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FEM modeling of hard turning with consideration of viscoplastic asymmetry and phase transformation

Uhlmann E., Mahnken R., Ivanov I. M., Cheng C.

Journal of Machine Engineering

2013

Vol. 13, No. 1

80--92

A material model for strain rate and temperature dependent asymmetric plastic behavior accompanied by phase transformation induced plasticity (TRIP) as an important phenomenon in steel production and machining processes was developed. To this end the well-known Johnson-Cook flow stress model has been extended by the concept of weighting functions considering the asymmetric plastic material behavior under tensile, compressive and torsion load. Furthermore, the extended Johnson-Cook model has been combined with the Leblond approach regarding the ductility increase by transformation induced plasticity occurring during hard turning of AISI 52100. On the basis of the theoretical approach for calculating the flow stress with consideration of the viscoplastic asymmetry, a material routine for the FEM-software DEFORM has been implemented. The material and friction model coefficients have been determined in accordance with force and surface temperature measurements during hard turning of AISI 52100. The model takes the phase transformations between martensite and austenite and the influence of externally applied stress on the austenite start temperature into account.

A combined chemical and biological heap leaching of an oxide gold-bearing ore.

Groudev S. N., Spasova I. I., Ivanov I. M.

Fizykochemiczne Problemy Mineralurgii

1999

Vol. 33

55-61

A heap consisting of an oxide gold-bearing ore contgaining 3.5 g/ton of gold and 14.0 g/ton of silver was leached by solutions containing amino acids of microbial origin and thiosulfate as gold-complexing agents. 68.4% of the gold and 53.6% of the silver were leached within 20 days in this way. The pregnant solutions after leaching were treated by cementation with metallic zinc. Mixed gold-bearing concentrations containing also zinc and copper as valuable components were the products from the cementation.