多向热应力作用下耐热钢材料热疲劳强度的试验研究和寿命推算

多向应力作用下的金属材料热疲劳问题．在７０年代初，日本学者平修工，井上达 雄等人曾进行过研究，提出了用当量应变范围评价多向应力作用下的热疲劳寿命方法． 作者在此基础上．对合金材料ＧＨ３６在较大应变范围下的热疲劳问题进行了研究。 试验机为热裂型．瞬时应力和应变用有限元法求出，然后定出裂纹萌生点的当量应变 范围。结果表明；在相同的当量应变范围，裂纹长度小于０．２ｍｍ；热疲劳寿命比当 量温度下的高温低周疲劳寿命低；当裂纹长度等于０．２ｍｍ，热疲劳寿命与当量温度 下的高温低周疲劳寿命相同。

Thermal Fatigue Strength and Life Assessment of High Temperature Alloys under Multiaxial Stress Condition

The thermal fatigue problems of metal material acted by multiaxial stress had been researched by S. Taira and T. Jnoue in 1970, and the conclusions are reach ed that the life of multiaxial thermal fatigue can be evaluated by effective strain range, and the curve of Nf is just the same as that of elevated temperature LCF life under the effective temperature By this theory, the alloy GH36 is researched in the condition of biger strain range in the paper. The thermal fatigae experiments are made On heat cracking fatigue experiment machine, the transient stress and the strain of the sample are analysed, and the effective strain range of crack initiation point in cooling and heating cycle is decided by FEM. It is shown that for the same effective strain range, when the length of crackle is smaller than 0.2 mm,the thermal fatigue life is lower than that of elevated temperature LCF in effective temperature, when the length of fatigue crackle is equal to 0.2 mm, the multiaxial thermal fatigue life of various upper limit temperature is just the same as that of elevated temperature LCF in effective temperature.