• 한국정밀공학회지
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• 제6권1호
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• pp.45-51
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• 1989

In metal cutting various types of chips are produced in consequence of cutting conditions. According to the type of chips the cutting mechanism is to be changed. Most of the cutting theory is based on the continuous chip because of its convenient analysis, but the occurrence of the saw-toothed chip depends upon the workpiece and/or the cutting conditions, one of which is titanium alloy used widely. Nowadays titanium alloys are used widely with the rapid development of aerospace structural engineering application, whereas the theory of cutting mechanism has not been established yet, and the formatting process has not been understood satisfactorily, either. Unfortunately several misconceptions, conflicting statements and statements needing further clarifi- cation are also found. In this paper an attempt is made to clarify the formation process of saw-toothed chips which are to be produced during the orthogonal cutting process of titanium alloys. They were machined at low speed to avoid the rapid tool wear. We observed the SEM-photographs of chips taken at the quick-st- opping device. It is hoped that a rational model of the mechanics of cyclic chip formation can be developed. The results obtained are as follows. 1. When a saw- toothed chip is formed, the shear band begins at the primary shear zone and trans- fers to the free surface, so that a segment is produced and it is completed by upsetting between the formatting segment and the formatted segment. 2. As the rake angle or the clearance angle increases in the machining of the titanium alloy, the chip approaches to that of the continous type. 3. When the rake angle and the clearance angle are increased the shear energy and the unit friction energy decrease, which shows the same aspect as that of the continuous chip.

• Journal of the Korean Wood Science and Technology
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• 제47권5호
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• pp.547-556
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• 2019

Thinned, small larch logs have small diameters and no value-added final use, except as wood chips, pallets, or fuel wood, which are products with very low economic value; however, their mechanical strength is suitable for structural applications. In this study, small larch logs were sawed, dried, and cut into square timbers (with a $90mm{\times}90mm$ cross section) that were laterally glued to form core panels used to manufacture cross-laminated timber (CLT) wall panels. The surface and back of these core panels were covered with 12-mm-thick structural plywood panels, used as cross bands to obtain three-ply CLT wall panels. This attachment procedure was conducted in two different ways: gluing and pressing (CGCLT) or gluing and nailing (NGCLT). The size of the as-manufactured CLT panels was $1,220mm{\times}2,440mm$, the same as that of the plywood panels. The final wall panels were tested under lateral shear force in accordance with KS F 2154. As the lateral load resistance test required $2,440mm{\times}2,440mm$ specimens, two CLT wall panels had to be attached in parallel. In addition, the final CLT panels had tongued and grooved edges to allow parallel joints between adjacent pieces. For comparison, conventional light-frame timber shear walls and midply wall systems were also tested under the same conditions. Shear walls with edge nail spacing of 150 mm and 100 mm, the midply wall system, and the fabricated CGCLT and NGCLT wall panels exhibited maximum lateral resistances of 6.1 kN/m (100%), 9.7 kN/m (158%), 16.9 kN/m (274%), 29.6 kN/m (482%), and 35.8 kN/m (582%), respectively.

• 한국전기전자재료학회논문지
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• 제11권11호
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• pp.954-962
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• 1998

Energy-trapped thickness vibrations of piezoelectric substrates are utilized in fabricating resonators and filters which have their operating frequencies in HF band. Normalized particle displacement distributions of the fundamental thickness shear vibration mode and overtone modes into the thickness direction in energy-trapped resonators and double-coupled filters were obtained by solving the wave equation and calculating the solved equations. These results show that as the number order of the harmonic mode in a energy-trapped resonator becomes larger, the degree of energy-trapping in the resonator increase, and if the conditions for energy-trapping become sufficiently weak, the energy-trapping effect of the harmonic mode which has the lower order disappears the earlier. Above simulation results were proved by the experiments.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.347-350
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• 2003

The metal forming behavior and defect formation in Ti-6Al-4V tube during hot backward extrusion were investigated. To predict the forming-defects such as shear band, inner cracks or surface cracks, dynamic material model(DMM) including Ziegler's instability criterion and modified Cockcroft-Latham fracture criterion(C-L model) were used. These models were coupled to the internal variables generated from FE analysis. The chilling effect and friction indicated a great influence on the deformation mode of the tube and the formation of surface cracks. The simulation results for the backward extrusion were compared with the experimental observations.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 추계학술발표대회 논문집
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• pp.264-267
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• 2004

