A New Experimental and Numerical Framework for Determining of Revised J-C Failure Parameters

Abstract

Since damage evolutions of materials play important roles in simulations, such as ballistic impacts and collisions, a new experimental and numerical method is established to determine the revised Johnson–Cook (JC) failure parameters of a 2618 aluminum alloy and a Ti-6Al-4V titanium alloy. Not only the strain distributions, but also the stress triaxialities of designed specimens with different notches, are analyzed and revised using the finite element (FE) model. Results show that the largest strain concentrated on the surface of the circumferential area where the initial damage happened, which coincided with the practical damage evolution in the FE model. The complete damage strain, which denoted the largest strain before fracture calculated by the picture, is put forward to replace the traditional failure strain. Consequently, the digital image correlation (DIC) method and the micro speckle are carried out to measure the complete strain from the circumferential area. In addition, the relationships between the complete damage strain, the revised stress triaxiality, the strain rate and the temperature are established by conducting the quasi-static and dynamic experiments under different temperatures. Finally, the simulations for the ballistic impact tests are conducted to validate the accuracy of the parameters of the revised JC damage model.

Keywords

• damage evolutions
• stress triaxiality
• complete damage strain
• the digital image correlation
• revised Johnson–Cook (JC) damage model