• Journal of Korean Society of Steel Construction
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• v.9 no.2 s.31
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• pp.237-248
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• 1997

Three types of fatigue cracks frequently observed in the crane runway girders are verified experimentally using two testing-purpose girders with the size of $6400{\times}600{\times}300$ in millimeters. The fatigue cracks are observed in the vicinity of load-bearing points, at the end of gusset plates and at the fillet welded joints between the lower flange and the web. The load-bearing-point cracks are initiated at the intersection of the fillet welds between the upper flange and the web, where the vertical stiffener is located. The cracks grow up toward the diagonal direction of the web. The cracks observed at the fillet welded joints grow up perpendicularly to the crane runway girder. Compared with the JSSC fatigue design code, the joint class is classified as follows: E for the vicinity of load-bearing points, G or H for the end of gusset plates and D for the lower fillet welded joints. The tests reveal that the class of joint classification at the end of gusset plates and at the lower flange coincides with the fatigue design code.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.2
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• pp.64-74
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• 1997

The necessity and importance of fatigue failure to variable load has been appreciated as the structural design technique develops and use of high tensile steel is increasing. This is much more appreciated for a large ship such as VLCC. The rigorous fatigue analysis and safety assessment should be, hence, carried out at the design stage to avoid the possibility of fatigue failure and to achieve the design result having a sufficient structural safety to fatigue strength. This paper deals with an efficient spectral fatigue analysis of ship structures by introducing the concept of stress influence coefficient. In the process included are probabilistic loading analysis, evaluation of long-term distribution of stress range and estimation of fatigue life applying the spectral fatigue analysis. An integrated computer program has been developed in which reliability analysis to fatigue strength is also included and has been applied to D/H VLCC.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.2
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• pp.307-315
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• 1989

In recent years, the fatigue design method by analysis for the mechanical components and the welded structures has much increased, instead of the fatigue design method by rule that has been widely used from the past days. When a fatigue design is conducted by that method, the basic informations, fatigue life curves are mainly obtained from the results of the strain controlled low cycle fatigue test. From these point of views, the low cycle fatigue test is coming to be given a much importance lately. In this paper, the strain controlled low cycle fatigue properties at room temperature in air environment were investigated for the low carbon forged steel, SF45A, and the rolled steel for the welded structure, SM 41B. Throughout the test, strain ratio, R, was maintained constant with the fully reversed condition, -1. As the experimental results, the cyclic stress-strain behaviours of the test materials were different each other, but the low cycle fatigue life-time of them appeared to show little difference in the region of this test conditions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1691-1694
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• 2005

The fatigue characteristic of a material or a structure is derived from fatigue tests of standard specimens. However test results of standard specimens are very different from those of real structures or components. Therefore, to calculate more accurate fatigue life, the geometrical effect and surface condition must be considered by comparing test results of standard specimens with those of real structures or components. Thus the object of this paper is to evaluate the fatigue characteristic of a real waterwork pipe by conducting fatigue tests with standard specimens and non-standard(plate-shaped) specimens of base metal and weld metal. Also, to evaluate fatigue characteristic based on life distribution, statistical fatigue characteristic was analyzed by the normal distribution and related data of P-S-N curve.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.1
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• pp.61-72
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• 2011

The influences of luminous environment on visual responses and fatigue sensation in art galleries were examined in this study. Field measurements and survey were performed in three galleries under various illuminance and luminous conditions. Result implies that vertical illuminance on art paintings needed to be somewhere between 200 lx and 300 lx to avoid visual discomfort. The vertical illuminance difference between consecutive paintings should not exceed 100 lx to keep visually comfortable environment. Visual comfort sensations were related to glare, visual stimulus, reflection from paintings, illuminance variation, and the sensation that subjects can clearly see the paintings. The sensation of fatigue was significantly influenced by the changes of luminous element that caused visual stimulus and discomfort. The sensation of eye fatigue among physical fatigue was primarily influenced by the glare, visual stimulus and comfort. The psychological fatigue was also influenced by eye fatigue, visual comfort, brightness and satisfaction with color of light.

