In order to solve the problems of excessive mass and unreasonable stress distribution of gearbox shell castings of high-power tractors, the static analysis of gearbox shell castings under the working conditions of first gear and reverse gear is carried out, and the topology optimization is carried out on the basis of static analysis, so as to realize the purpose of reducing the mass of gearbox shell castings.
The specific contents can be divided into four parts:
(1). According to the drawing, CATIA is used to establish the 3D digital model of gearbox housing casting. Import the built 3D digital analog into HyperMesh for pre-processing. Through modal calculation, the natural frequencies, damping ratio and vibration mode data of each order in the range of 0 ~ 1000Hz are obtained, which provides important indexes for the structural performance of the optimized gearbox shell casting.
(2). The modal test design of gearbox shell casting adopts the German m + P analyzer dynamic signal analysis system, selects the force hammer to excite the vibration box, and collects data through the force sensor and acceleration sensor. Set the sampling range as 1 ~ 2000Hz, analyze the frequency response function curve, obtain the natural frequencies and vibration modes of each order of the gearbox shell casting, and compare them with the calculated modal results to verify the correctness of the established finite element model.
(3). Calculate the load, carry out structural strength analysis, and study the shell stress distribution and deformation of gearbox shell casting under static load. Because the casting of the transmission housing is under the maximum stress under the working conditions of first gear and reverse gear, only the static analysis under these two working conditions is carried out.
(4). Based on the static analysis results of gearbox shell casting, the topology optimization is carried out on the premise of ensuring that the structural performance after optimization is higher than or little different from the original structure. The topology optimization method used in this paper is variable density method. The density of each element in the finite element model of gearbox shell casting is taken as the design variable, the minimum structural strain energy of gearbox shell casting is taken as the objective function, and the volume ratio is taken as the constraint function. According to the results of topology optimization, the gearbox shell casting is improved, such as the change of wall thickness, the arrangement of stiffeners, chamfering treatment and so on. Finally, the static and modal analysis of the improved structure is carried out to ensure that the improved structure meets the use requirements.