FE Analysis of Critical Testing Parameters in Kolsky Bar Experiments for Elastomers at High Strain Rate

Abstract

The main aim of this research is to present complete methodological guidelines for dynamic characterization of elastomers when subjected to strain rates of 100/s–10,000/s. We consider the following three aspects: (i) the design of high strain rate testing apparatus, (ii) finite element analysis for the optimization of the experimental setup, and (iii) experimental parameters and validation for the response of an elastomeric specimen. To test low impedance soft materials, design of a modified Kolsky bar is discussed. Based on this design, the testing apparatus was constructed, validated, and optimized numerically using finite element methods. Furthermore, investigations on traditional pulse shaping techniques and a new design for pulse shaper are described. The effect of specimen geometry on the homogeneous deformation has been thoroughly accounted for. Using the optimized specimen geometry and pulse shaping technique, nitrile butadiene rubber was tested at different strain rates, and the experimental findings were compared to numerical predictions.

Evaluating the effect of environmental conditions on high compressive strain rates in unfilled and filled neoprene rubbers

“…12,19 In the current investigation, an in-house split-Hopkinson (Kolsky) pressure bar was used for the compression experiments at high strain rates. 16 Specifically, Ti-6A1-4V alloy bars with a diameter of 12.7 mm were used. Although the bar material could be changed to provide a lower impedance mismatch with neoprene, the data collected using titanium alloy bars were of sufficient quality for the study presented in this paper.…”

“…9,15 In order to record elastomers' response to high strain rates, a dynamic MTS or Kolsky bar equipment can be used, as they can function in high-speed deformation. [16][17][18] During a Kolsky bar test, the specimen is sandwiched between two slender rods, the input and output bars, or incident and transmitted bars, which are instrumented with strain gauges. [19][20][21] A loading system, typically a gas gun, propels a shorter third rod or striker into the incident bar.…”

High-Strain-Rate Compression of Elastomers Subjected to Temperature and Humidity Conditions

“…The most commonly used equipment to test materials that are subjected to a high strain rate of small or large deformation is the split-Hopkinson (Kolsky) pressure bar [11][12][13][14]. Although there is no standard design for it, most researchers use an apparatus that includes two long cylindrical elastic bars (incident and transmission) and a striker launching mechanism (such as a gas gun) [15,16].…”

“…In the current paper, natural rubber, silicone and EPDM specimens were exposed to high-strain-rate compression by using split-Hopkinson (Kolsky bar) equipment that was built in-house for testing soft materials [7,16]. To analyze their response to environmental variations from the ambient conditions, we initially applied temperature changes in dry conditions.…”

Viscoelastic Properties of Inert Solid Rocket Propellants Exposed to a Shock Wave

“…Stress-strain relations for HTPB propellant samples subjected to very high strain rates ( > 10 3 s À 1 ) have been obtained using the split-Hopkinson pressure bar (i. e. Kolsky bar) [21], even though these strain rates exceed the ignition rates (i. e. 1 m/s-6 m/s) of the solid rocket propellant [16]. In the Kolsky bar experiments, the stress-strain response of elastomers (e. g. HTPB propellant) under compressive loading can be measured as a function of strain rates that range from 10 2 s À 1 -10 4 s À 1 [22]. However, the literature is lacking high strain rate experiments of HTPB propellant under tensile loading, at rates that exceed the ignition rates.…”