Current Trends in Atomistic Study on Fatigue (original) (raw)
ボルト∙ナット締結体の疲労強度に及ぼすピッチ差の影響とその解析モデルの提案
Transactions of the JSME (in Japanese), 2015
The high strength bolts and nuts are widely used in engineering structures. To investigate the pitch difference on the fatigue strength of bolt, a slight pitch difference is considered between the bolt and nut. Here, the pitch of the nut is α μm larger than the pitch of the bolt. The fatigue experiment is conducted with varying pitch difference. The results show that the fatigue life is extended to about 1.5 times of the one of normal bolt and nut by introducing the suitable pitch difference under the high stress amplitude. According to the detailed observation on the fractured specimens, it is found that the fractured positions and the crack distributions vary depending on the pitch difference. To clarify the improvement mechanism of the fatigue strength, the finite element method is applied to calculate the stress amplitude and mean stress at each bottom of bolt threads. It is found that the finite element analytical model considering the incomplete nut threads is useful for predicting the crack initiation under different pitch difference introduced.
Notch fatigue properties of a Ti-29Nb-13Ta-4.6Zr alloy for biomedical applications
Journal of Japan Institute of Light Metals, 2005
The effects of microstructures on notch fatigue propertes of a Ti-29Nb-13Ta-4.6Zr alloy TNTZ subjected to various thermo-mechanical treatments were investigated in this study. The notch fatigue strengths of TNTZ subjected to aging at 673 K and 723 K after solution treatment or cold rolling at stress concentration factors of 1 without the notch , 2 and 6 in both low and high cycle fatigue life regions are greater than those of as-cold rolled and as-solutionized TNTZ, and TNTZ subjected to aging at 598 K after solution treatment or cold rolling. A single fatigue crack initiates on a specimen surface and at the tip of the notch at stress concentration factors of 1 and 2. While, a few cracks initiate the tip of the notch having a stress concentration factor of 6. Notch sensitivity factor of TNTZ is almost equal to or smaller than those of other materials such as Ti-6Al-4V, CP-Ti, S35C, S45C and SUS304. It is considered that the notch sensitivity factor decreases with decreasing the width of lath like a phase and its volume fraction.
Journal of Japan Institute of Light Metals, 2005
The effects of microstructure and contact pressure on fretting fatigue characteristics of a Ti-4.5Al-3V-2Mo-2Fe alloy with a Widmanstätten a structure were investigated in comparison with that with an equiaxed a structure in this study. In fretting fatigue of the Ti-4.5Al-3V-2Mo-2Fe alloy with a Widmanstätten a structure in a high cycle fatigue life region, and that with an equiaxed a structure in low and high cycle fatigue life regions, the fretting fatigue life does not change linearly with contact pressure, and the fretting fatigue life shows the minimum at a certain contact pressure. In a low cycle fretting fatigue region of the alloy with Widmanstätten a structure, the fretting fatigue life changes linearly with changing in contact pressure. At contact pressures over a certain value, fretting fatigue life of the alloy tends to become nearly constant in each fatigue life region. At relatively lower contact pressures, the main small crack in the alloy with equiaxed a structure tends to be formed at uneven wear damaged parts by fretting wear in the slip region in each fatigue life region. At relatively higher contact pressures, the main small crack in the alloy with equiaxed a structure tends to be formed at the boundary between slip and stick regions in each fatigue life region. The main small crack in the alloy with Widmanstätten a structure tends to be formed in the slip region in each fatigue life region.
Effect of Atomization of Impact Droplets by Surface Texturing using High-Speed Camera
JAPANESE JOURNAL OF MULTIPHASE FLOW
The promoting evaporation of urea-water solution by atomization is required to improve the purification efficiency of NOx for the urea SCR system. This study proposed an innovative method of atomization which processed a surface texture to the impingement walls of the spray droplet. The atomization mechanism in this method was verified by the high qualitative visualization of the impingement droplets.
外部圧迫による筋血流量の変化が低強度運動時の筋放電量と最大筋力に及ぼす影響
Taiikugaku kenkyu (Japan Journal of Physical Education, Health and Sport Sciences), 2011
In‰uence of decreased muscular blood ‰ow induced by external compression on muscle activation and maximal strength after a single bout of low-intensity exercise.
Evaluation of Mental Stress Level on simple tasks using a Duffing oscillator
The Proceedings of the Dynamics & Design Conference, 2016
Serious accidents have happened in many cases caused by the decrease of arousal level, and it is known that the arousal level decreases due to driving and simple tasks, such as an easy calculatation. System to accurately evaluate arousal level in real time in order to prevent such accidents is required. In this paper, we examined whether the parameters of the mathematical model could be used as a method to evaluate the arousal level. The modified Duffing oscillator was proposed as a mathematical model to perform simplified parameters identification. It was applied to EEG data, which is obtained by EEG acquisition experimentation in relaxed states and concentrated state. As a result of the parameters identification in theta band, alpha band, beta band, and 4-30 Hz band, it is shown that t h e parameter B is repeating increase and decrease with time progress of each experiment. A result of investigating a correlation between conventional arousal level and parameter B shows a significant correlation. It is suggested that the parameter B of the modified Duffing oscillator is related to the conventional arousal level and it can calculate the arousal level in real time since this evaluation method of arousal level does not require to analyze each band.
Nippon Eiseigaku Zasshi (Japanese Journal of Hygiene), 2011
Objective: In this study, we investigated the relationships of neutrophil functions with lifestyle factors (namely, subjective stress, exercise habits, smoking habits, alcohol-drinking habits, and selfperceived status health) and health behavior in the Chinese urban elderly. Methods: We performed a health survey of the elderly aged 65 years or older living in Tianjin. The subjects were 42 males (69.1±4.1 years old) and 41 females (69.1±4.1 years old). Investigations of subjective stress, exercise habits, smoking habits, alcohol-drinking habits, and self-perceived health status were performed. The phagocytosis and superoxide productivity of neutrophils were measured by the nitroblue tetrazolium (NBT) reduction method. In addition, leukocyte count and serum total protein (TP) level were examined. Results: The investigations revealed the associations of health behavior (p<0.05) and self-perceived health (p<0.10) with the balance between phagocytosis and subsequent superoxide production. Conclusions: The present study revealed that there were correlations of neutrophil functions with lifestyle factors (subjective stress, exercise habits, smoking habits, alcohol-drinking habits, and self-perceived status health) and health behavior in the Chinese urban elderly.