Study On Characteristic Parameters And Correlation Of New Model Of Plastic Friction Under Complex Stress State

Friction is a natural phenomenon that affects almost all objects in motion.In the plastic forming process,the friction caused by the plastic deformation between the mold and the workpiece is more complicated than the mechanically driven friction.The influencing factors and friction characteristics of friction have become the research hotspots in the field of tribology and plastic processing.Many researchers have shown that the classic Coulomb friction model or shear friction model proposed by Amontons and Coulomb cannot accurately describe the friction during plastic forming.Therefore,scholars from various countries have established a new friction model through finite element method for analysis.Finite Element Analysis(FEA)is a widely used method that provides a powerful tool for the development and optimization of plastic processing processes.Used to predict the results of various forming processes and reduce development costs by replacing expensive experimental tools.The accuracy of the simulation is critically dependent on the boundary conditions.Therefore,friction modeling plays an important role in the plastic forming process.In this paper,a three-dimensional plastic friction model based on shear rate is established based on rigid-plastic finite element method,and a new model calculation program is written by Fortran programming language.The operating principle of the program system of the new model is to convert the measured horizontal displacement of the joint into the displacement velocity,and input the displacement velocity into the program system as the initial boundary condition,and calculate the friction shear stress and the shear strain rate.Experiments and numerical calculations are used to verify the accuracy of the new friction model.In this paper,1060 aluminum alloy materials were used as experimental materials,and five cube specimens with different heights and the same cross-sectional area were developed for upsetting experiments.Two kinds of roughness test pieces of the same height are used for coMParison.Taking 1mm as the theoretical reduction,the coordinates of the two lines perpendicular to each other on the neutral plane after each pressing are measured,and the obtained node coordinates are converted into displacement speed and then input into the new model program,and finally the test is obtained.Friction shear stress and shear strain rate on the contact surface,and study the relationship between the two.