Estimation of hot stamping lubricant efficiency under dynamic loading conditions

This paper presents a unique methodology which focusses on the quantitative determination of anti-friction properties of lubrication for large strains under dynamic loading. To compare the anti-friction properties of lubricants, a special-purpose stamp was designed. Workpieces with hubs consisting of eight radial wedge-type branches having different constituent convergence angles were stamped using a stamping tool. Under conditions of dynamic loading, a new criterion (coefficient) of lubricant effectiveness is proposed. Furthermore, a coefficient that quantitatively considers the stability of the technological lubricant properties in relation to geometrical changes is suggested. Regression models were developed for titanium alloys linking these two coefficients to allow the evaluation of the effectiveness of four variants of lubricant. It was found that lubricants composed of cubic bore nitride, water-soluble polymer, polyacrylamide and water have the best anti-friction efficiency of the tested lubricant samples.