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经过退火的纯铜、纯铝和一种铝合金试件的动态应力-应变曲线己经用实验测定出来,实验时是用这些材料所制的短棒从一支压缩空气鎗中射击出去,冲击在一根钢质压力杆上。从实验得知铜和铝的动态曲线显著地高出静态曲线之上,而对该种铝合金没有显著的应变率的影响。用这些动态实验结果来检查塑性波傅播与应变率无关的理论所作的预测,得知这—理论能得出杆端产生的永久应变与它的冲击速度的合理关系。理论估计的应变分布是不能合人满意的,铜捧的低速冲击实验结果中,有迹象说明这一简单的理论需要依照Malvern所提出的方式修正。为重复冲击影响所作的一些实验指出将应变硬化的简单假说(即是金属在它先前所受的最大应力以前一直是弹性的)应用于塑性波傅播时会得出不实际的数值结果。能沿这三种金属的退火试件弹性传播的最大应力进行了测量,其结果同静态屈服应力是相当重合的。其他工作者对铜和铝观察到的不规则的结果应归于他们把静态和动态载荷联合起来的缘故。这两种载荷间的应力-应变曲线差异足以使简单理论变为无效。
The dynamic stress-strain curves of annealed pure copper, pure aluminum and an aluminum alloy specimen have been experimentally determined using a short rod made of these materials, shot from a compressed air gun, shocked On a steel pressure rod. It has been experimentally found that the dynamic curves of copper and aluminum are significantly above the static curve without any significant strain rate effect on the aluminum alloy. Using these dynamic experimental results to examine the prediction of plastic wave propagation independent of strain rate theory, we know that this theory yields a reasonable relationship between the permanent strain at the rod end and its impact velocity. The theoretically estimated strain distribution is unsatisfactory, and in the copper-clad low-velocity impact test, there are indications that this simple theory needs to be corrected in the manner suggested by Malvern. Some experiments conducted to study the effect of repeated shocks have shown that applying the simple hypothesis of strain hardening (that is, until the metal was always elastic before it was subjected to the maximum stress it has experienced) can yield unrealistic numerical results when applied to plastic wave propagation. The maximum stress that can propagate along the elastic propagation of the annealed specimens of these three metals was measured and the result is quite coincident with the static yield stress. The irregular results observed by other workers on copper and aluminum are due to their association of static and dynamic loads. The stress-strain curve difference between these two loads is enough to make the simple theory ineffective.