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Strain Rate Dependency of Dynamic Flow Stress of Steel Iron at Very High Strain Rates

极高应变率下钢铁动态流变应力的应变率依赖性

基本信息

批准号：
11650102
负责人：
SAKINO Kiyotaka
金额：
$ 0.32万
依托单位：
Hosei University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11650102/
关键词：
High Speed Deformation Steel Iron Strain Rate Dependency Hopkinson Bar Method Thermally Activated Process 鉄の活性化エネルギー

项目摘要

Strain rate sensitivity of a flow stress in BCC metals is known to increase greatly in the high strain rate ranges above about 1×10^3/s. High strain rate tests are performed for low carbon iron using a modified Hopkinson pressure bar system in a strain rate range mainly from about 4×10^3 to 5×10^4/sec. At first, in order to evaluate the effects of the instantaneous strain rate and strain rate history on the dynamic flow stress of the iron at very high strain rates, the strain rate change tests are made in the strain rate range from about 10000 to 20000/sec. The results indicate that the instantaneous strain rate plays a dominant role. Furthermore, to evaluate the strain rate dependency of the dynamic flow stress at high strain rates, the stress-strain rate curve using activation energy E(τ) for deformation of pure iron obtained by Aono et al. is used. The flow stress at quasi-static strain rate region is controlled by the mechanism of a thermal activation of dislocations over short range barriers. The flow stress at strain rates ranging from about 1/sec to 2×10^4/sec is controlled by the thermally activated process of formation of kink pairs, however at higher strain rates a second rate controlling mechanism appears to be predominant.

在约1×10~(-3)/S的高应变率范围内，体心立方金属中流动应力的应变率敏感性显著增加。用改进的霍普金森压杆系统对低碳铁进行了高应变率试验，应变率范围主要为4×10~(-3)~5×10~(-4)/秒。首先，为了评价瞬时应变率和应变率历史对铁在很高应变率下的动态流动应力的影响，在10000~20000次/秒的应变率范围内进行了应变率变化试验。结果表明，瞬时应变率起主导作用。此外，为了评价高应变率下动态流动应力的应变率相关性，利用激活能E(τ)得到了纯铁变形的应力-应变率曲线。使用的是。准静态应变率区的流动应力受位错在短程势垒上的热激活机制控制。在应变速率约为1~2×10~(-4)/s范围内，流动应力受扭结对形成的热激活过程控制，但在较高应变速率下，第二速率控制机制占主导地位。