A Study On Analytic Method Of Mechanical Fatigue In Cylinder Block Key Parts

China is a country with the highest automobile products in the world. The reliability of automobile is one of the most important performances to the level of technology. It has a significant impact on the product competitiveness. Strengthened combustion and lightweight structures are2main trends in vehicle engine technology. It puts forward the new challenge to the design for main loaded structures in engine.This thesis conducted the study on mechanical fatigue of cylinder block. The influence of loads and structures to fatigue lives in key parts of cylinder block is studied by simulation and fatigue test. The improving design of structure is conducted according to simulation and test results.Contents of this thesis can be briefly listed as:1. The fatigue life distribution of495diesel cylinder block under a working condition is simulated and obtains the key parts including bulkhead and upper part of cylinder block.2. The fatigue lives of bulkhead under fatigue test load and operation load are simulated, The results show that the existing fatigue test load is valid; The fatigue lives of cylinder block under the two means of applying loads in fatigue test are simulated and compared, the results show that in bulkhead area the influence by different applying load means can be ignored.3. The cylinder block fatigue test rig are developed on the basis of above study and reference of test rig in foreign country. Two different loads can be applied on the test rig.4. The cylinder block fatigue tests are conducted on the developed test rig. The test results are compared with the simulation results. The weak positions in bulkhead are almost the same with the positions that fracture occurred during tests. The fatigue lives of bolt hole area are simulated after fatigue crack occurred in this area. The fatigue weak position obtained by simulation is same as position where crack occurred in fatigue tests. Then the fatigue lives are simulated and compared after design change near thread engage area. The results showed that increasing thickness near the last engage thread is a valid method. It is verified by the tests results after improving design.