Verification of a New Fracture Criterion Using LS-DYNA

Several fracture models are available in the material library of LS-DYNA. This paper is concerned with a newly developed constitutive model that covers the full range of plasticity till the onset of fracture. It is understood that the fracture initiation in uncracked solids is an ultimate result of a complex damage accumulation process. Such damage is induced by plastic deformations. A new damage model is proposed to incorporate the pressure sensitivity and the Lode angle dependence through a nonlinear damage rule using a reference fracture strain on a restricted loading path. The onset of fracture is predicted by integrating incremental damage along the actual loading path. In this cumulative fashion, fracture can be predicted for complex loading paths, which are not limited to the restricted loading in which the pressure is constant. This modified model also incorporates the coupling between the damage and the strain hardening function. The new fracture model is implemented to LS-DYNA as a user defined material subroutine. A series of benchmark tests and simulations have been performed to verify this model. The loading situations of these tests cover a wide range of standard laboratory testing, which include uniaxial tension of a round bar, uniaxial tension of a hollow bar and the three-point bending of a rectangular bar. A remarkable agreement between the experimental and numerical results is achieved.