Inhomogeneous Work-Softening During Cyclic Loading of SAE 4140 in Different Heat Treated States
Inhomogeneous Work-Softening During Cyclic Loading of SAE 4140 in Different Heat Treated States
复制标题
不同热处理状态下SAE 4140循环加载过程中的不均匀功软化
DOI：
10.1007/978-94-009-6821-9_14
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发表时间：
1983
影响因子：
2.6
通讯作者：
E. Macherauch
中科院分区：
文献类型：
--
作者：
D. Eifler;E. Macherauch
采用应力控制的推拉试验研究了SAE 4140钢正火态和不同调质态试样的显微组织对疲劳行为的影响。在循环加载的初始阶段，归一化试样表现出准弹性行为，其次是不均匀的加工软化效应。在达到最大塑性应变幅后，出现一个塑性应变均匀的加工硬化期，而淬火和回火试样在疲劳寿命的无裂纹期表现出截然不同的行为。在所有情况下，在准弹性初始阶段之后，不依赖于所选择的回火处理（Tt > 450°C），发生加工软化，直到裂纹萌生。光弹性研究表明，工作软化出现非常本地化。在以后的使用寿命中，试样首先软化的区域不断积累塑性应变。因此，塑性应变特别集中在小的疲劳区。通常，循环变形过程似乎主要限于一个或两个疲劳区。在这些区域中，裂纹开始、扩展并最终导致试样的失效。
Stress-controlled push-pull tests have been performed to investigate the influence of microstructure on the fatigue behavior of normalized as well as different quenched and tempered specimens of SAE 4140. In the initial stage of cyclic loading, normalized specimens exhibit quasi elastic behavior followed by inhomogeneous work-softening effects. After reaching a maximum plastic strain amplitude, a work-hardening period follows with homogeneous plastic strains.On the other hand, quenched and tempered specimens show quite a different behavior in the crack free period of fatigue life. Independent of the tempering treatment chosen (Tt > 450°C) in all cases after a quasi elastic initial period work-softening occurs until crack initiation. Photoelastic investigations reveal that work-softening appears extremely localized. The areas of the specimen’s softening first continuously accumulate plastic strain during further life. Thus, plastic strains are particularly concentrated on small fatigue zones. Very often, cyclic deformation processes seem to be mainly restricted to one or two fatigue zones. In these zones, cracks initiate, grow and finally lead to failure of the specimen.