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An Elasto-Viscoplastic Formulation that Accounts for Effect of Pore Air on Powder Compression Process

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  034027,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.14091) @2003
Authors:   B. Mittal, V.M. Puri
Keywords:   Dry powder compression, PSU-EVP model, elasto-viscoplasticity, pore air compression, cubical triaxial tester, triaxial testing, mechanical property determination

The aim of this research was to measure and analyze the rate-dependent mechanical behavior of a dry industrial powder (named MZF powder) undergoing compression in a medium pressure flexible boundary cubical triaxial tester (CTT). The mechanical behavior of the powder was modeled using a new elasto-viscoplastic model (PSU-EVP model). The mechanical properties of MZF powder were studied under different types of stress paths: isotropic (or HTC) and shear (or CTC). Three different compression rates of 0.62, 6.21, and 20.7 MPa/minute were studied at pressures below 14 MPa. Test results demonstrated that the compression and shear responses of the powder were non-linear. Also, MZF powder exhibited varying elastic and plastic deformation at different pressure levels that were quantified by developing numerous statistical correlations (R2>0.90). For example, the average bulk modulus and shear modulus values for MZF powder increased linearly with pressure (R2>0.90) at all compression rates. From the data collected, it was proved that the CTT is a reliable tool for gathering triaxial test data on powders with high consistency and reproducibility of test results (coefficient of variation or COV = 15%). Additional parameters for the PSU-EVP model were also quantified.

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