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Zhenjun Yang - One of the best experts on this subject based on the ideXlab platform.
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automatic modelling of cohesive Crack Propagation in concrete using polygon scaled boundary finite elements
Engineering Fracture Mechanics, 2012Co-Authors: Ean Tat Ooi, Chongmin Song, F Tinloi, Zhenjun YangAbstract:An automatic cohesive Crack Propagation modelling methodology for quasi-brittle materials using polygon elements is presented. Each polygon is treated as a subdomain that is modelled by the scaled boundary finite element method (SBFEM). Generalised stress intensity factors (SIFs) based on matrix power function solutions of singular stress fields obtained from the SBFEM following standard finite element stress recovery procedures is used to evaluate the Crack Propagation criterion and determine the Crack Propagation direction. Interface elements model the fracture process zones and are automatically inserted into the polygon mesh as the Crack propagates. A shadow domain procedure couples the polygons and interface elements. It computes the load–displacement response and Crack Propagation criterion, taking into account the cohesive tractions on the Crack edges that are modelled as side-face tractions in the SBFEM. Cracks are propagated using a simple, yet flexible local remeshing procedure that can remesh any arbitrary polygon. Only minimal changes are made to the global mesh structure each time the remeshing algorithm is called. Five cohesive Crack Propagation benchmarks are modelled to validate the developed method and demonstrate its salient features.
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polygon scaled boundary finite elements for Crack Propagation modelling
International Journal for Numerical Methods in Engineering, 2012Co-Authors: Ean Tat Ooi, Chongmin Song, F Tinloi, Zhenjun YangAbstract:SUMMARY An automatic Crack Propagation modelling technique using polygon elements is presented. A simple algorithm to generate a polygon mesh from a Delaunay triangulated mesh is implemented. The polygon element formulation is constructed from the scaled boundary finite element method (SBFEM), treating each polygon as a SBFEM subdomain and is very efficient in modelling singular stress fields in the vicinity of Cracks. Stress intensity factors are computed directly from their definitions without any nodal enrichment functions. An automatic remeshing algorithm capable of handling any n-sided polygon is developed to accommodate Crack Propagation. The algorithm is simple yet flexible because remeshing involves minimal changes to the global mesh and is limited to only polygons on the Crack paths. The efficiency of the polygon SBFEM in computing accurate stress intensity factors is first demonstrated for a problem with a stationary Crack. Four Crack Propagation benchmarks are then modelled to validate the developed technique and demonstrate its salient features. The predicted Crack paths show good agreement with experimental observations and numerical simulations reported in the literature. Copyright © 2012 John Wiley & Sons, Ltd.
David Taylor - One of the best experts on this subject based on the ideXlab platform.
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physically short Crack Propagation in metals during high cycle fatigue
International Journal of Fatigue, 2009Co-Authors: Ciro Santus, David TaylorAbstract:Abstract In metals, during high cycle fatigue on plain specimens, almost the entire fatigue life is spent as short Crack initiation and Propagation. The fatigue short Crack life can be schematically divided into two subsequent phases: microstructurally short Crack and physically short Crack. Recently, Chapetti proposed a physically short Crack threshold and Propagation driving force model [Chapetti MD. Fatigue Propagation threshold of short Cracks under constant amplitude loading. Int J Fatigue 2003;25(12):1319–1326]. In his model the physically short Crack behavior is obtained from the long Crack Propagation, just introducing the reduced threshold due to unsaturated closure. In the present paper the physically short Crack Propagation is similarly modeled by means of a driving force equation, but independent from the long Crack Propagation. In this way, a better description of the short Crack behavior is provided, however short Crack Propagation data is required. Physically short Crack Propagation model parameters were obtained, by fitting experimental data drawn from the literature, for two aluminum alloys and a titanium alloy at two different heat treatment conditions and load ratios. By calculating the physically short Crack plus long Crack Propagation, and assuming microstructurally short Crack as part of the initiation stage, a purer information about Crack initiation can be drawn from the S – N curves, and it is shown in the paper for the investigated materials. A precise Crack initiation size and the number of cycles just for initiation are then provided. This information is useful to accurately predict fatigue life for blunt notched and for thick components, where the Propagation is much higher than in the small plain specimen. A validation of the model was obtained by predicting the fatigue life of a notched specimen. An accurate prediction was obtained both when the initiation was much smaller than Propagation and when almost the entire fatigue life was initiation.
