Prediction of the Sandia Fracture Challenge using a shear modified porous plasticity model

Blind analyses of the localization and ductile fracture behavior of an arbitrarily shaped coupon, performed for the Sandia Fracture Challenge, are presented. These analyses were performed using a shear-modified Gurson porous plasticity model that was calibrated using standard mechanical test data. The blind predictions were found to be in good agreement with experimental data, thus increasing confidence in the calibration methodology where test data is not available. In addition to the analyses submitted to the Challenge, additional non-blind analyses examining the role of both as-machined versus nominal coupon geometry and the selected value of initial porosity were conducted. It was found that by capturing the as-machined, out of tolerance, geometry in numerical calculations the fracture mode was altered from tension to shear. This agrees well with the experimental observation that all in-tolerance coupons failed in a tensile mode while all out-of-tolerance coupons failed in a shear mode. Additionally, it was found that by modifying the initial void volume fraction to a lower value still within the range that the calibration methodology provided, calculations capturing this as-machined geometry were able to closely match experimental results.