• Journal of the Society of Naval Architects of Korea
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• v.40 no.3
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• pp.54-60
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• 2003

Fatigue strength of offshore structures or ship structures is significantly decreased due to corrosive environment condition such as sea water and/or coal, crude oil of cargoes, compared to that of on shore structures. In corrosive environment, fatigue strength of structures also depends on characteristics of weld material heat affected zone(HAZ). In this research work, rotary bending fatigue tests of parent material and HAZ of TMCP steel were performed in order to investigate the initiation and propagation of cracks both in air and in NaCl solution. Comparison of fatigue strength In relation with the salinity of NaCl were carried out as well. According to the test results weld material or HAZ of TMCP steel showed higher fatigue strength than that of the parent material. The fatigue strength of TMCP steel decreases drastically in NaCl solution compared to that of in air environment. In particular, more reduced fatigue strength is observed in 1% NaCl solution than in 3% NaCl solution.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.3
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• pp.40-46
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• 2001

An integrated analysis for the thermo-elastic deformation, fatigue, wear and brittle damage evolution of the shrink-fitted die with multi stress-ring of dissimilar materials is presented. A simple numerical algorithm for the moving elastic boundaries characterizing the contacts of the insert and multi stress-rings is presented. The initial stress distribution in the die due to shrink-fit is considered and the traction at the die surface contacting with the work piece is obtained by analyzing the elasto-plastic deformation of work piece. Elastic analysis of the separate-type die is performed and then the evolution of brittle damage, wear and fatigue life are predicted. This integrated analysis is applied to the extrusion die with two layers of stress-rings and the results are discussed in detail.

• Journal of Korean society of Dental Hygiene
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• v.8 no.1
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• pp.73-91
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• 2008

In order to investigate the complaint rates of subjective fatigue symptoms and the degree of job-satisfaction among dental hygienists based on their socio-demographic and job characteristics and to find out the factors related with subjective fatigue symptoms and job satisfaction. The study subjects were recruited from 274 dental hygienists who worked at dental hospitals and clinics in Daejon city and South Chungcheong Province during the period between Jan. 5 and Feb. 11, 2008. They were asked to complete the self-administered questionnaires asking about their socio-demographic characteristics. job characteristics. daily life styles, job satisfaction and subjective fatigue symptoms, and the major finding of the results were as follows : 1. The mean scores of job satisfaction were 3.12V0.47 of the total full scores(5.00). and the highest scores were in the sub-domain of interpersonal relationship. and the lowest scores were pay. The scores of job satisfaction by socio-demographic characteristics and daily life styles were not significantly differences, but in job characteristics, significantly increased with those feeling satisfied with their job. those with appropriate amount of duty amount, those free of jop autonomy, those feeling satisfied with their monthly income. satisfactory personal relations at work. 2. The mean scores of subjective fatigue symptoms were 27.6V10.9 of the total full scores(60.0), and the highest scores were in the sub-group of bodily projection of fatigue(Group III), and they were followed by difficulty in concentration(Group II). dullness and sleepness(Group I) in their decreasing order of magnitude. The scores of job satisfaction by socio-demographic characteristics and daily life styles were significantly increased with the group of lower age, the group of irregularly breakfast habit and the worse subjective health status. Based on job characteristics. the score of subjective fatigue symptoms were significantly increased with those group of lower clinical career and monthly income, those feeling unsatisfied with their job, those with inappropriate amount of duty amount. those satisfactory personal relations at work 3. The correlation of subjective fatigue symptoms with job satisfaction showed a negative correlation with rM-0.198(pM0.000), and job satisfaction were higher according to the lower subjective fatigue symptoms. The correlation among the scores of sub-domain of job satisfaction and the sub-group of subjective fatigue symptoms were significantly positive correlation. 4. The affecting factors of significance on job satisfaction included clinical career, duty amount salary satisfaction, with the explanatory power of 32.9%. Those on subjective fatigue symptoms included the eucation and the subjective health statuts, with the explanatory power of 20.8%. When considering these results, the job-satisfaction and the subjective fatigue symptoms were significantly correlated with the job related factors than factors of socio-demographic characteristics and daily life styles. In addition. if job environments of dental hygienist can improved. their job-satisfaction and subjective fatigue symptoms are suggested to be betters.

• Journal of Ocean Engineering and Technology
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• v.11 no.2
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• pp.57-69
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• 1997

The objetive of this study is to compare the mechanical proprties of 6000 series Al-Mg-Si aluminum alloy (AC120) with 5000 series Al-Mg aluminum alloy (TG25), and to investigate the influence of corrosion solution for fatigue life. Comparing of TG25 and AC120 alloy sheets, TG25 alloy sheets showing higher plastic ratio and total elongation have better formability than AC120 alloy sheets. The hardness of nugget area was a little higher than that of base metal area. Also, grain coarsening was observed in HAZ(Heat Affected Zone). In a corrosion fatigue experiment, the fatigue life decreased as concentration increased, when a dipping time was constant. The life decreased as dippling time increased, when a concentration was constant.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1647-1650
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• 2003

