본 연구는 제조업 남성 근로자들의 직무스트레스와 피로와의 관계에서 사회적 지지의 매개효과를 검토하는 것을 목적으로 수행하였다. 대상: 조사대상은 제조업 공장에 근무하는 남성 근로자 352명이었다. 방법: 자료 수집은 2020년 4월 1일부터 5월 31일까지의 기간 동안에 구조화된 자기기입식 설문지를 이용한 설문조사에 의하였다. 수집된 자료는 SPSS 23.0 통계프로그램을 사용하여 상관분석, 위계적 회귀분석 및 Sobel test로 분석하였다. 결과: 연구결과, 조사대상자의 피로증상은 업무요구도와 유의한 양의 상관관계를 보인 반면, 업무의 자율성, 상자의 지지 및 동료의 지지와는 유의한 음의 상관관계를 보였다. 직무스트레스와 피로와의 관계에서 사회적 지지의 매개효과를 검증한 결과, 직무스트레스가 높을수록 사회적 지지는 낮아지는 것으로 나타났으며(F=63.93, p<0.01), 피로수준은 높아지는 것으로 나타났다(F=58.64, p<0.01). 직무스트레스를 통제한 상태에서 사회적지지가 피로에 미치는 영향 또한 통계적으로 유의하였으며(F=43.83, p<0.01), 이 때 직무스트레스의 β값이 0.352로 매개변수를 거치지 않았을 때의 β값인 0.545보다 작아 사회적지지가 매개효과를 가지는 것으로 나타났다. Sobel test 결과에서 사회적 지지는 직무스트레스와 피로의 관계에서 부분적 매개역할을 하였다(Z=-4.15, p<0.01). 결론: 위와 같은 결과는 직장에서의 사회적 지지는 근로자의 피로와 관련 있는 직무스트레스를 완화시키는 매개효과가 있을 가능성을 시사한다.

This study investigates the effect of fatigue stress on the damping capacity in a damaged Fe-22Mn-12Cr-3Ni-2Si- 4Co damping alloy under fatigue stress. α’ and ε-martensite forms by fatigue stress in the damaged Fe-22Mn-12Cr-3Ni-2Si- 4Co damping alloy under fatigue stress. The α’ and ε-martensite forms with the specific direction and surface relief, or they cross each other. With an increasing fatigue stress, the volume fraction of α’-martensite and ε-martensite increases. With an increasing fatigue stress, the damping capacity increases with an increase in the volume fraction of ε-martensite. The increase in the damping capacity in the damaged Fe-22Mn-12Cr-3Ni-2Si-4Co alloy under fatigue stress strongly affects the increase of ε-martensite formed by fatigue stress, but the damping capacity of the damaged Fe-22Mn-12Cr-3Ni-2Si-4Co damping alloy under fatigue stress is strongly controlled by a large amount of α’-martensite.

Fatigue crack growth retardation of 304 L stainless steel is studied using a neutron diffraction method. Three orthogonal strain components(crack growth, crack opening, and through-thickness direction) are measured in the vicinity of the crack tip along the crack propagation direction. The residual strain profiles (1) at the mid-thickness and (2) at the 1.5 mm away from the mid-thickness of the compact tension(CT) specimen are compared. Residual lattice strains at the 1.5 mm location are slightly higher than at the mid-thickness. The CT specimen is deformed in situ under applied loads, thereby providing evolution of the internal stress fields around the crack tip. A tensile overload results in an increased magnitude of the compressive residual stress field. In the crack growth retardation, it is found that the stresses are dispersed in the crack-wake region, where the highest compressive residual stresses are measured. Our neutron diffraction mapping results reveal that the dominant mechanism is by interrupting the transfer of stress concentration at the crack tip.

