Reliability Analysis Of Engine Block Using Multi-body Dynamics

Block, which is the most crucial part in engine, has its structure and force-enduring condition with high level of complication. With the improvement of engine's strength, statics method based on loading experience or partial model could not reach the precision requirement of block reliability analysis. The application of strength calculation combined with multi-bodies dynamics and finite element method which recently is widely used on crankshaft can rarely be adopted in block calculation because of its complication. A six-line engine was set as the research objection of which reliability was analyzed by the method compounded of multi-body dynamics method, film lubrication calculation, finite element method and Python language program. The results indicate that the 6th main bearing displays poor performance on lubrication and the middle gap on the wall of which could be easily damaged.The main contents of this paper include:1,Multi-body dynamics calculation coupling crankshaft and block was analyzed with NONL main bearing units, and oil film lubrication of main bearings was calculated with EHD2 main bearing units. Main bearing forces of these two results were compared and the oil film lubrication performance of the 6th and 7th main bearings was analyzed.2,The reliability of the whole block covering a work cycle was analyzed by the method combined with finite element method and multi-body dynamics calculation coupling crankshaft and block. The block stress was calculated by finite element method and fatigue strength of the whole block was analyzed based on dynamic load data of the block components covering a work cycle, which were extracted from the result of multi-body dynamics calculation. The stress results were reprocessed in Python language program before fatigue strength calculation because of the incapability of fatigue analysis software to deal with the huge stress result files directly.3,The reliability of the main bearing wall was analyzed by finite element method combined with oil film lubrication of main bearings. Total pressures of main bearings were extracted from oil film lubrication results, and mapped on the main bearing mesh applied Python language program. Then stress of main bearing wall was calculated by finite element method and fatigue strength was analyzed.4,Main bearing wall stress was calculated by statics method, and it was compared with the result from dynamics method. It shows that minimum safety factor of the main bearing wall calculated by dynamics method is smaller than the one by statics method, and more dangerous areas were figured out by dynamics method.5,Fatigue-testing of block was carried out by up-down method. The relation between the test and these three simulation methods was studied.In conclusion, the safety factor distribution of the whole block can be got through the simulation method for block stress based on multi-bodies dynamics which has integrated and global advantage in the reliability analysis of the whole block. When it comes to reliability analysis of main bearing wall, it works with higher precision and less work load. Therefore, this method could be applied in block research and optimization with high level of reliability.