Mahmood Mamivand - One of the best experts on this subject based on the ideXlab platform.
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phase field modeling of Crack Propagation in shape memory ceramics application to zirconia
Computational Materials Science, 2020Co-Authors: Ehsan Moshkelgosha, Mahmood MamivandAbstract:Abstract Shape memory ceramics (SMCs) are promising candidates for actuators in extreme environments such as high temperature and corrosive applications. Despite outstanding energy dissipation, compared to metallic shape memory materials, SMCs suffer from a sudden brittle fracture. While the interaction of Crack Propagation and phase transformation in SMCs have been subject of several experimental and theoretical studies, mainly at the macroscale, the fundamental understanding of the dynamic interaction of Crack Propagation and martensitic transformation is poorly understood. In this work, we use the phase field framework to fully couple the martensitic transformation to the variational formulation of brittle fracture. The model is parameterized for single crystal zirconia which experiences tetragonal to monoclinic transformation during Crack Propagation. For the mode I of fracture, the opening mode, Crack shows an unusual Propagation path that is in good agreement with the experiments and indicates the significant role of phase transformation on the Crack Propagation path. The investigation on the effect of lattice orientation on Crack Propagation shows that the lattice orientation has a significant influence not only on the Crack Propagation path but also on the magnitude of the transformation toughening. In a constrained crystal the maximum (minimum) toughening, under mode I loading, occurs when the crystal lattice orientation makes the angle of 50 (90) degrees with the Crack surface.
Hans Albert Richard - One of the best experts on this subject based on the ideXlab platform.
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Crack Propagation in fracture mechanical graded structures
Frattura ed Integrità Strutturale, 2015Co-Authors: Britta Schramm, Hans Albert RichardAbstract:The focus of manufacturing is more and more on innovative and application-oriented products considering lightweight construction. Hence, especially functional graded materials come to the fore. Due to the application-matched functional material gradation different local demands such as absorbability, abrasion and fatigue of structures are met. However, the material gradation can also have a remarkable influence on the Crack Propagation behavior. Therefore, this paper examines how the Crack Propagation behavior changes when a Crack grows through regions which are characterized by different fracture mechanical material properties (e.g. different threshold values ?KI,th, different fracture toughness ?KIC). In particular, the emphasis of this paper is on the beginning of stable Crack Propagation, the Crack velocity, the Crack Propagation direction as well as on the occurrence of unstable Crack growth under static as well as cyclic loading. In this context, the developed TSSR-concept is presented which allows the prediction of Crack Propagation in fracture mechanical graded structures considering the loading situation (Mode I, Mode II and plane Mixed Mode) and the material gradation. In addition, results of experimental investigations for a mode I loading situation and numerical simulations of Crack growth in such graded structures confirm the theoretical findings and clarify the influence of the material gradation on the Crack Propagation behavior. KEYWORDS. Functional fracture mechanical gradation; Crack Propagation direction; TSSR-concept; Experimental investigations; Numerical simulations.
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Crack Propagation in fracture mechanical graded structures
Gruppo Italiano Frattura, 2015Co-Authors: Britta Schramm, Hans Albert RichardAbstract:The focus of manufacturing is more and more on innovative and application-oriented products considering lightweight construction. Hence, especially functional graded materials come to the fore. Due to the application-matched functional material gradation different local demands such as absorbability, abrasion and fatigue of structures are met. However, the material gradation can also have a remarkable influence on the Crack Propagation behavior. Therefore, this paper examines how the Crack Propagation behavior changes when a Crack grows through regions which are characterized by different fracture mechanical material properties (e.g. different threshold values KI,th, different fracture toughness KIC). In particular, the emphasis of this paper is on the beginning of stable Crack Propagation, the Crack velocity, the Crack Propagation direction as well as on the occurrence of unstable Crack growth under static as well as cyclic loading. In this context, the developed TSSR-concept is presented which allows the prediction of Crack Propagation in fracture mechanical graded structures considering the loading situation (Mode I, Mode II and plane Mixed Mode) and the material gradation. In addition, results of experimental investigations for a mode I loading situation and numerical simulations of Crack growth in such graded structures confirm the theoretical findings and clarify the influence of the material gradation on the Crack Propagation behavior
K Tanaka - One of the best experts on this subject based on the ideXlab platform.
