• Explosives and Blasting
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• v.34 no.2
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• pp.1-9
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• 2016

In this study, the field tests were performed on V-cut, PLHBM 1 hole, PLHBM 2 hole in gneiss area in order to compare the effects of the vibration decay of a tunnel cut-hole according to the number of PLHBM holes with scaled distance. Based on the prediction equation of blasting vibration from the result of the tests, the decay rate of vibration were confirmed 21.8~61.1% using PLHBM 1 hole, 35.7~79.3% using PLHBM 2 hole for scaled distance within $10{\sim}100m/kg^{1/2}$ on the basis of V-cut PPV. As the scaled distance was increased, the effect of vibration decay was decreased. The effect of vibration decay of cut-hole for intial PLHBM 1~2 hole was significantly high.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.1
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• pp.58-65
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• 2003

The aramid fiber reinforced metal laminates(AFRMLs) used for the wing part fair flight suffer the cyclic bending moment of variable amplitude during service. The fatigue crack propagation and delamination behavior in AFRMLs containing a saw-cut and circular hole was investigated using the average stress criterion(ASC) model. Mechanical tests were carried out using the cyclic bending moment of 4.9 N . m and delamination was observed by ultrasonic C-scan images. In case of AFRMLs containing a saw-cut fatigue crack propagated in aluminum matrix, inducing delamination. However, in case of AFRMLs containing a circular hole, delamination formed with two types under cyclic bending moment of 4.9 N . m. First, delamination formed along the fatigue crack in aluminum matrix. Second, delamination formed without any fatigue crack around the circular hole. Therefore, delamination was formed depending on the stress distribution near the circular hole.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.278-285
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• 2001

Aluminum/Aramid Fiber Reinforced Plastic(Al/AFRP) laminates are applied to the fuselage-wing intersection. The main objective of this study was to evaluate the delamination zone behavior of Al/AFRP with a saw-cut and circular hole using average stress criterion and the effect of notch geometry. Mechanical tests were carried out to determine the cyclic-bending moment and delamination zone observed ultrasonic C-scan pictures. In case of Al/AFRP containing saw-cut specimen, the shape and size of the delamination zone formed along the fatigue crack. However, in case of Al/AFRP containing circular hole specimen, the shape and size of delamination zone formed two types. first type, delamination zone formed along the fatigue crack. Second type, not observed fatigue crack. Therefore, delamination zone was formed dependently of the circular hole shape.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.567-572
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• 2000

From the experimental study of W-EDM for alloyed steel, the characteristics such as Hand Drum Form and surface roughness have been observed and evaluated for various conditions. In square hole, the increase of IP as to made condition, the calculate high value of surface roughness. Also compare dimensionless square hole with circle hole' graph, In circle hole, if a value of surface roughness IP 6 in a side of circle it show a 0.4${\mu}{\textrm}{m}$ and in IP 8, 0.6${\mu}{\textrm}{m}$, in IP 10, 0.7${\mu}{\textrm}{m}$, in IP 12, 0.8${\mu}{\textrm}{m}$ higher than before. This figure show the surface roughness is higher than before, because a table move in either X-axis or Y-axis in square hole, on the contrary, in circle there table move in X-axis and Y-axis at the same time. hand drum form getting small when wire tension increase 1000gf to 1500gf, at the same working conditions. The smaller of off time, the maller of hand drum form in same condition and same wire tension. but if you compare square hole with circle hole' graph, hand drum form displayed in maintained term of working condision, on the contrary, in case of square hole variation of hand drum form is more increase than a grow of IP

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.10a
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• pp.43-48
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• 2001

In this study, the characteristics of the surface around a hole on inlet and outlet of product which are manufactured by face mill or end mill cutting with a hole or a pocket in its surface, are investigated. Furthermore, experiment for optimization of process conditions to minimize the change of characteristics of milling cut surface after a hole cutting operation, is implemented. Applying the results in this study to surface manufacturing of mold products whose surface is uneven or metal products made by diecasting, reducing the number of sequence process to obtain fine surface is expected.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.5
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• pp.1-6
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• 2002

This study is to investigate the characteristics of the surface around a hole on inlet and outlet of product which are manufactured by face mill or end mill cutting with a hole or a pocket in its surface. Furthermore, experiments for optimization of process conditions to minimize the change of characteristics of milling cut surface after a hole cutting operation are implemented. This result is apply to manufacture of mold products and metal products by diecasting.

