A practical methodology is being developed to characterize elastic-plastic fatigue crack growth (EPFCG) behavior. The methodology will be implemented in engineering software for crack growth analysis and life prediction of advanced reusable aerospace propulsion systems. The correlating parameter upon which the methodology is based is the range of the J-integral, ΔJ. Existing J solutions are summarized, and robust methods for developing new J solutions under various loading configurations are introduced and validated. Some practical crack growth algorithms required to translate a J calculation into a quantitative prediction of EPFCG life are highlighted. Crack closure plays a significant role in the engineering characterization of EPFCG rates, and simple algorithms to estimate closure stresses are described. Other algorithms address the tearing-fatigue interaction near final instability and the estimation of required material properties. Early results from experimental verification tests are reported.

No abstract

The objective of this project was to evaluate the use of the Johnson-Cook strength and failure models in an adiabatic finite element model to simulate the puncture of 7075-T651 aluminum plates that were studied as part of an ASC L2 milestone by Corona et al (2012). The Johnson-Cook model parameters were determined from material test data. The results show a marked improvement, in particular in the calculated threshold velocity between no puncture and puncture, over those obtained in 2012. The threshold velocity calculated using a baseline model is just 4% higher than the mean value determined from experiment, in contrast to 60% in the 2012 predictions. Sensitivity studies showed that the threshold velocity predictions were improved by calibrating the relations between the equivalent plastic strain at failure and stress triaxiality, strain rate and temperature, as well as by the inclusion of adiabatic heating.

This paper describes the challenge problem associated with the 2014 Sandia Verification and Validation (V&V) Challenge Workshop. The problem was developed to highlight core issues in V&V of engineering models. It is intended as an analog to projects currently underway at the Sandia National Laboratories—in other words, a realistic case study in applying V&V methods and integrating information from experimental data and simulations to support decisions. The problem statement includes the data, model, and directions for participants in the challenge. In addition, the workings of the provided code and the “truth model” used to create the data are revealed. The code, data, and truth model are available in this paper.