A continuum damage mechanics-based approach to study bolt clamping force effect on the fracture strength of a plate containing a fastener hole with symmetrical edge cracks

A numerical investigation is conducted to analyze the clamping force effect on the fracture strength of holed plates with symmetrical edge cracks, made from Al-Alloy7075-T6, subjected to longitudinal tensile load by quasi-brittle damage evolution, and the results were compared with the available experimental tests. The continuum damage mechanics method and finite element method, along with the Chaboche plasticity hardening model coupled with damage mechanics, were employed to capture accurately the material's mechanical behavior. A quasi-brittle fracture approach was investigated by employing a two-scale damage method with meso-scale volume including a micro-scale volume inside it, in which voids and microcracks develop and cause macroscopic fracture. The meso-scaled volume was considered to have elastic-plastic behavior; however, the micro-scale volume was considered to have elastic-plastic behavior coupled with damage. A finite element package was utilized to simulate bolt clamping and applied load to obtain stress and strain distributions on the holed plate, and the damage was calculated in a code written by the authors. The fracture strength of the bolted cracked plate obtained by the simulation and the code is in good agreement with the experimental results, showing two scale quasi-brittle fracture method coupled with damage can predict the fracture strength in cracked members.