• Journal of Korean Society of Steel Construction
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• v.26 no.6
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• pp.617-626
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• 2014

In this paper, experiments for the evaluation of tensile strength of steel plate with bolt hole and bearing strength of bolted connection were performed, where bolt holes were punched by drilling and oxygen torch, respectively. For the tensile tests, drilled and oxygen torch punched steel plate specimens of 10mm and 15mm thickness were made from structural angles and H-shapes, respectively. For the bearing strength evaluation, test specimens were fabricated with base plates and splice plates those were also punched by drilling and oxygen torch, respectively. The Vicker's hardness were measured around the bolt hole to investigate material property change due to heat effect by oxygen torch cut. Numerical analysis was also performed to investigate the bearing strength of bolted joints due to the increase of hardness around the bolt hole by oxygen torch cut.

• Explosives and Blasting
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• v.25 no.1
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• pp.31-43
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• 2007

In most tunnel constructions in South Korea, blasting has been widely used as an excavation method. In tunnel blasting, the center-cut to induce first free surface is very important for enhancing excavation efficiency and reducing vibration caused by exploding. This paper introduces new center-cut method named SAV-cut (Stage Advance V-cut) developed on the concept of V-cut. Significant features of SAV-cut are the center hole and stepwise ignition. Many field tests and numerical analysis were carried out to analyze the mechanical behavior and blasting vibration. From the results, the newly developed SAV-cut was proved as an effective center-cut method for both increasing blasting efficiency and decreasing blasting vibration.

• Journal of Korean Society of Steel Construction
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• v.12 no.2 s.45
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• pp.197-207
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• 2000

A transient heat transfer analysis and thermo-elastic analysis have been performed for the residual stress distribution on the fillet weldment used by finite element method. Specimen is fabricated single-pass fillet welding. This computation was performed for conditions including surface heat flux and temperature dependent thermo-physical properties using by heat input as parameter. Also, cut-off temperature of residual stress estimation by thermo-elastic analysis is determined. The fillet weldment were measured to determined their residual stress distributions for using hole-drilling method. As result, it was found that large tensile residual stress is about material yield strength, and the numerical simulation results for finite element method similar to residual stresses by hole-drilling method and other exiting research. Also, cut-off temperature is effectively determined by temperature which calculated maximum thermal stress equal to material yield strength.

• Corrosion Science and Technology
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• v.23 no.2
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• pp.145-153
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• 2024

In the automotive industry, the hole expanding test is widely used to assess the formability of punched holes in sheets. This test provides a good representation of formability within the framework defined by the ISO 16630 standard. During hole expanding tests on galvanized high strength steels, a negative effect was observed when there was a delay between hole punching and expansion, as compared to performing both operations directly. This effect is believed to be caused by hydrogen aging, which occurs when hydrogen diffuses towards highly-work hardened edges. Therefore, the aim of this study is to demonstrate the migration of hydrogen towards work-hardened edges in high strength Zn-coated steel sheets using a novel Thermal Desorption Analyzer (TDA) designed for small samples. This newly-developed TDA setup allows for the quantification of local diffusible hydrogen near cut edges. With its induction heating and ability to analyze Zn-coated samples while reducing artifacts, this setup offers flexible heat cycles. Through this method, a hydrogen gradient is observed over short distances in shear-cut galvanized steel sheets after a certain period of time following punching.