The gearboxes, which make up the core component of the metro train bogie, should be lightweight and highly reliable in order to guarantee the security and comfort of train operation. The transient dynamic analysis is performed on a certain type of domestic metro train gearbox as the research object to obtain the load borne by the gearbox body during operation. Then, the strength of the box is analysed. Finally, a lightweight design is completed using the topology optimization design method under the condition that the strength performance of the box is not reduced. The findings reveal that the weight of the optimized box is 145.8 kg, 12.27% reduction; the maximum deformation is 0.05981 mm, 14.46% reduction; and the maximum stress is 66.34 MPa, 7.41% reduction.
The complex curved boundary of the topology optimization model is not conducive to industrial manufacturing hence the necessity to reconstruct the geometrical model. This study presents a general method for the boundary regularization fitting reconstruction of a topological optimization model based on the Freeman code. This method is performed as follows: the unit vector is defined; the vectorized expression of the Freeman code boundary is established; through the concept of the boundary bending parameter, determination of the bending degree of the Freeman code boundary is established; an elemental structure analysis method is proposed, and the logic of the automatic extraction of the control points of the Freeman code boundary fitting is achieved. This method proposes a series of innovative technical methods, such as unit vector definition, boundary bending matrix, and elemental structure analysis method, and designs a complete set of structural analysis logic for a Freeman code type boundary, which can automatically analyze the structure feature of the 8-connected Freeman code boundary, extract the fitting control points on the boundary, and complete the automatic fitting and reconstruction of the boundary. This method is robust and applicable to all Freeman code boundaries. The entire process is automated.
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