• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.7 s.250
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• pp.826-832
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• 2006

For the improvement of safety and endurance in welded steel structure, it is needed to consider welding residual stress distribution and rolling directional characteristics of materials. In this study, it was investigated experimentally about characteristics of fatigue crack propagation according to welding residual stress and rolling in FCAW(flux cored arc welding) butt-jointed steel plates. SS400 steel plates of 3mm thickness were selected and tested for this study. When the angles between tensile loading direction and rolling direction in welded materials are increased from $0^{\circ}\;to\;90^{\circ}$, their fatigue crack propagation rates are increased. These results are same as predicted increments of fatigue crack propagation rate when stress ratio is increased from 0 to 0.5. When the angles of rolling direction and welding direction to tensile loading direction are $0^{\circ}\;and\;90^{\circ}$ respectively, fatigue crack propagation rate in welded material is lowest.

• Journal of the Korean Society of Safety
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• v.27 no.5
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• pp.42-48
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• 2012

Peel-tension fatigue experiments were conducted for investigating on fatigue strength of mechanical press joints of SPCC steel sheet used in the field of the automobile industry. In addition, finite element method analysis on the peel-tension specimen was conducted using HyperMesh and ABAQUS softwares. The cold rolled mild steel was used to join the T-shaped peel-tension specimen with a button diameter of 5.4 mm and a punch diameter of 8.3 mm. The fatigue limit load amplitude was found to be 112.4 N at the number of cycles 106, indicating that the ratio of fatigue limit load to static peel-tension strength was about 8%. This value suggests that the mechanical press joint is highly vulnerable to peel-tension load rather than to tensile-shear load, considering that the ratio of fatigue limit load to static tensile-shear strength was about 43%. Fatigue failure mode was found to be interface-failure mode.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.345-348
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• 2004

For practical applications, the evaluation of reliability or endurance of HTS conductors is necessary. The mechanical properties and the critical current, $I_c$, of multifilamentary Bi-2223 superconducting tapes, externally reinforced with stainless steel foils, subjected to high cycle fatigue loading in the longitudinal direction were investigated at 77K. The S-N curves were obtained and its transport property was evaluated with the increase of repeated cycles at different stress amplitudes. The effect of the stress ratio, R, on the $I_c$ degradation behavior under fatigue loading was also examined considering the practical application situation of HTS tapes. Microstructure observation was conducted in order to understand the L degradation mechanism in fatigued Bi-2223 tapes.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.4
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• pp.160-167
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• 2012

This paper is concerned with a particular fracture mechanics parameter ${\Delta}K_{th}$, known as the 'threshold stress intensity range', or 'fatigue threshold'. This threshold ${\Delta}K_{th}$ constitutes, as it were, a hinge between the notion of crack initiation and the notion of crack growth. It has often been thought that, like the endurance limit, it could be an intrinsic criterion of the material. The study was conducted on a SA-508 pressure vessel steel used in the nuclear power industry. This material exhibits a typical threshold effect in the range of the crack growth rates which were determined; that is, below approximately $da/dN=10^{-6}mm/cycle$, the slope of the da./dN versus ${\Delta}K$ curve is almost vertical. The value of ${\Delta}K_{th}$ was determined at a growth rate of $10^{-7}$ mm/cycle according to the ASTM Standard for threshold testing. The fatigue threshold values are in the range 21 $kg/mm^{3/2}$ to 12 $kg/mm^{3/2}$ depending on the stress ratio effect.

• Journal of the Korean Society of Clothing and Textiles
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• v.38 no.3
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• pp.397-403
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• 2014

In this study, various types of Jumchi Hanji were made to develop shroud materials as a new use for Hanji. The properties of Hanji (basis weight, thickness, apparent density, bulk, tensile strength, wet tensile strength, elongation ratio, tear strength, bursting strength, and folding endurance) are measured. In all cases, Jumchi Hanji had a higher thickness, lower apparent density and higher bulk than Hanji because pores in the intervals of mulberry fiber are composed of bulk. So, it is considered to carry a value as a textile material. As for the results of the strength analysis of Jumchi Hanji, Jumchi technique enhances 25% of elongation ratio, which is regarded the most important role in textiles and 35% of bulk. Moreover, it was shown that it enhanced overall strength. In conclusion, it implies the possibility of applying it as a shroud material. Jumchi Hanji is thought to have enough potential to be developed as a material to carry the characteristics of Hanji in the textile market.

