Dynamic stress equilibration in split Hopkinson pressure bar tests on soft materials

2004 ◽  
Vol 44 (3) ◽  
pp. 300-312 ◽  
Author(s):  
B. Song ◽  
W. Chen
Keyword(s):  
Dynamic Stress ◽  
Split Hopkinson Pressure Bar ◽  
Soft Materials ◽  
Hopkinson Pressure Bar ◽  
Split Hopkinson ◽  
Pressure Bar

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.

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].

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.

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.

scholarly journals Dynamic Stress-strain Compressive Response of Soft Tissue using Polymeric split- Hopkinson Pressure Bar

2019 ◽  
Vol 8 (9) ◽  
pp. 341-347
Keyword(s):  
Dynamic Stress ◽  
Soft Tissues ◽  
Split Hopkinson Pressure Bar ◽  
Compressive Strain ◽  
Strain Rates ◽  
Hopkinson Pressure Bar ◽  
Stress Strain ◽  
Rate Dependent ◽  
Split Hopkinson ◽  
Pressure Bar

The characterization of soft tissues subjected to higher compressive strain rates is of increasing importance as the material properties of soft tissues were commonly used in impact applications such as automotive safety and crashworthiness for biofidible numerical modeling of the human body. Due to less availability of stain rate dependent data in the open literature and various challenges in the characterisation of soft tissues under impacts, need were felt for characterisation of soft tissues at higher strain rates. The purpose of this study is to investigate the dynamic mechanical behavior of soft tissues at varying compressive strain-rates. The viscoelastic split Hopkinson pressure bar (SHPB) is designed and developed to predict the high rate compressive behavior of soft tissues. The primary benefit in using viscoelastic bars is the reduced bar impedance allowing for high-quality measurements of the transmitted and reflected stress wave signals. The dynamic behavior of goat muscles has been measured at higher strain rates ~500-1200 s-1 using a polymeric SHPB apparatus. The dynamic stress-strain response of muscle tissue exhibits non-linear behavior under compressive loadings and is strain-rate dependent.

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.

Analysis of the Impact of the Frequency Range of the Tensometer Bridge and Projectile Geometry on the Results of Measurements by the Split Hopkinson Pressure Bar Method

2013 ◽  
Vol 20 (4) ◽  
pp. 555-564 ◽  
Author(s):  
Wojciech Moćko
Keyword(s):  
Test Bench ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Deformation ◽  
Spectral Width ◽  
Hopkinson Pressure Bar ◽  
Computing Environment ◽  
Split Hopkinson ◽  
Pressure Bar ◽  
The Impact ◽  
Bench Model

Abstract The paper presents the results of the analysis of the striker shape impact on the shape of the mechanical elastic wave generated in the Hopkinson bar. The influence of the tensometer amplifier bandwidth on the stress-strain characteristics obtained in this method was analyzed too. For the purposes of analyzing under the computing environment ABAQUS / Explicit the test bench model was created, and then the analysis of the process of dynamic deformation of the specimen with specific mechanical parameters was carried out. Based on those tests, it was found that the geometry of the end of the striker has an effect on the form of the loading wave and the spectral width of the signal of that wave. Reduction of the striker end diameter reduces unwanted oscillations, however, adversely affects the time of strain rate stabilization. It was determined for the assumed test bench configuration that a tensometric measurement system with a bandwidth equal to 50 kHz is sufficient

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