• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.331-332
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• 2002

Most manufacturing processes such as welding, cutting and molding generate residual stresses on the surface of manufactured parts. Tensile residual stress is harmful to the surface integrity, which results in reduced fatigue life and causes other structural failures when the service stresses are superimposed on the residual stresses. In the research, the residual stresses of the high hardness steel (over $H_{RC}60$) workpiece (SKD11) machined by the hard turning were measured using Hole-drilling Method. Residual stress in the surface of hard turned workpiece was mainly appeared to be compressive stress.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.348-352
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• 2004

Recently the steel parts used for automiles and trains are required to be used under higher stress than ever before in need of the weight down. However, threr are a lot of problems with developing such of fatigue strength and fatigue life are mainly focused on by adopting residual stress. And got the following characteristics from crack growth test carried out stress ratio. Fatigue life shows more improvement in the Un-peening material. And Compressive residual stress of surface on the Shot-peening processed operate resistance force of fatigue. So we cam obtain fallowings. (1) The fatigue crack growth rate on stage II is conspicuous with the size of compressive residual stress and is dependent of Paris equation. (2) Although the maximum compressive residual stress is deeply and widely formed from surface, fatigue life does not improve than when maximum compressive residual stress is formed in surface. (3) The threshold stress intensity factor range is increased with increasing compressive residual stress.

• Journal of the Korean institute of surface engineering
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• v.37 no.4
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• pp.226-233
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• 2004

The residual stresses on the surfaces of low carbon 12Cr steels used as a nuclear steam turbine blade material have been studied by controlling the flame hardening surface treatments. The temperature cycles on the surfaces of 12Cr steel were controlled precisely as a function of both the surface temperature and cooling rate. The final residual stress state generated by flame hardening was dominated by two opposite competitive contributions; one is tensile stress due to phase transformation and the other is compressive stress due to thermal contraction on cooling. The optimum processing temperatures required for the desirable residual stress and hardness were in the range of $850^{\circ}C$ to $960^{\circ}C$ on the basis of the specification of GE power engineering. It was also observed that the high residual tensile stress generated by flame hardening induced the cracks on the surfaces, especially across the prior austenite grain boundaries, and the material failure virtually, which might limit practical use of the surface engineered parts by flame hardening.

• Journal of Welding and Joining
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• v.29 no.2
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• pp.56-63
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• 2011

his paper aimed to understand the residual stress in the dissimilar metal welds of nuclear power plant. Two kinds of residual stress were considered, which caused by welding and machining. Residual stress due to mechanical machining was measured by hole-drilling technique and x-ray diffraction method for the SA508 and F316L. Weld residual stress at dissimilar metal weld between SA508 and F316L was evaluated by FEA. Residual stress profiles were obtained for the inside surface and through thickness of welds. Machining effect was also analyzed by FEA. According to the residual stress measurement, it was observed that mechanical machining can generate tensile stress on the surface of the test material. However, FEA results showed that mechanical machining did not increase the tensile stress on the surface of weld region. Further study with more elaborate measurement and numerical analysis is required to identify the effect of machining on residual stress in the dissimilar metal weld region.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.390-395
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• 2008

This study is performed to understand three dimensional characteristics of weld residual stress for the surface weld on the stainless steel plate. AISI 304 plate with one path weld on the surface was used as a test specimen. Finite element analysis was done to analyze thermal transient and residual stress due to weld. The result of finite element analysis was validated by previous paper and measurement data. Among various techniques for residual stress measurement, instrumented ball indentation method was applied. The calculated residual stresses by finite element analysis showed good agreement with the measured results.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.1
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• pp.82-90
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• 2003

Nowadays, many components used in machinery industry is required lightness and high strength. The shot-peening method is used in order to improve the fatigue life of spring steel(JIS G SUP-9) which is used in suspension of automobile. The compressive residual is induced in this shot-peening process. This paper investigated the effect of the residual compressive stress on the fatigue crack growth characteristics. Main results are summarized as follows. 1. The fatigue crack growth rate on stage II is conspicuous with the level of compressive residual stress and is dependent on Paris equation. 2. Although the maximum compressive residual stress is deeply and widely formed from surface, it does not improve the fatigue life comparing when maximum compressive residual stress is formed in surface. 3. The threshold stress intensity factor range is increased with increasing compressive residual stress. 4. In fracture surface of fatigue crack growth it is investigated that compressive residual stress remarkably retards fatigue crack growth.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.4
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• pp.539-547
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• 2010

Laser shock peening is useful to improve fatigue characteristic of multiple number of metals and alloys. This process induces a compressive residual stress on the metal surface, and when tensile load is applied, growth of crack is delayed and which changes the characteristic of the metal surface. It is an innovative surface treatment technique for strengthening metals. Specimens of SM45C are used in this study. The effect of an inertial tamping layer on the residual stress field using laser shock peening setup and Nd:YAG laser power is evaluated. Residual stress distribution measured by X-ray diffraction. As a result of this study it can be presented that following condition of Nd:YAG laser power and inertial tamping layer parameters, compressive residual stress is generated on the surface of the SM45C. Results to experimental data indicate that laser shock peening has great potential as a means of improving the mechanical performance of the metal surface.

• Journal of Ocean Engineering and Technology
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• v.7 no.2
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• pp.68-78
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• 1993

Fatigue crack shape variation by a residual stress during crack growth and life predition are studied. An analytical method is presented to predict the influence of a residual stress due to heattreatment on crack shape variations. Computer simulation results using this me thod are graphically shown that crack growth rate to surface direction are decreased due to compressive residual stress exisiting in surface area. These results are commpared with experimental results. The fatigue life is also predicted by computer simulation of crack aspect ratio variation which is based on the surface crack length increment per unit cycle calculated from a-N diagram. Predited life is about 12 percent lower than experimental life.

• Journal of Welding and Joining
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• v.27 no.4
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• pp.32-37
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• 2009

Alloy 600 and Alloy 82/182 materials have been used widely in PWR plants. But these materials are known to be susceptible to PWSCC(Primary Water Stress Corrosion Cracking). Recently, there have been several PWSCC events in major components due to repair welding, because repair welding in the dissimilar metal welds during the construction increases residual stress significantly on the inner surface of welds. In this paper, various residual stress analyses for repair welding were performed using FEM to check the effect of repair welding on residual stress distributions in PZR safety/relief nozzle. The results indicate that for inside surface repair welding, high tensile residual stress is developed on the inside surface of the nozzles.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.281-287
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• 2002

Nowadays, many components used in machinery industry is required lightness and high strength. Therefore, the effects of compressive residual stress by shot-peening which is method to improve fatigue lift of spring steel (JISG SUP-9), which used in suspension of automobile, on fatigue crack growth characteristics was investigated with considering fracture mechanics. So, we can obtain followings 1. The fatigue crack growth rate on stage II is conspicuous with the size of compressive residual stress and is dependent on Paris equation. 2. Although the maximum compressive residual stress is deeply and widely formed from surface, fatigue life does not improve than when maximum compressive residual stress is formed in surface. 3. The threshold stress intensity factor range is increased with increasing compressive residual stress. 4. In fracture surface of fatigue crack growth it is investigated that compressive residual stress remarkably retards fatigue crack growth.