• International Journal of Precision Engineering and Manufacturing
• /
• v.9 no.4
• /
• pp.57-62
• /
• 2008

The aim of this investigation was to extract the fatigue properties at the designated fatigue life of copper foil and observe the mean stress and stress amplitude effects on both the fatigue life and the corresponding surface morphology. Tensile tests were performed to determine the baseline monotonic material properties of the proportional limit and ultimate tensile strength. Constant amplitude fatigue tests were carried out using a feedback-controlled fatigue testing machine. The mean stress and the stress amplitude were changed to obtain the complete nominal stress-life curves. An atomic force microscope was utilized to observe the relationship between the fatigue damage and the corresponding changes in surface morphology. A Basquin's exponent of-0.071 was obtained through the fatigue tests. An endurance limit of 122 MPa was inferred from a Haigh diagram. The specimen surface became rougher as the number of fatigue cycles increased, and there was a close relationship between the fatigue damage and the surface roughness evolution.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.37 no.1
• /
• pp.26-32
• /
• 2014

Mental fatigue is inevitable in the workplace. Since mental fatigue can lead to decreased efficiency and critical accidents, it is important to manage mental fatigue from the viewpoint of accident prevention. An experiment was performed to evaluate mental fatigue using the formant frequency analysis of human voices. The experimental task was to mentally add or subtract two one-digit numbers. After completing the tasks with four different levels of mental fatigue, subjects were asked to read Korean vowels and their voices were recorded. Five vowel sounds of "아", "어", "오", "우", and "이" from the voice recorded were then used to extract formant 1 frequency. Results of separate ANOVAs showed significant main effects of mental fatigue on formant 1 frequencies of all five vowels concerned. However, post-hoc comparisons revealed that formant 1 frequencies of "아" and "어" were most sensitive to mental fatigue level employed in this experiment. Formant 1 frequencies of "아" and "어" significantly decrease as the mental fatigue accumulates. The formant frequency extracted from human voice would be potentially applicable for detecting mental fatigue induced during industrial tasks.

• 제어로봇시스템학회:학술대회논문집
• /
• 1987.10b
• /
• pp.713-716
• /
• 1987

A new approach to the real-time measurement of muscle fatigue by using adaptive filtering algorithm is proposed. Unlike previously reported methods, it can estimate the muscle fatigue at every sample as the EMG signal statistics change. As a result, the muscle conduction velocity ranged between 4.2-5m/s at low tension and 3-4m/s at fatigue state.

• 제어로봇시스템학회:학술대회논문집
• /
• 1998.10a
• /
• pp.352-355
• /
• 1998

A musculotendon model is investigated to show muscle fatigue under the repeated functional electrical stimulation (FES). The normalized Hill-type model can predict the decline in muscle force. It consists of nonlinear activation and contraction dynamics including physiological concepts of muscle fatigue. A muscle fatigue as a function of the intracellular acidification, pHi is inserted into contraction dynamics to estimate the force decline. The computer simulation shows that muscle force declines in stimulation time and the change in the estimate of the optimal fiber length has an effect only on muscle time constant not on the steady-state tetanic force.

• Journal of Korean Institute of Industrial Engineers
• /
• v.33 no.1
• /
• pp.44-51
• /
• 2007

The purpose of this study was to identify the relationship between the cumulative fatigue of trunk muscles andthe period of recovery time during repetitive lifting and lowering tasks with symmetric and asymmetric postures.Ten subjects participated in the experiment. Subjects had 1, 2, 3, 4 and 5 minutes recovery time respectivelywhile they were performing the lifting and lowering task repeatedly for 3 minutes with the weight equivalent to25% level of MVC. EMG signals from ten trunk muscles were collected and the fatigue level was analyzedquantitatively. In results, the local muscle fatigue was no longer accumulated when 5 minutes recovery time wasgiven in symmetric position. For asymmetric position, it took longer minutes to prevent the fatigue accumul-ation. Different trunk muscles indicated slightly different recovery patterns in terms of MPF (Mean Powerfrequency) value.This result would help ergonomist design the length of recovery time to control the cumulative fatigue of trunkmuscles in industry with repetitive lifting and lowering task.

