(Dr. Jonathan Colton, advisor)
"Sheet Metal Forming Using Rapid Prototyped Tool"
The demand for rapid, low-cost die fabrication and modification technology is greater than ever in sheet metal forming industry. This is due to the fact that the need for faster turn-around times and more efficient means of producing prototype and short-run tooling is increasing in today’s ever-competitive business environment.
One category of rapid tooling technology involves the application of advanced polymers and composite materials to fabricate metal forming dies. Despite their advantages in lead time and cost reductions, polymer dies for sheet metal forming application have several drawbacks. Due to their lack of strength as compared to conventional die materials, the use of polymer dies is often limited to prototype or short-run production. Also, because the mechanisms by which they fail are not fully understood, the dies still are designed on the basis of experience and intuition. Therefore, it is desirable to be able to estimate tool life and to take necessary measures to increase tool life during the tool design phase.
The objectives of the proposed research are (1) to develop a method to predict the fatigue life of a polymer die and (2) to establish optimal die design guidelines. The focus will be on rapid prototyped, alumina-filled, polyurethane-based dies in sheet metal forming operation. The study will begin with the determination of dominant process parameters based on the results from finite element analysis. Finite element models for 90º V-die bending and deep drawing processes will be used. The effects of process parameters on stress distribution in the die will provide guidelines to the modification of die design for achieving the desired die life.
In addition, the fatigue failure mechanism will be investigated to predict the fatigue life of the die. To establish a fundamental understanding of the fatigue behavior of the polyurethane-based die material, fatigue properties will be identified from mechanical testing. The test data will be incorporated into the stress-based fatigue analysis to obtain the number of cycles to crack initiation. The analysis results will be validated by comparison with experimental data. The research will provide a new set of engineering material data for the advanced polymer as well as potential applications in the design technology of rapid prototyped tools.