FGH95粉末高温合金蠕变裂纹扩展有限元数值模拟研究

Finite Element Analysis of Creep Crack Growth in FGH95 Powder Metallurgy Superalloy

对FGH95粉末高温合金标准CT试样在700℃下的蠕变裂纹扩展过程进行了有限元数值模拟研究。FGH95合金假设为弹性-蠕变体,蠕变变形采用Norton模型描述。蠕变裂纹扩展模拟时考虑了两种裂纹扩展速率,分别为3.25×10-2mm/h(快速裂纹扩展)和6.5×10-4mm/h(慢速裂纹扩展)。数值模拟结果表明:FGH95合金在700℃下发生蠕变裂纹扩展时,弹性变形引起的标准CT试样加载线位移Ve在总位移中起主导作用,蠕变变形引起的加载线位移Vc很小,加载线位移率比值■c/■远小于1,蠕变变形被限制在临近裂纹扩展路径的细长条带状区域内,裂纹尖端没有发生大范围蠕变变形。上述结果说明FGH95合金在700℃下为蠕变脆性材料,应力强度因子可作为FGH95合金高温疲劳裂纹扩展的有效驱动力参数。

Creep-crack growth in a standard compact-tension specimen has been at 700℃ simulated for an elastic/creeping material,FGH95 powder metallurgy superalloy using the finite element code.The Norton power-law model was used for describing the creep behavior of FGH95.In the simulation,two cases of crack growth rates,relatively fast（3.25×0-2mm/h） and slow（6.5×0-4mm/h）,were considered.The numerical simulation result shows that,in the process of crack growth of FGH95 at 700℃,the load-line deflection due to elasticity（Ve） dominates the total deflection（V）,with only small part due to creep（Vc）.For both cases,the ratio of the load-line deflection rate due to creep（■） to the total deflection rate（■） was found to be well below 1.0,i.e.,■/■=1.0,and the creep zone was limited in a narrow banding area without large scale creep deformation near the crack tip.The result suggests that the crack growth behavior of FGH95 at 700℃ can be classified as creep-brittle,and stress intensity factor K will be the candidate parameter for crack growth driving force of FGH95 at elevated temperature.