Abstract
Effects of tensile residual stress induced by coiling on delayed fracture of coil springs caused by hydrogen embrittlement were investigated The evaluation method using strain gauge installed on coil spring was developed to detect the delayed fracture. This method was made certain of its effect by the experiment applyed to cold formed coil spring having high tensile residual stress dipped in dilute hydrochloric acid. The new method made it clear that higher material strength of coil spring brought the delayed fracture chracteristics drop due to its high strength itself and increase of tensile residual stress.