Conventional airport concrete pavement design uses empirical design method presented by FAA but it is not accurate because it does not consider environment load. In case of mechanistic - empirical design method used overseas, it needs to be modified according to domestic conditions. In this paper, a stress regression model considering environmental load and dual tandem gear load is developed as a mechanical - empirical design process and verified by fatigue model calibration. First of all, literature review was conducted on airports using DT gear as a design aircraft among domestic airports, and the physical properties of concrete pavement layers of each airport were identified. In addition, the environmental load is divided into the temperature load and the moisture load, and the temperature load is calculated from the climatic data of the region where the domestic airport is located, and the moisture load is calculated through the drying shrinkage prediction model developed through the previous study. The stresses occurring in concrete slabs under environmental loads and traffic loads were predicted using FEAFAA, which is a finite element analysis program, and factors predicted to affect concrete pavement were selected for the stress regression.As a result of the sensitivity analysis of the selected factors, the joint spacing, slab thickness, gear load, and road bearing capacity coefficient affected the stress behavior of the slab by more than 5% of the reference stress.According to the mechanical design, the finite element analysis was carried out for the consideration of only the traffic load and the environmental load and the traffic load based on the design factors. Based on the analysis results, multiple regression analysis was performed using the statistical analysis program SPSS and the stress regression equation was calculated. Then, the stress model for the environmental load and the traffic load was calculated and the final stress model with each stress model as the independent variable was derived. Using the calculated stress regression model, the stress was calculated and the bending strength of the concrete was divided to calculate the stress - to - strength ratio, and the appropriate fatigue model was selected and the correction was performed by the least squares method. This study was supported by Incheon International Airport Corporation(BEX00625)

본 논문에서는 페이즈필드 설계법 기반의 피로 제약 조건 구조물의 위상최적설계를 수행하였다. 페이즈필드 설계법의 도입으로 기존의 위상최적설계법에서 발생하기 쉬운 중간 영역의 크기를 크게 감소시켰다. 수정된 upper bound P-norm의 도입으로 모든 지점의 응력 성분을 고려하면서, 전역적 응력값이 국부적 최대 응력값과 근사한 값을 가질 수 있도록 설정하였다. 또한 기존의 피로 파괴 제약 조건 위상최적설계에서 다루지 않았던 응력 수정 계수에 대한 고려를 위하여 위상최적설계 결과물의 1차 주응력 성분을 고려하여 응력 수정 계수를 도입하고 이에 따라 허용 응력 진폭 값을 수정 하였다. 이를 통하여 인장 응력으로 인한 내구 한도 감소 요인을 반영한 체계적인 설계 방안을 제시하였다.

The purpose of this study was to examine the relationship of fatigue and stress in seafarers. Ninety healthy adults were recruited and cumulative fatigue, stress index and stress resistance of seafarers were measured using autonomic nervous system analysis device (SA-6000; Medicoa Co. Ltd. Korea). The stress index had a significant correlation with the degree of resistance (p<.01). Cumulative fatigue and the stress index had a strong positive correlation (r=.781) with the stress resistance, cumulative fatigue had a strong negative correlation (r=.782) (p<0.01). Furthermore, the stress index had a strong negative correlation with the degree of resistance (r=.924) (p<.01). The present study indicate that there are significant correlation between the cumulative fatigue and stress index, cumulative fatigue and stress resistance, as well as stress index and stress resistance in the seafarers (p<.01).

목 적 : 본 연구에서는 피로와 스트레스가 안구건조에 미치는 영향을 알아보고자 하였다. 방 법 : 만 19세 이상 성인 365명을 대상으로 설문 자료를 이용하여 대상자의 인구사회학적 변인, 피로심 각도 척도, 스트레스 척도, 안구건조 척도를 자기 기입식으로 하였으며, 단면연구를 시행하였다. 결 과 : 안구건조가 여성에서 유의한 차이로 높게 나타났으며, 음주를 많이 할수록, 만성 질환이 있는 사 람에게서 안구건조가 높게 나타났다. 40세 이상, 흡연자, 수술한 눈에서 안구건조가 조금 높게 나타났으나 유의한 차이를 보이지 않았다. 반면에, 렌즈 착용한 그룹에서 안구건조가 유의한 차이로 높게 나타났다. 고 피로 그룹일수록 안구건조정도가 높았으며, 스트레스 지수가 증가할수록 안구건조도 증가하는 것으로 나타 났다. 피로가 높은 군에서 안구건조 위험도가 1.53배 높았으며, 콘택트렌즈 착용하는 군에서는 안구건조 위 험도가 3.87배 높게 나타났다. 결 론 : 피로와 스트레스가 높을수록 안구건조를 많이 느끼는 것을 확인하였다.

