possibility of the reoccurrence of the fatigue crack was removed by the measures which we took, under the assumed loading condition.
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Li, Dong-Feng, i Noel P. O’Dowd. "Investigating Ductile Failure at the Microscale in Engineering Steels: A Micromechanical Finite Element Model". W ASME 2012 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/pvp2012-78802.
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In this study, we present a microstructure-based micromechanical model to quantify failure mechanisms in engineering steels. Crystal plasticity at the microscale, governed by crystallographic slip, is explicitly taken into account in the frame-work of continuum mechanics. Furthermore, it is assumed that material damage at the microscale is controlled by the accumulated equivalent plastic strain, such that failure occurs once this strain exceeds a threshold. Both single- and poly-crystalline materials containing sufficient numbers of grains are investigated under a representative macroscopic loading. The calibration of the present model relies on uniaxial tensile test data. Both austenitic stainless steels (such as 316H) and martensitic steels (such as P91) are examined to illustrate the application of the method. The micromechanical modelling provides insights into understanding of the mechanical response at the microscale in engineering steels.
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Iizuka, Hiroshi, Jun Yamashita i Akihiko Tokuda. "Fatigue Failure Mechanism of CVT Rubber Belts". W ASME 2007 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/detc2007-34044.
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The fatigue failure mechanism was investigated for the rubber CVT (continuously variable transmission) belts. There are three major crack initiation modes in the rubber CVT belts, namely the adhesive rubber crack, the backing rubber crack and the bottomland crack. Especially, the mode of the adhesive rubber crack is important to strengthen the rubber CVT belts, because the crack is the most difficult to find out during the driving. In this study, the failure morphology of the damaged belts was observed using an optical microscope and a X-ray CT scan after some fatigue tests. Moreover, the failure mechanism of the adhesive rubber crack was discussed basing on the FEM and simplified mechanical analyses. The fatigue damage was accumulated along the interface between the cog rubber and the adhesive rubber. The interface was de-bonded by the shearing strain, which was induced by the dishing deformation of the belt within the pulley groove.
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Bhate, Dhruv, Kaushik Mysore i Ganesh Subbarayan. "A Multiscale Damage Accumulation Theory for Solder Joint Failure". W ASME 2009 InterPACK Conference collocated with the ASME 2009 Summer Heat Transfer Conference and the ASME 2009 3rd International Conference on Energy Sustainability. ASMEDC, 2009. http://dx.doi.org/10.1115/interpack2009-89399.
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In heterogeneous micro structures that include several grains, secondary phases and interfaces, cracks are known to initiate and grow through different mechanisms. The failure processes however are not well understood. Solder alloys in general, and Pb-free alloys in particular possess complex, heterogeneous microstructures that evolve in fracture in ways that are challenging to model. Often, underlying a fracture observed under a microscope is a hierarchy of fracture-related phenomenon from atomic to macro length-scales. In this paper we develop a failure model inspired by information theory and continuum thermodynamics to capture the multiscale fracture processes in solder joints. We systematically develop measures of dissipation from continuum thermodynamics for materials described by J2 plasticity theory. Crack growth is known to be dissipative and such measures are natural candidates for predicting failure within a mechanics framework. The dissipation estimates, multiple fracture mechanisms and the notions of continuity, monotonicity and composition borrowed from information theory suggest a single model as being capable of predicting both ductile and brittle types of failures.
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Kanaga Karuppiah, K. S., Angela L. Bruck i Sriram Sundararajan. "Evaluation of Friction Behavior and Contact Area Dependence at the Micro and Nanoscales". W ASME/STLE 2007 International Joint Tribology Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ijtc2007-44216.
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In this work, we have compared the friction behavior of two different materials (a) mica and (b) ultra-high molecular weight polyethylene (UHMWPE) at two length scales. The friction experiments were carried out at the nanoscale with an atomic force microscope (AFM) and at the microscale, with a custom-built microtribometer. The material interface (Si3N4 probe) and the environmental conditions (RH < 10%) were kept the same at both the scales. The friction data obtained were analyzed for dependence on normal load or contact area, based on which, a coefficient of friction has been reported or an appropriate contact mechanics theory was applied and an interfacial shear strength value was calculated for the material pair. Friction between a silicon nitride and UHMWPE interface resulted in contact area dependence at both the length scales, for the applied load ranges of our experiment. Friction between silicon nitride and mica at the nanoscale showed an initial nonlinearity and then exhibited damage and linearity with normal load beyond certain loads. At the microscale, the mica-silicon nitride interface resulted in a linear friction behavior.