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Fatigue Crack Propagation in short-fiber reinforced plastics
Gruppo Italiano Frattura, 2015Co-Authors: K Tanaka, K. Oharada, D. Yamada, K. ShimizuAbstract:The influence of fiber orientation on the Crack Propagation behavior was studied with single edgenotched specimens which were cut from an injection-molded plate of short-fiber reinforced plastics of polyphenylenesulphide (PPS) reinforced with 30wt% carbon fibers. Specimens were cut at five fiber angles relative to the molding direction, i.e. = 0° (MD), 22.5°, 45°, 67.5°, 90° (TD). Fracture mechanics parameters derived based on anisotropic elasticity were used as a Crack driving force. Macroscopic Crack Propagation path was nearly perpendicular to the loading axis for the cases of MD and TD. For the other fiber angles, the Crack path was inclined because the Crack tended to propagate along inclined fibers. For mode I Crack Propagation in MD and TD, the resistance to Crack Propagation is improved by fiber reinforcement, when the rate is correlated to the range of stress intensity factor. The Crack Propagation rate, da/dN, was slowest for MD and fastest for TD. For each material, the Crack Propagation rate is higher for larger R ratio. The effect of R ratio on da/dN diminished in the relation between da/dN and the range of energy release rate, GI. Difference among MD, TD and matrix resin becomes small when da/dN correlated to a parameter corresponding the Crack-tip radius, HGI, where H is compliance parameter. Fatigue Cracks propagated under mixed loading of mode I and II for the fiber angles other than 0° and 90°. The data of the Crack Propagation rate correlated to the range of total energy release rate, Gtotal, lie between the relations obtained for MD and TD. All data of Crack Propagation tend to merge a single relation when the rate is correlated to the range of total energy release rate divided by Young’s modulus
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Crack Propagation in lead free solder under cyclic loading of mode i and ii
Principles and Practice of Constraint Programming, 2013Co-Authors: K TanakaAbstract:Crack Propagation tests of lead-free solder were conducted using centerCrackedplates for cyclic tension-compression and thin-walled tubular specimens forcyclic torsion. Both specimens have an initial notch as a Crack starter. In fatigueloading with fast loading rates, the path of Crack Propagation under tensioncompressionwas macroscopically straight, perpendicular to the maximum principalstress direction. In tubular specimens under cyclic torsion, at the high strain range, theCrack propagate in shear mode II along the maximum shear direction. At low strainrange, four Cracks are formed from the initial silt and propagate showingmacroscopically tensile mode. The introduction of creep components by tension holdpropromoted shear-mode Crack Propagation under tension compression. For fatigueloading, the Crack Propagation rate was expressed as a power function of the fatigue Jintegraland the relation was not much different between tension-compression andcyclic torsion. The tension hold, or the creep component, during tension-compressionloading greatly accelerates the Crack Propagation rate. Both cycle-dependent fatiguePropagation and time-dependent creep-fatigue Propagation of Cracks took place byjoining microCracks formed along the maximum shear planes ahead of the Crack tip
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creep fatigue Crack Propagation in lead free solder under various strain waveforms
Transactions of the Japan Society of Mechanical Engineers. A, 2011Co-Authors: K Tanaka, Ryota Sakai, Takuya Hirasawa, Yusuke Sakagawa, Kazunari FujiyamaAbstract:Crack Propagation tests of lead-free solder were conducted using center-notched plates under strain-controlled conditions of fast-fast (pp), slow-slow (cc), slow-fast (cp), and fast-slow (pc) strain waveforms. A method to estimate creep J-integral and fatigue J-integral from load-displacement relations was proposed, and those integrals were used to correlate the Crack Propagation rate. For the case of pp waveform, the Crack Propagation rate was expressed as a power function of the fatigue J-integral. For the other cases, the creep component greatly accelerates the Crack Propagation rate when compared at the same values of the fatigue J-integral. The creep Crack Propagation rate was expressed as a power function of the creep J-integral for each case of cp, pc and cc waveforms. The Crack Propagation rate for cp and pc waveform is higher than that for cc waveform. In fatigue loading under pp waveform, the path of Crack Propagation was macroscopically straight, perpendicular to the maximum principal stress direction. The introduction of creep components by slow strain rates promoted shear-mode Crack Propagation. The predominant feature of fracture surfaces observed by scanning electron microscopy was striations for pp waveform, and grain boundary fracture for cp and pc waveforms. Grain fragmentation was evident on the fracture surface made under cc waveform.
