The Research On Fatigue Life Prediction Method Of Diesel Cylinder Block

The cylinder block is one of the most important components of the engine. As theskeleton and infrastructure of the entire engine, the cylinder block bears extremely complexload during engine’s operation, and the magnitude and direction of these loads are constantlychanging with the crank angle’s changing. The cylinder can not occur cycle fatigue failurewithin the design life, because it is different from other engine parts, we can not completelyrepair cylinder fatigue damage. Therefore, the reliability of the cylinder has an importantimpact on overall engine performance, and it determines the entire life of the engine in someway. So it is very necessary to make an in-depth study on the cylinder block fatigue. Thispaper using the CY4102BZQ diesel engine cylinder block as the research object, make anin-depth study on the dynamic stress analysis of fatigue cylinder block by using the theory offinite element.Firstly, this paper summarizes the basic theory of fatigue. It described the current body ofresearch at home and abroad, classifies a detailed inductive analysis of the mechanism offatigue.One entire cylinder (cylinder) and the two adjacent half cylinders (second cylinder and4-cylinder) of the CY4102BZQ diesel engine are established as a combination of structuresolid model. We import the solid model into the finite element pre-processing software ANSA.Then we defines parts, materials and properties. We simplifies the structure combined withthe structural characteristics of the various parts with the prerequisite of the calculationaccuracy. And we make a reasonable choice of the element type, element size for the meshingof the composite structure. Eight contact relationship are defined, such as the contact of thecylinder head with bolts, the contact of the cylinder block and the bolts, and so on.Displacement constraints are also defined at the support points and the cut surface of thecomposite structure of the cylinder block. Finally, the creating of the finite element model ofthe cylinder block is complete.Then this paper does a transient dynamics analysis on the finite element model by thefinite element software ANSYS. The stress and displacement time histories of each node are obtained. And then do an analysis on the stress distribution of the high-stress position. Itprovides a theoretical basis for design optimization of the cylinder block, and data for thefatigue life analysis of the cylinder block.Detailed discussion of Some theories to calculate the fatigue life such as the fatigue lifecalculation mode, the load spectrum, and the fatigue cumulative damage theory are made inthis paper. It import the result of the transient dynamics analysis into fatigue analysis softwareDesignLife, and calculate out the fatigue life of the cylinder block. And finally we make ananalysis of the calculation results.Finally, we make a research on the influencing factors of the fatigue of the cylinder block.We summarize the dangerous areas of the cylinder block prone to fatigue failure combinedwith the actual operation of the engine. And then we make a study on the analysis methods ofthe impact factors sensitivity on the fatigue dangerous areas.