A Case Study for the Low Fidelity Modeling of Threaded Fasteners Subject to Tensile Loadings at Low and High Strain Rates

Abstract

A series of tests on NAS1352-06-6P threaded fasteners were coupled with analysis to fit constitutive models, evaluate multiple modeling approaches, and ultimately predict failure. Experiments loading the fasteners in tension at both quasistatic and dynamic loading rates were performed to obtain calibration and validation data for the analysis. The fastener was modeled with two low-fidelity approaches — a “plug” of hex elements retaining the nominal fastener geometry (without threads) and a “spot weld”, which incorporates similar geometry but the fastener is sliced near its mid-plane to define a tensile load-displacement relationship between the two exposed surfaces — to accommodate the use of these modeling methods in a larger, more detailed finite element analysis. Both modeling approaches were calibrated using quasistatic test data and then extended to the dynamic analyses to compare with the analogous test results. The analysis accurately reproduces most acceleration time-histories observed in the dynamic testing but under predicts failure, indicating the possible presence of strain rate effects that have been neglected in the constitutive models.

Mesh size effects on fracture locus of high strength bolts: A mesoscale critical equivalent plastic strain (MCEPS) approach

“…Hedayat et al [21] and D'Aniello et al [22] used a simplified model to evaluate the mechanical properties of bolts. Mersch et al [23] predicted the failure of threaded bolts using geometrically-simplified finite element models. Song et al [24] simulated the fracture of stainless-steel bolts with the element deletion method by the Lee-Wierzbicki model, the load-deformation behavior under ultimate strength matched well with experimental data.…”