Abstract
Simulation of the material failure under high strain rate conditions is one of the most difficult problems in the finite element analyses, and many researchers have tried to understand and reproduce dynamic material fracture. In this study, we investigate a failure criterion that minimizes the mesh dependency at high strain rates and incorporates the criterion into the Johnson-Cook constitutive relationship by developing a user-defined material model. Impact tests were performed using a gas-gun system in order to investigate the response of the 7075-T651 aluminum plate in high-speed collision. On the other hand, numerical simulations are carried out by considering various element sizes and the relationship between element size and failure strain is inversely obtained using numerical results. By accommodating the relationship into the damage model and implementing in the user-defined material model, mesh dependency is significantly reduced, and sufficient accuracy is achieved with alleviated computational cost than the existing damage model. This study suggests an element size-dependent damage criterion that is applicable for impact simulation and it is expected that the criterion is useful to obtain accurate impact responses with a small computational cost.
Highlights
An impact is defined as a mechanical process that involves the collision of two or more bodies.The relevant engineering has a wide range of applications, such as the safety assessment of buildings and nuclear reactor vessels, the assessment of the crashworthiness of vehicles, the protection of cargo and barriers, and the design of military vehicles and armor systems
In the finite element analysis, the accuracy of the numerical solution depends on the element
In the finite element analysis, the accuracy of the numerical solution depends on the element size, and significant computational cost is essential to attain sufficient accuracy
Summary
An impact is defined as a mechanical process that involves the collision of two or more bodies. Various failure strain values have been applied in other studies [14,15], which means that the failure strain values vary depending on the researcher or numerical model. Villavicencio et al confirmed the dependence of the failure strain on the element size for impact simulation on circular aluminum plates [20]. Grag and Abolmaali performed numerical analyses by varying the failure criterion according to the element size in the analysis of the reinforced concrete box culverts [21] and Ehlers applied element length-dependent failure strain in fracture of the thin circular plate [22]. Numerical simulations are conducted to observe the effects of element size and failure strain on the perforation response depending on the strain rate. The relationship between the element size and failure strain is applied to the damage model, and we verify the efficiency and accuracy of the damage model
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