Dynamic Brazilian Test of Brittle Materials Using the Split Hopkinson Pressure Bar and Digital Image Correlation

Strain ◽  
2014 ◽  
Vol 50 (6) ◽  
pp. 563-570 ◽  
Author(s):  
J. J. Chen ◽  
B. Q. Guo ◽  
H. B. Liu ◽  
H. Liu ◽  
P. W. Chen
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Split Hopkinson Pressure Bar ◽  
Brittle Materials ◽  
Brazilian Test ◽  
Image Correlation ◽  
Hopkinson Pressure Bar ◽  
Split Hopkinson ◽  
Pressure Bar

On the use of non-cylindrical specimens in a split-Hopkinson pressure bar

2011 ◽  
Vol 46 (8) ◽  
pp. 866-878 ◽  
Author(s):  
O Sen ◽  
S A Tekalur ◽  
P Maity
Keyword(s):  
Cross Section ◽  
Split Hopkinson Pressure Bar ◽  
Slenderness Ratio ◽  
Kolsky Bar ◽  
Image Correlation ◽  
Cylindrical Shape ◽  
Hopkinson Pressure Bar ◽  
Split Hopkinson ◽  
The Cross ◽  
Pressure Bar

Despite the practice of using cylindrical specimens in a split-Hopkinson pressure bar (Kolsky bar) experiment, the use of non-cylindrical prismatic specimens is not uncommon. This is convenient when testing extra-soft materials like brain tissues, muscles, or samples that are brittle and cannot be machined to an exact cylindrical shape (like bone-samples). The use of a non-cylindrical sample with a flat surface also renders the specimen amenable to a two-dimensional image correlation algorithm. This research aims to show the feasibility of using non-cylindrical specimens in a Kolsky bar. For this, experiments were conducted with a model material for different model cross-sections at a nearly constant strain rate in the split-Hopkinson pressure bar. The findings suggest the use of a suitable characteristic cross-section dimension of the specimen to determine the critical slenderness ratio while selecting a non-cylindrical prismatic specimen. It has been shown that if the specimen design is governed by the suggested slenderness criterion, then there is no effect of specimen length or cross-sectional shape on the stress–strain curve of the material. Through the use of a computational code, the research also shows the effect of non-uniform axial stress distribution along the cross-section of the specimen, resulting due to specimen geometry. On quantification of the stress non-uniformity along the cross-section of the specimen, the findings indicate that the magnitude of the non-uniformity is both small and temporary.

scholarly journals Use of the Kolsky method for dynamic tests of brittle media

2018 ◽  
Vol 174 ◽  
pp. 02022 ◽  
Author(s):  
Anatoliy Bragov ◽  
Leonid Igumnov ◽  
Andrey Lomunov ◽  
Alexander Konstantinov ◽  
Dmitriy Lamzin ◽  
...  
Keyword(s):  
Split Hopkinson Pressure Bar ◽  
Dynamic Test ◽  
Brittle Materials ◽  
Fiber Reinforced Concrete ◽  
Dynamic Tests ◽  
Hopkinson Pressure Bar ◽  
Kolsky Method ◽  
Indirect Tension ◽  
Split Hopkinson ◽  
Pressure Bar

The dynamic test techniques used to obtain the mechanical properties of brittle materials are described. The techniques are based on the fundamental Kolsky method using the Split-Hopkinson Pressure Bar. Dynamic tests are characterized by high intensity and short duration and the influence of inertia on their results should be ruled out which is especially important for brittle media. The prerequisites and assumptions presented methods are described to justify the validity of the obtained data. The methods allow to obtain dynamic deformation diagrams at compression, splitting, indirect tension, shear and triaxial stress state and also to determine the ultimate strength, strain and time properties of brittle materials. The techniques are approved in the tests of ceramic bricks, finegrain concrete and fiber-reinforced concrete.

scholarly journals A Method for Selecting Software for Dynamic Event Analysis: II — The Taylor Anvil and Dynamic Brazilian Tests

