Study On Deformation Reconstruction Of Structural Parts Of Heavy-Duty NC Machine Tool Based On Inverse FEM

The processing ability of heavy-duty machine tools is an important reflection of national industrial level and comprehensive strength.The key factor reflects the processing ability of machine tools is the processing accuracy.The mechanical and thermal deformation of the gantry structure and the base are the main factors affect the processing accuracy.Therefore,it is of great significance to study the real-time monitoring and online compensation of structural deformation for improving the processing accuracy of heavy-duty machine tools.The structure parts of heavy-duty machine tools are irregular in shape and have many interactions.It is difficult to obtain the load information.The common deformation measurement can not meet the deformation monitoring requirement of structure parts of heavy-duty machine tools.In this paper,inverse Finite Element Method(iFEM)is proposed to reconstruct the displacement field of the gantry structure and the base.The iFEM makes up the relation between nodal degree of freedom(DOF)and analytical strain by the strain matrix,establishes the error least-squares function for analytical strain and experimental strain,obtains DOF by solving the minimum value of the error least-squares function,and uses the shape functions to obtain the displacement field of structural parts.The iFEM can obtain the displacement field of structure when the load information is unknown and some strain data of the measured structure is missing.It has great advantages in the deformation monitoring of the structure with complex shape and unknown load information.The main research results of this paper are as follows:(1)The structure simplification and load analysis of the gantry structure and the base have been carried out.According to the simplified model,the beam element and quadrilateral element were used to mesh the grids and number the nodes,and the iFEM algorithm has been compiled.The iFEM has been improved according to the requirements of the point arrangement,and the single-side point arrangement of the elements has been realized.(2)The point arrangement requirements of the gantry structure and the base have been discussed,and the point arrangement planning of structural parts has been put forward.According to the deformation analysis,the number of measured points of gantry structure was reduced.The problems of measured points missing and global stiffness matrix singularity have been solved by using "Virtual Point Arrangement Method".Combined with ANSYS simulation analysis,the correctness of the point arrangement planning has been verified.(3)The experimental systems of deformation reconstruction of the gantry structure and the base have been designed,and the measuring principles of FBG and strain rosettes were described.With the measured strain data as input,the iFEM can obtain the reconstructed displacement field of structural parts.The experimental results show that the displacement field reconstructed by the iFEM coincides with the displacement field simulated by ANSYS,which verifies the correctness of the iFEM for deformation monitoring of the structural parts of heavy-duty machine tools.