Large-strain time-temperature equivalence in high density polyethylene for prediction of extreme deformation and damage

• Published in: EPJ Web of conferences Vol. 26; p. 1057
• Main Authors: Hiermaier, S., Furmanski, J., Brown, E.N., Clements, B., Cady, C.M., Gray, G.T.
• Format: Journal Article
• Language: English
• Published: EDP Sciences 2012
• ISBN: 2759807576; 9782759807574
• ISSN: 2100-014X; 2100-014X
• DOI: 10.1051/epjconf/20122601057

Time-temperature equivalence is a widely recognized property of many time-dependent material systems, where there is a clear predictive link relating the deformation response at a nominal temperature and a high strain-rate to an equivalent response at a depressed temperature and nominal strain-rate. It has been found that high-density polyethylene (HDPE) obeys a linear empirical formulation relating test temperature and strain-rate. This observation was extended to continuous stress-strain curves, such that material response measured in a load frame at large strains and low strain-rates (at depressed temperatures) could be translated into a temperature-dependent response at high strain-rates and validated against Taylor impact results. Time-temperature equivalence was used in conjuction with jump-rate compression tests to investigate isothermal response at high strain-rate while exluding adiabatic heating. The validated constitutive response was then applied to the analysis of Dynamic-Tensile-Extrusion of HDPE, a tensile analog to Taylor impact developed at LANL. The Dyn-Ten-Ext test results and FEA found that HDPE deformed smoothly after exiting the die, and after substantial drawing appeared to undergo a pressure-dependent shear damage mechanism at intermediate velocities, while it fragmented at high velocities. Dynamic-Tensile-Extrusion, properly coupled with a validated constitutive model, can successfully probe extreme tensile deformation and damage of polymers.