軟鋼の変動荷重における捩りクリープ試験

概要

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Torsional creep tests of a mild steel were carried out under varying stress levels at 500℃ by using thin walled tubular test pieces. In the present test conditions under constant stress, buckling occurs within the range of primary creep, where the relation between strain γand time t is expressed by Andrade's equation, γ=γ_0+βt^n, like as in tensile creep tests. For varying stress tests, stress level is varied to the lower stress of τ_n=-12.8, -6.4, 0 kg/mm^2 and is maintained for 60 min after the upper stress τ_0=12.8 kg/mm^2 for 60 min, and the cycle is repeated. The instantaneous strain, creep rate, and total creep are greater when the previous stresses are higher in the reverse direction. Accordingly, the creep resistance is increasing with test time, and yet the increase is smaller when the stress returns to the constant τ_0 from higher τ_n. The instantaneous recovery of strain in releasing of stresses is constant if the stresses were in the same height, and is not varied by the number of cycles. The rate of recovery strain under τ_n=0, i.e. during the rest of load, is in linear relation with time when the both are shown by logarithmic coordinate, and is not affected by the number of cycles.
社団法人日本材料学会の論文
1959-03-15