Research On The Influence Of Loading Method Of Fatigue Simulation Test On Failure Model Of V-type Cylinder Block

With the development of high speed,high power density and high combustion pressure of engine,the operation conditions of engine become stricter and stricter.It also puts forward higher requirement towards the reliability of cylinder block.As one of the main research methods to study the reliability of cylinder block,fatigue simulation test has been widely used.However,different loading methods of fatigue simulation test make different results on local load and failure model of cylinder block.There is no unified conclusion of which loading method is better and which should be used under specific condition,especially for the V-type cylinder block.A V12 diesel engine was studied based on CAE analysis and fatigue simulation test.Research on the influence of four loading methods of fatigue simulation test on local load and failure model of the cylinder block was made.The four loading methods were opposite-cylinder loading method,diagonal-cylinder loading method(?),diagonal-cylinder loading method(?)and four-cylinder loading method.Material parameters,loads and contact setup were the same during the four loading methods except for the location and quantity of the cylinders and loading fixtures,which was convenient to conduct the research.They couldn't be applied to fatigue simulation test one by one due to the restriction of test condition.Therefore,the research route was set as follows: Firstly the finite element model of opposite-cylinder loading method was validated based on the combination of simulation and experiment.Secondly,the other loading methods were studied with CAE analysis on the basis of the accuracy of the finite element model of opposite-cylinder loading method.The research work was as follows: Firstly,crankshaft dynamic calculation model was built and force and bearing moment of main bearing seats were obtained,which offered a reference for the pressure load of fatigue simulation test.Secondly,the finite element model of opposite-cylinder loading method was built and stress,safety factor and fatigue life of the cylinder block were calculated.Thirdly,fatigue simulation test of opposite-cylinder loading method was conducted to validate the FEM model.Following the same analysis parameters and steps,the FEM models of the other three loading methods were built and stress,safety factor and fatigue life of the cylinder block were obtained as well.Finally,comparative analysis was made of four loading methods using the calculation results.The analysis showed that the four-cylinder loading method made the strictest and the most comprehensive results and should be used in priority.The diagonal-cylinder loading method(?)made the most optimistic and the least scientific results which was bad for the reliability verification.It shouldn't be used in fatigue simulation test.The error between opposite-cylinder loading method and four-cylinder loading method was 10% above,some regions were more than 100%.The error between diagonal-cylinder loading method(?)and four-cylinder loading method was under 10% in the vast major regions.Therefore,diagonal-cylinder loading method(?)was an effective alternative method if four-cylinder loading method couldn't be used due to the restriction of the experiment.What's more,opposite-cylinder loading method should be used cautiously.