膜致应力对应力腐蚀裂尖力学特性的影响

Effect of Film-Induced Stress on Mechanical Properties at Stress Corrosion Cracking Tip

摘要:

氧化膜破裂理论是目前定量预测核电高温水环境中镍基合金应力腐蚀开裂速率应用最为广泛的理论模型之一，其中应力强度因子是衡量应力腐蚀开裂速率的重要参量。为进一步了解氧化膜破裂机理及裂纹扩展驱动力特性，提出了膜致应力强度因子。为了深入了解膜致应力强度因子在 EAC 裂纹扩展过程中裂尖的力学状况，在不考虑外载的情况下，从理论和数值模拟两方面分析研究了EAC 裂尖基体金属区域的应力应变分布状态，得出了膜致应力强度因子对裂尖Mises应力、等效塑性应变、拉伸应力、拉伸应变及拉伸应变梯度的影响规律，为提高定量预测高温高压水环境中镍基合金及不锈钢 EAC 扩展速率精度奠定基础，进而完善了氧化膜破裂机理。

Abstract:

Oxide film rupture theory has become one of the most popular models to quantitatively predict the stress corrosion cracking (SCC) rate at crack tip of nickel-based alloys in high temperature and high pressure environments, and stress intensity factor has become an important parameter to measure the stress corrosion cracking rate. In order to further understand the fracture mechanism of the oxide film and the driving force of crack growth, film-induced stress intensity factor is proposed. To understand the effect of film-induced stress intensity factor on the micro-mechanical state at the tip of EAC, the stress-strain in the base metal at the EAC tip was simulated and discussed using a commercial finite element analysis code. And then the effect of film-induced stress intensity factor on Mises stress, equivalent plastic strain, tensile stress, tensile strain and tensile plastic strain gradient of crack tip was obtained, which provides a parameter to improve the quantitative predication accuracy of EAC growth rate of nickel-based alloys and austenitic stainless steels in the important structures of nuclear power plants. Therefore the oxide film rupture theory was improved.