• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.1
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• pp.75-82
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• 1987

It is the objective of this study to estimate J-integral by numerical analysis, in which J-integral as aparameters in fracture mechanics can be used to evaluate unstable ductile fracture which is a important problem with respect to structural stability when the scope is beyond small scale yielding criteria. For this, 8-node isoparametric singular element as crack tip element of a cracked material was used to solve plastic blunting phenomenon at crack tip, and crack opening was forced to start when J-value was exceeding fracture toughness $J_{IC}$ of the material. And crack propagation behaviour was treated by using crack opening angle. From this study, it was shown that crack opening, stable propagation and unstable opening point of the cracked material found by using J-value obtained from this study were accord with the other study, so think, J-value obtained from this study can be directly used as a parameter in fracture mechanics to deal with the problem of stable propagation of crack and unstable ductile fracture.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.7
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• pp.1082-1088
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• 2001

Nowadays study on recycling disused plastics for automobiles was lively progressed. Rubber and talcum powder was added to retrieve degradation of physical properties caused by recycling disused polypropylene. The effect of the temperature, the fatigue load and the loading speed on DEN(double edged notch) specimen which was made by the pp-rubber composites during fracture was studied by. DEN specimen was made on PP-rubber composites through the injection molding. With increasing temperature the fracture strength was linearly decreased and the fracture energy was increased by $0^{\circ}C$ and after that decreased. In the same temperature the fracture strength during increasing the notch radius was hardly increased. The fracture behaviour at low and high loading speed was different entirely. At high loading speed plastic region was small and fracture behaviour was seen to brittle fracture tendency. With increasing fatigue load fracture energy was first rapidly decreased and subsequently steady when radius of notch tip was 2mm, but Maximum load during fracture scarcely varied. The deformation mechanism of polypropylene-rubber composites during fracture was studied by SEM fractography. A strong plastic deformation of the matrix ahead of the notch/crack occurred. The deformation seem to be enhanced by a thermal blunting of the notch/crack.

• Archives of Plastic Surgery
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• v.36 no.6
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• pp.773-778
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• 2009

Purpose: The authors propose the new classification of fatty - type gynecomastia(lipomastia) which can serve as a guide for modifying the periareolar technique. Methods: A retrospective analysis was made of 1000 cases of lipomastia operated on in the last 17 months. The extent of the clinical result, the technique employed, and the complications were observed. On the basis of this review the authors observed that at grade I(fat component < 50 ml, fibroglandular component < 3 g each breast), flattening of the thorax can be achieved by means of stab incision, ultrasound - assisted lipectomy(UAL), scavenging suction - assisted lipectomy(SAL) and tissue shaving. At grade II(50 < < 150 ml, 3 < < 5 g), stab incision, UAL, SAL and pull - out method(POM) using small curved scissors. At grade III(150 < < 300 ml, 5 < < 15 g and prominent inframammary fold(IMF)), minimal incision (5 - 6 mm), UAL, SAL and POM using small angulated scissors, and blunting IMF. At grade IV (300 < < 500 ml, 15 < < 30 g, and glandular ptosis), minimal incision (5 - 6 mm), UAL, SAL, fibroglandular excision using small angulated scissors, cutting IMF and fixation of nipple - areola complex(NAC) becomes necessary. At grade V (> 500 ml, > 30 g and ptosis), small incision (7 - 8 mm), UAL, SAL, fibroglandular excision using large angulated scissors, cutting IMF, upper repositioning of NAC and delayed circumareolar skin reduction or chest lifting becomes necessary. Results: The complications were minimal but there were hematoma (n = 7), infection (n = 3) and hypertrophic scar (n =13). Almost patients were satisfied with the outcome. Conclusion: This simple classification may help in choosing the most suitable treatment, thus avoiding insufficient or invasive treatments and undesirable scars.

• Korean Journal of Materials Research
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• v.30 no.6
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• pp.292-300
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• 2020

In this study, the effect of tempering on the stretch-flangeability is investigated in 980 MPa grade dual-phase steel consisting of ferrite and martensite phases. During tempering at 300 ℃, the strength of ferrite increases due to the pinning of dislocations by carbon atoms released from martensite, while martensite is softened as a consequence of a reduction in its carbon super-saturation. This strength variation results in a considerable increase in yield strength of the steel, without loss of tensile strength. The hole expansion test shows that steel tempered for 20 min (T20 steel) exhibits a higher hole expansion ratio than that of steel without tempering (T0 steel). In T0 steel, severe plastic localization in ferrite causes easy pore formation at the ferrite-martensite interface and subsequent brittle crack propagation through the highly deformed ferrite area during hole expansion testing; this propagation is mainly attributed to the large difference in hardness between ferrite and martensite. When the difference in hardness is not so large (T20 steel), on the other hand, tempered martensite can be considerably deformed together with ferrite, thereby delaying pore formation and hindering crack propagation by crack blunting. Eventually, these different deformation and fracture behaviors contribute to the superior stretch-flangeability of T20 steel.