Stress analysis of some unsymmetric screwed connections

Abstract

Unsymmetric shapes and loadings were studied using four frozen-stress photoelastic models. Pure tension was applied to all bolt heads. All the bolt shanks were necked. Three of the blocks were rectangular in cross-section, one was circular with a flat. Two tests represented clamping only; two tests modelled clamping and an offset separating force on a bolted joint causing bending. Results from two previously published tests with axisymmetric blocks are included as a basis for comparisons. The maximum stresses in screw and block always occur near the start of contact. Their values depend on thread configuration at the start of contact, not on the block cross-section. Using pitch-average curves as datum allowed analysis of the maximum variations from these curves. In the tests carried out, RMS values of these variations are doubled by making the block unsymmetric and quadrupled by introducing bending.