FEM model and constraints
When the geometric model is set up, the FEM model needs to be analyzed and the related constraints are set.
1. FEM model: in order to accurately simulate the geometric structure of parts in unit network, preprocessing is meshed by Femap, using 10 node quadrilateral mesh, mesh size 6mm, away from hot spots, and appropriately increasing mesh size.
2. Constraints: the center of the door frame and the drive bridge junction is fixed as a fixed point, restraining the direction of the X, Y, and Z axis, only allowing the rotation of the axis. At the load center, 500mm loads the magnitude and direction of the load. It considers the weight and dynamic coefficient of the inner frame, the size is: (3000+500) x1.4x10=49000N and the direction of the force is vertical downward.
The results of FEM analysis are compared before and after the change of the load and the position of the adding force point before and after the change of the overlap degree. For this overlap change, the FEM analysis mainly includes two aspects:
1. The stress of the new and old door frame hot spot (hot spot) before and after the changes are compared.
(1) Change the stress situation of hot spot before and after, such as Figure 4 and figure 5.
After the change, the stress of the 4 stress concentration parts decreased, the maximum decreased by 5.9%, and the minimum decreased by 3.1%.
2. According to the change of the force of the wheel axle on the door frame, the change of the stress of the roller shaft is analyzed.
Due to the increase of the maximum lifting height of the modified rear door frame, the bending deformation increases after the change, this leads to the increase of the force on the roller shaft.
The results and conclusions of the analysis
1. The overlap degree does not increase the stress of the hot spot, but it has a slight decreasing trend. Therefore, after changing, it can meet the design requirements without changing.
2. When the portal is raised to the maximum height of 4525mm, the force of the roller shaft increases and the stress increases by 15%. If the customer has been in accordance with the load bearing before the change to the maximum height, is bound to affect the service life of the roller shaft, so if the customer needs to use the door frame after the change, the lifting height to between 4325mm and 4525mm, the corresponding bearing capacity to reduce 15%, to ensure the strength and service life of the door frame.
3. By FEM analysis, can effectively analyze the changes before and after the stress change, by limiting the bearing weight to ensure the door shelf life, compared with the traditional design method, save time, improve costs and related test work, is a kind of effective analysis method.
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