2008 ◽  
Author(s):  
J. M. Lacy ◽  
S. R. Novascone ◽  
W. D. Richins ◽  
T. K. Larson
Keyword(s):  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Brazilian Test ◽  
Benchmark Problems ◽  
Hopkinson Pressure Bar ◽  
Cylinder Test ◽  
Split Hopkinson ◽  
Dynamic Yield ◽  
The Subject ◽  
Pressure Bar

New nuclear power reactor designs will require resistance to a variety of possible malevolent attacks as well as traditional dynamic accident scenarios. The design/analysis team may be faced with a broad range of phenomena including air and ground blasts, high-velocity penetrators or shaped charges, and vehicle or aircraft impacts. With a host of software tools available to address these high-energy events, the analysis team must evaluate and select the software most appropriate for their particular set of problems. The accuracy of the selected software should then be validated with respect to the phenomena governing the interaction of the threat and structure. Several software codes are available for the study of blast, impact, and other shock phenomena. At the Idaho National Laboratory (INL), a study is underway to investigate the comparative characteristics of a group of shock and high-strain rate physics codes including ABAQUS, LS-DYNA, CTH, ALEGRA, ALE3D, AUTODYN, and RADIOSS. In part I of this report published in 2007, a series of five benchmark problems to exercise some important capabilities of the subject software was identified. The benchmark problems selected are a Taylor cylinder test, a split Hopkinson pressure bar test, a free air blast, the dynamic splitting tension (Brazilian) test, and projectile penetration of a concrete slab. Part II — this paper — reports the results of two of the benchmark problems: the Taylor cylinder and the dynamic Brazilian test. The Taylor cylinder test is a method to determine the dynamic yield properties of materials. The test specimen is a right circular cylinder which is impacted against a theoretically rigid target. The cylinder deforms upon impact, with the final shape depending upon the specimen density, the impact velocity, and the dynamic yield stress, in turn a function of strain and strain rate. The splitting tension test, or Brazilian test, is a method to measure the tensile strength of concrete using a cylindrical specimen. The specimen is loaded diametrically in compression, producing a fracture at the center of the specimen that propagates toward the loading points until the cylinder is split. To generate a dynamic load, different methods such as a drop-weight or a split Hopkinson pressure bar are employed. The Taylor anvil and dynamic Brazilian test analyses are presented, including discussion of the analysis approach for each of the five subject software packages and two vendor submittals; comparison of results both among the codes and to physical test results; and conclusions as to the applicability of the subject codes to these two problems. Studies of the remaining three benchmark problems and overall conclusions will be presented in future publications.

scholarly journals EVALUATION OF HOPKINSON BAR EXPERIMENTS USING MULTIPLE DIGITAL IMAGE CORRELATION SOFTWARE TOOLS

2019 ◽  
Vol 25 ◽  
pp. 1-5 ◽  
Author(s):  
Marcel Adorna ◽  
Stefan Brodner ◽  
Jan Falta ◽  
Petr Zlámal ◽  
Tomáš Fíla
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
High Speed ◽  
Software Tool ◽  
Image Correlation ◽  
Hopkinson Pressure Bar ◽  
Custom Made ◽  
Dynamic Experiments ◽  
Complementary Strain ◽  
Pressure Bar

Three different tools for Digital Image Correlation (DIC) were used for evaluation of dynamic experiments performed using custom Open Hopkinson Pressure Bar (OHPB) apparatus. High strain-rate measurements were performed on specimens of advanced cellular materials with predefined structure and negative Poisson’s ratio. Low impedance polymethyl methacrylate (PMMA) bars instrumented with foil strain-gauges were used for dynamic loading of the specimens. Experiments were observed using a pair of high-speed cameras for imaging of loading process in sufficient quality. Custom developed evaluation DIC tool implemented in Matlab, open-source Matlab tool (NCorr) and commercial DIC software (ISTRA 4D) were all used for evaluation of image sequences recorded by high-speed cameras. Comparison of results obtained using all three different DIC tools and results of complementary strain-gauge measurement are shown in this paper. Verification of reliability of custom made DIC software tool is presented.

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.

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