The Experts below are selected from a list of 438048 Experts worldwide ranked by ideXlab platform
Jurg Schweizer - One of the best experts on this subject based on the ideXlab platform.
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Modeling of crack propagation in weak snowpack layers using the discrete element method
The Cryosphere, 2015Co-Authors: Johan Gaume, A. Van Herwijnen, G Chambon, Jurg SchweizerAbstract:Abstract. Dry-snow slab avalanches are generally caused by a sequence of fracture processes including (1) Failure initiation in a weak snow layer underlying a cohesive slab, (2) crack propagation within the weak layer and (3) tensile fracture through the slab which leads to its detachment. During the past decades, theoretical and experimental work has gradually led to a better understanding of the fracture process in snow involving the collapse of the structure in the weak layer during fracture. This now allows us to better Model Failure initiation and the onset of crack propagation, i.e., to estimate the critical length required for crack propagation. On the other hand, our understanding of dynamic crack propagation and fracture arrest propensity is still very limited. To shed more light on this issue, we performed numerical propagation saw test (PST) experiments applying the discrete element (DE) method and compared the numerical results with field measurements based on particle tracking. The goal is to investigate the influence of weak layer Failure and the mechanical properties of the slab on crack propagation and fracture arrest propensity. Crack propagation speeds and distances before fracture arrest were derived from the DE simulations for different snowpack configurations and mechanical properties. Then, in order to compare the numerical and experimental results, the slab mechanical properties (Young's modulus and strength) which are not measured in the field were derived from density. The simulations nicely reproduced the process of crack propagation observed in field PSTs. Finally, the mechanical processes at play were analyzed in depth which led to suggestions for minimum column length in field PSTs.
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discrete element Modeling of crack propagation in weak snowpack layers
International Snow Science Workshop 2014 Proceedings Banff Canada, 2014Co-Authors: Jurg SchweizerAbstract:Dry-snow slab avalanches are generally caused by a sequence of fracture processes including (1) Failure initiation in a weak snow layer underlying a cohesive slab, (2) crack propagation within the weak layer and (3) tensile fracture through the slab which leads to its detachment. During the past decades, theoretical and experimental work has gradually led to a better understanding of the fracture process in snow involving the collapse of the structure in the weak layer during fracture. This now allows us to better Model Failure initiation and the onset of crack propagation, i.e. to estimate the critical length required for crack propagation. On the other hand, our understanding of dynamic crack propagation is still very limited. For instance, it is not uncommon to perform field measurements with widespread crack propagation on one day, while a few days later, with very little changes to the snow- pack, crack propagation does not occur anymore. Thus far, there is no clear theoretical framework to interpret such observations, and it is not clear how and which snowpack properties affect dynamic crack propagation. To shed more light on this issue, we performed numerical propagation saw test (PST) experiments applying the discrete element (DE) method and compared the numerical results with field measurements based on particle tracking. The goal is to investigate the influence of weak layer Failure and the mechanical properties of the slab on crack propagation. Crack propagation veloci- ties and distances before fracture arrest derived from the DE simulations were in good agreement with experimental data suggesting that the simulations can reproduce crack propagation in PSTs.
Venkitanarayanan Parameswaran - One of the best experts on this subject based on the ideXlab platform.
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experimental and numerical investigation on the uni axial tensile response and Failure of fiber metal laminates
Composites Part B-engineering, 2017Co-Authors: Ankush P Sharma, Sanan H Khan, Venkitanarayanan ParameswaranAbstract:Abstract Fiber metal laminates (FMLs) consist of layers of thin metallic sheets and fiber reinforced composite layers bonded together. In the present study, the tensile response of FMLs consisting of aluminum 2024-T3 (Al) sheets of thicknesses 0.2, 0.4, and 0.6 mm and uni-directional glass-fiber reinforced composite layers are investigated. FMLs having three different stacking sequences, all having the same total metal layer thickness were prepared using the hand layup process. The results of the tensile tests indicated that the layup sequence did not have any influence on the initial modulus of the FMLs. However, the ultimate strength and the post ultimate strength behavior of the FMLs are significantly affected by the layup sequence. In order to gain more insight into the sequence of damage evolution, a detailed finite element analysis (FEA) of the tests was also carried using the commercial software ABAQUS. The Hashin Failure criterion was used to Model Failure of composite layers and cohesive surface interaction was used to capture inter-layer delamination.
