Creep-ratchetting of Heat Resisting Steels at Elevated Temperature in Multiaxial Stress State

在两种耐热钢上提高温度的爬行-棘轮行为：在600 ° C的2 1/4Cr-1 Mo钢和在650 ° C的SUS 304不锈钢，在多轴压力状态下进行了实验性测试。在机械修补测试中，在组合的稳定轴向压力和循环剪切下，在两种钢材上发现了可分辨的轴向应变累积。“轴向应变累积变得更大，具有降解的循环剪切率。”在2 1/4 Cr-1 Mo钢和较大的爬行应变路径上的爬行测试中，在独特的静态爬行测试中观察到的。在SUS 304上的压力控制的creep-ratchetting测试中，两种都在独特的和多重的压力状态中，行为受到压力比率的强烈影响，以评估现有的非弹性固定性equation的准确性，以及对高于相关的creep-ratchetting测试的数字模拟。“超定位模型和两个统一模型：Chaboche模型和Miller模型，已被用于模拟。统一的模型给一些测试的结果更好， E.。g.，当你沿着循环的压力路径前进时，你就会发现cree-plastic的相互作用。However，对统一模型中材料常数的确定比其在超位置模型中的更难。所有这些型号都很难准确地准确地加快Creep-ratching行为，而且还需要进一步的改进。Creep-ratching行为在房间温度上也对SUS 304和两个碳钢进行了调查，在统一和多轴压力状态下也进行了调查。The phenomenological constitutive models for the creep-ratchetting have been presented。FEM program has been developed based on the unified constitutive equation presented by Chaboche。该程序是通过一个不寻常的张力和一个未标记的板的张力的数字测试进行的。适应性的时间--已经被讨论过了。

Creep-ratchetting behavior at elevated tempareture on two types of heat resisting steels: 2 1/4Cr-1Mo steel at 600゜c and SUS304 stainless steel at 650゜c, has been experimentally examined in multiaxial stress state. In the mechanical retchetting tests under combined steady axial stress and cyclic shear straining, remarkable axial strain accumulation is found on both steels. The axial strain accumulation becomes larger with decreasing cyclic shear strain rate. In the creep test along circular stress path on 2 1/4Cr-1Mo steel, larger creep strain is observed than in uniaxial static creep tests. in the stress-controlled creep-ratchetting tests on SUS304, both in uniaxial and multiaxial stress states, the behavior is strongly affected by the stress ratio.To evalate the accuracy of the existing inelastic constitutive equations, the numerical simulations to the above-mentioned creep-ratchetting tests have been coducted by the equations. The superposition model and two of the unified models: the Chaboche model and the Miller model, were used for the simulation. The unified model gives better results for some of the tests, e. g., the creep along circular stress path, since they account the cree-plasticity interaction. However, the determination of material constants in the unified models are more difficult than that in the superposition model. All of these models can hardly express accurately the creep-ratchetting behavior guantitatively, and the further improvement is required.Creep-ratechetting behavior at room temperature has also been investigated on SUS304 and a carbon steel both in uniaxial and multiaxial stress state. The phenomenological constitutive models for the creep-ratchetting have been presented.The FEM program has been developed based on the unified constitutive equation presented by Chaboche. The program was checked through the numerical tests of s uniaxial tension and a tension of notched plate. The adaptive time-step has been discussed.