American Journal of Applied Sciences 5 (4): 296-300, 2008 ISSN 1546-9239 © 2008 Science Publications Corresponding Author: Ahmad Baharuddin Abdullah, School of Mechanical Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang, MALAYSIA, Tel: +604-5996332, Fax: +604-5941025 296 The Effect of Corner Radii and Part Orientation on Stress Distribution of Cold Forging Die Ahmad Baharuddin Abdullah, Kam Shwu Ling and Zahurin Samad School of Mechanical Engineering, Universiti Sains Malaysia Engineering Campus, 14300 Nibong Tebal Penang, MALAYSIA Abstract : One of the most critical problems in cold forging is the huge stresses generated from the deformation of metal leads to die failure. The distribution of stresses mainly depends on geometry of the die. An approach to optimal design in cold forging die geometry and orientation are presented in this paper. The impression cold forging dies of the Universal joint was generated using three-dimensional CAD modeling software, SolidWorks. This CAD modeling software coupled with FEA tools, COSMOSWorks. The paper emphasizes on effect of the corner radius and dies orientation on stress distribution. Keywords : Cold forging die, corner radii, orientation, stress distribution INTRODUCTION Cold forging is one of the most widely used metal forming processes, where a bulk of material is compress at room temperature with no heating of the initial slug or inter-stages to produced the desired shape and size. The process produces greater dimensional accuracy than hot forming, and does not produce scale. However, the plastic flow characteristics of the workpiece require higher forging pressures and at the same time induce stress onto the die [1] . As a result, this will affect performance of the die including service life and quality of finished parts. There are many researches show that this problem can be solved by applying appropriate methods either by improving the cold forging process or by improving the die design. The purpose is the same, which to reduce the stress on die that resulted during the forging operation. The important factors in the process design of cold forging are the shape of pre-form and the number of pre-forgings. Process conditions and sequence of process design are very important in improving the forging process. Process condition such as the stress- strain relationship of the billet and die materials, the friction between the billet and the die, etc [2] . The resulted stress on die can be reduced by improving the die design. For example: (i) Improve the die material properties; Usually, die materials must be hardened to withstand severe service conditions, but also need to have enough ductility to prevent their cracking and brittle fracture. (ii) Design the flash at appropriate location with proper size and shape; normally, flash is used to release the working pressure during forging operation. (iii) Select the optimal corner radius for the die Numbers of research have been done in reducing stress such as by dividing the process into multi-steps [3] . Some of them emphasis on introducing new design approach such as pre-chamfering, spread extrusion and relief axis [4] and double tapered insert and split insert design [5] . Stress can also be reduced by focusing on the highest loaded zone and suggest several solution such as by increasing the transition radii [6] . Many parameters have been consider such as land width, petal angle and rake angle are taken into consideration [7] and changing the die material [5] . Catastrophic failure is due tensile stress especially at stress concentration region of the die i.e. at fillets and corner and to avoid this type of failure two recommendations are suggested i.e. by changing the die profile or use pre-stress elements [8] . In