THE INFLUENCE OF VISCOPLASTICITY IN THE INTERPRETATION OF THE RING TEST

In this work, a new semi-analytical study of the flat ring-compression test, having a 'built-in' ability to measure interface friction, has been proposed. This method, on the basis of the upper-bound method, ta kes into account the viscoplastic behavior of the material. A signific ant influence of the strain-rate sensitivity exponent m on the determi nation of the friction factor (m) over bar has been found. The calcula tions have shown that neglecting nz leads to an under-estimation of th is friction factor. Thus, new calibration charts have been plotted in the range of m = 0-0.5 allowing the practical and easy estimation of ( m) over bar for a wide variety of viscoplastic materials. The results found for perfectly-plastic materials (m = 0) are in good agreement wi th those obtained by Avitzur.