• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.60-64
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• 2001

In this paper, the tension-compression fatigue test method and the fatigue life characteristics of carbon fabric/epoxy laminate coupon are presented. To avoid the buckling during the compression, a proper design for the test coupons is essential. The critical buckling loads for the coupons are calculated by assuming the coupons as columns under two types of fixed conditions. The first is that both ends of each coupon are perfectly clamped, the second is that both ends of each coupon are simply supported. The strain-load curves are obtained by compressing the representative coupons, on each surface of which a strain gage is attached. The buckling loads obtained from the tests are all between the two calculated critical buckling loads. All the coupons are broken by the compression during the fatigue tests. It is estimated to be the reason that the fatigue load causes delamination before the eventual failure of each coupon, and sequentially the micro-buckling in the delaminated region drives each coupon into fatigue failure during the compression. The S-N curve, the fatigue life characteristics of carbon fabric/epoxy is obtained.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.190-195
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• 2004

The compression-compression fatigue properties of the closed cell Al-Si-Ca alloy foams have been studied. The monotonic and cyclic compressive properties were compared with each other and the fatigue stress-life (S-N) curves were presented. In compression-compression fatigue, the crushing was found to initiate in a single band which broadens gradually with additional fatigue cycles. Progressive shortening of the specimen took place due to a combination of low cycle fatigue failure and cyclic ratcheting which is in accordance with the findings of previous researchers [1-3]. Young's modulus of the foam was found to decrease with the increasing strain in case of fatigue test however in case of monotonic compression test the value of Young's modulus increased with the strain (number of cycles). The endurance limit on the basis of $10^{7}$ cycles obtained by extrapolating the experimental results were 0.98 MPa and 1.70 MPa for load ratios 0.1 and 0.5 respectively which are 34 % and 59 % of the plateau stress.

• The Korean Journal of Emergency Medical Services
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• v.23 no.3
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• pp.67-81
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• 2019

Purpose: The purpose of this study was to compare the difference in compression quality and fatigue levels in a rescuer for three different hand techniques used in cardiopulmonary resuscitation (CPR). Methods: The participants were paramedic students at the basic life support provider level. The hands-only CPR was performed for 10 minutes for each of the three hand techniques without disruption, and the quality of chest compressions and fatigue levels were analyzed. Results: There was no difference between the sexes in the chest compression quality and the physiologic parameters before and after compression. Among the quality indexes of chest compression with each of the techniques performed for 10 minutes, the mean depth (p<.01) and mean accuracy (p=.000) of the compression were found to be higher in the five finger fulcrum technique, while the mean compression rate and relaxation accuracy showed no significant differences. Regarding fatigue levels, the five finger fulcrum technique caused lesser subjective fatigue as compared to other techniques (p<.05), although the heart rate and blood pressure revealed no difference. Conclusion: The five finger fulcrum technique was found to be better than the other techniques in terms of chest compression quality and subjective levels of fatigue, indicating that it should be used in CPR education.

• The Korean Journal of Emergency Medical Services
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• v.16 no.2
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• pp.31-41
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• 2012

Purpose : The purpose of the present study is to analyze the accuracy and fatigue felt by lay persons receiving CPR training when they perform hands only CPR (HOCPR) and traditional CPR (TCPR). The performance of CPR data will provide the criteria of dispatcher guidelines for the general public. Methods : For 2 minutes duration, HOCPR was conducted by 51 subjects and TCPR was conducted by 48 subjects. The accuracy measurement of chest compressions was based on the 2010 AHA guideline; the subjective fatigue level in before and after experiment was measured by a self-administered questionnaire. Results : There were no significant differences between the average depth, chest compression depth and chest compression location in terms of chest compression accuracy. However, there were significant differences between the two experimental groups in the accuracies for average speed and chest compression speed. The subjective fatigue level showed no significant difference. Conclusion : The experimental group performing HOCPR showed more accurate compression speed and lower fatigue level. These results suggested that HOCPR would be more effective in training the lay persons in accordance with the voice-instructed CPR.

• Journal of Biosystems Engineering
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• v.37 no.1
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• pp.51-57
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• 2012

Purpose: The compression strength of corrugated fiberboard containers used to package agricultural products rapidly decreases owing to various environmental factors encountered during the distribution of unitized products. The main factors affecting compression strength are moisture absorption, long-term top load, and fatigue caused by shock and vibration during transport. This study characterized the durability of corrugated fiberboard containers for packaging fruits and vegetables under simulated transportation conditions. Methods: Compression tests were done after corrugated fiberboard containers containing fruit were vibrated by an electro-dynamic vibration test system using the power spectral density of routes typically traveled to transport fruits and vegetables in South Korea. Results: To predict loss of compression strength owing to vibration fatigue, a multiple nonlinear regression equation ($r^2=0.9217$, $RMSE=0.6347$) was developed using three independent variables of initial container compression strength, namely top stacked weight, loading weight, and vibration time. To test the applicability of our model, we compared our experimental results with those obtained during a road test in which peaches were transported in corrugated containers. Conclusions: The comparison revealed a highly significant ($p{\leq}0.05$) relationship between the experimental and road-test results.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.8
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• pp.142-147
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• 2009

