• 한국생산제조학회지
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• 제24권6호
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• pp.589-593
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• 2015

The demand of high cycle fatigue behavior on plate material is increasing because of its various applications. However, the high-cycle fatigue life data of the plate material is very rare compared to the rod material. Thus, in this study, a plate specimen is designed for the ultrasonic fatigue test because it is time efficient as compared to the conventional fatigue test. To apply the ultrasonic fatigue test, the specimen design is required to resonate at 20 kHz. Therefore, the dynamic elastic modulus was determined by measuring the resonance frequency with a piezoelectric element and laser doppler vibrometer (LDV). As a result, the plate specimen is designed and demonstrated using the ultrasonic fatigue testing machine. The ultrasonic fatigue test results were compared with the hydraulic fatigue test results.

• Structural Engineering and Mechanics
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• 제46권3호
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• pp.387-402
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• 2013

A dynamic load protocol has been used to experimentally simulate fatigue behavior in cold-formed metal panels with screwed connections under wind loading. The specific protocol adopted is an adaptation of SIDGERS, originally developed for non-metallic membranes, which is composed of levels each under increasing load values. A total of 19 tests were performed on 3.35 m long by 0.91 m wide panels, identified as Type B-wide rib and Type E, both with screw connections at the edge and at the center, thus conforming two-span specimens. In some configurations the panels were fixed at the valleys, whereas crest-fixed connections were also investigated. Reinforcing the connections by means of washers was also investigated to evaluate their efficiency in improving fatigue capacity. The experimental results show maximum load capacities in improved connections with washers of approximately twice of those with classical connections.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2018년도 춘계학술대회 논문집
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• pp.72-72
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• 2018

A dynamic fatigue characteristic of dental implant system has been evaluated with applying single axial compressive shear loading based on the ISO 14801 standard. For the advanced dynamic fatigue test, multi-directional force and motion needed to be accompanied for more information of mechanical properties as based on mastication in oral environment. In this study, we have prepared loading and motion protocol for the multi-directional fatigue test of dental implant system with single (Apical/Occlusal; AO), and additional mastication motion (Lingual/Facial; LF, Mesial/Distal; MD). As following the prepared protocol (with modification of ISO 14801), fatigue test was conducted to verify the worst case results for the development of highly stabilized dental implant system. Mechanical testing was performed using an universal testing machine (MTS Bionix 858, MN, USA) for static compression and single directional loading fatigue, while the multi-directional loading was performed with joint simulator (ADL-Force 5, MA, USA) under load control. Basically, all mechanical test was performed according to the ISO 14801:2016 standard. Static compression test was performed to identify the maximum fracture force with loading speed of 1.0 mm/min. A dynamic fatigue test was performed with 40 % value of maximum fracture force and 5 Hz loading frequency. A single directional fatigue test was performed with only apical/occlusal (AO) force application, while multi directional fatigue tests were applied $2^{\circ}$ of facial/lingual (FL) or mesial/distal (MD) movement. Fatigue failure cycles were entirely different between applying single-directional loading and multi-directional loading. As a comparison of these loading factor, the failure cycle was around 5 times lower than single-directional loading while applied multi-directional loading. Also, the displacement change with accumulated multi-directional fatigue cycles was higher than that of single directional cycles.

• Journal of Welding and Joining
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• 제20권2호
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• pp.59-64
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• 2002

When the vehicle travels in an actual road, resistance spot weldments of the vehicle structure are exposed to complex loading state. Since the fatigue strength in resistance spot weldment of vehicle body can be determined by effect of residual stresses and loading state of driving, estimating actual loading state and considering residual stress effect are needed. In this study, Fatigue stress-fatigue life relation concerned residual stress effect was obtained by thermo elastic plastic finite element analysis. And applied loading in resistance spot weldments of vehicle body was calculated by dynamic analysis. Presumption of fatigue life was performed using proposed method

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.372-377
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• 2008

Camber with positive deflection is one of the very important design parameters in the manufacture of railway coach. Positive camber is defined as concave shape such as an arch and it increases the strength of structure remarkably. But during the operation of a structure, the positive camber turns into negative camber and it loses the strength of structure. Therefore we should consider the camber effect when we evaluate the fatigue strength of negative cambered structure. For this purpose, we made a model of negative cambered locomotive car body and performed structural analysis and also we measured the dynamic loads at critical points during commercial line operation. Fatigue strength of locomotive was calculated by applying Miner's damage accumulation rule. Fatigue strength of the two locomotives which have different camber were compared to find out the effect of camber on dynamic load amplitude. We found that the more negative camber a locomotive had, the shorter fatigue strength obtained.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.317-320
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• 2008

Between traffic-induced vibration of a bridge and fatigue damage of its attached structures are very closely related. But any evaluation and design method considering the fatigue damage is not established yet. As an experimental method of evaluation of the fatigue durability, a method based on cumulative damage using a stress range histogram has been often used. However, to use the method, the fatigue durability of unmeasured points could not be evaluated. Then, in this paper, dynamic analysis of a sign frame on a bridge is carried out based on the vibration data of the bridge. And model optimization was performed for good agreement between measured responses and computed responses. As a result, we could get stress range histograms and calculate fatigue durability of unmeasured points.

