International Journal of Fracture最新文献

We study multiple transverse cracking of symmetric laminates in the framework of the variational approach to fracture. Considering the Griffith model, we assume that several cracks can appear instantaneously through the whole thickness of the core layer, separating the bar in n elastic segments. We show that the energy minimization implies the bifurcation from solutions with uniform crack spacing to non uniformly spaced solutions, a phenomenon ignored in the literature for perfect systems. The stability of uniformly spaced solutions crucially depends on the concavity of the elastic compliance of each elastic segment as a function of the segment length. We compute this function and its derivatives numerically with domain-derivative techniques for a large set of geometric and material parameters. Our results indicate that the change of concavity and the related instability is a robust qualitative property that becomes quantitatively relevant in the case of laminates with thin and soft outer layers.

This study presents numerical analyses for edge chipping by impact loading. As a numerical analysis method, we extend Particle Discretization Scheme Finite Element Method (PDS-FEM) developed by the authors to be able to simulate fracture due to impact loading. We performed simulations targeting edge chipping of soda-lime glass by impact of rigid steel sphere and examined the crack morphology while varying the diameter of the impactor, the impact velocity, and the impact distance. The proposed method successfully simulates the 3D complex crack pattern on edge chipping such as Hertzian cone crack and conchoidal chip scar. The method also reproduces the change of crack morphologies depending on the impact force and the impact distance. Also, a series of numerical analyses is presented to reveal the effect of the impactor geometry on the chip dimensions. The height of chip is independent of the impactor geometry while the width of chip depends on it. According to the agreement with experimental results, it is confirmed that the proposed method is capable of realizing edge chipping due to impact loading.

The phase-field fracture method (PFM) requires an extremely fine mesh to accurately capture the crack topology, which is computationally expensive. In this work, a new adaptive mesh refinement method is proposed for phase-field fracture. Based on the phase field increment, a volume weighted Quickselect algorithm is used to determine the coarsen region and the refined region. The speed of the crack propagation is predicted to control the size of the refined region, which reduces unnecessary degrees of freedom. Several benchmark numerical examples are simulated and the results demonstrate the efficiency and accuracy of the proposed method. In the numerical examples, the computational time using this method is reduced by about 90% compared with the standard PFM.

Herein, we focus on understanding the microstructure-fracture correlations in a Ti–6Al–4V alloy additively manufactured via electron beam melting (EBM) and subjected to various post-process heat-treatments. Specifically, the as fabricated material is subjected to a sub-transus heat-treatment followed by air-cooling and a super-transus heat-treatment followed by either air- or furnace-cooling. Next, a series of in-situ single edge notch tension (SENT) tests are carried out under a high-resolution digital optical microscope. The panoramic high-resolution images captured during the in-situ tests are then used to characterize the planar deformation on the specimen surface using microstructure-based digital image correlation (DIC). The results of the in-situ SENT tests together with DIC and post-mortem fractographic analyses provided us with a better understanding of the microstructure-fracture correlations in these materials. Our results show that the fracture mechanism of the as fabricated and sub-transus heat-treated materials is essentially the same, while the changes in the microstructure following the super-transus heat-treatments significantly affects the fracture mechanism. In this case, several microcracks of hundreds of microns in length first nucleate away from the deformed notch following extreme plastic deformation at discrete locations. Furthermore, the location of these microcracks in the super-transus heat-treated materials is extremely sensitive to the details of the underlying microstructure.