THE OSU FORMABILITY TEST
Forming processes are among the most frequently used in the fabrication of perforated metals. Formability is the term used to evaluate the capacity of a material to withstand the stretch/draw stresses of forming before splitting occurs. We have had a long-standing interest in testing formability because the standard mechanical tests to evaluating strength in materials, such as the tensile tests, had not correlated well with what actually occurs in forming operations.
Standard formability tests, such as the Limiting Dome Height test (LDH) showed good correlation to press performance, but required high capital investment (upward of $200,000) and lacked the ability to provide consistent from one location or machine to another.
Ohio State University and Interlaken Technology Corporation, with sponsorshipp by the Edison Materials Technology Center (EMTEC) designed a reproducible, accurate formability test and an inexpensive formability testing machine. Following a study conducted by General Motors Corp. that found that 80% of splitting failures occur near the plane strain condition, the OSU Formability Test reliably reproduces this strain state.
After several years work, the team succeeded in designing and refining both the machine and tooling for measuring formability to yield testing results that had one tenth the variation found in the old LDH tests, with time to peform reduced by a factor of 5 to 10, and a machine capital cost of approximately $50,000. The formability test machine has now been commercialized and more than 10 of them are in use in industry during the first years of availability.
These improvements make formability testing a practical reality for all sizes of forming companies.
Goals
Measure the formability of perforated sheets of stainless steel and aluminum and to develop the following relationships:
• Effect of % open area on formability.
• Effect of thickness and hole size on formability.
• Differences in the formability of materials- aluminum alloys 3003, 5052 and 6061 and the stainless steel types 304L, 316L and 409.
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