Structural Analysis And Optimization Of Engine Balance Shaft Shell

As the most commonly used automotive power plant,the imbalance of force and torque in the internal inertial force system of four-cylinder in-line engine is an important cause of engine vibration and noise.And the four cylinder machine can not rely on itself or the balance weight on the crankshaft to eliminate the vibration caused by the second-order reciprocating inertial force,therefore,the currently developed engines generally reduce the engine imbalance by installing a balance shaft assembly.In view of the fracture problem of the balance shaft shell of an engine equipped with the balance shaft assembly during the bench test,a special study were carried out to solve the fracture problem of the balance shaft shell.In this paper,the engine balance shaft assembly is the research object.The structure analysis and optimization of the balance shaft shell are carried out by using UG,ADAMS,ANSYS Workbench and other software.The specific work includes the following contents:(1)According to the two-dimensional drawing of the balance shaft assembly,the UG software is used for solid modeling and assembly of all parts of balance shaft assembly.(2)Introduce the simplified three-dimensional model of the balance shaft assembly into the ANSYS Workbench software,and perform modal analysis on it.By comparing the extracted 1~6 order modal frequency and the calculated balance shaft operating frequency,it is ruled out that the shell is broken due to insufficient rigidity and low modal frequency.(3)The multi-body dynamic analysis of the balance shaft assembly is carried out by using ADAMS software,and the stress of each bearing hole of the balance shaft shell is obtained.Use this as the boundary condition for strength analysis and fatigue analysis.(4)The ANSYS Workbench software is used to analyze the strength of the balancing shaft shell,and the maximum stress results of four working conditions are obtained,the maximum stress value is 181.66 MPa,which is lower than the tensile strength of YL113 228 MPa,excluding the shell structure is broken due to insufficient strength.(5)Applying the multi-body dynamics analysis of the balance shaft assembly to obtain the stress-time history of the shell as the fatigue load spectrum to carry out the fatigue analysis of the balance shaft shell.The minimum life of the balance shaft shell is about 20.55 hours,which is basically consistent with the time when the shell breaks during the bench test.Therefore,it is determined that the fracture reason of the balance shaft shell is the stress fatigue failure caused by repeated loading.(6)According to the fatigue analysis results,the second generation non-dominated classification genetic algorithm was used to optimize the structure of the balance shaft shell by ANSYS Workbench software.(7)The finite element analysis of the optimized shell structure is carried out again.The optimization results show that the method effectively solves the fracture problem of the balance shaft shell.This paper is a research that integrates modeling,analysis and optimization.It provides an effective method for solving the problem of structural fracture of the shaft shell structure.It also plays a reference role for others to determine the cause of mechanical structural fracture and solve the problem of it.