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本文通过试验分析了灰铸铁的同相和异相热疲劳及C-P型和P-C型高温低周疲劳特性,并应用弹塑性断裂力学方法对其寿命作了解析评价。试验和计算都表明,在相同应变范围下,同相和C-P型疲劳寿命分别高于异相和P-C型。这与低碳钢等材料结果相反。另外,计算值和试验吻合,说明J积分用作评价灰铸铁热疲劳强度的力学参量及本文所建立的力学模型和计算方法有效。文中从能量角度提出了一个用于描述裂纹扩展能力的参量ΔW_T,在相同ΔW_T值下,高温低周疲劳寿命和热疲劳相等。
In this paper, the in-phase and out-of-phase thermal fatigue and C-P and P-C low temperature fatigue characteristics of gray cast iron were analyzed through experiments. The life-span of the gray cast iron was analyzed and evaluated by the elasto-plastic fracture mechanics method. Both experiments and calculations show that in the same strain range, in-phase and C-P fatigue lives are higher than those of out-of-phase and P-C respectively. This is contrary to the results of materials such as mild steel. In addition, the calculated values are in good agreement with the experimental results, which shows that the J integral is used as a mechanical parameter to evaluate the thermal fatigue strength of gray cast iron and the mechanical model and calculation method established in this paper are effective. In the paper, a parameter ΔW_T for describing the crack propagation capability is proposed from the viewpoint of energy. Under the same value of ΔW_T, the high temperature and low cycle fatigue life is equal to the thermal fatigue.