Spinal fixation systems provide surgical versatility, but the complexity of their design reduces their strength and fatigue resistance. There is no published data on the mechanical properties of such screws. Screws were assembled according to a vertebrectomy model for destructive mechanical testing. A group of two assemblies was tested in static compression. One group was applied to surface a grit blasting method and another group was applied to surface a bead blasting method. Modes of failure, yield, and ultimate strength, yield stiffness, and cycles to failure were determined for six assembles. Static compression 2% offset yield load ranges was from 327 to 419N. Fatigue loads were determined two levels, 37.5% and 50% of the average load from static compression ultimate load. An assembly of bead blasting treatment only achieved 5 million cycles at 37.5% level in compression bending.

• Composites Research
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• v.23 no.5
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• pp.22-29
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• 2010

This paper describes the evaluations of tension-compression fatigue characteristics and life for glass fiber/epoxy laminate composite applied to railway bogie to reduce weight. Test samples of tension-compression fatigue were composed of glass fiber/epoxy 4-harness woven laminate composites with different stacking sequence of warp-direction, fill-direction and ${\pm}45^{\circ}$-direction. The tension-compression fatigue test was conducted with stress ratio (R) of -1 and frequency of 5Hz. Goodman diagram were used to evaluate the fatigue characteristics and life of glass fiber/epoxy 4-harness satin woven laminate composite. Anti-buckling jig was designed to prevent buckling of specimen under compression load. The test results showed that the fatigue characteristics of glass fiber/epoxy 4-harness satin woven laminate composite with stacking sequence of warp-direction had a good performance in comparison with that of SM490 used to conventional metal railway bogie.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.4 s.74
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• pp.337-345
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• 2006

In this study, to evaluate fatigue characteristics of developed composite bridge deck, compression fatigue test at girder support and flexural fatigue test for the 2.8m-long flexural test model were carried out. For the test specimen, DB 24 truck load was applied up to 2,000,000 cycles. In the compression fatigue test, behavior at deck tube and its bonded connection were evaluated. In the flexural fatigue test, deck behavior at mid-span and girder connection were evaluated.

• Journal of the Korean Society of Safety
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• v.9 no.3
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• pp.13-21
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• 1994

Effects of tensile and compression residual stresses in the welded SS41 and A17075-76 on fatigue crack propagation behavior are investigated when a crack propagates from residual stresses region. We propose the fatigue crack growth equation on tensile and compression residual stresses in welded metal. The results obtained in this experimental study are summarized as follows . 1 ) A fatigue crack growth equation which applied fatigue fracture behavior of the welded metal is proposed. (equation omitted) where, $\alpha$, $\beta$, ${\gamma}$ and $\delta$ are constants, and R$_{eff}$ is effective stress ratio [R$_{eff}$=(Kmin+Kres)/(Kmax+Kres)], Kcf is critical fatigue stress intensity factor. The constants are obtained from nonlinear least square method. The relation between crack length and number of cycles obtained by integrating the fatigue crack growth rate equation is in agreement with the experimental data. 2) The experimental results confirmed that the cause of crack extension and retardation by residual stresses has relation to the phenomenon of crack closure. 3) The relaxing trend of residual stresses by the crack propagation was greater In case of compressive residual stress than that of tensile residual stress in the welded metal.tal.

• The Korean Journal of Emergency Medical Services
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• v.26 no.2
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• pp.61-71
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• 2022

Purpose: This experimental study compared the chest compression quality, muscle activity, and subjective fatigue of paramedic students who did or did not wear a mask. Methods: The subjects of this study were 13 paramedic students at college D located in B city. Frequency percentages, mean standard deviations, and paired sample t-tests were conducted using the SPSS/WIN 23.0 program. Results: This study revealed that chest compression depths (t=-2.151, p=.053) and compression rates (t=-2.714, p=.019) were higher in mask-wearers, while muscle activity and subjective fatigue (t=2.382, p=.035) of the erector spinae (t=7.082, p=.001), rectus abdominis (t=4.776, p=.001), and pectoralis major muscles (t=3.193, p=.008) were lower in mask-wearers. Conclusion: The results of this study can be used as a basis to increase the resuscitation rates of cardiac arrest patients and provision of high-quality chest compressors to rescuers when infectious diseases recur in the future.