带裂纹试样内氢扩散过程的边界元分析

ANALYSIS OF HYDROGEN DIFFUSION PROCESS IN CRACKED SPECIMEN WITH BOUNDARY

建立了氢扩散问题的边界元分析方法,并对带裂纹试样内氢的扩散过程进行了数值模拟,给出了裂尖附近氢的聚集过程及氢浓度分布随时间变化的定量关系,进一步探讨了材料硬化参数H′及扩散方程中系数α对裂尖前缘氢浓度分布的影响。结果表明,裂尖塑性区内氢浓度随扩散时间的增加而升高,在一定时间范围内,裂尖前缘氢浓度会出现双峰值现象,随着时间推移,塑性区内会出现氢的高度浓集,在裂尖附近,其氢浓度可比基体氢浓度高出两个数量级。计算结果还表明,塑性区内氢的聚集程度随系数α的增大而升高,随硬化参数H′的增大而降低。文中还与有关的试验现象和结果进行了比较与讨论。

A boundary element method (BEM) for analyzing hydrogen diffusion problems has been established. Through numerical simulation of hydrogen diffusion process in cracked specimen, the hydrogen aggregation process near crack tip and the quantitative relationship of hydrogen concentration distribution with time are obtained. Moreover, the influence of hardening parameter H' and material parameter a on the hydrogen concentration distribution in front of crack tip is investigated with the BEM. It is shown that hydrogen concentration in the plastic zone near crack tip rises with diffusion time. In a certain time range, two hydrogen concentration peaks appear. With the lapse of diffusion time, severe aggregation of hydrogen takes place in the plastic zone. In the vicinity of crack tip, hydrogen concentraion can reach such a level as to two orders of magnitude higher than the bulk concentration. It is also shown that the degree of hydrogen aggregation in the plastic zone rises with the increase of material parameter α and with the decrease of hardening parameter H'. The calculation results are in pretty good agreement with experimental phenomena.