Stress and fatigue are general physical aspects of our daily lives. It has been shown that physical therapists have different levels of job stress and fatigue according to the type A/B behavior patterns. This study collected data from 212 physical therapists between October 28 and November 23, 2016 using an anonymous, self-administered questionnaire. The study results showed the proportion of physical therapists with the Type A behavior patterns(TABP) was 18% greater than that of physical therapists with the Type B behavior patterns(TBBP). In this study, physical therapists with TABP were compared with physical therapists with TBBP. The results indicated that physical therapists with TABP were more inclined to experience higher levels of overall job stress and fatigue from the following stress factors: physical environment, job requirement, and job autonomy. Therefore, the stronger the tendency toward TABP, the stronger the feeling of job stress and fatigue from physical environment, job requirement, and job autonomy. Those with a tendency toward TBBP showed positive correlations between job requirement and the total job stress score; thus, the stronger the tendency toward TBBP, the stronger the feeling of overall job stress and fatigue from job requirement. This study suggests that it is necessary to manage the job stress and fatigue of physical therapists with both TABP and TBBP and to manage the job stress and fatigue of physical therapists with the type A behavioral pattern.

The residual stress analysis and fatigue test of a steel plate with a hole were performed in order to investigate the effects of the cold expansion on the fatigue life of the plate. The cold expansion method is a metal forming process by expanding a hole in order to induce compressive tangential residual stresses near the hole. In this research, a S45C steel plate of 3.2 mm thickness with a hole of 4.318 mm diameter was cold expanded by using a mandrel, resulting in a degree of expansion 1.47%. A significant amount of compressive tangential residual stress of 502 MPa at the hole surface was calculated using the finite element analysis and the compressive residual stress was more widely spreaded in the entry and exit planes than the mid plane in the plate thickness. The compressive tangential residual stresses showed a very beneficial influence on the fatigue life of the plate by increasing 1.2 to 2 times longer lives compared to the plate without cold expansion, depending on the applied load levels. Fatigue crack initiated and propagated at the hole surface of the mandrel entrance region, where relatively lower magnitude of compressive residual stress was found than the other region.

Fatigue crack growth experiments were carried out on a 304 L stainless steel compact-tension(CT) specimen under load control mode. Neutron diffraction was employed to quantitatively measure the residual strains/stresses and the evolution of stress fields in the vicinity of a propagating fatigue-crack tip. Three principal stress components (i.e. crack growth, crack opening, and through-thickness direction stresses) were examined in-situ under loading as a function of distance from the crack tip along the crack-propagation path. The stress/strain fields, measured both at the mid-thickness and near the surface of the CT specimen, were compared. The results show that much higher compressive residual stress fields developed in front of the crack tip near the surface than developed at the mid-thickness area. The change of the stresses ahead of the crack tip under loading is more significant at the mid-thickness area than it is near the surface.

This study empirically examines how much effect levels of fatigue and stress of a construction worker have on disaster risks from the perspective of human factors concerning construction disaster risks. To achieve the purpose of this study, a survey was conducted with respect to construction workers working at large construction sites within the metropolitan area. The retrieved survey data were analyzed by using the statistical software programs, SPSS 18.0 and AMOS 8.0. The results of this study do not definitively lead to the conclusion that the level of fatigue or stress of construction workers result in disaster risks. However, it does show that the results vary depending upon the individual approach and treatment of stress and fatigue. In particular, this study revealed that disaster risk levels could increase through unsafe behavior intentions which were established as a mediator variable. Also, with respect to unsafe behavior intentions of construction workers leading to disaster risks, when examining the results that the level of mental fatigue, occupational stress and social-psychological stress of construction workers had a greater significant effect than the level of physical fatigue, this study demonstrates the importance of psychological and mental issues that could be easily overlooked with respect manual labor workers.

This study highlights the theme of human error of train drivers, conducting empirical analysis on the relationship between emergency stress, psychological fatigue, safety behavior, and accident. The hypothetical test results based on questionnaires received from 223 train drivers working at A subway firm indicate that emergency stress shows a significant positive effect on psychological fatigue, which in turn shows a significant negative influence on safety behavior. And safety behavior is shown having a significant negative relationship with accident. These results suggest the necessity of corporate-level approaches to depict the drastic causes of drivers’ emergency stress, and to effectively manage this stress, as well as the necessity of making effort to enhance safety behavior, and to prevent or reduce accidents.

