The frictional crack is extensively observed in natural phenomena like earthquake fracture, fracture at rock
fault line and in fracture of other geological materials. The contact between the flaw faces alters the stress
field in comparison to the stress field in an open condition or when not in contact. The crack growth
initiation in an open condition have been investigated sufficiently in literature. However, the frictional crack
or closed crack in an anisostropic medium has hardly been addressed. The naturally occurring biological
materials such as bone, wood, cartilage, etc. are anisotropic as well as quasi-brittle in nature. Considering
the vital application of these naturally occurring composites, it calls for a thorough investigation. The
current research work performs compression test on wood with an embedded central pore for different
contact surface conditions and orientation of pore. In addition to that, it carries out numerical simulation of
crack growth initiation and propagation using cohesive zone model (CZM) considering quasi-brittle nature
of wood. Further, it verifies the applicability of classical fracture criteria for friction crack propagation in
wood.
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The macroscopic behavior of plasma sprayed zirconia coatings is greatly affected by their microstructure, and phenomena that occur at this scale, such as micro-craking and cracks closure. The present study investigates the effect of micro-porosities and micro-craking on compressive waves mitigation, material compaction, and macroscopic fracture. A procedure to generate 3D digital twins that faithfully represents the microstructure is developped using the discrete element method (DEM) and analysis of scanning electron microscope (SEM) images. Static and dynamic compressive loadings are applied to 3D and 2D twins to identify their macroscopic behavior. Local damage mechanisms and their influence on the waves mitigation and the macroscopic damage are observed and discussed related to the current knowledge in the literature.
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It is known that damage or inelastic softening can cause an ill-posed problem leading to localization and mesh-dependence in finite element simulations. Here, a nonlocal hardening variable is introduced in a finite deformation Eulerian formulation of inelasticity. This nonlocal variable is defined over an Eulerian region of nonlocality, which is a sphere with radius equal to a characteristic length, defined in the current deformed geometry of the material. The influence of the nonlocal hardening variable is studied using an example of a plate that is loaded by a prescribed boundary displacement causing formation of a shear band. Predictions of the applied load vs. displacement curves and contour plots of the total distortional deformation of the plate and the hardening variable are studied. It is shown that the characteristic material length controls the structure of the shear band developed in the plate.
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We study the intermittent damage evolution preceding compressive failure using a non-local damage model accounting for material disorder and long-range elastic interactions. Our theoretical predictions are successfully compared with experiments carried on a model elasto-damageable 2D solid where damage evolution is tracked at both the global and local scale. Finally, we show how our understanding of these failure precursors can be harnessed for predicting the remaining lifetime of structures under compression.
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