• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.5
• /
• pp.1765-1775
• /
• 2013

The application of FRP wire as a mean of improving strength and ductility capacity of concrete cylinders under axial compressive load through confinement is investigated experimentally in this study. An experimental investigation involves axial compressive test of three confining amounts of FRP wire and three concrete compressive strengths. The effectiveness of FRP wire confinement on the concrete microstructure were examined by evaluating the internal concrete damage using axial, circumferential, and volumetric strains. The axial stress-strain relations of FRP wire confined concrete showed bilinear behavior with transition region. It showed strain-hardening behavior in the post-cracking region. The load carrying capacity was linearly increased with increasing of the amount of FRP wire. The ultimate strength of the 35 MPa specimen confined with 3 layer of FRP wire was increased by 286% compared to control one. When the concrete were effectively confined with FRP wire, horizontal cracks were formed by shearing. It was developed from sudden expansion of the concrete due to confinement ruptures at one side while the FRP wire was still working in hindering expansion of concrete at the other side of the crack. The FRP wire failure strains obtained from FRP wire confined concrete tests were 55~90%, average 69.5%, of the FRP wire ultimate uniaxial tensile strain. It was as high as any other FRP confined method. The magnitude of FRP wire failure strain was related to the FRP wire effectiveness.

• Proceedings of the KWS Conference
• /
• 1992.04a
• /
• pp.63-63
• /
• 1992

본 연구에서는 Zn도금강판의 mash seam용접부의 조직학적 특성 및 도금층 및 인산염 coating의 용접 접합 계면에서의 거동율 검토하여 용접과정율 단계별로 분리 파악하여 계면 파단의 mechanism을 제시하였다. 이와 더불어, mash seam용접부에서 발견 되는 결함의 종류 및 방지대책에 관하여서도 언급하였다.

• Korean Journal of Materials Research
• /
• v.2 no.6
• /
• pp.468-476
• /
• 1992

Stress rupture properties and fracture behavior of Ni microalloyed W were studied using direct load creep tester at 100$0^{\circ}C$, 110$0^{\circ}C$ and 120$0^{\circ}C$ in $H_2$. At the same grain size, 15${\mu}$m, the 100hr. stress rupture strength of W-0.4wt% Ni was 23% higher than that of W-0.2wt%Ni due to the grain growth during test. The minimum creep rate of W-0.2wt%Ni was decreased with an increase in initial grain size. By increasing the Ni content of Ni microalloyed W, rupture time was increased owing to the smaller number and size of cavity. All the specimens showed intergranular fracture by grain boundary sliding and nucleation, growth and coalescence of cavities at grain boundary.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.13 no.3
• /
• pp.35-44
• /
• 1993

The objective of this study is aimed at developing a new class of polymer concrete, in which hydration of cement and curing of a thermosetting resin can take place simultaneously during the mixing of concrete components. For the selected mix-proportion of the new polymer, the physical and mechanical properties needed for designs are presented. These important properties are compressive strength, flexural strength, split tensile strength, direct strength, fatigue characteristics and fracture parameters. The observed properties are always compared with conventional concrete to serve as reference for engineer in deciding or selecting the proper materials for their projects, and shore protecting structure.

• Journal of the Microelectronics and Packaging Society
• /
• v.10 no.4
• /
• pp.81-86
• /
• 2003

Electromigration of Sn-3.5Ag solder bump was investigated using flip chip specimens which consisted of upper Si chip and lower Si substrate. While the resistance of the flip chip sample did not almost change until the time right before the failure, the resistivity increased abruptly at the moment when complete failure of the solder joint occurred in the flip chip sample. At current densities of $3\times 10^4$∼$4\times 10^4$A/$\textrm{cm}^2$, the activation energy for electromigration of the Sn-3.5Ag solder bump was characterized as ∼0.7 eV. Failure of the Sn-3.5Ag solder bump occurred at the solder/UBM interface due to the formation and propagation of voids at cathode side of the solder bump.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.46 no.6
• /
• pp.471-478
• /
• 2018

