Abstract   Knowing the amount of residual stresses and find technological solutions to minimize and control them during the production operation are an important task because great levels of deformation which occurs in single point incremental forming (SPIF), this induce highly non-uniform residual stresses. In this papera propose of a method for multilayer single point incremental forming with change in thickness of the top plate (0.5, 0.7, 0.9) mm and lubrication or material between two plates(polymer, grease, grease with graphite, mos2) to knowing an effect of this method  and parameters on residual stresses for the bottom plates. Also compare these results for the bottom plates with the single plate at same thickness 0.9 mm.The results showed that when increase thickness of the top plate the value of residual stresses will decrease for bottom plates and when used graphite with grease between two plates gives less residual stresses (R.S = 60.173 MPa.) reverse when used Mos2 which will gives a larger residual stresses (R.S = 146.617 MPa.) in the bottom plate. Keywords: Multilayer Single Point Incremental Forming (SPIF), Residual Stresses, Lubrication.

Bending process is the one important process in the sheet metal forming in many industries, the main problem of bending process is the spring back phenomenon which is happens after removing the punch. This research involves theoretical and experimental study of the effect of holding time on spring back value of sheet material in V-bending die with 90 0 , with different rolling direction and different holding time (0,10,20,30) min. (Al -Si) alloy having the thickness of (2 mm) were employed as the work pieces material for all experiments. The results revealed that as the hold time increases, the spring back decrease and spring back ratio increases.

Springback forecasting of sheet formation is constantly remarkable problem in the métier, due to their influence the great in the definitive shape of the product. Study presents effects of pretension in tow rolling direction (0, 45 degree) on the springback behavior of the (Brass 65-35) sheet under V-die bending by an experimental. The pretension ranges from five different pretensions levels starting from 11% to 55% from total strain in each rolling direction by increment of 11%. used in punching that was performed at a constant deformation velocity of (5 mm/min) then bent on a 90° V-shaped die for the springback evaluation. The results from experiment indicate that the springback increase with pretension ratio and the springback in 45 degree is higher in rolling direction.