针对几何形状完全相同但材料不同的两种涡轮叶片,采用相同的试验方法进行高温低周疲劳试验,普通铸造K403合金叶片和定向凝固DZ22B合金叶片却在不同的部位破坏,K403合金叶片在试验考核的榫齿部位断裂,而DZ22B合金叶片的榫齿在叶身根部断裂前均未出现裂纹.为了解释上述试验结果,展开了两类叶片试验条件应力场的有限元分析和定向凝同叶片晶粒形貌的数值模拟.研究结果表明:相同几何结构的普通铸造叶片和定向凝固叶片,其应力分布趋势相似,应力峰值均出现在叶片第一榫齿处;定向凝固叶片的失效模式与普通铸造叶片不同,其破坏不仅与应力场分布有关,而且受叶片各部位的晶粒形貌影响,叶片的失效不一定发生在应力最大的部位.%Under high temperature Iow cycle fatigue (LOF) loads, directional solidification (DS) turbine blades present quite different failure features as compared with equiaxed (EQ) turbine blades with identical geometry and similar stress distribution. All the EQ blade specimens fractured in the key section located at the serration part of the blade. However, this part of the DS blade specimens exhibited no microcrack before the fracture in the root of the blade body. Obviously, the damage characteristic of the DS blade is different from that of the conventional EQ blade, which fractures at the highest stress point. Further theoretical investigation indicates that grain structure of the DS blade has a significant impact on both the properties of the material and its subsequent load capacity. For the DS blade, the LCF damage is not only related to its stress field, but also affected by the microstructure of various parts.
展开▼