Static tests of the composite wing structure were performed to verify damage tolerance design. Both 5 cases of DLLT and 3 cases of DULT were completed to meet requirements for static strength. After inducing BVID and open hole damages on the critical areas of the composite wing based on associated regulations, the DULT and fracture test were performed. In major wing parts, the measured strains and displacements agreed well with those of structural analysis. The initial structural fracture occurred at the area having minimum margin of safety as expected by analysis. As a result, it was confirmed that results from analytic model and strength evaluation were similar to behaviors of the composite wing structure.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.13 no.1
• /
• pp.153-158
• /
• 2005

Titanium alloy has widely been used as material for automotive parts because it has high specific strength. It is also light and harmless to human body. But, we have little design data about the creep behaviors of the alloy. Therefore, in this study, creep tests under four constant stress conditions have been conducted with low different temperature conditions. A series of creep tests had been performed to get the basic design data and life prediction of titanium products and we have gotten the fallowing results. First, the stress exponents decrease as the test temperatures increased. Secondly, the creep activation energy gradually decrease as the stresses became bigger. Thirdly, the constant of Larson-Miller parameter on this alloy was estimated as about 7.5. And for the last, the fractographs at the creep rupture showed the ductile fracture due to the intergranullar rupture.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1996.11a
• /
• pp.321-327
• /
• 1996

울진 3,4호기 안전주입계통의 용량 변화가 가상적인 대형파단 냉각재상실사고 거동에 미치는 현상을 파악하여 이를 후속호기 계통설계 및 사고해석을 위한 안전주입계통의 최적화에 활용하고자 하였다. 본 논문에서 해석은 USNRC 가 승인한 ABB-CE 평가 모델을 적용하여 수행하였으며, 이의 결과 대형파단 사고시 안전주입탱크 용량을 울진 3,4호기의 60% 까지 줄였을 때에도 경수로용 비상노심냉각계통 허용기준$^{(1)}$ 을 만족하였다. 또한 저압 안전주입계통을 고려하지 않았을 경우, 안전주입탱크 용량을 울진 3,4호기의 60%, 고압 안전주입유량을 울진 3,4호기의 175%로 가정했을 때 경수로용 비상노심냉각계통 허용기준을 만족함을 확인하였다.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.11 no.4
• /
• pp.54-61
• /
• 2002

Inconel 690 alloy has widely been used in power plant and high temperature facilities because it has high thermal resistance and toughness. But we have little design data about the creep behaviors of the alloy. Therefore, in this study, an apparatus has been designed and built for conducting creep tests under constant load conditions. A series of creep tests on Inconel 690 alloy have been performed to get the basic design data and life prediction of inconel products and we have gotten the following results. First, the stress exponents decrease as the test temperatures increase. Secondly, the creep activation energy gradually decreases as the stresses become bigger. thirdly, the constant of Larson-Miller Parameters on this alloy is estimated about 10. And last the fractographs at the creep rupture show both the ductile and the brittle fracture according to the creep conditions.

• Journal of Korean Society of Steel Construction
• /
• v.28 no.5
• /
• pp.303-312
• /
• 2016

Many researches on the application of stainless steels as structural steels have been performed thanks to their material properties such as superior ductility and corrosion resistance. Ferritic stainless steels(STS430) with little or no nickel have been used increasingly in building structure because it is inexpensive compared to austenitic stainless steels(STS304) with nickel, but provide performances similar to the austenitic stainless steel. This paper deals with block shear fracture behavior of base metal in stainless steel welded connection. Although the block shear fracture behavior for welded connection due to stress triaxiality is different from that of bolted connection, the block shear strength of welded connection in current design specifications has been predicted based on that of bolted connection. The main parameters are weld length and welding process(Arc and TIG welds). The ultimate strengths of TIG welded specimens were higher than those of arc welded specimens and current design predictions by AISC, EC3 etc. were compared with test strengths.