304不锈钢室温和高温单轴循环塑性的实验研究

EXPERIMENTAL STUDY ON UNIAXIAL CYCLIC PLASTIC BEHAVIOR OF 304 STAINLESS STEEL AT ROOM AND HIGH TEMPERATURE

对３０４不锈钢进行了室温和高温单轴应变控制和应力控制下的系统循环试验．揭示和分析了循环应变幅值、平均应变及其历史和温度历史对材料应变循环特性的影响以及应力幅值、平均应力及其历史以及温度对循环棘轮行为的影响．也讨论了应变循环和应力循环间交互作用对材料循环塑性行为的影响．研究表明，无论单轴应变循环特性还是非对称单轴应力循环下的棘轮效应不仅取决于当前温度和加载状态，而且强烈依赖于其加载历史，研究得到了一些有助于３０４不锈钢室温和高温单轴循环行为本构描述的结果．

Many structural parts are often subjected to complex cyclic loading and temperature history. The accumulated plastic strain produced in the asymmetrical stress cycling is called ratcheting strain and may result in the initial failure of structure. Some studies have revealed and modeled the ratcheting behavior of sone structure metals. However, the effects of loading and temperature history have not been considered well yet. The interaction between the strain cycling and stress cycling has not been discussed. In order to provide the experimental basis for constitutive modeling, an experimental study is carried out for the cyclic plastic behaviors of 304 stainless steel subjected to uniaxial strain and stress cycling at room and high temperature. The effects of strain amplitude, mean strain, temperature and their histories on the cyclic plastic behaviors are investigated, and the influences of stress amplitude, mean stress and their histories on the ratcheting are also analyzed at room and high temperature. The interaction of strain cycling and stress cycling is discussed. It is shown that either uniaxial strain cyclic property or ratcheting depends not only on the current temperature and loading state, but also on the previous history. At room and high temperature, 304 stainless steel features cyclic hardening initially, and the rate of cyclic hardening increases with the increase of strain amplitude. The material has an apparent memorization for the prior maximum strain amplitude of load history. However, as temperature increases, the memorization for maximum strain amplitude disappears gradually. The effect of temperature history on cyclic plastic behavior gradually decreases with the increase of intermediate temperature. The ratcheting strain and its rate rise with the increases of mean stress and stress amplitude. The prior higher mean stress and stress amplitude cycling restrains the ratcheting behavior of subsequent loWer mean stress and stress amplitude cycling. With the temperature increased, the ratcheting strain and its rate increase greatly. After prior stress cycling, the cyclic hardening or softening rate of material under strain cycling is lore than that without stress cycling, and the memorization of material for maximum strain amplitude declines. The prior strain cycling restrains the ratcheting behavior of subsequent stress cycling.