scholarly journals Wave Dispersion and Attenuation in Viscoelastic Split Hopkinson Pressure Bar

1998 ◽  
Vol 5 (5-6) ◽  
pp. 307-315 ◽  
Author(s):  
Z.Q. Cheng ◽  
J.R. Crandall ◽  
W.D. Pilkey
Keyword(s):  
Split Hopkinson Pressure Bar ◽  
Soft Materials ◽  
Wave Dispersion ◽  
Hopkinson Pressure Bar ◽  
Viscoelastic Wave Propagation ◽  
Split Hopkinson ◽  
Linear Viscoelastic ◽  
Basic Equations ◽  
Pressure Bar ◽  
Dispersion And Attenuation

A viscoelastic split Hopkinson pressure bar intended for testing soft materials with low acoustic impedance is studied. Using one-dimensional linear viscoelastic wave propagation theory, the basic equations have been established for the determination of the stress—strain—strain rate relationship for the tested material. A method, based on the spectral analysis of wave motion and using measured wave signals along the split Hopkinson pressure bar, is developed for the correction of the dispersion and attenuation of viscoelastic waves. Computational simulations are performed to show the feasibility of the method.

Wave Dispersion and Attenuation in Viscoelastic Split Hopkinson Pressure Bar

2013 ◽  
Vol 535-536 ◽  
pp. 547-550
Author(s):  
Hafiz Sana Ullah Butt ◽  
Pu Xue
Keyword(s):  
Split Hopkinson Pressure Bar ◽  
Soft Materials ◽  
Wave Dispersion ◽  
Wave Number ◽  
Hopkinson Pressure Bar ◽  
Integer Multiple ◽  
Split Hopkinson ◽  
The Difference ◽  
Pressure Bar ◽  
Dispersion And Attenuation

The Split Hopkinson Pressure Bar (SHPB) is most commonly used facility to obtain material properties at high strain rates. Testing of soft materials using this method requires that bars made of low impedance material should be used, in order to improve signal-to-noise ratio of transmitted stress. However, utilization of such bars poses some difficulties in data processing as the wave dispersion and attenuation becomes noticeable due to their viscoelastic nature. Wave propagation coefficients of a viscoelastic pressure bar are evaluated using incident and reflected strain waves generated through impact of two different length striker bars. Two approaches are proposed for propagation coefficient measurement in this study, namely direct and waves-overlap. Using two approaches, it is found that the calculated attenuation coefficients are same, while the wave numbers are different. The difference in wave number in the case of two approaches is due to the difference in calculated phase change of incident and reflected waves, which is found as integer multiple of 2Π. Moreover, propagation coefficients calculated through different striker impacts are found different. The propagation coefficient found through long striker impact, when used for propagation response prediction of waves generated by short striker impact, resulted in high oscillations in predicted waves.

Quasistatic and Dynamic Compressive Behavior of Gelatin

2010 ◽  
Author(s):  
Jiwoon Kwon ◽  
Ghatu Subhash
Keyword(s):  
Split Hopkinson Pressure Bar ◽  
Rate Sensitivity ◽  
Polymeric Materials ◽  
Soft Materials ◽  
High Rate ◽  
Constitutive Behavior ◽  
Hopkinson Pressure Bar ◽  
Property Data ◽  
Split Hopkinson ◽  
Pressure Bar

Gelatin has been extensively used as a tissue stimulant. Determination of properties and tits constitutive behavior is crucial to successful use of gelatin in these applications. In this study, ballistic gelatin was used because the recipe to prepare the gelatin and its quasi-static strength (250 bloom) of this particular type of gelatin is well known [1]. Although the study for high rate deformation is important to understand the damage from blast impact, majority of the currently available material property data is in quasi-static range [2,3]. Generally, polymeric materials (including human tissue) exhibit highly rate sensitive response [4]. Therefore, the understanding of the constitutive behavior for these materials at high rate loading is essential. This study will provide the rate sensitivity of gelatin by comparing the response under quasi-static and dynamic loading. In order to investigate the dynamic behavior of gelatin, the split Hopkinson pressure bar (SHPB) was used in this study. Because use of a solid metallic bar to test such soft materials does not provide an adequate transmitted signal, a polymer split Hopkinson pressure bar (PSHPB) was used to reduce the impedance mismatch between bar and soft gelatin specimen. The nature of dispersion and attenuation was corrected using an iterative scheme developed earlier [5].

scholarly journals ‘Seeing’ Strain in Soft Materials

Molecules ◽  
2019 ◽  
Vol 24 (3) ◽  
pp. 542 ◽  
Author(s):  
Zhiyong Xia ◽  
Vanessa D. Alphonse ◽  
Doug B. Trigg ◽  
Tim P. Harrigan ◽  
Jeff M. Paulson ◽  
...  
Keyword(s):  
High Speed ◽  
Split Hopkinson Pressure Bar ◽  
Color Change ◽  
Soft Materials ◽  
Image Correlation ◽  
High Rate ◽  
Hopkinson Pressure Bar ◽  
Dimethyl Siloxane ◽  
Split Hopkinson ◽  
Pressure Bar

Several technologies can be used for measuring strains of soft materials under high rate impact conditions. These technologies include high speed tensile test, split Hopkinson pressure bar test, digital image correlation and high speed x-ray imaging. However, none of these existing technologies can produce a continuous 3D spatial strain distribution in the test specimen. Here we report a novel passive strain sensor based on poly(dimethyl siloxane) (PDMS) elastomer with covalently incorporated spiropyran (SP) mechanophore to measure impact induced strains. We have shown that the incorporation of SP into PDMS at 0.25 wt% level can adequately measure impact strains via color change under a high strain rate of 1500 s−1 within a fraction of a millisecond. Further, the color change is fully reversible and thus can be used repeatedly. This technology has a high potential to be used for quantifying brain strain for traumatic brain injury applications.

Dynamic Compression Testing of Soft Materials

2002 ◽  
Vol 69 (3) ◽  
pp. 214-223 ◽  
Author(s):  
W. Chen ◽  
F. Lu ◽  
D. J. Frew ◽  
M. J. Forrestal
Keyword(s):  
Split Hopkinson Pressure Bar ◽  
Dynamic Equilibrium ◽  
Dynamic Compression ◽  
Soft Materials ◽  
Specimen Thickness ◽  
Strain Rates ◽  
Hopkinson Pressure Bar ◽  
Split Hopkinson ◽  
Pressure Bar ◽  
Strain Responses

Low-strength and low-impedance materials pose significant challenges in the design of experiments to determine dynamic stress-strain responses. When these materials are tested with a conventional split Hopkinson pressure bar, the specimen will not deform homogeneously and the tests are not valid. To obtain valid data, the shape of the incident pulse and the specimen thickness must be designed such that the specimens are in dynamic equilibrium and deform homogeneously at constant strain rates. In addition, a sensitive transmission bar is required to detect the weak transmitted pulses. Experimental results show that homogeneous deformations at nearly constant strain rates can be achieved in materials with very low impedances, such as a silicone rubber and a polyurethane foam, with the experimental modifications presented in this study.

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