• Journal of the Korean Society for Heat Treatment
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• v.25 no.1
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• pp.14-21
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• 2012

The effects of cutting condition and tempering temperature for the shape of cutting chip were investigated. For this purpose, a lead-free brass containing 1wt.% of Bi extruded at $750^{\circ}C$ in straight turning was used in this study. The cutting chip preferred was mainly found to be loose form of arc chips with curling discontinuity, and these were formed by shear fracture. However, some of fragmental element chip were found to be mixed when tempering temperature was as high as $500^{\circ}C$. The form and size of chip was more affected by feed rate than by tempering temperature and cutting rate. In addition, the cutting surface was observed to be formed more rough in the case of high feed rate and low cutting rate compared to low feed rate and high cutting rate.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.1
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• pp.78-89
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• 1993

A new theory based on the modified momentum and energy conservation has been proposed in order to overcome the drawbacks included in previous theories which are used for the determination of dynamic yield stresses and the investigation of dynamic behavior of metals. Then the improvements suggested by the new theory have been manifested through the analysis of the error included in the measurement of deformed length and through the comparison between the new theory, existing theories, and experimental results performed by previous workers. Meanwhile rod impact test has been performed which uses a compressed- air system for the acceleration of flat-ended cylindrical free-cutting brass rods. From the geomtrical measurements of deformed length, the dynamic yield stress of free-cutting brass has determined.

• 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.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.5
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• pp.124-129
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• 2001

The experimental study was the cutting characteristics of non-ferrous metals. The experimental apparatus was used the turning machine and diamond tool. This aimed at lading the optimal cutting conditions by measuring surface farm and roughness. Used non-ferrous metals were aluminum, brass and oxygen-free copper. As well, according to changing cutting conditions such as feed rate by measuring cutting farce and surface roughness and according to cutting conditions the non-ferrous metals studied about cutting properties.

• Journal of the Korean Society for Heat Treatment
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• v.24 no.3
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• pp.133-139
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• 2011

This study has been investigated for tensile properties with lead-free brass containing 1 wt.% of Bi. And also characteristic of corrosion resistance was analyzed by polarization test. An increase of tempering temperature was found to tend to decrease tensile strength, and percentage of elongation was shown to be the lowest value at $300^{\circ}C$. On the other hand, the elongation was increased with an increase of tempering temperature after $300^{\circ}C$. The change of mechanical properties was closely related with the content and shape of acicular Witmanst$\ddot{a}$tten ${\alpha}$ formed at the interface of ${\beta}$ phase as well as in ${\beta}$ phase. Tensile strength had a tendency to be decreased with an increase of test temperature. The elongation was shown to be the lowest value at around $300^{\circ}C$, while it began to increase as test temperature rose after $300^{\circ}C$. It might be speculated that the reason that elongation was decreased was found to form bismuth film at the interface of ${\alpha}/{\beta}$ phase leading to be easily brittle when loaded by tensile stress. The lead-free brass containing 1 wt.% of Bi had similar characteristic of corrosion resistance with a free-cutting brass with 3.4 wt. % of Pb in spite of higher fraction of ${\beta}$ phase.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.12
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• pp.142-147
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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 leaded 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 ]ending 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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• 2003.06a
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• pp.1491-1494
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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 103/s∼104/s. This type of test procedure has been used to examine the dynamic response of materials in various modes of testing. In this paper, dynamic deformation behaviors of rubber materials widely used for the isolation of vibration from varying structures under dynamic loading are determined using a Split Hopkinson Pressure Bar technique.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.4 no.4
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• pp.28-33
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• 2005

Recently, trends of TFT-LCD toward larger scale and thinner thickness continue. so, demands of Light Guide Panel (LGP) which is to substitute for prism sheet are appeared. Functions of LGP obtaining polarization of light of the prism sheet as well as the incidence and reflection of light are demanded. This prism type LGP to complete functions of the existing LGP and polarization at once must be supported by micro machining technology of LGP surface. In this research, the machining characteristics of the various materials were analysed by shaping using V-shaped single crystal diamond tool. The characteristics are machined surface, machining force due to the variation of cutting depth. Used specimens are engineering materials, which are 6:4 brass, oxygen-free copper, Al6061, PC, PMMA. The FFT analysis of the measured cutting force was conducted. The cutting characteristics were analyzed and the optimum cutting conditions with materials were established.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.53-57
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• 1996

The side burrs and shape distortion resulting from the micromachining of an array of V-shape microgrooves in optical components were experimentally invesigated and a simplified model for their formation is proposed. Burr/shpae distortion should be kept to a minimum level since they degrade the characteristics and performance of these parts. The focus of this study is on the influence of depth of cut and workpiece material. The workpiece materials use were brass, bronze and copper. From the obsevation of the chip shape and burr/shape distortion, the proposed model, that the compressive force at the cutting edge causess the ductile uncut chip material to flow plastically outward toward the free surface to result in a burr, was verified.