Within the elastic range, the limiting value of the stress up to which the stress and strain are proportional, is called the limit of proportionality. In this region, the metal obeys Hooke’s law, which states that the stress is 色金属中常常出现。 铁和镍存在明显的弹性proportional to strain in the 范围，铜，锌，锡等即使elastic range of loading (the 在相当低的应力值下弹性material completely regains 也表现得不是很充分。实its original dimensions after 际上依靠测试仪器的精确the load is removed). In the 性可以使比例极限和弹性actual plotting of the curve, the proportionality limit is obtained at a slightly lower value of the load than the elastic limit. This may be attributed to the time-lag in 极限区分得更清晰。 the regaining of the original 当在弹性极限之上增大dimensions of the material. 载荷时会产生塑性变形。This effect is very no-ferrous metals. While iron and of elasticity, copper, zincfound to be imperfectly elastic even at relatively（相当地） low values of stresses. Actually the elastic limit is distinguishable（可区分的） from the limit more clearly depending upon the measuring instrument. When the load is increased beyond the elastic limit, plastic deformation starts. 同时，试件发生加工硬化。于载荷增加的速度。这一点叫做屈服极限点。一开在这一点后开始迅速地发屈服应力叫做屈服极限。 试件从Q到S在到T不动期间的应力-应变关系表示为曲线上的QRST时的载荷称为断裂载荷。最大荷载值S除以试件的横截面积为金属的最大拉伸强度或简单地称为拉伸强度。 frequently noticed in some 到达某点后变形的速度快nickel exhibit clear ranges 始一直在抵抗载荷的金属（锌）, tin（锡）, etc, are 生形变，也就是，屈服。proportionality（比例性） 断地延长。在这个塑性流sensitivity（灵敏性） of the 段。在T点试件断裂，此Simultaneously the specimen gets work-hardened. A point is reached when（这时） the more rapidly than the 弹性极限，金属应该就会deformation starts to occur 逻辑上来说，一旦超过increasing load. This point 屈服直至最后断裂，在应is called the yield point Q. 力值上应该没有增加。但the metal which was 是实际的曲线却记录了在resisting the load till then, 超过弹性极限后的增加了starts to deform somewhat 的应力。这种现象的发生rapidly, i. e. , yield. The yield stress is called yield limit. The elongation of the specimen continues form Q to S and then to T. the stess-strain relation in this plastic flow period is indicated by the portion QRST of the curve. At T the specimen breaks, and 可能有两种原因： 1. 材料的应变强化； 2. 由于塑性变形引起的试件横截面积的缩小。 （For Christ was God, and suffered on account of us, being himself the Father, that he might be able to save us.因为基督就是上帝，为我们受苦，他this load is called the breaking load. The value of the maximum load S divided by the original 自己身为父，好叫祂也能救赎我们。） 由于加工硬化，金属在发生塑性变形时会变得越cross-sectional area of the 来越硬。金属拉伸越长它specimen is referred to as 的直径越小。这种现象一the ultimate tensile strength 直持续到曲线上的S点。 of the metal or simply the tensile strength. once the elastic limit is starts to yield, and finally break, without any increase in the value of stress. But the curve records an the elastic limit is exceeded. Two reasons can be given for this behavior: of the material; 超过S点后，面积减少速度。应变变得很大，面局部效应。叫做颈缩。 横截面积减小的速度非降低。 示了材料的延展性。 Logically speaking, 的速度超过了应力增加的exceeded, the metal should 积的减少在某些点产生了increased stress even after 常快；以至于实际上载荷1. the strain hardening 伸长率和面积减少率表2. the of of the diminishing specimen, plastic cross-sectional area suffered on account the deformation. The more plastic deformation the metal undergoes, the harder it becomes, due to work-hardening. The more the metal gets elongated the more its diameter(and hence, cross-sectional area) is decreased. This continues until the point S is reached. After S, the rate at which the redution in area takes place, exceeds the rate at which the stress increases. Strain becomes so high that the redution in
机械设计制造及其自动化专业英语翻译 - 图文
