The frame of the beam straightening machine is a solid frame composite structure, which is a preloaded structure composed of a base, a column, an upper beam, a tie rod, and a nut. The frame of the beam straightener is a symmetrical structure with biaxial symmetry. During preloading, the force of the frame also has biaxial symmetry, so when the finite element analysis of the frame is carried out in the preloaded state, only a quarter of the structure is taken to establish a finite element model. In the straightening state, the force is only uniaxially symmetric. At this time, the half-structure of the frame is taken to establish a finite element model. After necessary simplification, the finite and non-geometric model of the half-structure of the beam straightening machine frame is obtained. The spherical bearing surface of the upper beam is simplified to a circular plane.
Finite Element Mechanical Model
FENGWEI uses special finite element analysis software to mesh the model and add boundary conditions. During mesh division, the edge length of the element is manually controlled, and the four-node tetrahedral element is used to automatically divide the finite element mesh. Take 1/4 of the structure to divide the finite element mesh and prepare it for use in the preloaded state. In the straightening state, mirror the 1/4 frame structure together with the finite element mesh to obtain the finite element mesh model of the semi-structure of the frame, so that the symmetry of the frame structure and the finite element mesh is achieved.
After the finite element meshing is completed, the following boundary conditions are set to form the finite element mechanical model.
Stress in a preloaded state
In the preloaded state, the stress of the frame is mainly represented by the tensile stress on the tie rod and the compressive stress of the column and the upper and lower beams.
From the analysis results of the original structure, the following conclusions can be drawn:
(1) The strength of the frame is sufficient only under the action of the preload.
(2) In the straightening state, the compressive stress of the column is reduced, but remains negative, indicating that the pre-tightening force of the screw is sufficient (1277.4t/piece). The equivalent stress of the upper beam end face stress rise is very close to the yield limit of the material, and the thickness of the plate can be appropriately thickened. The base stress value is small.
(3) From the perspective of deformation, the deformation of the base is large, and there is bending of the plate itself.
It can be seen that the structure of the beam straightening frame is not reasonable enough, and it is necessary to optimize it.
Structure optimization ideas and steps
The aforementioned upper beam end
The surface stress value is very close to the yield limit of the material, while the base stress value is small, and the high-stress area is only in a small local area. Therefore, first, consider improving the structural stress distribution and stress value level, and then adjust the structure and improve the frame stiffness when the structural stress is reasonable.
In the preloaded state, the stress distribution of the frame is the same as that of the original structure, but its compressive stress value is much lower than that of the original structure. Comparing the analysis results, the following conclusions can be drawn:
(1) After the structural adjustment, the frame stress has been improved, the frame strength is sufficient, and the screw preload is also sufficient.
(2) However, the stiffness of the beam straightening machine frame is greatly reduced. From the constraints and deformation of the frame, the deformation of the frame base is the main reason for the reduction of the frame stiffness, but the stress value of the base is not high. , the larger deformation is mainly caused by the structural form. Therefore, to improve the rigidity of the rack, the structural form of the rack base should be adjusted. The effective way is to turn the opening structure of the base into a box-shaped structure and properly reinforced it.
Judging from the situation during preloading, the deformation of the beam straightening machine frame is the same, because, during the preloading, the deformation of the frame is mainly the compression deformation of the column and its adjacent parts, while the part far from the column is not deformed. very small.