Stochastic Load Transfer Model for Fastened Joints

摘要

In the investigation presented in this document, the capabilities and limitations of two well-know full-field techniques, namely the digital image correlation (DIC) and the thermoelastic stress analysis (TSA), are assessed. The main goals of this project are to assess the limitations of the two experimental techniques, determine if either technique can detect differences in the strain field of varying clamping loads, and subsequently compare the experimental results to a finite element model (FEM). Double-lap shear joint specimens made of aluminum 2024 and having three clamping torques were tested using both techniques. All the specimens were subjected to eight low-frequency varying-amplitude-loading. The DIC measurements provided the distribution of the in-plane displacement over the joint. The in-plane strain distribution over the same area was calculated from the measured displacements by applying least-squares minimization. The assessment of the in-plane strain distribution allowed identification of the location of regions subjected to high levels of normal and shear strains around the joint. The analysis of the FEM model agreed to within 8 percent of the DIC measurements when the friction coefficients between the different surfaces in contact were reduced to 25 percent of their published values.