• Journal of Welding and Joining
• /
• 제27권6호
• /
• pp.36-42
• /
• 2009

In the present day, new performances are demanded for automobile body steel sheet for example, light weight, durability, resistance corrosion and environmental protection. For an improvement of resistance corrosion, European automobile companies developed pre-sealed steel in 1990's. Pre-sealed steel have organic coated layer upper zinc coated layer. Evaluating a resistance spot weldability of pre-sealed steel plate is important because resistance spot welding is used mainly in automobile body joining process. In this study, evaluating a weldability of pre-sealed steel plate was carried out using lobe diagram, dynamic resistance and high-speed image. Usually, Pre-sealed steel has poor weldability than GA steel's. To improve a weldability of pre-sealed steel sheet, pre-current was applied to welding process. Pre-current is applied prior to base-current. In conclusion, the weldability of pre-sealed steel has been improved than GA steel's by applying pre-current.

• 운동영양학회지
• /
• 제25권2호
• /
• pp.8-14
• /
• 2021

[Purpose] The purpose of this study was to investigate the effects of a high-fat high-sucrose (HFHS) diet on previously reported adaptations of cardiac morphological and contractile properties to resistance training. [Methods] Twelve-week-old rats participated in 12-weeks of resistance exercise training and consumed an HFHS diet. Echocardiography and skinned cardiac muscle fiber bundle testing were performed to determine the structural and mechanical adaptations. [Results] Compared to chow-fed sedentary animals, both HFHS- and chow-fed resistance-trained animals had thicker left ventricular walls. Isolated trabecular fiber bundles from chow-fed resistance-trained animals had greater force output, shortening velocities, and calcium sensitivities than those of chow-fed sedentary controls. However, trabeculae from the HFHS resistance-trained animals had greater force output but no change in unloaded shortening velocity or calcium sensitivity than those of the chow-fed sedentary group animals. [Conclusion] Resistance exercise training led to positive structural and mechanical adaptations of the heart, which were partly offset by the HFHS diet.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2009년도 춘계 학술논문 발표대회 산업계
• /
• pp.75-78
• /
• 2009

It was investigated fire resistance properties and mechanical properties of high strength concrete column using ECC(Engineered Cementitious Composites) permanent form by KS F 2257 Methods of fire resistance test for elements of building construction and compression test for application of precast concrete column method of high rise building in this study. As a test result, it was appeared that ECC permanent form is available as fire resistance method of high strength concrete and new precast concrete construction method for facilitating construction of high rise building.

• 한국안전학회지
• /
• 제21권3호
• /
• pp.8-15
• /
• 2006

It is no wonder that mechanical structures are accompanied by problems related to corrosion after being exposed to long hours of work. Corrosion of mechanical structures has been the most serious problem in the field of industry. The present study employed a laser beam irradiation test to improve the corrosion resistance of degraded Cr-Mo steel, which was used for more than 60,000 hours. To find the optimum irradiation test condition for the corrosion resistance of degraded Cr-Mo steel, hardness and residual stress measurements, micro-structural observation, and the electrochemical potentiokinetic reactivation (EPR) tests were performed with changes in laser beam test conditions including laser beam output, diameter, and velocity. Thus, the present study indicates that the optimum test condition and absorption energy for a laser beam test need to be determined to enhance corrosion resistance of degraded Cr-Mo steel.

• Journal of Mechanical Science and Technology
• /
• 제14권10호
• /
• pp.1041-1050
• /
• 2000

In this paper the effect of specimen thickness on fatigue crack growth with the spatial distribution of material properties is presented. Basically, the material resistance to fatigue crack growth is treated as a spatial stochastic process, which varies randomly on the crack surface. The theoretical autocorrelation functions of fatigue crack growth resistance with specimen thickness are discussed for several correlation lengths. Constant ${\Delta}K$ fatigue crack growth tests were also performed on CT type specimens with three different thicknesses of BS 4360 steel. Applying the proposed stochastic model and statistical analysis procedure, the experimental data were analyzed for different specimen thicknesses for determining the autocorrelation functions and probability distributions of the fatigue crack growth resistance.

• 한국표면공학회지
• /
• 제36권5호
• /
• pp.398-405
• /
• 2003

The stainless steel wire requires good corrosion resistance and mechanical properties, such as drawing ability, combined with a high resistance to corrosion. For increasing drawing ability of stainless steel, Ni coating methods have been used in this study. However, there is no information on the electrochemical corrosion behavior of drawed wires after Ni coating. To investigate corrosion resistance and mechanical property of drawed wire, the characteristics of Ni coated wires have been determined by tensile strength tester, hardness tester, field emission scanning microscope, energy dispersive x-ray analysis and potentiodynamic method in 0.1 M HCl. The drawed stainless steel wires showed the strain-induced martensitic structure, whereas non-drawed stainless steel wire showed annealing twin in the matrix of austenitic structure. The hardness and tensile strength of drawed stainless steel wire were higer than that of non-drawed stainless steel wire. Electrochemical measurements showed that, in the case of drawed stainless steel o ire after Ni coating, the corrosion resistance and pitting potential increased compared with non-coated and drawed stainless steel wire due to decrease in the surface roughness.

