Experimental results are presented for damage accumulation in 10GN2MFA and 15Kh2MFA steels studied with the LM-hardness method at different stress states under cyclic loading at room and elevated temperatures that are consistent with the service conditions of structure elements. Damage accumulation kinetics is examined at primary and secondary creep stages in view of the multiaxial stress state and creep strain effects on the homogeneity coefficient. A higher level of initial strain on cyclic creep gives rise to more intensive damage accumulation in the metal, leading to the earlier onset of fracture in comparison with the smaller initial strain. Experimental critical homogeneity coefficients are given that correspond to the plastic strain stability loss when the stable deformation of the metal with its further fracture is affected by the reduction in the cross-section area and hardening modulus. The rate of homogeneity change in examined steels at different ratios of principal cycle stresses on cyclic creep is evaluated. The significant effect of a stress state at equilibrium between strain hardening and softening of the structure (specimen) metal at the secondary creep stage, is demonstrated. The effect of a stress state and temperature on damage accumulation kinetics of examined materials, in particular on the useful life of the metal on cyclic creep is established.

中文翻译：

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不同温度下循环载荷下平面应力状态下耐热钢的损伤累积动力学

提出了在室温和高温下循环载荷下，采用LM-硬度方法研究的10GN2MFA和15Kh2MFA钢在不同应力状态下损伤累积的损伤累积结果，这些结果与结构元件的使用条件一致。考虑到多轴应力状态和蠕变应变对均匀系数的影响，在初级和次级蠕变阶段检查了损伤累积动力学。周期性蠕变中较高的初始应变水平会导致金属中更密集的损伤积累，与较小的初始应变相比，会导致更早的断裂发生。当横截面面积和硬化模量的减小影响了金属及其进一步断裂的稳定变形时，给出了与塑料应变稳定性损失相对应的实验临界均质系数。评估了在主蠕变应力对循环蠕变的不同比率下，被检查钢的均质性变化率。在二次蠕变阶段，应力状态在结构（试件）金属的应变硬化和软化之间达到平衡时，产生了显着影响。确定了应力状态和温度对所检查材料的损伤累积动力学的影响，特别是对金属在周期性蠕变下的使用寿命的影响。评价了在主蠕变应力对循环蠕变的不同比率下，受检钢的均匀性变化率。在二次蠕变阶段，应力状态在结构（试件）金属的应变硬化和软化之间达到平衡时，产生了显着影响。确定了应力状态和温度对所检查材料的损伤累积动力学的影响，特别是对金属在周期性蠕变下的使用寿命的影响。评估了在主蠕变应力对循环蠕变的不同比率下，被检查钢的均质性变化率。在二次蠕变阶段，应力状态在结构（试件）金属的应变硬化和软化之间达到平衡时，产生了显着影响。确定了应力状态和温度对所检查材料的损伤累积动力学的影响，特别是对金属在周期性蠕变下的使用寿命的影响。