• 한국기계연구소 소보
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• s.9
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• pp.83-93
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• 1982

The influence of different heat treatment conditions on microstructure, mechanical and fatigue properties of Spheroidal Graphite cast Iron with 0.4-0.6% Mn was investigated. 1) Maximum tensile strength was arrived by tempering at about $450^{\circ}C$after quenching. Tempering at higher than $600^{\circ}C$ was changed martensitic structure to ferritic structure and secondary graphites were precipitated. 2) The relationship between matrix hardness and total hardness of the specimens are as following. [HB]$T$=0.7[HB] [HB]$M$+35 Maximum tensile strength was arrived at the total hardness of HB400-450. 3) Endurance ratio decreases with increasing total hardness, and fatigue limits can be presumed from as following. $\sigmaf$=$\sigmat$

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2002.11a
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• pp.133-140
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• 2002

Catalytic combustion known as one of the traditional oxidation methods of VOC gas is restricted to its applicable fields because of its reaction characteristics. But recently innovative improvement of catalytic endurance makes its applicable range broader from MEMs to industrial power generation. Therefore, control technologies based on the catalytic combustion characteristics are researched and developed dynamically. Especially, the stable control of catalytic combustion is an essential factor in a view of maximizing its efficiency. In this research, the fuel equivalence ratio and the preheating temperature of mixture gas is controlled by catalytic combustion system enhanced in heat transfer with high temperature heat exchanger. As a result the combustion characteristics of system was investigated, and both passive and active control type were compared and analyzed.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.1
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• pp.77-82
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• 1999

This study was conducted on the properties of exhaust emissions of diesel oil and fish oil blended with diesel oils using a direct injection diesel engine at different loads, and on the conditions of carbon deposits of diesel oil and 40% blend oil in the combustion chamber after 20 hours operation at $\frac{1]{2}$ load. The properties of exhaust emissions by fish oil blended with diesel oils showed no significant difference with diesel oil. However, soot emissions decreased, increasing the ratio of fish oil. Carbon deposits by fish oil blended with diesel oils were high level compared with diesel oil, which might be overcome by preheating of fuel oil and operating conditions.

• Journal of the korean Society of Automotive Engineers
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• v.5 no.2
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• pp.31-40
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• 1983

A study was made of the effect of cold working and stabilizing temperature on the fatigue properties of Aluminum alloy 5083. The amount of cold working ranged from 14% to 35% and stabilizing temperature was 120.deg. C-160.deg. C. Rotary bending fatigue test was carried out, and it was found that 1) E specimen that had been cold worked by the cold reduction of 35% and stabilized at 160.deg. C for 2 hours was showed the most excellent fatigue limit and endurance ratio and, 2) By the results of the between crack propagation behavior and stress intensity factor, E specimen was showed the better resistance to fatigue crack growth than others.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.5
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• pp.830-835
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• 2012

A research for application of LDSMC(Low Density Sheet Molding Compound) composite is in progress for lightening the weight. This paper has performed fatigue test and simulation of external panel for Korean commercial vehicle. Before the fatigue test, static test was carried out. From the test, the structural safety was investigated using Goodman diagram. After the static test performance, the fatigue test was conducted at a range of load frequency 5Hz, a stress ratio(R) of 0.05 and an endurance limit of $10^6$ to obtain the S-N curve. The S-N curve is applied to the fatigue analysis of the external panel assembly. The result of FEM analysis was in accord with the experimental result within 83% confidence. It showed that the process to set up the safety range of allowable error is required in process of the design and simulation verification.