• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.12
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• pp.2972-2979
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• 2000

Dynamic characteristics of powder metal is very important to mechanical structures requiring high strength or endurance for impact loading. But owing to distinctive property of powder metal, that is relative, it has been investigated restrictively compared to static characteristics. The objectives of this study is to investigate dynamic characteristics of powder metal and compare it to a fully density material. To find the characteristics, an explicit finite element method is used for simulation of Split Hopkinson Pressure Bar experiment based on the stress wave propagation theory. We obtained a dynamic stress-strain relationship and dynamic behavior of powder metal, as well as the variation of material properties during dynamic deformation.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.945-950
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• 2001

Vacuum interrupters that is used in various switchgear components such as circuit breakers, distribution switches, contactors, etc. spreads the arc uniformly over the surface of the contacts. The electrode of vacuum interrupters is used sintered Cu-Cr material satisfied with good electrical and mechanical characteristics. Because the closing velocity is 1-3m/s, the deformation of the material of electrodes depends on the strain rate and the dynamic behavior of the sintered Cu-Cr material is a key to investigate the impact characteristics of the electrodes. The dynamic response of the material at the high strain-rate is obtained from the split Hopkinson pressure bar test using cylinder type specimens. Experimental results from both quasi-static and dynamic compressive tests with the split Hopkinson pressure bar apparatus are interpolated to construct the Johnson-Cook equation as the constitutive relation that should be applied to simulation of the dynamic behavior of electrodes. To evaluate impact characteristic of a vacuum interrupter, simulation is carried out with five parameters such as initial velocity, added mass of a movable electrode, wipe spring constant, initial offset of a wipe spring and virtual fixed spring constant.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.7
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• pp.1073-1081
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• 2001

Many researches have published numerous papers about the high-strain-rate obtained from Split Hopkinson Pressure Bar(SHPB) tests. And 6.5wt%Si steel is widely known as an excellent magnetic material because its magnetostriction is nearly zero. Single crystals are prepared by the Floating Zone(FZ) method, which melts the alloy by the use of a high temperature electron beam in a pure argon gas condition. In this paper, the fracture behavior of the poly crystals and single crystals (DO$_3$phase) of Fe-6.5wt%Si alloy by SHPB test is observed. The comparison of high-strain-rate results with static results was done. Obtained main results are as follows: (1) Fe-6.5wt%Si alloy has higher strength at high-strain-rate tensile. SHPB results of polycrystal are twice as high as static results. (2) From the fractography, the cleavage steps are remarkably reduced in the SHPB test compared with the static test.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.5
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• pp.511-518
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• 2010

The split Hopkinson pressure bar (SHPB) has been widely used to determine the mechanical properties of materials at high loading rates. However, to ensure test reliability, the source of measurement error must be identified and eliminated. During the experiment, specimens were placed between the incident and the transmit bar. Contact friction between the test bars and specimen may cause errors. In this study, numerical experiments were carried out to investigate the effect of friction on the test results. In the SHPB test, the stress measured by the transmitted bar is assumed to be the flow stress of the test specimen. However, performing numerical experiments, it was shown that the stress measured by the transmit bar is axial stress components. When the contact surface is frictionless, the flow stress and axial stress of the specimen are approximately equal. On the other hand, when the contact surface is not frictionless, the flow stress and axial stress are no longer equal. The effect of friction on the difference between the flow stress and axial stress was investigated.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.378-381
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• 2008

The buckling behavior of cylindrical shape-memory alloy and aluminum tube is investigated at room temperature using a split Hopkinson pressure bar and an Instron hydraulic machine with a specially designed recording system. The shape-memory alloy at superelastic property regime buckles gradually in quasi-static loading, and fully recovers upon unloading. However, the buckling of aluminum tube is sudden and catastrophic, and shows permanent deformation. This gradual buckling of shape-memory alloy is associated with the forward and reverse transformation of stress-induced martensite and seems to have a profound effect on the unstable deformation of tube structures made from shape-memory alloy.

• Journal of Mechanical Science and Technology
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• v.17 no.6
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• pp.787-795
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• 2003

Mechanical properties of the materials used for transportations and industrial machinery under high strain rate loading conditions such as seismic loading are required to provide appropriate safety assessment to these mechanical structures. The Split Hopkinson Pressure Bar (SHPB) technique with a special experimental apparatus can be used to obtain the material behavior under high strain rate loading conditions. In this paper, dynamic deformation behaviors of the aluminum alloys such as A12024-T4, A1606 IT-6 and A17075-T6 under both high strain rate compressive and tensile loading conditions are determined using the SHPB technique.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.1
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• pp.196-204
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• 2003

Mechanical properties of the materials used for transportations and industrial machinery under high strain rate loading conditions such as seismic loading are required to provide appropriate safety assessment to these mechanical structures. The split Hopkinson Pressure Bar (SHPB) technique with a special experimental apparatus can be used to obtain the material behavior under high strain rate loading conditions. In this paper, dynamic deformation behaviors of the aluminum alloys such as A12024-T4, A16061-T6, and A17075-T6 under both high strain rate compressive and tensile loading conditions are determined using the SHPB technique.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.11
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• pp.158-165
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• 2003

A specific experimental method, the Split Hopkinson pressure bar (SHPB) technique has been widely used to determine the dynamic material properties under the impact compressive loading conditions with strain rate of the order of 10$^3$/s∼l0$^4$/s. In this paper, dynamic deformation behaviors of rubber materials widely used for the isolation of vibration from structure under varying dynamic loading are determined by using plastic SHPB technique. A transition point to scope with the dynamic deformation behavior of rubber-like material is defined in this paper and used to characterize the specifics of the dynamic deformation of rubber materials.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.107-112
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• 2003

Mechanical properties of the materials used for transportations and industrial machinery under high strain rate loading conditions such as high impact loading are required to provide appropriate safety assessment to varying dynamically loaded mechanical structures. The Split Hopkinson Pressure Bar(SHPB) technique with a special experimental apparatus can be used to obtain the material behavior under high strain rate loading conditions. In this paper, the dynamic deformation behavior of a brass under both high strain rate compressive loading conditions has been determined using the SHPB technique.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.790-794
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• 1997

Mechanical properties of the materials used for transportations and industrial machinery under high strain rate loading conditions such as seismic loading are required to provide appropriate safety assessment to those mechanical structures. The Split Hopkinson Pressure Bar(SHPB) technique with a special experimental behavior under high strain rate loading condition In this paper, dynamic deformation behaviors of A15052-H32 under high strain rate tensile loading are determined using the SHPB technique.