Effects of Stress Wave Forms on Low Cycle Corrosion Fatigue Strength

Studies have been made on the influence of trapezoidal stress wave forms on low cycle corrosion fatigue strength. The electrode potential of the specimens has been observed against the saturated calomel electrode during cycles. The corrosion fatigue strength is much affected by the stress wave forms. The stressless time, the varying stress time and the maximum stress time in one cycle show each effect on the life of specimens, and the deleterious effect of the varying stress time is the most conspicuous. The potential variation during one cycle has close relations with the lives

Effects of Stress History and Corrosive Environment on Fatigue Crack Propagation

The effects of stress history and corrosive environment on fatigue crack propagation of a mild steel are discussed under the constant and the variable stress amplitude, and the corrosion fatigue strength under service load is made clear as follows ; The crack initiation of corrosion fatigue is very early but the crack rate in saline and in water becomes smaller than that in air from a certain value of crack depth. This may be due to the wedge action of metal oxide in cracks. In hydrochloric acid the decrease of the crack rate is not observed because of the dissolution of metal oxide. Under high-low two-step stress history, both in air and in saline the crack propagation is delayed for a considerable period after the stress change and the subsequent crack rate is nearly equal to the expected one for the lower stress. Under continuously decreasing stress history as well, both in air and in saline the crack rate becomes smaller than the expected one based on the linear cumulative damage hypothesis. This is due to the deceleration effect corresponding to the delay in crack propagation under high-low stresses. On the other hand, under low-high two-step stress history, the crack rate in air after the stress change is the same as expected, while the rate in saline is greater for a while after the stress change due to the balance of the metal oxide produced on the crack wall and the opening of the crack, and then gradually decreases to the expected one. The acceleration effect of the crack propagation, however, tends to diminish at a smaller increasing rate of the stress amplitude under continuously increasing stress history. ∫(dn/N) under the various stress patterns may be estimated by considering the acceleration effect and deceleration effect. For example, ∫(dn/N)≅l is concluded in saline under two-stress repeated block history and under stress varying up and down in a short period because of the mutual offset of the acceleration effect and the deceleration one. Since the life of smooth specimens in corrosive environments is wholly occupied by crack propagation, the same argument for notched specimens mentioned above may be applicable to the corrosion fatigue of smooth specimens under various stress histories

金属の疲労に及ぼすふん囲気の影響に関する基礎的研究

京都大学0048新制・課程博士工学博士工博第138号新制||工||108(附属図書館)2115京都大学大学院工学研究科機械工学専攻(主査)教授 遠藤 吉郎, 教授 河本 実, 教授 平 修二学位規則第5条第1項該当Kyoto UniversityDA

Tribological Properties of Diamond-Like Carbon Films with Surface Nano-Structure Formed by Femtosecond Laser Pulses

We report tribological properties of diamond-like carbon (DLC) film of which surface has been nanostructured with femtosecond (fs) laser pulses. For this study, the fs-laser processing technology has been developed to produce a uniformly nanostructured DLC surface over a wide area of 15 x 15 mm 2 . The results have demonstrated that the DLC surface has an excellent frictional performance by coating a MoS 2 layer on the nanostructured surface, where the friction coefficient of DLC surface was observed to decrease down to 0.07 from 0.18 for the steel ball and to 0.02 -0.04 from 0.08 for the WC-Co ball used in the friction test machine

Hereditary inclusion body myopathy with a novel mutation in the GNE gene associated with proximal leg weakness and necrotizing myopathy [10]

金沢大学医学部附属病院神経内科全文公開20080