繰返圧縮荷重を受けるコイルばねの変形および強さ

Abstract

For the coiled compression spring of steel wire, the authors researched experimentally on the creep under static and repeated stresses and also on the effect of three kinks of treatment, that is, untreated, heat-treated and setting.The results obtained are as follows:(1) In the case of the coiled springs that were applied to the present experiments, the limit of proportionality of the spring is raised by annealing at 300°C about twice as much as that of untreated one, and further increased 20 per cent more by setting.On the other hand, the value of spring constant was decreased 1.5 per cent and 6.4 per cent by annealing and setting respectively. The residual shearing strain decreased about 10 per cent by annealing and setting.(2) In the tests under large repeated loads the spring produces a fatigue rupture, but under large static load it does not produce a rupture even after several hundreds hours, while the residual strain gradually increases.The strain under small repeated loads becomes constant within 106 stress cycles and that under static loads becomes constant within one hundred hours.(3) The residual strains at N=107 (150 hours) for repeated load were larger than that for static load.