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creep fatigue Crack Propagation in lead free solder under cyclic loading with various waveforms
Engineering Fracture Mechanics, 2010Co-Authors: K TanakaAbstract:Abstract Crack Propagation tests of lead-free solder were conducted using center-notched plate specimens under cyclic tension–compression of three load waveforms: pp waveform having fast loading and unloading, cp-h waveform having a hold time under tension, and cc-h waveform having a hold time under tension and compression. In the case of fatigue loading, i.e. pp waveform, the path of Crack Propagation was macroscopically straight and perpendicular to the maximum principal stress direction, showing tensile-mode Crack Propagation. The introduction of the creep components by hold time in cc-h and cp-h waveforms promoted shear-mode Crack Propagation. For fatigue loading of pp wave, the Crack Propagation rate was expressed as a power function of the fatigue J integral and the relation was identical for load-controlled and displacement-controlled conditions. The creep component due to the hold time greatly accelerates the Crack Propagation rate when compared at the same values of the fatigue J integral or the total J integral (the sum of fatigue J and creep J integrals). The creep Crack Propagation rate was expressed as a power function of the creep J integral for each case of cp-h and cc-h waveforms. The Crack Propagation rate for cp-h waveform is higher than that for cc-h waveform. The predominant feature of fracture surfaces was striations for pp waveform and grain boundary fracture for cp-h waveform. Grain fragmentation was abundantly observed on the fracture surface made under cc-h waveform.
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effect of load waveform on creep fatigue Crack Propagation in lead free solder
Journal of The Society of Materials Science Japan, 2010Co-Authors: K Tanaka, Takuya Hirasawa, Yusuke Sakagawa, Kazunari FujiyamaAbstract:Crack Propagation tests of lead-free solder were conducted using center-notched plates under cyclic tension-compression of three waveforms : pp waveform having fast loading and unloading rates, cp-h waveform having a hold time under tension, and cc-h waveform having a hold time under tension and compression. In fatigue loading at fast loading-unloading rates, i.e. pp waveform, the path of Crack Propagation was macroscopically straight, perpendicular to the maximum principal stress direction. The introduction of creep components by tension and compression holds in cc-h waveform promoted shear-mode Crack Propagation even under tension-compression loading. For fatigue loading of pp waveform, the Crack Propagation rate was expressed as a power function of the fatigue J-integral and the relation was identical for load-controlled and displacement-controlled conditions. The creep component due to the hold time greatly accelerates the Crack Propagation rate when compared at the same values of the fatigue J integral or the total J integral (the sum of fatigue J and creep J integrals). The creep Crack Propagation rate was expressed as a power function of the creep J integral for each case of cp-h and cc-h waveforms. The Crack Propagation rate for cp-h waveform is higher than that for cc-h waveform. The predominant feature of fracture surfaces was striations for pp waveform and grain boundary fracture for cp-h waveform. Grain fragmentation was evident on the fracture surface made by cc-h waveform.