• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2001.11a
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• pp.81-86
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• 2001

산업의 발전과 함께 소비3자의 욕구는 제품의 질적, 감성적 향상을 요구하고 있으며, 또한 최근 각종 공학의 눈부신 발전에 힘입어서 자동차의 성능, 안락성 등이 크게 향상되면서 운전자의 운전 중 피로감 제거에 관심이 높아지고 있다. 본 연구는 주관적인 피로감 평가 방식 중 졸림감(KSS), 피로감 용어 및 신체 불편도를 이용하여 평가를 수행하였다. 졸림감 및 피로감 용어는 차종 및 자세에 따라 약간의 차이가 있었지만, 대체적으로 시간이 지남에 따라 불편함의 정도가 심해졌다. 신체 불편도에 대한 평가결과 엉덩이, 요추, 어때, 좌우 발목 부위가 불편한 것으로 나타났다. 이러한 결과들은 차종별 또는 운전자세에 따라 통계적으로 유의한 차이를 보이기도 했다. 이러한 연구 결과를 통해서 동환경 시스템의 기초 데이터를 확보할 뿐만 아니라, 자동차를 설계하는데 있어, 보다 안락하고 편안한 운전환경을 만들 수 있는 기초자료로써 활용이 가능할 것이다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.4
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• pp.437-442
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• 2014

The equipment or with a constant torque and a variable stress due to axial vibration such as the turbine-generator system in nuclear power plant show the fatigue fracture behavior. Thus this study whoul aim to measure the torsional stress and analyze the fatigue fracture behavior. To achieve this, we manufactured the equipment similar with turbine-generator system and applied various torsional vibration stress due to external load. In particular, the evaluation was conducted with the existing evaluation methods of the fatigue behavior of known stress-life, strain-life, crack growth assessment methods. With increasing the external load and independent methods tends to decrease the fatigue life was confirmed up to 10 times in 5 kV external load compared to without external load.

• Journal of Korean Society of Steel Construction
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• v.20 no.6
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• pp.731-740
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• 2008

This paper deals with the fatigue behavior and strength of a new-type of steel-concrete composite bridge deck. The new-type composite bridge deck consists of corrugated steel plate, welded T-beams, stud-type shear connectors and reinforced concrete filler. A total of eight composite bridge deck specimens were fabricated, the fatigue tests were conducted under four-point bending test with three different stress ranges in constant amplitude. According to the test results, the fatigue crack generated at the welding part of the corrugated steel plate, progressed down to the bottom of the steel plate and encountered the crack, which came out from the opposite side at the same position. After the two cracks were connected at the bottom of the steel plate, the lower flange was cut off and the fatigue crack developed up to the T-beam. And the displacements and strains of fatigue test specimens were increasing with cyclic loading number, these were changed sharply at the fatigue failure. The fatigue results are compared with the design S-N curves specified in the Korea Highway Bridge Design Specifications and data in NCHRP 102 and NCHRP 147 report. The new-type composite bridge deck has a stress category of C, which means that new-type composite bridge deck can be designed by the current fatigue design specifications provided for steel members.

• Journal of Welding and Joining
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• v.15 no.3
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• pp.12-20
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• 1997

구조의 용접접합부에는 재료의 항복응력 크기의 용접잔류응력이 발생되고, 이 잔류응력 상태에서는 응력비(최소응력/최대응력)의 영향이 거의 없다는 것이 일정 진폭 하중조건의 피로실험결과로부터 알려져 있다. 이와 관련하여, 용접구조의 설계 단계에서는 초기 용접잔류응력이 그래도 잔류한 소형실험편의 일정진폭하중 상태의 피로실험 결과로부터 도출된 피로설계선도(S-N 선도)를 이용, 변동하중에 의한 응력 진폭의 밀도분포만으로 일생동안의 누적피해도를 구해 피로강도를 평가하는 것이 일 반적이다. 지금까지는 선박용접구조의 경우도 이러한 개념으로 피로강도 평가를 수행 하였으나, 일반적인 육상 또는 해상 용접구조물과는 달리, 화물의 적재 등의 정하중 이력에 의한 응력변동폭은 피로를 유발하는 파랑 응력변동폭보다 상당히 크다. 그리 고, 정하중에 의해 용접접합부에 인장응력을 발생시키는 하중이력을 받을 경우, 초기 용접잔류 응력은 상당히 저하될 것으로 생각된다. 본 연구에서는 인장응력을 유발하는 정하중 이력에 의해 저하된 용접잔류응력분포와 이러한 잔류응력분포를 가진 선측 종늑골 용접접합부의 피로강도를 검토한다.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2001.05a
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• pp.186-189
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• 2001

