The Experimental And Simulated Research On Electric Hot Incremental Forming

The incremental forming has some outstanding advantages such as die-less and low-cost, it has wide application prospect in the field of single and mini-batch production and pilot production but has difficulty in manufacturing hard-forming and high strength sheet. Electric hot incremental forming introduces resistance heating into normal incremental forming and can improve the plastic of the sheet by increasing the temperature, which makes forming easy. At present, there is little study on electric hot incremental forming and is no study on forming plate with electric hot incremental forming. This thesis studied the formability, the temperature and the forming angle limits of the plate under different process conditions by testing the process of electric hot incremental forming to obtain the influence laws and the optimum parameters. At the same time this thesis analyzed the change of the thickness, the stress, the strain and the forming force of the plate by finite element simulation to provide some base for the subsequent study of electric hot incremental forming.After building the test devices and selecting different currents, this thesis conducted experimental research of electric hot incremental forming plate and studied the influence laws of the different currents on the formability of the plate. The results showed that, the heating efficiency is not obvious in the current of100A and200A, the formed parts are ideal in current of500A, and the formed parts are easy to fracture in the current of300A and400A. Meanwhile this thesis studied the influences of the current, the forming speed and the forming step on the temperature field of the contact zone and the forming angle limits of the plate by conducting orthogonal test in the base of the present test conditions. This thesis established an experience formula which consists of initial temperature and temperature gradient according to the measured temperature. The results showed that, only the current has influence on the initial temperature, and the parameters have no influence on the temperature gradient. The highest temperature is obtained when the current is500A. the forming speed is12r/min and the forming step is0.4mm. And the current has great influence on the forming angle limit. The highest forming angle limit is obtained when the current is500A, the forming speed is19r/min.For deep analysis in deformation mechanisms of the plate during the process of electric hot incremental forming, this thesis created a finite element model in ANSYS/LS-DYNA using the forming trajectory data extracted with MATLAB by setting the contact option and loading the established temperature experience formula. Then this thesis analyzed the change of the thickness, the stress, the strain and the forming force of the plate by simulating the process of electric hot incremental forming in different current. The results showed that, the current has no influence on the distribution of the thickness, the stress and the strain. And the major principal stress and the forming force improve with the decrease of the current. There is three forming process of the plate, the rolling deformation, the shear deformation and the tensile deformation. The thinnest position appears nearby the contact area which is in accord with the broken area of the plate in the tests.