# Failure Analysis of Gantry Crane Slewing Bearing Based on Gear Position Accuracy Error
## 2 Slewing Bearing Mechanical Analysis and Test  
### Model Construction  
Due to the large size of the three-row roller slewing bearing of the MQ4038 port gantry crane and the large number of internal structural contact parts, larger computational resources are required. Therefore, according to the actual loading characteristics of the slewing bearing, reasonable assumptions and simplifications are made to the model on the basis of less influence on the analysis process [11; 12]:  
1. Disregarding the influence of components such as cages, seals, retaining bolts, etc., on the analysis process.
2. Ignoring chamfers, excessive rounding, and some step structures that have less influence on the analysis process [13; 14; 15].
3. Assuming the pinion is rigidly connected to the turntable structure and ignoring the influence of components in the slewing mechanism.
4. Accessories such as stairs and cabs are ignored in the modeling because they have less influence on the main structural forces.  
Referring to the design parameters of the gantry crane, slewing bearing structure parameters. and design drawings, we established the 3D models of the gantry crane turntable structure, slewing bearing, and cylinder structure, which are shown in Figures 1-3. All of the components are assembled in Solidworks according to the actual matching position relationship.  
In order for FEM software to correctly identify the assembly model, the assembly model needs to be pre-processed to ensure the integrity of the model and the correctness of the fit relationship. The Simulation module in Solid works is a finite element analysis module, which can pre-process a 3D model to ensure the correctness of the model after it is imported into ANSYS Workbench. Otherwise, ANSYS Workbench will consume a great deal of computation time and computer memory resources for analysis, resulting in a lower analysis time of the assembly model and even causing problems such as non-convergence of the analysis results.  
Due to the large overall size of the assembly and the limited functionality of the simulation analysis module compared to professional finite element software such as ANSYS Workbench, the assembly mesh can be divided in Simulation first in order to save analysis time and memory, and if the mesh can be reasonably divided, it means that the modeling can be successfully imported into ANSYS Workbench. Since there are many components in the model, it is difficult to mesh the whole assembly if the default meshing  
Figure 1: (**a**) Drive pinion model; (**b**) slewing bearing model.  
Figure 3: (**a**) Pinion and large gear ring meshing model; (**b**) assembly body model.  
Figure 2: (**a**) Turntable structure model; (**b**) cylinder structure model.  
method is used, so a local mesh control method is used for meshing, so that each component is assigned different mesh sizes according to the needs. The schematic diagram of the grid after the division is shown in Figure 4.  
Once the meshing is complete, it can be preliminarily judged that the assembled model essentially meets the analysis requirements, so the file is converted into X_T format for subsequent smooth import into ANSYS Workbench software.