Page 27 - MetalForming May 2014

procedures are changes in the die design to control material flow.
3) Lock in the stresses. Mechanical stiffeners are designed into the stamping.
Each category contains numerous possible solutions to springback problems.
Virtual Forming: Using software to evaluate sheetmetal formability has been in industrial use (as opposed to university and research environments) for more than two decades. The current metalforming programs are part of a major transition to virtual manufac- turing that includes analysis of welding, casting solidification, molding of sheet/ fibre compounds and automation.
Computer simulation of metalform- ing is identified more correctly as com- puterized forming-process develop- ment or even computerized die tryout. The more highly developed software programs closely match the forming of sheetmetal virtual stampings to the physical stampings in the press shop.
A full range of analysis capabilities is available to evaluate AHSS as a new stamping analysis or to compare AHSS stampings to conventional mild-steel stampings. These programs allow rapid what-if scenarios to explore different types and grades of AHSS, alternative processing or even design optimiza- tion. During selection of process and die-design parameters, the software will evaluate how each new input not only affects the outputs, but also will show wrinkles and generate a press- loading curve. Problem areas or defects can be traced backwards through the forming stages to the initiation of the problem. The most comprehensive software allows analysis of multistage forming, such as progressive dies, transfer presses or tandem presses. The effects of trimming and other offal removal on the springback of the part are documented.
Running all of the parts in the virtual world at the same time and comparing compatibility is a big step forward for press shops and the final assembly sta- tions. The virtual press shop becomes even more important for AHSS,
because their higher strengths reduce the size of the formability windows. To generate a meaningful output, metal- formers must partner with their steel suppliers to obtain the actual steel properties to input into the virtual- forming software.
Case Studies
The latest edition of the guidelines includes results of a program by the
Auto/Steel Partnership to evaluate forming of10 AHSS stampings, from initial design through virtual forming to physical forming and test evalua- tion. Included are springback com- pensation, post-launch analysis and lessons learned. Studying these stamping trials illustrates what can be accomplished when all parties come together as partners and not enemies. MF
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