发动机缸盖残余应力的测量及分析

采用盲孔法测量3组发动机铝合金缸盖裂纹附近和敏感部位的残余应力情况,分析缸盖内的残余应力对其裂纹产生的具体影响。考虑到缸盖的复杂结构特点和选择的测点位置,测试选用钻铣床钻盲孔和铣断通油管及其侧板,并在钻盲孔释放残余应力和铣削过程中通过30通道应变仪DRA-30A记录测点的应变时域曲线。对测试结果的分析和研究表明:通油管部分的残余应力以压应力为主,下缸体的上表面以拉应力为主,这种上压下拉的残余应力分布情况是缸盖内产生裂纹的主要原因;测点4处产生裂纹的可能性较大,测点7处通油管对下缸体的局部拉伸作用最为明显;B90组结构设计和加工工艺在3组试样中最为合理。据此测试结果和研究结论改进产品的结构和工艺后,该种缸盖满足设计要求。

Measurement and Analysis of Residual Stresses in Engine Cylinder Head

The specific impact of residual stresses in aluminum-alloy engine cylinder head on crack forming was analyzed,while adopting the blind-hole method to measure the level and distribution of the residual stresses in the cracking areas and some other sensitive parts of three groups.Considering cylinder head′s complex structure and the position of the measuring points,the processes of drilling blind holes and milling the pipelines and their side plates were conducted by a milling and drilling machine in this study.The time-domain curves of strain at the measuring points were recorded by a 30-channel strain gauge(DRA-30A) during stress releasing in the processes of drilling and milling.The test results showed that the primary cause of cracks in the cylinder head is,that the residual stresses in the pipelines is mainly compressive stress but in the top surface of the lower part it is tensile stress.The highest possible area of forming crack is in Point 4,and the most obvious tensile effect on the lower part resulted from the pipeline in Point 7.The structure design and processing technology of Group B90 are the most reasonable in all three groups.According to the test results and research conclusion,the new cylinder head can meet the design requirements after improving the structure and processing technology.