• Journal of Welding and Joining
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• 제31권2호
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• pp.30-36
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• 2013

Recently the use of ultra high strength steels(UHSS) in structural and safety component is rapidly increasing in the automotive industry. Furthermore, it commonly use in tailor welded blank laser welding process before hot stamping to reduce lightweight vehicle. However TWB process is to be a problem about welded strength after hot stamping because it's welded before heat treatment. Therefore, in this study, laser welds of TWB after heat treatment were analyzed for changes in the characteristics, especially the impact on the oxidation and decarburization in order to prevent pre-coated Al-Si layer welds on the properties for intensive investigation. As a result, the degradation of the TWB weldments changes in the heat treatment conditions alone, without any pre-treatment of the coating layer has confirmed that there is a limitation on the improvement. Furthermore Al-Si elements are overall distributed on the weldment and it specially concentrated along the fusion line. Hardness value of Al-Si segregation area is less than 350Hv and tensile strength showed just 78~83% compared with substrate. Accordingly, we proved that both side Al-Si coating should be removed in order to ensure the strength of the substrate.

• The Korean Journal of Pain
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• 제25권4호
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• pp.213-220
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• 2012

Background: It has been demonstrated that the expression of tumor necrosis factor-${\alpha}$ (TNF-${\alpha}$) and apoptotic cell death in the dorsal root ganglion (DRG) following spinal nerve constriction injury play a role in the initiation and continuation of hyperalgesia and allodynia. The present study was designed to investigate the effects of ethyl pyruvate (EP) on mechanical and cold allodynia, TNF-${\alpha}$ expression, and apoptosis in DRG after spinal nerve ligation injury. Methods: Rats were divided into 3 groups: control, pre-EP, and post-EP. EP (50 mg/kg) was intraperitoneally injected 30 minutes before (pre-EP) or after (post-EP) surgery. Behavioral tests to determine mechanical and cold allodynia were conducted before surgery and 4 and 7 days after surgery. Seven days after surgery, TNF-${\alpha}$ protein levels in DRG were evaluated by enzyme-linked immunosorbent assay, and DRG apoptosis was determined by immunohistochemical detection of activated caspase-3. Results: Treatment with EP significantly reduced mechanical and cold allodynia following spinal nerve ligation injury. TNF-${\alpha}$ protein levels in the pre-EP ($4.7{\pm}1.2$ pg/200 ${\mu}g$; P < 0.001) and post-EP ($6.4{\pm}1.8$ pg/200 ${\mu}g$; P < 0.001) groups were 2-3 times lower than the control group ($14.4{\pm}1.2$ pg/200 ${\mu}g$). The percentages of neurons and satellite cells that co-localized with caspase-3 were also significantly lower in the pre-EP and post-EP groups than the control group. Conclusions: These results demonstrate that EP has a strong anti-allodynic effect that acts through the inhibition of TNF-${\alpha}$ expression and apoptosis in DRG after spinal nerve ligation injury.

• Journal of Mechanical Science and Technology
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• 제20권2호
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• pp.197-204
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• 2006

The purpose of this study is to evaluate the AE characteristics for the basemetal, PWHT (post-weld heat treatment) and weldment specimens of SA-516 steel during fracture testing. Four-point bending and AE tests were conducted simultaneously. AE signals were emitted in the process of plastic deformation. AE signal strength and amplitude of the weldment was the strongest, followed by PWHT specimen and basemetal. More AE signals were emitted from the weldment samples because of the oxides, and discontinuous mechanical properties. AE signal strength and amplitude for the basemetal or PWHT specimen decreased remarkably compared to the weldment because of lower strength. Pre-cracked specimens emitted even lower event counts than the corresponding blunt notched specimens. Dimple fracture from void coalescence mechanism is associated with low-level AE signal strength for the basemetal or PWHT. Tearing mode and dimple formation were shown on the fracture surfaces of the weldment, but only a small fraction produced detectable AE.

• 대한기계학회논문집A
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• 제32권11호
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• pp.1010-1015
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• 2008

In this study, the characteristics of aluminum tube hydroformed products at different extrusion type and heat treatment conditions were investigated. For the investigation, as-extruded, full annealed and T6-treated Al 6061 tubes at different extrusion type were prepared. To evaluate the hydroformability, free bulge test was performed at room temperature to $300^{\circ}C$. Also mechanical properties of hydroformed products at various pre- and post-heat treatments were estimated by hexagonal prototype hydroforming test at $250^{\circ}C$. And the tensile test specimens were obtained from hexagonal prototype hydroformed tube. As a results, hydroformability of full annealed tube is $5{\sim}8%$ higher than that of extruded and T6-treated tube. The tensile strength and elongation of T6-post heat treated indirect extrusion tube were more than 330MPa and 12%, respectively. However, T6 pre treated hydroformed product represents high strength, 330MPa and low elongation, 8%. Therefore, Hydroformability of Al6061 tube showed similar value for both extrusion types. However flow stress of direct tube showed $20{\sim}50MPa$ lower value than indirect tube.

• 대한기계학회논문집B
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• 제23권3호
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• pp.330-341
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• 1999

An experimental study for the two types of burners used in the non-oxidizing direct fired furnaces of the heat treatment process for the cold rolled plate has been carried out to investigate the combustion characteristics and the oxidization of the surface of steel plate. A steep temperature gradient and entrainment of residual oxygen were found near the heating surface in the flame of the nozzle mixing burner which has strong swirl velocity component. It was concluded that the elimination of the residual oxygen and the increase of the temperature of combustion gas on the heating surface are needed to enhance the performance of the burners for application to the non-oxidizing direct fired furnaces.

