• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.6 s.177
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• pp.1438-1445
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• 2000

To determine dynamic characteristics of materials, a program was developed under base of stress wave propagation theory for SHPB with explicit finite element method. Through the program, all kinds of quasi-static stress-strain curves can be directly converted to dynamic stress-strain curves at any strain rate. This simulation results were compared with experimental results in the references and they are in a good agreement with each other.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.8 s.173
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• pp.92-99
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• 2005

Tungsten heavy metal is characterized by a high density and novel combination of strength and ductility. Among them, 90W-7Ni-3Fe is used for applications, where the high specific weight of the material plays an important role. They are used as counterweights, rotating inertia members, as well as fur defense purposes(kinetic energy Penetrators, etc.). Because of these applications, it is essential to detemine the dynamic characteristics of tungsten alloy. In this paper, Explicit FEM(finite element method) is employed to investigate the dynamic characteristics of tungsten heavy metal under base of stress wave propagation theory for SHPB, and the model of specimen is divided into two parts to understand the phenomenon that stress wave penetrates through each tungsten base and matrix. This simulation results were compared to experimental one and through this program, the dynamic stress-strain curve of tungsten heavy metal can be obtained using quasi static stress-strain curve of pure tungsten and matrix.

• Tunnel and Underground Space
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• v.22 no.5
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• pp.339-345
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• 2012

Information on the deformation behavior and fracture strength of rocks subjected to dynamic loadings is important to stability analyses of underground openings underground vibration due to rock blasts, earthquakes and rock bursts. In this study, Split Hopkinson Pressure Bar (SHPB) system was applied to estimate dynamic compressive and tensile fracture strengths of limestone and also examine deformation behavior of limestones under dynamic loadings. A micro-focus X-ray CT scanner was used to observe non-destructively inside the impacted limestone specimens. From the dynamic tests, it was revealed that the limestone have over 140MPa dynamic compressive strength and the strain-rate dependency of the strength. Dynamic Brazilian tensile strength of the limestone exceeds 21MPa and shows over 3 times static Brazilian tensile strength.

• Explosives and Blasting
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• v.37 no.1
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• pp.14-23
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• 2019

It has been an always issue for the blasting or the impact analysis to consider the strength characteristics of the rock materials associate with loading rate dependency. Due to the nature of transient loading, the dynamic rock test requires a careful technique to achieve the stress equilibrium state of the specimen. In this study, to investigate the relationship between the rock dynamic strength and the stress equilibrium state, a series of dynamic uniaxial compression tests for Pocheon granite were performed. As a result, the unbalanced stress state on the specimen can lead to the premature failure on the specimen and the less estimation of dynamic strength characteristic as well as the overestimation of strain rate. Consequently, a careful consideration of rock fracture process to achieve the dynamic force balance on the specimen should be required to make an reasonable evaluation of rock dynamic strength.

• 한국지구물리탐사학회:학술대회논문집
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• 2009.10a
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• pp.198-202
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• 2009

Split Hopkinson pressure bar(SHPB) is used to obtain compressive stress-strain data and deformation characteristics of brittle materials such as rock and concrete. SHPB demands both dynamic stress equilibrium condition and nearly constant strain rate before the failure of the specimen. Pulse shape technique, which places a thin metal disk between launched impact bar and incident bar, should be adopted to satisfy both conditions. In this study, metallic disks with various shapes were used to control the incident impact wave. The results show that the peak value of stress and the length of waves increased with decreasing thickness and diameter of the pulse shaper. In order to investigate shape and strain rate-dependency of the pulse shapers, dynamic compressive stress-strain curves were obtained and analyzed.

