Path dependent high strain, strain-rate deformation of polymer toroidal elements

Abstract

Experimental and numerical analyses on recovery of polymer deformation after demolding in the hot embossing process J.The dynamic behavior of toroidal elements (o-rings) is investigated at the range of global engineering strains up to 0.7 and strain rates about 100 s À1 . It was observed that the corresponding average dynamic stiffness of rubber toroidal elements increases up to 3 times in comparison with their quasistatic compression. The viscoelastic dynamic model using linear strain-rate dependence and Hertz damped model did not satisfactory agree with experimental data in investigated range of strains and strain-rates. In order to reflect experimental results, a modified viscoelastic model with power-law strain-rate dependence was proposed. Path dependent deformation of o-rings with different levels of pre-compression was investigated under dynamic loading conditions. It was found that dynamic response of pre-compressed o-rings at the initial strain range of 0.04-0.25 is similar to the behavior of uncompressed o-rings, but further increasing pre-compression to 0.4 and 0.5 results in different force-strain curves demonstrating memory effect. This phenomenon is explained using a model incorporating dependence of dynamic force on initial pre-compression introducing critical level of dynamic strain, after which memory of initial pre-compression fades. This model predicts that force history of weakly compressed o-rings (initial strain 4%) on the stage of loading represents an envelope for all other data in agreement with experiments. In all cases, the dynamic behavior was characterized by stiffer force-displacement curves in comparison with quasistatic compression of o-rings. V C 2014 AIP Publishing LLC. [http://dx.

Attenuation of short strongly nonlinear stress pulses in dissipative granular chains

“…This dissipation can be due to viscoelastoplastic deformation of contacts [22,23], which in general has nonlinear dependence on strains [24][25][26]. Another strongly nonlinear discrete metamaterial composed from steel cylinders and rubber o-rings (with better tunability than system with Hertzian contacts [27][28][29][30]), demonstrated nonlinear dependence on strains and strain rates being sensitive to loading path [31,32].…”