• Proceedings of the KSME Conference
• /
• 2004.11a
• /
• pp.178-183
• /
• 2004

For developing fatigue design curve of cast stainless steels that would be used in piping material of domestic nuclear power plants, a low-cycle fatigue test rig was built. It is capable of performing tests in pressurized high temperature water environment of PWR. Cylindrical specimens of CF8M were used for the strain-controlled environmental fatigue tests. Fatigue life was measured in terms of the number of cycles with the variation of strain amplitude at 0.04%/s strain rates. The disparity between target length and measured length of specimens was corrected by using finite element method. The corrected test results showed similar fatigue life trend with another previous results.

• Journal of the Korean Society of Safety
• /
• v.14 no.1
• /
• pp.41-48
• /
• 1999

The fatigue life tests were performed in strain control with triangular and hole-time wave-forms at $650^{\circ}C$. The fatigue lifes were investigated according to waveform examining damage mechanisms, which could be used to predict the fatigue life and estimate the remaining life. The results obtained are as follows; The fatigue lifes were in order of the fast-fast>the fast-slow>the slow-fast in the triangular waveforms, and the fatigue lifes in slow-fast waveforms got shorter in the hold-time waveforms. The damage mechanisms of the fracture surfaces were transgranular fracture in the fast-fast, the fast-slow waveforms and intergranular fracture in the slow-fast waveform.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.28 no.4
• /
• pp.410-418
• /
• 2004

The multiaxial fatigue test under in-phase and out-of$.$phase load were performed to study what degradation phenomenon affects fatigue life with virgin and 3600 hrs degraded materials. The various kind of fatigue data fur fatigue life prediction were acquired under pure axial and pure torsional load of fully reversal condition. The models which was investigated are: 1) the von Mises equivalent strain range, 2) the critical shear plane approach method of Fatemi-Socie(FS) parameter, 3) the modified Smith-Watson-Topper(SWT) parameter. The result showed that, fatigue life by material degradation are decreased and life prediction which was used the FS parameter is not conservative but the best result.

• The Journal of Korean Academic Society of Nursing Education
• /
• v.20 no.2
• /
• pp.175-183
• /
• 2014

Purpose: The aim of this study was examine effects of fatigue, anxiety, depression, social support, and spiritual well-being of supportive education program for hospice patients's family. Method: Using a non-equivalent control group pre-post quasi-experimental design, 70 study subjects were assigned into two groups, experimental group (n=35) and the control group (n=35). Measures were fatigue, state-anxiety, depression, social support, and spiritual well-being to test for the effects of supportive education program for hospice patients's family. Data analyzed using $x^2$ test, t-test with SPSS/WIN 19.0 version. Results: The experimental group receiving supportive education program for hospice patients's family had a significant changes of fatigue, state-anxiety, depression, social support, and spiritual well-being. Conclusion: The supportive education program for hospice patients's family is an effective intervention to enhance social support and spiritual well-being and to decrease fatigue, anxiety and depression.

• Food Science and Biotechnology
• /
• v.18 no.1
• /
• pp.275-277
• /
• 2009

Swimming enhancing effects of ssanghwatang fermented with Saccharomyces cerevisae in mice were investigated, and then the blood biochemical parameters related to fatigue were measured. Compared to the control group, the swimming time was significantly increased in fermented ssanghwatang (FST) group from day 4 ($29.27{\pm}4.73$ vs. $50.27{\pm}9.05\;min$, p<0.05). The lactate level, an important indicator of fatigue, was drastically lower in FST group than in control group ($2.13{\pm}0.13$ vs. $1.40{\pm}0.12\;mmole/L$, p<0.01). These results suggest that FST possesses stimulatory effects which can enhance exercise performance and reduce fatigue.