The Study On The Formative Theory And Influcing Factors Of The Less Bending

Sheet metal forming due to its characteristic such as high Material utilization, material stable accuracy, low cost of mass production, the efficiency high and so on has been widely used in the automotive, aviation. Sheet metal forming is a common kind of technology in sheet metal forming. When the distance of the die is too small, the less bending will happen. The less bending is one of the defects which affects the precision of the workpiece.For the problem of the less bending, making the less bending as the researching object and basing on large-scale nonliner finite element software MARC, the process of the less bending is simulated, the reason for the less bending is analysed and the critical criterion is proposed.As a result, the rules that the radius of the die, the radius of the punch, the thickness of the sheet metal and the frictional coefficient affect the critical width of the die are obtatined.The mathematical model of the sheet metal bending is established and the contact problem between the sheet metal and the corner radius of the die is simplified to the plane strain problem which the column contact with the half infinite plane. The state that the deformation of the sheet metal reach to the limit of the elastic deformation at the tangency point of the die's corner radius and the slope is considered as the critical criterion of the less bending. Then the formula of die's critical width is deduced based on the elastic and plastic contact theory.Experimental device of sheet metal bending was designed and the rules that the radius of the die, the radius of the punch and the thickness of the sheet metal affect the critical width of the die are studied by experiment. The experimental results are contrasted with the mathematical formula's calculative results .It is proved that the consistency between the formula's calculative results and experimental results is good.