THE RELATIONSHIP BETWEEN INDENTATION AND UNIAXIAL CREEP IN AMORPHOUS SELENIUM

Ultralow load indentation techniques can be used to obtain time-depend ent mechanical properties, termed indentation creep, of materials. How ever, the comparison of indentation creep data to that obtained during conventional creep testing is difficult, mainly due to the determinat ion of the strain rate experienced by the material during indentation. Using the power-law creep equation and the equation for Newtonian vis cosity as a function of-stress and strain rate, a relationship between indentation strain rate, epsilon(I) = h/h, and the effective strain r ate occurring during the indentation creep process is obtained. Indent ation creep measurements on amorphous selenium in the Newtonian viscou s flow regime above the glass transition temperature were obtained. Th e data were then used to determine that the coefficient relating inden tation strain rate to the effective strain rate is equal to 0.09, or e psilon = 0.09 epsilon(I)