• 소성∙가공
• /
• 제8권3호
• /
• pp.309-309
• /
• 1999

Effects of rare earth metals addition and aging treatment on corrosion resistance and mechanical properties of super duplex stainless steels were investigated using optical/SEM/TEM metallographic examination, an X-ray diffraction test, a potentiodynamic anodic polarization test and a tensile test. The performance of the experimental alloy with 0.32% REM addition was compared with commercial super duplex stainless steel such as SAF 2507 when they were exposed to solution annealing heat treatment and aging treatment. The corrosion resistance in CF environments and mechanical properties of the experimental alloy were found superior to those of the commercial duplex stainless steel. The REM with larger atomic radii than those of Cr, Mo and W may fill vacancies inside the matrix and around the grain boundaries, retarding formation of harmful intermetallic σ and χ phases. In addition, fine REM oxides/oxy-sulfides (1-3㎛) seemed to enhance the retardation effects. With REM additions, strength and ductility increased due to the phase and grain refinement caused by fine REM oxides and oxy-sulfides.

• Steel and Composite Structures
• /
• 제36권3호
• /
• pp.321-337
• /
• 2020

Contemporary design and construction of steel-concrete composite structures employs the use of prefabricated concrete elements and demountable shear connectors in order to reduce the construction time and costs and enable dismantling of elements for their potential reuse at the end of life of buildings. Bolted shear connector with mechanical coupler is presented in this paper. The connector is assembled from mechanical coupler and rebar anchor, embedded in concrete, and steel bolt, used for connecting steel to concrete members. The behaviour and ultimate resistance of bolted connector with mechanical coupler in wide and narrow members were analysed based on push-out tests and FE analyses conducted in Abaqus software, with focus on concrete edge breakout and bolt shear failure modes. The effect of concrete strength, concrete edge distance and diameter and strength of bolts on failure modes and shear resistance was analysed. It was demonstrated that premature failure by breakout of concrete edge occurs when connectors are located 100 mm or closer from the edge in low-strength and normal-strength reinforced concrete. Furthermore, the paper presents a relatively simple model for hand calculation of concrete edge breakout resistance when bolted connectors with mechanical coupler are used. The model is based on the modification of prediction model used for cast-in and post-installed anchors loaded parallel to the edge, by implementing equivalent influence length of connector with variable diameter. Good agreement with test and FE results was obtained, thus confirming the validity of the proposed method.

• Journal of Mechanical Science and Technology
• /
• 제19권5호
• /
• pp.1158-1168
• /
• 2005

A shunt from the left ventricle to the left anterior descending artery is being developed for coronary artery occlusive disease, in which the shunt or conduit connects the the left ventricle (LV) with the diseased artery directly at a point distal to the obstruction. To aid in assessing and optimizing its benefit, a computational model of the cardiovascular system was developed and used to explore various design conditions. Computational fluid dynamic analysis for the shunt hemodynamics was also done using a commercial finite element package. Simulation results indicate that in complete left anterior descending artery (LAD) occlusion, flow can be returned to approximately 65% of normal, if the conduit resistance is equal for forward and reverse flow. The net coronary flow can increase to 80% when the backflow resistance is infinite. The increases in flow rate produced by asymmetric flow resistance are enhanced considerably for a partial LAD obstruction, since the primary effect of resistance asymmetry is to prevent leakage back into the ventricle during diastole. Increased arterial compliance has little effect on net flow with a symmetric shunt, but considerably augments it when the resistance is asymmetric. The computational results suggest that an LV-LAD conduit will be beneficial when the resistance due to artery stenosis exceeds 27 PRU, if the resistance is symmetric. Fluid dynamic simulations for the shunt flow show that a recirculating region generated near the junction of the coronary artery with the bypass shunt. The secondary flow is induced at the cutting plane perpendicular to the axis direction and it is in the attenuated of coronary artery.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
• /
• pp.493-496
• /
• 2003

Electrical characteristic of tracking resistance, volume resistance, insulation breaking strength etc. and mechanical characteristic are required to high voltage insulation insulator silicone rubber. Tracking resistance is adding much ATH to improve tracking resistance as the most important factor among them. But, there is problem that mechanical strength grows worse rapidly adding much ATH. Therefore, this research studied effect that flame retardant gets to tracking resistance during factor that influence to tracking resistance.