The speed reducer plays a crucial role in the conversion and transmission of power in a mining car. It effectively reduces the output speed and increases the output torque. Its strength and lifespan directly affect the overall performance of the mining car. The speed reducer is bolted to the rear axle housing flange, and the rear axle housing nose cone and stabilizer bar are connected to the frame, thus achieving the connection between the speed reducer and the frame. The speed reducer is also connected to the tires via a torque tube, linking the tires to the frame. The speed reducer plays a vital and critical role in a mining car; therefore, its structural strength and rigidity must be comprehensively considered during design and production.
HyperMesh is a high-efficiency finite element pre- and post-processor capable of building various complex finite element and finite difference models. It has excellent interfaces with various CAD and CAE software and features efficient mesh generation capabilities. This paper utilizes HyperMesh's pre- and post-processing to mesh the reducer frame, add boundary conditions, build a finite element model, and perform finite element analysis using a third-party solver to verify whether its strength meets design requirements, thus providing theoretical reference for the design.
Finite element model establishment and HyperMesh processing of the gearbox frame
Mesh generation based on HyperMesh
In HyperMesh's automated mesh generation module with geometric surfaces, imported surface data sometimes contains defects such as gaps, overlaps, and misalignments. Boundary misalignment often causes mesh distortion, resulting in low element quality and poor solution accuracy. Therefore, geometric cleanup before analysis becomes crucial, determining whether the analysis can proceed and impacting its efficiency and accuracy. By eliminating misalignments and pinholes, compressing the boundaries between adjacent surfaces, and removing unnecessary details, the speed and quality of the overall mesh generation can be improved, thus enhancing computational accuracy.
Figure 1 shows the model of the entire frame after meshing. Before meshing, some small oil pipes in the model were removed, and some small oil holes and other places that were not under stress or were under very little stress were filled.
Material parameters
The material properties of the frame and bolts used in the analysis are shown in Table 1.
Mesh Model
The bearing section has a relatively complex structure, using tetrahedral elements with element sizes ranging from approximately 5 to 25 mm. Other parts use hexahedral elements with element sizes ranging from approximately 5 to 10 mm. Transition surfaces are connected using Tie elements. Bolt dimensions range from 1.5 to 2.5 mm. The total mesh size is 1.8 million.
Boundary conditions
Firstly, the force transmitted from the bearing, hub, and motor to the frame is applied by establishing a bearing point in the stress area. The bearing point is coupled to the stress-bearing part, and the force is applied to the bearing point. Fixed constraints are placed at the connection point with the rear axle housing.
Calculation results
Mining trucks encounter various road conditions during actual operation. This paper selects five relatively harsh working conditions in mining areas: wavy road surface, uneven road surface, tortuous road surface, turning on flat road, and starting on slope, to verify the strength and stiffness of the reducer frame under these conditions. The finite element model established using HyperMesh is imported into a finite element solver for solving, yielding the distribution of strength and stiffness of the reducer frame under different working conditions. Due to confidentiality and space limitations, this paper only presents the overall stress and strain contour maps under uneven road surface conditions.
Overall stress distribution
The maximum stress of the entire frame, considering the bolt preload, occurs at the bottom bolts at 694 MPa. These high-stress areas are located on the upper and lower sides of the frame near the outer side of the front bearing. This is because one end of the frame is fixed, which is equivalent to a cantilever beam model, while the other end bears the force in the y-direction transmitted from the tires, causing the lower part to be under tension and the upper part to be under compression, resulting in this stress distribution effect.
Deformation size
The calculated deformation diagram of the frame under uneven road conditions shows that the relative deformation between the front bearing of the wheel hub and the oil seal is approximately 0.96 mm, which is less than the design value. Therefore, the deformation of the frame will not affect the performance of the oil seal.
in conclusion
(1) The finite element model of the reducer frame was established by applying HyperMesh, the mesh was optimized, the number of unnecessary elements was reduced, the modeling time was greatly shortened, the efficiency and accuracy of computer analysis were improved, and the analysis experience was provided for the application of HyperMesh in the analysis of reducer frame.
(2) A finite element model was established using HyperMesh and solved using a third-party solver to obtain the stress and strain distribution of the reducer frame under different working conditions, providing a basis for the design of the reducer frame.
