• Composites Research
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• v.36 no.1
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• pp.42-47
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• 2023

In this paper, we present a fatigue life prediction methodology using multiple S-N curves according to the different stress states of laminated composites. The stress states of the plies of the laminated composites are classified into five modes: longitudinal tension or compression and transverse tension or compression, and shear according to the maximum stress criterion and Puck's criterion with a scaling factor K. This methodology has advantages in computational cost, and it can also consider microstructural characteristics of the composites by applying different S-N curves. The S-N curves for the fatigue analysis are obtained by experimental fatigue test. The proposed methodol is implemented into commercial software, ABAQUS user material subroutine and therefore, the fatigue analysis is conducted using the structural analysis results. The finite element (FE) simulation results are presented for unidirectional composites with and without open-hole. The FE simulation results show that the stress condition is different depending on the fiber orientation of the unidirectional composite, so the fatigue life is calculated with different S-N curves.

• Fashion & Textile Research Journal
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• v.20 no.3
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• pp.343-352
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• 2018

The objective of this study is to investigate the market of fitness compression wear as well as to design an optimal fitness compression wear by analyzing the muscle and movement characteristics of the elderly women in Korea. In this regard, research for functional garments is needed to increase muscle activity of elderly people during physical exercise. Firstly, we investigated the brand, design, size, material, and pattern of fitness wear based on the market survey. Secondly, we identified preference, evaluation items, evaluation method, and pattern design method based on the literature review. Finally, in addition, the motion type, range, angle to improve the muscle strength of the elderly were investigated and the maximum muscle strengths of each motion were analyzed by using 2007 Size Korea data (n = 386). It is also designed for muscle fatigue through exercise and rapid fatigue recovery after exercise. The evaluation methods for fitness compression wear were classified as motor functionality, physiological comfort, pattern and material suitability evaluations. The muscle strength at leg (pushing force) and waist (lifting force) of the ages of 60 to 69 years old showed 239.3 N and 274.5 N, respectively, which were the lowest forces compared to younger age groups. By applying these results to the design process of fitness wear, it is anticipated that the fitness wear will have a proper fit to the body shape of elderly people in South Korea as well as it can increase muscle efficiency to promote physical capability and healthy life for senior people.

• Journal of Welding and Joining
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• v.27 no.6
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• pp.31-35
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• 2009

When conducting CTOD test, especially in thick welded steel plate, fatigue pre-cracking occasionally failed to satisfy the requirements of standards thus making the test result invalid. Internally accumulated residual stress of test piece has been thought as one of the main reasons. The propagation of fatigue crack, started from the tip of machined notch, which might have propagated irregularly due to residual stress field. To overcome this kind of difficulty three methods to modify the residual stress are suggested in standard i.e. local compression, reverse bending and stepwise high-R ratio method. In this paper not only multi pass welding but also local pre-compressing process of thick steel plate has been simulated using finite element method for clarifying variation of internal welding residual stress. The simulated results show that welding residual stress is compressive in the middle section of the model and it is predominantly increased after machining the specimen. Comparing as-welded state all component of the welding residual stress changing to compressive in the tip of machine notch whereas residual stress of the outer area remain as tensile condition relatively. Analysis results also show that this irregular residual stress distribution is improved to be more uniformly by applying local compression.

• Steel and Composite Structures
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• v.4 no.2
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• pp.149-167
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• 2004

Offshore platforms have to serve in harsh environments and hence are likely to be damaged due to wave induced fatigue and environmental corrosion. Welded tubular joints in offshore platforms are most vulnerable to fatigue damage. Such damages endanger the integrity of the structure. Therefore it is all the more essential to assess the capacity of damaged structure from the point of view of its safety. Eight internally ring stiffened fatigue damaged tubular joints with nominal chord and brace diameter of 324 mm and 219 mm respectively and thickness 12 mm and 8 mm respectively were tested under axial brace compression loading to evaluate the reserve capacity of the joints. These joints had earlier been tested under fatigue loading under corrosive environments of synthetic sea water and hence they have been cracked. The extent of the damage varied from 35 to 50 per cent. One stiffened joint was also tested under axial brace tension loading. The residual strength of fatigue damaged stiffened joint tested under tension loading was observed to be less than one fourth of that tested under compression loading. It was observed in this experimental investigation that in the damaged condition, the joints possessed an in-built load-transfer mechanism. A bi-linear stress-strain model was developed in this investigation to predict the reserve capacity of the joint. This model considered the strain hardening effect. Close agreement was observed between the experimental and predicted results. The paper presents in detail the experimental investigation and the development of the analytical model to predict the reserve capacity of internally ring stiffened joints.

• The Korean Journal of Emergency Medical Services
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• v.25 no.3
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• pp.81-92
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• 2021

Purpose: The aim of the study is to measure the quality of cardiopulmonary resuscitation (CPR) and the fatigue of rescuers wearing PPE (Level D) during a CPR session and to ultimately provide suggestions of safety standards for rescuers. Methods: 36 subjects were enrolled in the study. The subjects were divided randomly into three groups of two-members, three-members, and four-members. Each group performed CPR for 30 minutes. Blood lactate concentration, heart rate, rating of perceived exertion, chest compression depth and rate were measured before experiment and after each cycle. Results: There was a difference in the blood lactate concentration during CPR cycle by member of shifts (p=.014). The blood lactate concentration increased during CPR (p=.000). Subjective fatigue was a significant difference of chest compression in cycles 3, 4, and 5 for the member of shifts during CPR (p=.049, p=.009, p=.015). Depth and rate of chest compression were not different for the member of shifts during CPR. Conclusion: It is necessary to establish standards for the member of shifts during CPR, to reduce the fatigue of rescuers.