• Composites Research
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• v.35 no.1
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• pp.38-41
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• 2022

In this study, the strain rate dependent tensile and compressive properties of PP-LGF and TPO was investigated under the high strain rate by using the Split Hopkinson Pressure Bar (SHPB). The SHPB is the most widely used apparatus to characterize dynamic mechanical behavior of materials at high strain rates between 100 s^-1 and 10,000 s^-1. The SHPB test is based on the wave propagation theory which was developed to give the stress, strain and strain rate in the specimen using the strains measured in the incident and transmission bars. In addition, to verify the strain data obtained from SHPB, the specimen was photographed with a high-speed camera and compared with the strain data obtained through the Digital Image Correlation (DIC).

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.349-354
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• 2001

The split Hopkinson pressure bar has been used for a high strain rate impact test. Also it has been developed and modified for compression, shear, tension, elevated temperature and subzero tests. In this paper, SHPB compression tests have been performed with pure titanium at elevated temperatures. The range of temperature is from room temperature to $1000^{\circ}C$ with interval of $200^{\circ}C$. To raise temperature of the specimen, a radiant heater which is composed of a pair of ellipsoidal cavities and halogen lamps is developed at high temperature SHPB test. There are some difficulties in a high temperature test such as temperature gradient, lubrication and prevention of oxidation of specimen. The temperature gradient of specimen is affected by the variation of temperature. Barreling occurred at not properly lubricated specimen. Stress-strain relations of pure titanium have been obtained in the range of strain rate at $1900/sec{\sim}2000/sec$ and temperature at $25^{\circ}C{\sim}1000^{\circ}C$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.7
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• pp.891-897
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• 2013

In this study, the compressive deformation behaviors of aluminum alloy under high strain rates were investigated by means of a SHPB test. An acoustic emission (AE) technique was also employed to monitor the signals detected from the deformation during the entire impact by using an AE sensor connected to the specimen with a waveguide in real time. AE signals were analyzed in terms of AE amplitude, AE energy and peak frequency. The impacted specimen surface and side area were observed after the test to identify the particular features in the AE signal corresponding to the specific types of damage mechanisms. As the strain increased, the AE amplitude and AE energy increased whereas the AE peak frequency decreased. It was elucidated that each AE signal was closely associated with the specific damage mechanism in the material.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.6
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• pp.617-622
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• 2012

Structures are often subjected to various types of loading such as static, dynamic, or impact loading. Therefore, experimental and numerical methods have been employed to find adequate material properties according to the conditions. The Split-Hopkinson pressure bar (SHPB) test has frequently been used to test engineering materials, particularly those used under high strain rates. In this study, the compressive deformation behaviors of aluminum alloy under impact conditions have been investigated by means of the SHPB test. The experimental results were then compared with those of finite element analyses. It was shown that reasonably good agreement with the true stress-strain curves was obtained at strain rates ranging from 1000 $s^{-1}$ to 2000 $s^{-1}$. When the strain rate increased by 30%, the peak stress in particular increased by 17%, and the strain also increased by 20%.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.5
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• pp.363-372
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• 2020

Dynamic compressive material properties at high strain rates is essential for improving the reliability of finite element analysis in dynamic environments, such as high-speed collisions and high-speed forming. In general, the dynamic compressive material properties for high strain rates can be obtained through SHPB equipment. In this study, SHPB equipment was used to acquire the dynamic compressive material properties to cope with the collision analysis of Woven tpye CFRP material, which is being recently applied to unmanned aerial vehicles. It is also used as a pulse shaper to secure a constant strain rate for materials with elastic-brittle properties and to improve the reliability of experimental data. In the case of CFRP material, since the anisotropic material has different mechanical properties for each direction, experiments were carried out by fabricating thickness and in-plane specimens. As a result of the SHPB test, in-plane specimens had difficulty in securing data reproducibility and reliability due to fracture of the specimens before reaching a constant strain rate region, whereas in the thickness specimens, the stress consistency of the specimens was excellent. The data reliability is high and a constant strain rate range can be obtained. Through finite element analysis using LS-dyna, it was confirmed that the data measured from the pressure rod were excessively predicted by the deformation of the specimen and the pressure rod.