• 패션비즈니스
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• 제7권6호
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• pp.50-56
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• 2003

Chitosan has been widely applied to the products in various industries such as textile fabrics, apparels, foods, medical area, etc. Cochineal has long been employed as one of natural dyestuffs in the textile industry. The effect of chitosan pre-treatment on the low-stress physical and mechanical properties of cochineal-dyed fabrics including cotton, silk, nylon and polyester fabrics was investigated in this study. The chitosan treatment and mordanting of the fabrics changed the bending, shear, compression, and surface properties of the fabrics. In cotton fabric specimens, while the increase of B(bending rigidity) of cotton is relatively high, the increase of G(shear rigidity) of cotton is relatively low. In nylon and PET fabric specimens, while the increase tendency of B is relatively low, that of G is high compared to the corresponding cotton fabrics.

• 마이크로전자및패키징학회지
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• 제28권4호
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• pp.109-114
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• 2021

상압 수소 플라즈마 전처리가 구리-구리 직접 본딩에 미치는 영향에 대해서 조사하였다. 상압 수소 플라즈마 처리를 통해 구리 박막의 표면 산화층을 환원시킬 수 있었음을 GIXRD 분석을 통해 확인하였다. 플라즈마 파워가 크고 플라즈마 처리 시간이 길수록 환원력 및 표면 거칠기 관점에서 효과적이었다. DCB를 이용한 계면 결합 에너지 측정에서 상압 수소 플라즈마 전처리 후 300℃에서 본딩한 경우 양호한 계면 결합 에너지를 나타내었으나, 본딩 온도가 낮아질수록 계면 결합 에너지가 낮아져 200℃에서는 본딩이 이루어지지 않았다. 습식 전처리의 경우 250℃ 이상에서 본딩한 경우 강한 결합력을 보였으며, 200℃에서는 낮은 계면 결합 에너지를 나타내었다.

• 한국표면공학회지
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• 제49권6호
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• pp.549-554
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• 2016

Low melting metals are difficult to weld because it is vaporized. But epoxy resin make bonding possible using low melting material and dismissal materials. This study is to improve the bonding strength of epoxy and substrate by mechanical and electrochemical methods. In case of mechanical work, bonding strength is 17.6MPa and in case of pre-work, bonding strength is 15.3MPa. When anodizing and mechanical work is applied, bonding strength is 25.3Mpa is increased 165%. When anodizing is applied, bonding strength is 27.6Mpa.

• 대한기계학회논문집
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• 제15권6호
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• pp.1982-1989
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• 1991

본 연구에서는 AISI 강은 대부분 열처리후에 사용되는 고강도강으로 용접시 발생하는 높은 잔류응력 분포를 제거 또는 감소시키기 위해서 여러가지 방법이 사용된 다. 잔류응력 제거는 용접후 풀림처리를 하면 잔류응역이 제거된다. 그러나 풀림 처리 하기전에 용접부에 높은 잔류응력 제거는 용접후 풀림처리를 하면 잔류응력이 제 거된다. 그러나 풀림처리 하기전에 용접부에 높은 잔류응력에 의해 균열이 생성될 수 있으므로 용접시 높은 잔류응력이 생성되지 않도록 예열 및 후열처리를 필요로한 다. 그러므로 본 연구에서는 예열 및 후열이 잔류응력 분포에 어떠한 영향을 주는가 를 실험적인 방법에 의해 연구하였다.

• Forest Science and Technology
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• 제14권4호
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• pp.160-168
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• 2018

The seeds of Elaeocarpus serratus, a tropical underutilized fruit tree are characterized by hard seed coat and consequent poor water uptake and low germination. To improve the regeneration through seeds, various parameters such as viability of seeds, water uptake, and effect of seed mass on germination and pretreatments were performed using a completely randomized design (CRD). Tetrazolium (TZ) test was conducted using fresh, mature seeds revealed $50{\pm}2.56%$ mean viability. Seeds of different weight classes showed similar pattern of water uptake and the saturation level was achieved at 60 hrs of soaking. Seeds belong to weight class 2.6-3.5g were germinated ($12.5{\pm}1.26%$) with $175{\pm}1.75days$ (d) of mean time taken for germination (MTG). Germination capacity of seeds varied significantly among different populations and Varkala population gave $12.5{\pm}1.1%$ germination with $174.6{\pm}2.5d$ MTG. Among various seed treatments, mechanical scarification was superior in germination and significant reduction in MTG ($p{\leq}0.05$). The mechanical scarification by complete removal of seed coat resulted in $49.2{\pm}1.52%$ germination within a short period of time ($9.52{\pm}0.89d$ MTG). However, the complete removal of seed coat without damaging to embryo is a difficult task. An alternate treatment (Mechanical scarification II) by making cracks on nut faces vertically followed by soaking in distilled water for 24 hrs gave $48.4{\pm}1.73%$ germination with significantly reduced MTG ($12.14{\pm}0.56d$) over unsoaked, untreated control ($6.5{\pm}1.84%$ germination and $197.18{\pm}1.79d$ MTG; $p{\leq}0.05$). This treatment (Mechanical scarification II) is therefore recommended for E. serratus seeds as it can adopt easily and can achieve 7 fold increases in germination over control. The recorded germination through mechanical scarification is in tune with realized viability percentage of the seeds.