# Failure Analysis of Gantry Crane Slewing Bearing Based on Gear Position Accuracy Error
## 3 Analysis of Results
### Mechanical Simulation Results
#### 3.1.2. Gear Tooth Meshing Displacement  
The overall displacement of the pinion and the large gear ring is presented in Figure 14a, and the slewing mechanism produced a deflection in the \(x\)-axis direction. In order to further analyze the gear mesh situation and examine the changes in the axial relationship between the two, the model at the gear mesh was locally enlarged, as shown in Figure 14b. Both the pinion gear and the large gear ring are deflected, and by plotting the position of the linear deflection of the edge of the width of the teeth of both, it is found that there is an angle between the two. It can be judged that the parallel state of the gear axis has been affected. The pinion gear and large gear ring X-direction displacement is shown in Figure 15a. In the two-gear tooth mesh, the pinion gear tooth's upper-end face horizontal displacement value is 15.0023 mm, the gear tooth's lower-end face horizontal displacement value is 13.1464 mm, and the difference between the upper- and lower-end face horizontal displacement values is 1.86 mm. As can be seen from Figure 15b, the slewing support large gear ring gear tooth's upper-end face horizontal displacement value is 12.9531 mm, the  
Figure 14: (**a**) Deflection of pinion and large gear ring; (**b**) edge clamping angle of pinion and large gear ring tooth width. Figure 13: Different displacements exist between the inner ring and outer ring of the slewing support. horizontal displacement value of the lower-end face of the gear teeth is 12.6987 mm, and the difference between the upper- and lower-end face horizontal displacement values is 0.25 mm. According to the size of the pinion gear and large gear ring tooth width, combined with the initial position relationship between the two and the position relationship after the generation of relative displacement, the size of the angle generated by their axes is calculated. From Figure 16, it can be seen that the pinion axis offset angle is larger than the large ring axis offset angle, and the angle between the two axes is 0.48\({}^{\circ}\). Consequently, it can be obtained that the meshing relationship of the gears is affected, and the upper part of the large ring gear teeth is subjected to the abnormal extrusion of the pinion. The stress value of the teeth at the engagement of the large gear ring of the slewing bearing is small, with a size of 51.159 MPa, while the stress value of the upper tooth root is the largest, with a size of 252.05 MPa, which is approximately 5 times higher than the stress value of the lower tooth root. The stress result is compared with the stress value of the upper tooth root when the gear is ideally engaged (205.08 MPa), and the stress value increased by approximately 23%. Although the gear tooth stress value does not exceed the allowable stress (348.14 MPa), the gear tooth meshing situation is not ideal, the stress values at the upper and lower tooth roots differ greatly, and the stresses at the root of the gear teeth are not uniform. The local magnification of the tooth root stress situation is shown in Figure 17. The upper root area is the main stress area, and at the corner of the tooth root,  
Figure 16: Diagram of gear axis angle after being loaded. Figure 15: \(X\)-axis displacement of gear: (**a**) Pinion; (**b**) large gear ring. there is a stress concentration phenomenon, which is consistent with the extrusion of the pinion on its gear teeth. Before loading, due to the limitation of the displacement of its roller seat, the pinion and the large ring gear ring of the slewing ring are in a good meshing state, the stress at the root of the slewing ring is uniform, and the load of the gear teeth is ideal. After loading, due to the displacement of the cylinder structure and the internal structure of the slewing bearing, the gear axis has a certain angle of inclusion, which affects the meshing relationship between the gear teeth, resulting in the concentration of the upper tooth root stress at the meshing of the large ring gear.