Papers by Keyword: Fatigue Limit

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Authors: Takahiro Matsueda
Abstract: Aspect ratio is a key factor to calculate stress intensity factor (SIF) K using fracture mechanics. While cracks are approximated to be semi-circle or semi-ellipse for simply evaluation, their shapes are changed by stress concentration source. In this study, a new method to modify aspect ratio of a crack at a notch root is proposed. Modified aspect ratio in this method succeeded to decrease prediction error of fatigue crack initiation stress, σw1 which was calculated using experimental value.
80
Authors: Jian Ming Zhai, Xiao Yang Li
Abstract: The performances of material fatigue can be illustrated by the S-N curve, the p-S-N curve and the fatigue limit, which are very important to engineering and the mechanical design. Recently, the author proposed a new method to determine a conditional probability density distribution surface(CPDDS) of the material, and the surface can reflects most properties of the material’s fatigue. Methods to obtain the theoretical fatigue limit and the p-S-N curve are introduced in this paper on the basis of previous study. The methods are applied on the fatigue test data of C45 steel, and the p-S-N curves that obtained by various methods are compared in this paper.
256
Authors: Tae Gyu Kim, Hyun Soo Kim, In Duck Park, Hye Sung Kim
Abstract: In this study, we investigated the fatigue characteristics of SMA40 materials as a potential application in connecting rod material for an automobile. Average fatigue life of 168,700 cycles and fatigue limit of 437 MPa was determined from SMA40 specimens. However, when tested under fretting condition, decrease in fatigue lifetime was 20% and fatigue limit was reduced to 350 MPa.
279
Authors: Sung Cheol Yoon, Chang Sung Jeon, Won Kyung Kim, Jeong Guk Kim, Sang Hoon Chang
Abstract: This paper describes the results of structural analysis and loading test of a bogie frame. The purpose of the analysis and test is to evaluate the safety and functionality of the bogie frame under maximum load. The bogie system consist of the bogie frame, suspensions, wheel-sets, a brake system and a transmission system. Of these components, the bogie frame is the major component subjected to the vehicle and passenger loads. The evaluation method used the JIS E 4207 specifications throughout the FEM analysis and static load test. The test results have shown the bogie frame to be safe and stable under design load conditions.
645
Authors: Sung Cheol Yoon
Abstract: The truck that is used as running equipment for freight car support is a core structural part that supports the load of the car body and that greatly influences the safety of freights and vehicles, as well as their running performance. The running equipment is composed of truck frames, wheels and wheel axles, independent suspensions, and brakes. Among these components, the truck frame supporting the load of the vehicles and freights may be the most important one. This study was carried out to analyze the structure of truck frames and to determine whether they are safe when the maximum vertical load, breaking load, and front and rear loads are applied to them. This was done by subjecting the truck frames to stress tests and then measuring the stress on each of their parts. Before the load test, a structural-analysis program was used for the stress distribution analysis of the truck frame. To measure the stresses based on the results of the structural analysis, strain gages were attached to the surfaces of truck frames [1].
405
Authors: Sung Cheol Yoon, Jeong Guk Kim, Kwang Sun Baik, Byeong Choon Goo, Kang Youn Choe
Abstract: The truck that is used as running equipment for freight car support is a core structural part that supports the load of the car body and that greatly influences the safety of freights and vehicles, as well as their running performance. The running equipment is composed of truck frames, wheels and wheel axles, independent suspensions, and brakes. Among these components, the truck frame supporting the load of the vehicles and freights may be the most important one. This study was carried out to analyze the structure of truck frames and to determine whether they are safe when the maximum vertical load, breaking load, and front and rear loads are applied to them. This was done by subjecting the truck frames to stress tests and then measuring the stress on each of their parts. Before the load test, a structural-analysis program was used for the stress distribution analysis of the truck frame. To measure the stresses based on the results of the structural analysis, strain gages were attached to the surfaces of truck frames. The results of the stress tests showed that truck frames have a safe vehicle load design.
210
Authors: Sung Cheol Yoon, Jeong Guk Kim, Sung Hyuk Park, Kwang Sun Baik, Kang Youn Choe
Abstract: This paper describes the results of structural analysis and loading test of a bogie frame. The purpose of the analysis and test is to evaluate the safety and functionality of the bogie frame under maximum load. The bogie system consist of the bogie frame, suspensions, wheel-sets, a brake system and a transmission system. Of these components, the bogie frame is the major component subjected to the vehicle and passenger loads. The evaluation method used the JIS E 4207 specifications throughout the FEM analysis and static load test. The test results have shown the bogie frame to be safe and stable under design load conditions.
49
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.
106
Authors: Takahiro Matsueda
Abstract: Crack size measurement is necessary in order to calculate stress intensity factor (SIF), K. Definition of the initial crack size in plain specimens is more complex than notched specimens because artificial defects are not introduced. In this study, the effect of difference between initial crack size calculated with both average grain size and maximum shear mode crack size on K, and fatigue limit value, σw were examined. A new alternative method to predict endurance limit of plain specimen, σw with a combination of threshold stress in shear mode and in Mode I was proposed.
85
Authors: Takahiro Shikama, Shinji Yoshihara, Yoshimasa Takahashi, Hiroshi Noguchi
Abstract: In general, aluminum alloy does not exhibit distinct fatigue limit (knee point) in the S-N diagram. The growth of a small fatigue crack of precipitation-hardened Al-Mg-Si system alloy (6061-T6) was investigated to clarify the mechanism of non-appearance of distinct fatigue limit (knee point) in the S-N diagram. The small crack was analysed in detail by replica method, scanning electron microscope (SEM), and Electron Back Scatter Diffraction Patterns (EBSD). On the other hand, the existence of distinct fatigue limit (knee point) of new developed aluminum alloy by adding excess Mg to the 6061 alloy was found. In this study, the resistance of small crack growth of the developed alloy was compared with standard 6061 alloy. It was revealed that the resistance of crack growth of new developed alloy was higher than that of standard 6061 alloy in short crack region (l<1.0 mm).
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