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Determination of flow stress and friction in cold forging is of paramount importance. In this work, an inverse procedure is developed for predicting the Coulomb’s coefficient of friction and strain-dependent flow stress simultaneously based on the measurement of bulge and forging load. It is also established that in cold forging Coulomb’s coefficient of friction can be approximated as half the friction factor in Tresca (or constant friction) model. In the inverse procedure, forging load is estimated analytically but bulging is estimated by developing an empirical relation. The efficacy of the inverse procedure is ascertained by the data obtained from finite element method simulations. Finite element method was implemented in ABAQUS and validated with the results available in literature. In most of the cases, inverse procedure provides less than 5% error in the estimates of friction and flow stress. A sensitivity analysis is also carried out to study the effect of measurement error. It is observed that error in the estimation of friction is proportional to error in the measurement of bulge. The novelty of the method lies in the quickness and simplicity of the method.

The presented paper describes the topical problem in metal forging production. It deals with the choice of an optimal lubricant for forging of carbon steels and Ni-based alloys. Within the scope of the paper, the properties of several water-based colloidal-graphite lubricants were investigated. The physicochemical and technological properties of these lubricants are presented. It was found that physicochemical properties of lubricant compositions have an influence on friction coefficient value and as a result on die life during forging process. The ring compression method was used to estimate the friction coefficient value. Both mechanical press and screw press were used for the test. The comparative analysis of the investigated lubricants was carried out. The die life was estimated on the basis of statistics obtained with the help of an automated forging line. The practical recommendations were given to choose an optimal water-based colloidal-graphite lubricant for forging of carbon steel or Ni-based alloy.

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The aim of this paper is to predict accurately the flow stress of Al-Cu-Mg-Fe-Ni alloy at temperatures of the range 350-470 °C with the help of flow stress mathematical model that is based on the phenomenological approach. This model includes both hardening and softening processes which follow the deformation of aluminium alloy A92648 at temperatures from 350 °C to 470 °C and strain rates of 0.001-0.4 s -1 .

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