The Measuring Method about Flow Stress-Strain Characteristics of Plastics Using the Indenting Hardness Test by a Spherical Indenter

This study deals with the measuring method about flow stress-strain characteristics of plastics using the indenting hardness test by a spherical indenter. Firstly, hardness Pm(mean contact pressure)-total mean strain of an indentation ε_<ic> characteristics are obtained with the indenting experiments by a spherical indenter, and flow stress Y-total strain ε(=ε_<ic>) characteristics are measured using the uniaxial compression tests for plastic materials ; PMMA, ABS, PC and PE. Secondly, Hardness/Flow stress ratio C is formulated, C=9.8 Pm/Y:Y in MPa, as the function of the ratio (ε_<ic> / ε_r), ε_r is an elastic recovery strain (=Y/E_s, E_s : Young's modulus). Finally, it is shown that flow stress-strain characteristics from the elastic strain range to about the 10-15% strain range of plastics can be obtained using a one time indenting hardness test by a spherical indenter, by means of the calculation with the formulated equations in this paper and the former reports, and this method can be applied to the present hardness testing machines