Experimental And Numerical Investigation On The Buckling Forming Of Sheet Metal

In order to improve the inevitable disadvantages of sheet metal stamping technology,such as large forming load,serious thickness thinning and so on,a new special forming process--buckling forming is put forward based on the thought of "useful buckling".In buckling forming,the sheet metal can be induced to the specific buckling deformation and eventually become the needed parts by setting specific deflection or constraint artificially.In this paper,the buckling forming processes of Q235 steel,304 stainless steel and high strength steel QP980 sheet were studied by experiments and finite element simulations.According to the existing equipment conditions,a set of mechanical device that can convert the uniaxial pressure of servo compressor into multi-directional pressures or pull forces were independently designed and produced,based on which the buckling forming experimental platform was built;The influence of materials,boundary conditions,rolling directions,initial imperfections,aspect ratios,shapes and sizes on the buckling performance of the compression sheet metal were studied systematically;By using the finite element software ABAQUS 6.13,the buckling forming finite model of high strength steel QP980 was established initially,which includes flow stress model,yield criterion and hardening model;Besides,several typical solving methods of buckling problems in finite element simulation were introduced and verified in detail,and were compared with the experimental results,during which the dynamical explicit algorithm showed better performances than other methods.Furthermore,the buckling forming process and stamping process of high strength steel QP980 were conducted by finite element simulation,and the stress field and thickness distribution of the forming part were analyzed and compared.The conclusions are as follows:1.Compared with the stamping forming,the forming load of the buckling forming is much smaller,so it has a significant advantage in energy saving.2.Due to the active feeding mechanism in the process of buckling forming,the thickness thinning is very small when the forming completed.In the example of this paper,the thicknesses of the part sections after stamping process are obviously reduced and some reduction rates reach 10%,while the part after buckling forming have almost no thickness thinning.3.During the stamping process,the blank is mainly under the tensile state,while for the buckling forming process,the stress state is mainly compressive one.It is known that the compressive stress can promote plastic deformation and conduct better formability,which means that the part formability is better in buckling forming than stamping process.4.The stamping products usually require that the angle of side-wall is greater than 90°.Otherwise,the punch and back stroke cannot be achieved.While the buckling forming parts have no such limitation,so it has a wider design possibility for this forming method.5.Compared with stamping forming,the buckling forming is featured with poorer forming accuracy,worse force control and unmatured product design process.Thus,further researches are highly demanded.