Validation of Finite-Element Plasticity Models Using Full-Field Surface Strain Measurements

Fastened joints still represent the most common method for joining components within the aerospace industry. For fastened joints that experience high cyclical stresses, the application of the Split Sleeve Cold Expansion (SsCxTM) process has proven to be highly effective in extending the total fatigue life. This paper provides experimental strain measurements from around holes subjected to the SsCxTM process. Measurements on aluminum alloy coupons were taken using strain gauges and fiber optic strain sensors, with those measurements being used to validate the results from a three-dimensional (3D) digital image correlation (DIC) system. These validated experimental results were then compared to three separate finite-element analysis (FEA) process simulations each performed using one of three different material hardening models, Chaboche, kinematic and isotropic hardening. A finite-element leveling process was then used to compare the FEA results to the DIC measurements to highlight which hardening model provided the best correspondence to the DIC measurements. Although all hardening models provided reasonable similarity to the DIC results, for this particular aluminum alloy, an isotropic hardening model provided the best results.