• Elastomers and Composites
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• v.53 no.4
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• pp.220-225
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• 2018

Resilient pads play a major role in reducing the impact of loads on a rail in a rail-fastening system, which is essentially used for a concrete track. Although a compression set test is commonly used to measure the durability of a resilient pad, the static spring constant is often observed to be different from the fatigue test. In this study, a modified compression set test method was proposed to monitor the variations in the compression set and static spring constant of a resilient pad with respect to temperature and time. In addition, the life of the resilient pad was predicted by performing an acceleration test based on the Arrhenius equation.

• The Korean Journal of Emergency Medical Services
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• v.12 no.3
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• pp.43-53
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• 2008

Purpose : This study was designed to examine physiological changes in the body of rescuers conduct CPR according to the 2005 new guideline from American Heart Association. The ratio of artificial respiration has changed from 15 : 2 into 30 : 2 in 2005. The researcher tried to know the correlation between the physiological changes and the accuracy of CPR. Method : The examinees of this study were 26 students (Dept. of Emergency Medical Service). After the training, participants conducted 10 minute CPR and soon after the CPR, their vital signs were checked, and lactic acid and concentration of ammonia were analysed from their blood samples. Questionnaires to ask their subjective fatigue level were filled out after blood samples and 10 minute - CPR was performed. Results : 1) After the CPR, concentrations of ammonia were $149.71{\mu}{\ell}/d{\ell}$ and $162.17{\mu}{\ell}/d{\ell}$ in 15 : 2 and 30 : 2, respectively. The number was higher in 30 : 2 but it wan not statistically meaningful (p = .493). Log value of lactic acid was a little higher in 30 : 2 with 42 log($mmol/{\ell}$) and 54 log($mmol/{\ell}$) in 15 : 2 and 30 : 2, respectively but it was not statistically meaningful (p = .113). 2) Blood pressure in 15 : 2 and 30 : 2 were 118.50 mmHg and 125.08 mmHg while pulse in two different cases were 96.14 and 97.25, showing no statistically significant differences (blood pressure : p = .155, pulse : p = .841). 3) Subjective fatigue was a bit high in 30 : 2 with 5.93 and 6.92 points in 15 : 2 and 30 : 2 respectively but it was not statistically meaningful (p = .142). 4) In the 10 minute CPR, respiration accuracy was 96.21% in 15 : 2 and 94.79% in 30 : 2. There was no statistical significances between the two(p = .225). In the meanwhile, chest compression accuracy was 92.57% in 15 : 2 and 91.83% in 30 : 2. From the beginning to the end of chest compression, there showed no difference(p = .425). the type of CPR did not influence upon the accuracy of chest compression(p = .756). Conclusion : In the CPR conducted by skilled rescuers for 10 minutes, there were no statistically meaningful differences between 15 : 2 and 30 : 2 in the concentration of fatigue element in a blood, subjective fatigue, vital signs and accuracy of CPR. Therefore, 30 : 2 CPR recommended by American Heart Association need to be recommended and performed in scene size up.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.275-280
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• 1999

This study is object to program development of fatigue test for universal testing machine. Fatigue program is consist of test simulation, data analysis and print report by control fatigue testing program which expansively applies tension-compression tests with using oil pressure mechanism by Visual Basic software running under windows 98.

• Journal of Ocean Engineering and Technology
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• v.18 no.6 s.61
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• pp.84-90
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• 2004

Fatigue tests were conducted on SM45C steel using hour-glass shaped smooth tubular specimen under biaxial loading in order to investigate the crack formation and growth at room temperature. Three types of loading systems, were employed fully-reserved cyclic torsion without a superimposed static tension or compression fully-reserved cyclic torsion with a superimposed static tension and fully-reserved cyclic torsion with a superimposed static compression. The test results showed that a superimposed static tensile mean stress reduced fatigue life however a superimposed static compressive mean stress increased fatigue life. Experimental results indicated that cracks were initiated on planes of maximum shear strain whether or not the mean stresses were superimposed. A biaxial mean stress had an effect on the direction that the cracks nucleated and propagated at stage 1 (mode II).

• Journal of the Korea Society of Computer and Information
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• v.22 no.2
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• pp.105-110
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• 2017

We propose a effectiveness of the assistant pad during cardiopulmonary resuscitation and provide basic data for high quality cardiopulmonary resuscitation. The subjects of the study were 28 students in the emergency department who completed the BLS Health Care-Provider under the experimental study by the randomized crossover design. Data were analyzed by using SPSS 20.0 Version. The results of this study showed that chest compressions using assistant pads decreased pain and fatigue than normal chest compressions, and the depth of chest compressions was deeper than normal depth. The results of this study shows that the use of assistant pads between the one hand and the other hand during cardiopulmonary resuscitation may increase accuracy and depth were improved. Therefore intensive indicator also improved. However, with regard to the use of assistant pads, further studies will be needed to identify the potential for clinical use.