Papers by Keyword: S-N Curve

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Authors: Peng Gang Mu, Xiao Peng Wan, Mei Ying Zhao
Abstract: Based on an amount of fatigue experimental data of fiber reinforced plastic composite, a new three-parameter S-N curve model is proposed to describe the relationships between the loads and fatigue life under constant amplitude cyclic loading. As the logistic curve behaves as sigmoidal which is the similar with previous S-N models, and from this comparability, an S-N equation with logistic’ form has been established. The model can assess the fatigue behaviors of FRP under various loading conditions, such as, tension-tension (T-T), tension-compression (T-C) or compression-compression (C-C) loading under different stress ratios of the whole region of fatigue life. Several examples are employed to illustrate that the model has ability to fit several different sets of experimental data accurately.
Authors: Yong Yun Nam, Seung Ho Han, Jeong Woo Han, Byung Chun Shin
Abstract: The hot spot stress or the notch strain alleviates the welding detail dependency of S-N curve to some extent. This paper suggests a new stress model which alleviates the dependency further, thus the fatigue strengths of several welding details of same material can be evaluated with the S-N curve of the base material. A stress at the hot spot of a weld joint is decomposed into two components; linear rising one, and rapid rising one which is inversely proportional to the distance from the hot spot. For the stress decomposition, a formula is proposed with which the configuration of stress distribution near a hot spot is fitted exactly. The new stress model makes use of a geometric characteristic of the stress distribution curve by the formula. The stress model is applied to five different weld joints. As the result, the experimental fatigue data are plotted very closely to the S-N curve of the base material
Authors: Kazutaka Mukoyama, Koushu Hanaki, Kenji Okada, Akiyoshi Sakaida, Atsushi Sugeta, Izuru Nishikawa, Akira Ueno, Tatsuo Sakai
Abstract: The aim of this study is to develop a statistical estimation method of S-N curve for iron and structural steels by using their static mechanical properties. In this study, firstly, the S-N data for pure iron and structural steels were extracted from "Database on fatigue strength of Metallic Materials" published by the Society of Materials Science, Japan (JSMS) and S-N curve regression model was applied based on the JSMS standard, "Standard Evaluation Method of Fatigue Reliability for Metallic Materials -Standard Regression Method of S-N Curve-". Secondly, correlations between regression parameters and static mechanical properties were investigated. As a result, the relationship between the regression parameters and static mechanical properties (e.g. fatigue limit E and static tensile strength σB) showed strong correlations, respectively. Using these correlations, it is revealed that S-N curve for iron and structural steels can be predicted easily from the static mechanical properties.
Authors: Byeong Choon Goo, Jae Hoon Kim, Jung Won Seo, Chang Sung Seok
Authors: Hoda Eskandari, Ho Sung Kim
Abstract: A theory for mathematical framework is developed with axioms for fatigue damage, quantification and relativity concept, boundary conditions, and compatibility, allowing us to evaluate the validity of candidate damage equations/quantities on S-N plane for prediction of fatigue life. Manifestation points for accumulated damage were defined for boundary conditions by differentiating between damage accumulated before failure, and failure caused by damage at quantised fatigue loading cycles. A selected damage equation leading to a theoretical S-N curve was validated as an example.
Authors: Adam Lipski
Abstract: The paper presents a new thermographic method that enables simultaneous accelerated determination of the fatigue limit and the S-N curve. In the presented method, the fatigue limit was determined assuming a constant rate of temperature rise occurring in the second phase of a specimen fatigue life. The S-N curve was developed based on energy-related parameter with the assumption of its dependency on the stress amplitude. The tests made on C45 steel under reversed bending revealed that the fatigue limit value obtained from accelerated thermographic tests as compared to the value obtained using Staircase method differs by 10.0% maximum.The S-N curve obtained by accelerated thermographic method fits inside 95% confidence interval for the S-N curve obtained from the full test.
Authors: Przemysław Strzelecki, Janusz Sempruch, Krzysztof Nowicki
Abstract: The study discusses the issue of determining the accuracy of fatigue characteristics in a high-cycle fatigue range using analytical-experimental methods. The analytical-experimental methods are defined as a characteristic curve obtained using an analytical method and additional experiment aimed to increase its accuracy. The higher the amount of data the higher the characteristic curve accuracy. The study aims to address the question “what values should be determined experimentally to obtain an S-N curve in a high-cycle fatigue range with a satisfactory estimation of the fatigue life.
Authors: Przemysław Strzelecki, Janusz Sempruch, Tomasz Tomaszewski
Abstract: This paper presents two methods for estimating the S-N fatigue curve. The first is the traditional linear regression and staircase method. The other, alternative, method is based on random fatigue life, fatigue limit and probability. The both methods provide similar results but the latter one requires fewer test samples
Authors: Byeong Choon Goo
Abstract: A structural steel should satisfy various properties under varied conditions. Fatigue strength is one of them. When structural steels are used in the form of welded joints, fatigue strength is one of the key characteristics that should be considered. In this study, comprehensive fatigue tests of a structural steel with yielding strength of about 350 MPa and tensile strength of about 520 MPa were carried out. First, a lot of specimens: parent material plates, butt welded specimens with reinforcement removed, as-welded plates, plates with weld toe ground, load-carrying cruciform, non load-carrying cruciform, plates with transverse fillet welded rib, etc were prepared and tested. S-N curves for the above specimens were compared and analyzed. Secondly, some life-size rectangular beams were fabricated by welding and tested. It is found that annealing is detrimental to fatigue strength rather than beneficial. The experimental data and results may be used usefully by engineers.
Authors: Jiang Tao Xu, Yan Dong Song
Abstract: This paper based on the data of enterprise’s bench test, first set up the finite element analysis model for the front sub-frame by using the of professional finite element analysis software and fatigue life analysis software, then got the distribution information (such as the situation and the cycles) for the front sub-frame after analyzing, with these messages not only easily found out the danger area, but also provided reference for bench test improving, once more found a method that can forecast the life for mechanical products.
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