• 한국전문물리치료학회지
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• 제20권3호
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• pp.36-44
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• 2013

This study aimed to investigate the influence of shoe heel height and muscle fatigue on static and dynamic balance in young women. Thirty women who were used to wearing high heels volunteered to participate in this study. The shoe heel heights were 0 cm and 7 cm. And ankle plantar flexor fatigue was experimentally induced. Static and dynamic balance were measured using the one leg standing test (OLST) and the star excursion balance test (SEBT) in anterior, posteromedial, and posterolateral directions, respectively. Values in the OLST (shoe heel height 0 cm, $28.83{\pm}3.24$ sec to $26.12{\pm}6.13$ sec; and 7 cm, $24.75{\pm}7.09$ sec to $16.86{\pm}9.32$ sec) and the SEBT in anterior (shoe heel height 0 cm, $71.02{\pm}4.57%$ to $69.50{\pm}3.66%$; and 7 cm, $64.17{\pm}3.53%$ to $59.61{\pm}4.06%$) and posteromedial (shoe heel height 0 cm, $92.01{\pm}5.61%$ to $90.38{\pm}7.10%$; and 7 cm, $83.09{\pm}7.29%$ to $76.83{\pm}9.28%$) directions were significantly reduced when fatigue-inducing exercise was performed (p<.05). Furthermore, within these parameters, there were significant interaction effects between shoe heel height and fatigue condition (p<.05). These findings suggest that shoe heel height and muscle fatigue contribute to some changes in static and dynamic balance in young women, probably leading to negative effects on physical function during a variety of activities of daily living.

• 대한인간공학회지
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• 제27권3호
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• pp.15-22
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• 2008

The purpose of this study was to define the effects of noise and background music on the trunk muscle fatigue during dynamic lifting and lowering tasks. Six healthy male subjects with no prior history of low back disorders participated in this study. The participants were exposed to two levels of background noise such as 40dB noise and 90dB noise and three levels of background music such as no music, slow music, and fast music. Six different combinations of background noise and background music were played while the participants were performing the lifting task at 15% level of Maximum Voluntary Contraction. Electromyography signals from six muscles were collected and fatigue levels were analyzed quantitatively. In results, the 90dB noise increased trunk muscle fatigue and slowed down the recovery. The trunk muscle fatigue was the lowest when the fast music was played for as background. After recovery, the 90dB noise increased trunk muscle fatigue. The trunk muscle fatigue was the lowest when the slow music was played for as background. The results can be useful to manage the cumulative fatigue of trunk muscles due to background noise and music during repetitive lifting and lowering tasks in industry.

• 한국자동차공학회논문집
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• 제7권6호
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• pp.135-143
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• 1999

This investigation evaluates effects of notch depth, fatigue precrack length and side groove in impact specimen for estimation of a valid K1d by instrumented Charpy impact test. Specimen material is 6005-T6. for notch depth 2.0mm and 2.5mm specimens or within about 2mm fatigue precrack length with notch depth 2.0mm and 2.5mm specimens or within about 2mm fatigue precrack length with notch depth 2.0mm , dynamic fracture toughness [$K_{1d,(1)}$] obtained by crack initiation load($P_m$) should be used. Dynamic fracture toughness of side grooved specimens are overestimated to that of standard impact specimen about 15 %-20%. It is confirmed that the formula of dynamic fracture toughness obtained by impact absorbed energy is inappropriate for ductile materials.

• 한국지진공학회논문집
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• 제9권5호
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• pp.1-10
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• 2005

본 연구에서는 고속철도 강합성형 교통비 동적해석에 기반한 피로신뢰성평가 기법을 제시하고 동조질량감쇠기의 효과를 피로수명연장 측면에서 검토하였다. 피로 신뢰성 평가를 수행하기 위하여 S-N 곡선 및 선형누적손상이론을 이용하여 한계상태식을 설정하였다. 열차 속도와 교량 감쇠비의 불확실성을 고려하여 교량에 대한 반복적인 동적해석을 수행하고, 이 결과로부터 전체 교량수명동안에 교량이 받는 피로 손상도와 연관된 확률변수의 특성을 통계적으로 추정하였다. 최종적으로 결정된 확률변수와 한계상태식에 개선된 일계이차모멘트법(AFOSM)을 적용하여 피로 신뢰도 지수를 산정하였다. 40m 지간 강합성교량의 수치모사로부터 동조질량감쇠기 장착여부에 따라 피로 신뢰도 지수를 평가하고 그 결과를 제시하였다.