Johan Gaume - One of the best experts on this subject based on the ideXlab platform.
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Modeling of crack propagation in weak snowpack layers using the discrete element method
The Cryosphere, 2015Co-Authors: Johan Gaume, A. Van Herwijnen, G Chambon, Jurg SchweizerAbstract:Abstract. Dry-snow slab avalanches are generally caused by a sequence of fracture processes including (1) Failure initiation in a weak snow layer underlying a cohesive slab, (2) crack propagation within the weak layer and (3) tensile fracture through the slab which leads to its detachment. During the past decades, theoretical and experimental work has gradually led to a better understanding of the fracture process in snow involving the collapse of the structure in the weak layer during fracture. This now allows us to better Model Failure initiation and the onset of crack propagation, i.e., to estimate the critical length required for crack propagation. On the other hand, our understanding of dynamic crack propagation and fracture arrest propensity is still very limited. To shed more light on this issue, we performed numerical propagation saw test (PST) experiments applying the discrete element (DE) method and compared the numerical results with field measurements based on particle tracking. The goal is to investigate the influence of weak layer Failure and the mechanical properties of the slab on crack propagation and fracture arrest propensity. Crack propagation speeds and distances before fracture arrest were derived from the DE simulations for different snowpack configurations and mechanical properties. Then, in order to compare the numerical and experimental results, the slab mechanical properties (Young's modulus and strength) which are not measured in the field were derived from density. The simulations nicely reproduced the process of crack propagation observed in field PSTs. Finally, the mechanical processes at play were analyzed in depth which led to suggestions for minimum column length in field PSTs.
Shane B Underwood - One of the best experts on this subject based on the ideXlab platform.
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reliability analysis of fatigue life prediction from the viscoelastic continuum damage Model
Transportation Research Record, 2016Co-Authors: Padmini Gudipudi, Shane B UnderwoodAbstract:The fatigue resistance of asphalt concrete materials plays an important role in the service life of a pavement. Several empirical and mechanistic Models and efforts are under way toward improving these Models for accurate prediction of fatigue life. The reliability of predictions with these Models has not received substantial attention. This study used the simplified viscoelastic continuum damage Model to analyze the reliability of fatigue predictions. Modulus and fatigue tests were conducted on a standard dense graded asphalt mixture to characterize the Model and create deterministic fatigue life predictions. Monte Carlo simulations were then used to calculate the reliability of the fatigue predictions, given the variation in input parameters. The analysis was conducted for combinations of three experimental Failure criteria and two Model Failure criteria at two strain levels for a total of 12 study cases. Differences in reliability between the combinations of Failure conditions are identified and discus...
Chian Fong Yen - One of the best experts on this subject based on the ideXlab platform.
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A ballistic material Model for continuous-fiber reinforced composites
International Journal of Impact Engineering, 2012Co-Authors: Chian Fong YenAbstract:A ply-level material constitutive Model for plain-weave composite laminates has been developed to enable computational analyses of progressive damage/Failure in the laminates under high velocity ballistic impact conditions. In this Model, Failure-initiation criteria and damage evolution laws are introduced to account for the major fiber-Failure modes (tensile, compressive, punch shear and crush loading). In addition, two matrices related Failure modes (in-plane shear and through the thickness delamination) are also accounted for. These types of fiber and matrix Failure modes are commonly observed during a ballistic event. The composite-material Model has been implemented within LS-DYNA as a user-defined material subroutine and used successfully to predict the damage and ballistic behavior of composite laminates subjected to various ballistic impact conditions. It is hoped that the availability of this material Model will help facilitate the development of composite structures with enhanced ballistic survivability.