• Smart Structures and Systems
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• v.13 no.6
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• pp.943-957
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• 2014

When subjected to fatigue loading, the main failure mode of partially prestressed concrete (PPC) structure is the fatigue fracture of tensile reinforcement. Therefore, monitoring and evaluation of the steel stresses/strains in the structure are essential issues for structural design and healthy assessment. The current study experimentally investigates the possibility of using fiber Bragg grating (FBG) sensors to measure the steel strains in PPC beams in the process of fatigue loading. Six full-scale post-tensioned PPC beams were exposed to fatigue loading. Within the beams, the FBG and resistance strain gauge (RSG) sensors were independently bonded onto the surface of tensile reinforcements. A good agreement was found between the recorded results from the two different sensors. Moreover, FBG sensors show relatively good resistance to fatigue loading compared with RSG sensors, indicating that FBG sensors possess the capability for long-term health monitoring of the tensile reinforcement in PPC structures. Apart from the above findings, it can also be found that during the fatigue loading, there is stress redistribution between prestressed and non-prestressed reinforcements, and the residual strain emerges in the non-prestressed reinforcement. This phenomenon can bring about an increase of the steel stress in the non-prestressed reinforcement.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.8 s.239
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• pp.1085-1092
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• 2005

The OHT(Over Head Transportation) Vehicle transports heavy products quickly and repeatedly at the industrial workplace. The belt in the OHT vehicle is used to support the weight of the OHT Cage. The fatigue of the belt is caused by the dynamic load during the operation time. Since the fatigue fracture of the belt affects the safety at the workplace, the correct prediction of the dynamic load is necessary to calculate the fatigue life of the belt on the design step. In this paper a computer aided analysis method is proposed for the belt in the early design stage using dynamic analysis, stress analysis, belt tensile test, belt fatigue test and fatigue lift prediction method. From the dynamic load time histories and the stress of the belt FE model, a dynamic stress time history is produced. Using linear damage law and cycle counting method, fatigue life cycle is calculated. The method developed in this paper is used to reduce the time and cost for designing the OHT belt in different environment and condition.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.4
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• pp.453-461
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• 1999

The estimation of fatigue life at the design stage is very important in order to arrive at feasible and cost effective solutions considering the total lifetime of the structure and machinery compo-nents. In this study the practical procedure of prediction of fatigue life by use of cumulative damage factors based on Miner-Palmgren hypothesis and probability density function is shown with a $135,000m^3$ LNG tank being used as an example. In particular the parameters of Weibull distribution taht determine the stress spectrum are dis-cussed. At the end some of uncertainties associated with fatigue life prediction are discussed. The main results obtained from this study are as follows: 1. The practical procedure of prediction of fatigue life by use of cumulative damage factors expressed in combination of probability density function and S-N data is proposed. 2. The calculated fatigue life is influenced by the shape parameter and stress block. The conser-vative fatigue design can be achieved when using higher value of shape parameter and the stress blocks divded into more stress blocks.

• The Korean Journal of Rehabilitation Nursing
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• v.6 no.2
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• pp.152-163
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• 2003

Purpose; This study was done to investigate the effect of foot reflexology on vital signs, general fatigue, foot fatigue, mood, and blood glucose levels in noninsulin dependent patients. Method: The Research design of this study was nonequivalent control group quasi-experimental design. 18 patients were assigned to the experimental group, 24 patients to the control group. The data were obtained diaberic patients with ambulatory endocrine outpatients clinic patients from 40 years old to 70 years old. Experimental groups received foot reflex massage for 30minutes three times/week every other days, and Control groups did not received foot reflex massage. The dependent variables were blood pressure, pulse rate, visual analogue scale for general fatigue, foot fatigue, mood, and blood sugar levels. Data were analyzed with $X^2$ test, t-test and repeated measure ANOVA at .0.05 level of significance. Results: There were significant difference in the pulse rate, general fatigue, foot fatigue and mood according to group and time between pre and post foot reflexology. But this research did not prove to decrease blood sugar levels. Conclusions : Foot reflexology can imorove pulse rate, general and foot fatigue, and mood status in diabetus patients. So further research need to explore the effect of decreasing of blood sugar levels.

• Journal of Welding and Joining
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• v.17 no.2
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• pp.29-35
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• 1999

This study was intended to use for the fatigue test in real structures and offer basic data for optimum welding structure design. To this purpose, we obserded the effect of the size and distance of plug welding hole on the static strength and fatigue life of welding structure under the shear/bending load for the improvement of fatigue life of plug welding joint between S/MBR and C/MBR in the lower structure of large bus. The result below is shown through this study. 1) Static and fatigue strength are strongly influenced by the direction of plug weld hole distributed. 2) Distances and diameters of the distributed holes are little dependent on the static strengths 3) In case of the directions of the distributed plug weld holes are vertical to the loading pin, fatigue life is dependent on distance of the distributed hole. 4) In case of the directions of the distributed plug weld holes are parallel to the loading pin, fatigue life is dependent on distance of the hole diameter.