Cure monitoring and nondestructive characteristics of carbon fiber/epoxy composites were evaluated by the measurements of electrical resistance and acoustic emission (AE). Logarithmic electrical resistivity of the untreated single-carbon fiber composite increased suddenly to infinity when the fiber fracture occurred, whereas that of the electrodeposited composite increased relatively broadly up to infinity. As curing temperature increased. logarithmic electrical resistivity of steel fiber increased. On the other hand, electrical resistance of carbon fiber decreased due to the intrinsic electrical properties based on the band theory. The apparent modulus of the electrodeposited composite was higher than that of the untreated composite due to the improved interfacial shear strength (IFSS).

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.118-121
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• 2002

Polyvinylidene di-fluoride (PVDF) film sensor appeared to be practically useful for the structural health monitoring of composite materials and structures. PVDF film sensors were either attached to or embedded in the graphite/epoxy composite (CFRP) samples to detect the fatigue damage at the bondline of single-lap joints or the tensile failure of unidirectional laminates. PVDF sensors were sensitive enough to detect and determine the crack front in linear location since composites usually produce very energetic acoustic emission (AE). PVDF sensors are extremely cost-effective, as flexible as other plastic films, in low profile as thin as a few tens of microns, and have relatively wide-band response, all of which characteristics are readily utilized for the structural health monitoring of composite structures. Signals due to fatigue damage showed a characteristics of mode II (shear) type failure whereas those from fiber breakage at DEN notches showed that of mode I (tensile) type fracture.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.96-100
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• 2003

In the tensile loading of sheet metals made from polycrystalline aluminum alloys, a single deformation band appears inclined to the elongation axis in the early stage of plastic deformation, and symmetric double bands are observed in the later stage. This character of the localized deformation bands has been analyzed by a perturbation method. Macroscopic slip modes composed of slip planes and slip directions were assumed to describe the tensile and shear strains. Along time integration path, the value of the perturbation growth parameter was checked to find at which angle to the elongation axis the localized deformation bands are generated. It was shown that the mode of the localized deformation is related to asymmetry of material property.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.418-421
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• 2003

Specimens of Ti-10Ta-10Nb have been hot upset forged after heating to either the $\alpha$+$\beta$ and $\beta$-phase field. The variety temperatures (At 650, 700, 750, 800, 85$0^{\circ}C$) and strain rates (At 0.001, 0.01. 0.1, 1, 10 $s^{-1}$ ) were used. On the basis of flow stress data obtained as a function of temperature and strain rate in compression, a processing map for hot working has been developed. At strain rates lower than about 0.1 $s^{-1}$ and almost temperatures, processing efficiency exhibited high, but at 0.001 $s^{-l}$, and temperature 80$0^{\circ}C$, low because the Shear band has occurred. On the basis of the processing map, the optimum processing routes available for hot working of this material are outlined.d.

• 한국산업융합학회 논문집
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• 제10권2호
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• pp.81-88
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• 2007

In case of an urban tunnel, the displacement of ground base controls the tunnel design because it is built on shallow and unconsolidated ground many times. There are more insufficiency to describe the ground movement which coincides in the measured result of the situ because the design of an urban tunnel is dependent on the method of numerical analysis used to the existing elastic and elasto-plastic models. We studied about the prediction for the ground movement of a shallow tunnel in unconsolidated ground, mechanism of collapse, and settlement. Also this paper shows comparison with the existing elastic and elasto-plastic model using the unlinear analysis of the strain-softening model. We can model the real ground movement as the increasement of ground surface inclination or occurrence of shear band by using strain-softening model for the result of ground movement of an urban NATM tunnel.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 추계학술대회 논문집
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• pp.162-169
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• 2004

In press forming of sheet metals, the material sheet is usually subjected to very large plastic strain under in-plane stressing. Moreover, the sheet also very often is subjected to out-of-plane compressive force between tools such as the upper and lower dies, the blank holder and the die, and so forth. In this paper, it is clearly demonstrated theoretically that out-of-plane stress may notably raise the forming limit strain and thus it can be effectively utilized to avoid earlier fracture of the sheet in press forming.