• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.12 s.255
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• pp.1534-1542
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• 2006

In this paper, the concept of accelerated life test, which is a popular research field nowadays, is applied to the shot peened material. To predict the efficient and exact room temperature fatigue characteristics from the high temperature fatigue data, the adequate accelerated model is investigated. Ono type rotary bending fatigue tester and high temperature chamber were used for the experiment. Room temperature fatigue lives were predicted by applying accelerated models and doing reliability evaluation. Room temperature fatigue tests were accomplished to check the effectiveness of predicted data and the adequate accelerated life test models were presented by considering errors. Experimental result using Arrhenius model, fatigue limit obtain almost 5.45% of error, inverse power law has about 1.36% of error, so we found that inverse power law is applied well to temperature-life relative of shot peened material.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1180-1185
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• 2003

One of the main degradation of steam generator tubes is stress corrosion cracking induced by residual stress. The resulting damages can cause tube bursting or leakage of the primary water which contained radioactivity. Primary water stress corrosion crack occurs at the location of tube/tubesheet hard rolled transition zone. In order to investigate the effect of shot peening on stress corrosion cracking, stress intensity factors are calculated for the crack which is located in the induced residual stress field.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.1
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• pp.22-27
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• 2013

A shot blasting process is to improve the surface quality of stainless steels. The process is similar to a well-known shot peening that is used to strengthen the surface via the residual stress. In the shot blasting process, it is important to decide many parameters, such as the size, incident angle and velocity of shot balls, to effectively get rid of the iron oxide on the surface of stainless steels. In this study, the simulation of the shot blasting process is carried out by a finite element software, which can help to find out the optimal design parameters to cause the delamination of the iron oxide from the stainless steel substrate. The results obtained are also compared to those of the discrete element method to verify them.

• Korean Journal of Materials Research
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• v.8 no.3
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• pp.214-218
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• 1998

RF-PECVD로 합성된 a-C : H 박막의 내부압축응력 발생 원인을 규명하기 위하여 mesh에 RF power를 인가하는 새로운 장치를 고안, 기판지지대에 RF power를 인가하는 기존의 장치에서 합성된 시편과의 비교.분석을 수행하였다. Raman 분광 분석과 내부압축응력 측정 결과로부터 mesh 장치에 의해 합성되어진 시편의 $sp^{3}$$sp^{2}$비가 감소함에 따라 내부압축응력이 감소하는 것을 관찰할 수 있었으며, 또한 미세경도와 밀착강도를 측정하였다. 그리고 내부합축응력 발생에 대한 이온충돌효과를 확인하기 위해서 Ar보조가스를 첨가하였다. 그 결과 입자의 peening 효과에 의한 내부압축응력의 발생을 확인할 수 있었다.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.314-319
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• 2004

High temperature fracture toughness characteristics of shot peened spring steel(SUP-9), which is used for automobile suspension system and railroad, was investigated in this paper. Fracture tougness test for room temperature, $100^{\circ}C$ , and $200^{\circ}C$ were evaluated by material test system(MTS). The experimental results show that the fracture toughness was improved by peened and unpeened. The fracture toughness for high temperature were also improved by peened and unpeened.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.5
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• pp.89-94
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• 2008

Marine propeller is one of the most important element of ship, it must be taken care of design and maintenance of it. It is inevitable that corrosion pits have occurred on the marine propeller. If corrosion pits have occurred on the blades, they have been repaired ordinary by simple welding methods in shipyards. It must be that the strength is degraded in this process. In this paper, we represent the improvement method of fatigue strength degraded after repairing pits.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.1083-1088
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• 2005

As the industrial society develops rapidly, the weight reduction and high strength are demanded gradually. In case of the welded joint for the rolling stock which receives the repeat load, the structural failure can occur easily. However, if the shot peening technique is applied, the durability and the fatigue characteristics of the rolling stock will be improved because the hardness increases and the residual stress is induced. In this study, the fatigue characteristics of shot peened welled joints for the rolling stock was investigated. The crack initiation was examined and hardness was also evaluated. the results show that the fatigue characteristics of welded joints was improved.

• Journal of the Korean Institute of Landscape Architecture
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• v.34 no.5 s.118
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• pp.32-38
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• 2006

Roof greening in a city can contributes to not only providing network opportunities for dispersed greenspace patches but also bringing more greenspaces into a city. In addition, it can help to flooding and microclimate control in the city. Recently, a number of roof greening projects have been introduced, mainly to public buildings and schools. Roof peening need to offers both ecological functions and convenience and satisfaction for urban residents. This study aims to provide directions for improving ecological benefits and visual preference of roof greening. Twelve scene slides were adopted to measure people's visual preference. The survey results show that landscape images can be categorized into naturalness, visual diversity, uniqueness, and spatial flexibility. Physical scenes can be classified into type I mostly greened by plants, type II mixed between convenience facilities and plants, and type III constructed with pond. People show high preferences to type I and type II when visual diversity is high. The results of this study suggest to enhance the visual preference by considering visual diversity when applying the ecological design methods to improve naturalness for roof greening.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.3
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• pp.290-296
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• 2005

The contour method is based on the elastic superposition principle, and relies on deformations that occur when a residually stressed part is cut along a plane. During the cut, the part is constrained at a location along the cut so that deformations are restrained as much as possible. The displacement is applied to an elastic FE model of the half. When plasticity is involved in the relaxation process, the superposition principle is no longer valid, and stress error in the resulting measurement of residual stress would be caused. Residual stress states in a laser peened Ti-6Al-4V strip were taken for the FE simulation.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.1
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• pp.61-67
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• 2000

Gears are the most commonly used parts in automotive and industrial applications. One of most common modes of gear failures is tooth breakage, which is usually produced by the bending fatigue failure. It is important to manufacture the gears which can withstand the applied stresses in view of safety and economic requirement. This paper deals with bending fatigue strength for cold forged bevel gear. Especially, to compare fatigue characteristics for manufacturing processes difference, bending fatigue tests of bevel gears made by three different processes respectively. Results indicate that the fatigue strength of bevel gear is improved by cold forging process. Intergranular fracture is found on fatigue fracture surface, and dimples are observed on final fracture surface. The fatigue failure cannot be considered as a deterministic quantity, but must be characterized statistically. This study proposes a method to estimate bending fatigue lift of the bevel gear using the probability-load-life and Weibull analysis.