Scientific paper ID 1697 : 2018/3

Valentin Gaydarov, Galina Zamfirova

The influence of the loading speed on some micromechanical characteristics of a polypropylene was investigated. The measurements were performed by dynamic ultra micro hardness tester DUH – 211S by penetration depths measuring at constant loading rate. The indenter was a Vickers pyramid. The measurement mode was load – hold - unload till preset depth. Five loading speeds in the interval (1.25  20) mN/s were chosen. From dependences load - depth at different loading rate the following microindentation characteristics were determined: dynamic, Martens and indentation hardnesses, indentation elastic modulus, creep and elasticity. Linear dependences of the studied characteristics on logarithm of loading rate were established with correlation coefficient very close to one. The sensitivity of the indentation quantities were commented and attributed to the specific models for their calculation, as well as the degree of influence by the creep process, inevitable in the loading process. Dynamic and indentation hardnesses, as well as the indentation elastic modulus, are almost unaffected by this parameter. Martens hardness is sensitive to loading speed because it is calculated from the slope of the loading part of the indentation curve.

наноиндентация динамична твърдост индентационна твърдост дълбочинно-чувствителна индентация.nanoindentation dynamic hardness indentation hardness indentation Depth-sensing indentation.Valentin Gaydarov Galina Zamfirova


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