• Proceedings of the KSME Conference
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• 2001.06a
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• pp.895-900
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• 2001

It is very important for impact analysis to reflect the dynamic characteristics of materials as well as the static characteristics. As the dynamic behavior of a material is different from the static(or quasi-static) one due to the inertia effect and the stress wave propagation, an adequate experimental technique has to be developed to obtain the dynamic responses for the corresponding level of the strain rate. To determine the dynamic characteristics of materials, the Hopkinson bar (compression type) experiment is carried out. For using dynamic material properties, Johnson-Cook model is applied in impact analysis with explicit finite element method

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.4
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• pp.64-69
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• 2018

This paper investigates the compressive deformation behavior of direct metal tooling (DMT), processing titanium alloy (Ti-6Al-4V) parts under high strain loading conditions. Split Hopkinson Pressure Bar (SHPB) experiments were performed to determine the flow stress and the coefficients of the Johnson-Cook model. This model is described as a function of strain, strain rate, and temperature. SHPB experiments were performed to characterize the deformation behavior of specimens made with 3D printers, using Ti-6Al-4V material under high temperature and dynamic loading.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.134-135
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• 2005

The responses of nanocrystalline aluminum powder of different grain sizes, prepared by ball milling and consolidated into bulk specimens by hot pressing, were determined under quasi-static and dynamic compression. The experiments demonstrated that the reduction in grain size resulted in several-fold increase in hardness and strength; the responses of nanocrystalline aluminum was found to be strain-rate dependent.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.47-47
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• 2004

충격하중을 받는 재료의 거동에 관한 연구는 공학의 넓은 분야에 깊은 관계를 가지고 있다. 특히 동적하중을 받는 경계조건 하에서 사용되는 구조물을 정밀하게 설계 제작하는 필요성이 고조됨에 따라 여러 재료들의 고변형률 속도로 변형될 경우에 대한 역학적인 성질이 중요한 과제로 떠오르고 있다. 구조물의 건전성과 신뢰성을 향상시키기 위해서는 구조물이 실제적으로 받는 여러 조건의 하중하에서의 실험적으로 정밀하게 획득된 정확하고, 완벽한 재료 물성치가 필요하다. (중략)

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.629-633
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• 2006

We investigated a new longitudinal acceleration wave decomposition method in time domain. The proposed method separates up- and down-stream waves with an axial strain and axial acceleration measured at a single point on the transmission path. The advantages such as low computation load and easy implementation would be possible by developing time domain under the following assumptions; low frequency range, uniform cross sectional area and elastic wave propagation. We confirmed the feasibility and performance of the method through experiment using Split Hopkinson Pressure Bar (SHPB). The method can be effective in several applications, including active vibration control with wave view point, where real time wave decomposition is necessary.

• Design & Manufacturing
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• v.2 no.2
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• pp.1-5
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• 2008

Mechanical properties of the materials used for mold 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 high strain rate compressive loading conditions has been determined using the SHPB technique.

• Structural Engineering and Mechanics
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• v.55 no.2
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• pp.263-280
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• 2015

This paper describes a study of the collision of hard steel spheres against aluminium thin circular plates at speeds up to 140 m/s. The tests were monitored by a high speed camera and a chronoscope, which allowed the determination of the ballistic limit and the plate deformation pattern. Quasi-static material parameters were obtained from tests on a universal testing machine and dynamic mechanical characterization of two aluminium alloys were conducted in a split Hopkinson pressure bar. Using a damage model, the perforation of the plates was simulated by finite element analysis. Axisymmetric, shell and solid elements were employed with various parameters of the numerical analysis being thoroughly discussed, in special, the dynamic model parameters. A good agreement between experiments and the numerical analysis was obtained.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.5
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• pp.1134-1143
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• 1994

A study of adiabatic shear band formation and propagation of 4340 steel was done using the stepped speciment which was subjected to high velocity impact. The high velocity impact was performed on compression Hopkinson bar impact machine. After the controlled impact, the specimen was prepared for visual inspection. Numerical simulation was also performed with same geometrical dimension using explicit time integration finite element code. Experimental results were then compared with the numerical prediction. It was found that the numerical prediction is quite accurate, average thickness of adiabatic shear band is about $10{\mu}m$, the macro crack around shoulder is due to folding, and the deformation control ring is effective to freeze the propagation of adiabatic shear band.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.2067-2073
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• 2018

This paper will present the design of a novel-type velocity-controllable electromagnetic coil launcher (EMCL). By studying the influence of initial capacitor voltage on the velocity of an EMCL, the launcher voltage can be set to precisely adjust the velocity of projectile launching. The simulation of voltage and velocity in relation to time is obtained by Maxwell software. The experimental data show that for the launch accuracy to be achievable, the actual precision is 2%. Because of the excellent performance of Velocity-controllable EMCL, it can replace the air gun and applied to split Hopkinson pressure bar (SHPB).

• 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.