英語翻譯
2.Material flow optimisation in cold and warm forging
2.1.Avoiding laps
In certain conditions of deformation the material can buckle causing collapse of free surface
resulting in laps and folds.Laps are the defects that appear when free surface of material
folds over itself.From practical point of view the laps are very annoying kind of defects
because they tend to appear each time when we want to intensify deformation for cost
reduction,for example,when we try to skip preforming operation.The lap can occur in rib-
web forging at a variety of locations where the rib may buckle.Sometimes laps can appear
when we try to upset a billet with diameter to height ratio within admissible limit but due to
small deviations from ideal shape or non-parallel cuts the billet may buckle.
The fully automatic finite element mesh generation implemented in QForm ensures simulation of surface-to-surface contact that happens in a lap area.It is very important for reliable prediction of this defect.The program automatically increases mesh density in critical area when the surface starts to collapse.
This feature is illustrated by practical example of warm forging of the cam of oval shape with two round off-centre cavities of different depth.This is 3D problem.When using cylindrical billet the material first fills the shorter “arm” of the cam and then flows in circumferential direction towards its long “arm” and the laps occur on its upper and lower surfaces (Fig 1 b).The pin on the lower die is higher than on the upper die and lower lap is more developed then upper one.The program automatically detects the zones where the lap potentially may occur and automatically increases the mesh density there (Fig 2.b).Thus the program is able to detect the finest peculiarities of the material flow and is very sensitive.