Yield Function for Porous Metals With High Pressure Gas Pores

To reduce weight while maintaining high specific strength, Structural Porous Metals (SPM) are being developed. These materials are alloys containing an inert gas at very high pressures in distributed pores. The pores of gas are incorporated into the SPM during processing. Since the pores are closed at high pressures, the material can be processed by standard methods such as rolling or forging without collapsing the gas pores. This paper deals with the determination of the yield stress of these structural porous metals. The yield function is calculated by calculating the energy needed to deform the material to the yield point. In the case of SPM, the yield function must include the work needed to deform the gas pores as the material yields. The energy of deformation for the gas in the pores is evaluated according to the ideal gas law. The result of the analysis is then compared with classic yield functions for monolithic alloys.