본 연구에서는 2종류의 색온도(4000 K, 2700 K)조건 하에서 작업자의 피로도를 평가하기 위하여 피험자에게 검색작업을 부가하고 주관평가 및 생리신호를 측정하였다. 주관평가는 ME(Magnitude Estimation)법의 설문지를 사용했으며, 생리신호는 ECG, 맥파, 피부전도도, 피부온도, 호흡, 뇌파를 측정하여 그중 ECG신호를 분석하였다. ECG신호 파라미터로서 IBI, BPM, 평균 BPM, LF/HF, CSI, CVI, CV-RR를 분석한 결과, 특히 CSI, CVI, CV-RR가 피로도와 상관관계가 높았다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.3
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• pp.429-436
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• 2013

This study considers how the fatigue behavior and probabilistic properties of SAE1055 steel are related to its hardness level. SAE1055 steel was heat-treated using induction hardening. Five types of specimens were prepared (A: base material, B: through hardened material with HV390, C: through hardened material with HV510, D: through hardened material with HV700, and E: surface hardened material with HV700). Fatigue tests were performed under a stress ratio of R = -1 using a 4-point rotary bending fatigue tester. The fatigue behaviors were greatly influenced by the hardness, but the fatigue limit did not increase over a hardness of HV510. In addition, the effect of the hardness level on the failure mechanism was evaluated using a scanning electron microscope. The probabilistic properties of the fatigue life were investigated using a probabilistic S-N approach, and the effect of the hardness level on these properties was evaluated using a residue analysis.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05d
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• pp.188-194
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• 1996

현재 국내에서 관심이 고조되고 있는 원전 연장운전 방안의 일환으로, 주요 기기의 기술적 타당성 검토 대상기기 중 하나인 원자로 냉각재 배관 노즐의 피로수명 평가를 수행하였다. 본 노즐의 피로수명 평가는 원자로 냉각재 계통 노즐의 최종 설계문서에 제시된 응력해석 결과를 참조하여 ASME Code, Sec III의 절차에 따라 수행하였으며, 평가결과 이들 노즐의 설계수명 30년을 향후 40년 또는 그 이상 연장 운전할 경우에도 무리가 없는 것으로 판단된다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.5
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• pp.599-606
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• 2022

Strain gauges and the bridge weigh-in-motion (BWIM) method are the representative field measurement methods used for fatigue evaluationsof a steel bridge-in-service. For a fatigue reliability evaluation to assess fatigue damage accumulation, the effective stress range and the number of stress cycles applied as the fatigue details can be estimated based on the AASHTO Manual for Bridge Evaluations with the field measurement data of the target bridge. However, the procedure for estimating the effective stress range and the stress cycles from field measurement data has not been explicitly presented. Furthermore, studies that quantitatively compare differences in fatigue evaluation results according to the field measurement data type or processing method used are still insufficient. Here, a fatigue reliability evaluation is conducted using strain and BWIM data that are measured simultaneously. A frame model and a shell-solid model were generated to examine the effect of the accuracy of the structural analysis model when using BWIM data. Also, two methods of handling BWIM data when estimating the effective stress range and average daily cycles are defined. As a result, differences in evaluation results according to the type of field measurement data used, the accuracy of the structural analysis model, and the data handling method could be quantitatively confirmed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.2
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• pp.129-136
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• 2017

This study aims to assess the damage tolerance of the wing structure of aged aircraft with long-term service through the fatigue crack growth analysis and tests. For the fatigue-critical locations (FCL) W2 and W4 in the wing structure, the fatigue stress spectrum was derived based on a previous study. Thereafter, a crack propagation analysis for the FCLs was conducted using the commercial software $NASGRO^{TM}$. The algorithm for the fatigue stress spectrum was verified. Fatigue crack growth tests were then performed for two types of specimens: Type #1 was extracted from the wing structure of aged aircraft, and Type #2 was made of the same material as the wing structure. By comparing the experimental results of these specimens, we assessed the damage tolerance of the wing structure of aged aircraft with service time.

• The Journal of the Convergence on Culture Technology
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• v.8 no.6
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• pp.741-747
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• 2022

Fatigue lowers an individual's ability and makes it difficult to perform work. As fatigue accumulates, concentration decreases and thus the possibility of causing a safety accident increases. Awareness of fatigue is subjective, but it is necessary to quantitatively measure the level of fatigue in the actual field. In previous studies, it was proposed to measure the level of fatigue by expert judgment by adding objective indicators such as bio-signal analysis to subjective evaluations such as multidisciplinary fatigue scales. However this method is difficult to evaluate fatigue in real time in daily life. This paper is a study on the fatigue classification model that determines the fatigue level of workers in real time using speech data recorded in the field. Machine learning models such as logistic classification, support vector machine, and random forest are trained using speech data collected in the field. The performance evaluation showed good performance with accuracy of 0.677 to 0.758, of which logistic classification showed the best performance. From the experimental results, it can be seen that it is possible to classify the fatigue level using speech signals.