Experimental and analytical evaluation for elastic deformation behaviors of cold forging tool

Since the dimensional accuracy of forged parts are largely influenced by elastic behaviors of the tool material. The characteristics of elastic deformation at a forming tool are evaluated for a cold forged alloyed steel by experiment and FEM analysis. Elastic strain at the tool is measured dynamically using strain gauges attached to the surface of die for a ball stud mass-produced continuously in a cold former. Results of FEM analysis are compared to the experimentally measured values at two modeling approaches. The first approach is made by regarding the die as a rigid body at a forging cycle and analyzed the die stress by loading the die with the pressure from the deformed part. On the other hand, the second approach is adopted as that the die and workpiece are simultaneously considered as deformable bodies during contact. Since calculation of the elastic strain and deformation amount of tool can be made at each formation step by the second approach, the elastic deflection of die acts upon the dimension of forged part at each formation step. The second approach relatively takes more time for the simulation. However, the analysis result at the elastic assumption of tool is better for predicting not only the elastic strain of tool but also the dimensional accuracy of forged part.