The Objective of this work was to design Surface Antenna Structure (SAS) and investigate fatigue behavior of SAS that was asymmetric sandwich structure. This term, SAS, indicates that structural surface becomes antenna. Constituent materials were selected considering electrical properties, dielectric constant and tangent loss as well as mechanical properties. For the antenna performance, SSFIP elements inserted into structural layers were designed for satellite communication at a resonant frequency of 12.5 GHz and final demonstration article was 16${\times}$8 array antenna. From electrical measurements, it was shown that antenna performances were in good agreement with design requirements. In cyclic 4-point bending, flexure behavior was investigated by static and fatigue test. Fatigue lift curve of SAS was obtained. The fatigue load was determined experimentally at a 0.75(1.875kN) load level. SAS concept is the first serious attempt at integration for both antenna and composite engineers and promises innovative future communication technology.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.10a
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• pp.115-120
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• 1998

This paper is especially concerned with the weldment between support beam and square bar that plays important roles in control box of Expansion Joint as a bridge structure. Fatigue strength of the weldment is dependent on notch radius from welding defects and material properties. From which, tensile strength($\sigma$ult) and fatigue notch factor(Kf) become important factors to predict fatigue life. The fatigue notch sensitivity(η) for metals can be divided into two types : high and low notch sensitivity. In this work, the Expansion Joint weldment was found to have low notch sensitivity. Fatigue test of real structure was performed up to 106cycles to be compared with predicted endurance limit.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.108-111
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• 2003

The Objective of this work was to design Surface Antenna Structure (SAS) and investigate fatigue behavior of SAS that was asymmetric sandwich structure. This term, SAS, indicates that structural surface becomes antenna. Constituent materials were selected considering electrical properties, dielectric constant and tangent loss as well as mechanical properties. For the antenna performance, SSFIP elements inserted into structural layers were designed for satellite communication at a resonant frequency of 12.5 GHz and final demonstration article was $16\;{\times}\;8$ array antenna. From electrical measurements, it was shown that antenna performances were in good agreement with design requirements. In cyclic 4-point bending, flexure behavior was investigated by static and fatigue test. Fatigue life curve of SAS was obtained. The fatigue load was determined experimentally at a 0.75(1.875kN) load level. SAS concept is the first serious attempt at integration for both antenna and composite engineers and promises innovative future communication technology.

• Journal of Welding and Joining
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• v.16 no.4
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• pp.73-82
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• 1998

This paper is especially concerned with the weldment between support beam and square bar that plays important roles in control box of Expansion Joint as a brdige structure. Fatigue strength ({TEX}$$\sigma$_{ult}${/TEX}) of the weldment is dependent on notch factor ({TEX}$K_{f}${/TEX}) become important factors to predict fatigue life. The fatigue notch sensitivity (η) for metals can be divided into two types ; high and low notch sensitivity. In this work, the Expansion Joint weldment was found to have low notch sensitivity. The maximum strain distribution during static loading is similar to the FEM analysis. Fatigue test of real structure was performed up to {TEX}$10^{6}${/TEX} cycles to be compared with predicted endurance limit.

• Journal of Ocean Engineering and Technology
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• v.18 no.1
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• pp.22-27
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• 2004

An orthotropic steel deck system is widely adapted form for a long-span bridge. It has many advantages, such as the big reduction of dead weight, the simplicity for erection, and the reduction of the construction period. However, an orthotropic steel deck system requires a lot of welding work, which may result in defects and deformation of connection. Therefore, the research for the general behavior and fatigue strength of the several details in orthotropic steel deck bridge is necessary. The fatigue failure with distortion results from secondary stress by out-of-plane deformation; these kinds of cracks are very difficult to measure, and can not be precisely calculated through finite element analysis. This stress concentration phenomenon generates the fatigue failure around the lower scallop of the transverse rib. This paper presents improved details of the intersection between the longitudinal rib and the transverse rib of an orthotropic steel deck bridge by the third dimensional hit size test, and the finite element method, which can minimize local stress through parametric study.

• Journal of Hospice and Palliative Care
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• v.6 no.2
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• pp.164-171
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• 2003

Purpose : The purpose of this study was to provide information for developing a rehabilitation intervention that improves adaptation and the quality of life after mastectomy by investigating the level of physical function and fatigue in mastectomy patients. Methods : The subjects were 63 patients selected from St. Mary's Kangnam hospital Data were collected from March to June, 2003. Physical function was measured by the range of motion of the shoulder joint, shoulder function, and physical symptoms. fatigue was measured by using the Brief Fatigue Inventory (BFI). Results : The range of motion on the affected side was significantly lower than that in the healthy side. Shoulder function score was highest in the item of 'pull on pants', and lowest in the item of 'back zipper'. Physical symptom score was highest in the item of 'numbness', and lowest in the item of 'Itching sensation'. The highest item interfered by fatigue was 'normal work (includes both work outside the home and daily chores)'. Conclusion : The result of this study suggests that effective rehabilitation intervention for mastectomy patients should be needed to improve physical function, and reduce fatigue.