. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Design Details
Achieving light weight while meeting stringent structural strength requirements: • The casting configuration of the wheel hub was validated by extensive FEA-based structural (linear and non-linear) analysis, which helped establish the high stress and critical areas. The casting configuration was optimized through several iterations with FEA and casting process modeling simulations in conjunction with the rigging and process parameters.
• Process modeling predicted the location and approximate size of flaws like shrinkage, hot tears and porosity.
Utilizing smooth transitions and solid bolt holes: • Due to their relative size, the mounting bolt holes on the wheel hub were not designed to be as-cast and instead were machined out. In doing so, making those areas sound and free of any shrinkage or porosity was important.
• A smooth transition helped float the re- oxidation products while filling critical areas.
Using FEA and casting process modeling tools: Design failure mode effects analysis and process failure mode effects analysis, in conjunction with full blown structural FEA-based modeling, were conducted. A damage tolerance study established the critical high stress areas. At the same time, mold filling and solidification simulation estab- lished the predictable casting flaw size and loca- tions, which were mapped with the critical high stress areas and flaws established by the design and performance requirements. An adequate safety margin was added for the variability in the process and material properties.
METAL
Jiten Shah is president of Product Development & Analysis (PDA) LLC, Naperville, Ill., and a 25-year casting design and manufacturing veteran.
22 Metal casting Design & purchasing March/april 2010
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