夹杂对粉末高温合金裂纹扩展寿命的影响

采用有限元方法中的奇异单元,研究了当粉末高温合金FGH 95中存在由夹杂引起的裂纹时,夹杂对裂纹应力强度因子的影响;并在此基础上,利用Paris公式,计算了夹杂对裂纹扩展寿命的影响。研究结果表明:当夹杂处于裂纹的不同位置时,对应力强度因子的影响趋势也不同,且硬夹杂的影响趋势与软夹杂相反;存在软夹杂时,将夹杂当作初始裂纹,不考虑夹杂的影响得出的裂纹扩展寿命结果是安全的,而对于硬夹杂得出的结果偏于危险,对于FGH 95粉末高温合金,夹杂相对于基体材料其弹性模量偏小,为软夹杂,因此将夹杂当作初始裂纹计算裂纹扩展寿命时不考虑夹杂的影响,将得到偏于安全的裂纹扩展寿命计算结果。这一结论为简化粉末冶金涡轮盘的寿命分析提供了依据。

Influence of Inclusions on Crack Growth Life of Powder Metallurgy

The influence of inclusion on crack Stress Intensity Factor(SIF) of Powder Metallurgy(PM) FGH 95 was investigated using singular element method with fine mesh at crack front.The effect of inclusion on crack growth life of PM was also calculated by Paris formula.The result indicates that the influence of inclusions on crack SIF of PM changes with the alteration of the inclusion's location relative to the crack.When the crack is in the range of three times of the inclusion's radius,the inclusion can affect the SIF and it will not affect on it if the crack exceeds this range.When the radius of the crack approaches the radius of the inclusion,the influence of soft inclusions on SIF is contrary to the rigid inclusions.For the crack growth life,the influence of soft inclusion is also contrary to the rigid inclusions.The crack growth life without inclusions is shorter than with soft inclusions,but it is longer than that with rigid inclusions.Because the elastic module of the inclusion is smaller than the matrix,the inclusion in FGH95 is soft inclusion and the crack growth life without inclusions is longer than that with inclusions in FGH95.The conclusion can make the analysis of the PM turbine disks life simpler.