Thermo-mechanical fatigue cracks on the turbine housing of turbochargers are often observed in currently developed gasoline engines for them to adopt lightness and higher performance levels. Maximum gas temperatures of gasoline engines usually exceed 950℃ under engine test conditions. In order to predict thermo-mechanical failures by simulation method, it is essential to consider temperature-dependent inelastic materials and inhomogeneous temperature distributions undergoing thermal cyclic loads. This paper presented the analytical methods to calculate thermal stresses and plastic strain ranges for the prediction of fatigue failures on the basis of motoring test mode, which is commonly used for accelerated engine endurance test. The analysis results showed that the localized critical regions with large plastic strains coincided well with crack locations from a thermal shock test.

This study analyzes lifes and damages at automotive tie rod through the structural analyses with fatigue. The structural result of this study can be effectively utilized with the design of automotive tie rod by investigating prevention and durability against its damage.

This study attempted to evaluate the direct and indirect effect of emotional labor, job and psychosocial stress, and fatigue of beauty industry workers on their musculoskeletal diseases. The findings of this study showed that, among the workers with perceived symptoms of musculoskeletal diseases, the body part with the most commonly occurring symptom was the shoulder, followed by neck, low back, wrist, arm, foot and knee. As for the effect of work-related psychological factors on musculoskeletal diseases, it was found that the workers with musculoskeletal diseases were more affected by emotional labor and fatigue than non-symptom workers. It was also shown that when their job stress increased, the fatigue level also increased, though their psychosocial stress decreased. In addition, it was found that both direct and indirect effects of emotional labor on fatigue were high, and the indirect effect of job stress through fatigue on musculoskeletal diseases was significant.

본 연구에서의 미용업 종사자의 감정노동, 직무 및 사회심리적 스트레스, 피로도가 근골격계질환에 미치는 직․간접적인 영향을 평가하기 위하여 시도되었다. 그 결과 미용업 종사자의 근골격계질환 자각증사자는 신체부위 중 어깨의 근골격계 질환 관련 자각증상자가 가장 많았으며, 목, 허리, 손목, 팔, 발, 무릎 순으로 나타났다. 미용업 종사자의 감정노동 각 문항별 평가 결과는 ‘나는 기분이 나쁠 때 고객들에게 표현하지 않도록 최선을 다한다’의 문항이 3.92점으로 가장 높게 나타났으며, 이와 반 대로 ‘표현되는 행동과 실제 감정의 차이 때문에 혼란스러울 때가 있다’ 2.61점으로 나 타났다. 미용업 종사자의 작업 관련 심리적인 요인이 근골격계질환에 미치는 영향에 대하여 근골격계질환자가 무증상자에 비하여 감정노동과 피로도에 영향을 더 많이 받 는다는 것으로 나타났으며, 직무 스트레스가 증가할수록 사회심리적 스트레스는 낮아 지지만 피로도가 증가하는 것으로 나타났다. 감정노동이 피로도에 미치는 영향에서 직·간접적인 영향이 모두 높은 것으로 나타났으며 직무 스트레스가 피로도를 통해 근 골격계질환에 미치는 간접적인 영향이 큰 것으로 나타났다. 본 연구를 통하여 미용 종사자의 작업 관련 물리적․심리적 개선 방안 마련이 요구 되면 산업안전보건 분야의 정책적 관리 방안 마련을 제안한다.

A kart is a vehicle without the suspension system and the differential gear. The kart frame as an elastic body plays the role of a spring. By the cornering of a kart, rolling, pitching and twisting motions are induced in the kart frame. Also the slip or noncontact of the wheel and a permanent deformation of the kart frame can be induced. In order to examine closely this phenomenon of the twisting deformation, measurement and analysis on torsion working stress with strain gage and tracking system are needed. According to the measurement result, while steady state driving in a curve in general the torsion working stress of the kart frame will be increased depending on the vehicle velocity, but the kart frame will be not permanent deformed. However, analysis of the torsion working stress in comparison with torsion fatigue limit shows that while unsteady state driving as clash with same drive condition the racing kart frame will be deformed more quickly as the leisure kart frame.