Papers by Keyword: Fatigue Strength

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Authors: Kotoji Ando, Yasuharu Shirai, M. Nakatani, Y. Kobayashi, S. Sato
815
Authors: Myung Hyun Kim, Chung In Ha, Sung Won Kang, Jeong Hwan Kim, Jae Myung Lee
Abstract: Fatigue strength assessments with two types of load carrying fillet weldment under out-of-plane bending load have been carried out by using both hot spot stress and structural stress methods. Basis for the derivation of structural stress method is discussed in detail. Finite element analyses using shell elements models have been performed for the fatigue strength assessment of weldments. As a result of the fatigue strength evaluation for load carrying transverse fillet weldment, hot spot stress method is found to be consistent with structural stress method as well as measurement. Hot spot stress, however, estimated for the load carrying longitudinal fillet weldment exhibit large variation with respect to mesh size and element type while the calculated structural stress for the longitudinal fillet weldment is relatively independent of mesh size. The fatigue life estimation according to structural stress has been introduced with the master S-N curve.
995
Authors: Xiu Ning Peng, Wen Wu Lan
Abstract: According to experimental research on 10 specimen of steel bars under fatigue loading, remained static strength of bars has been measured. On the base of experimental data, a new fatigue strength (limit) measuring method of steel bars using in concrete structure has been set up. Experimental results and theoretic analysis show that the method can shorten time in experiment, reduce discreteness and improve the precision of data. The method may be used to measure fatigue limit of both not corroded and corroded bars (especially with local unsymmetrical corrosion pits) bearing fatigue loading, therefore it will be used to evaluate the residual fatigue expectation of reinforced concrete that bearing fatigue loads such as bridge structure which has served for a certain long of time and be used to make right decisions on repairing or removing structures under reversed loads.
840
Authors: Pu Zhang, Pei Quan Guo, Yan Ke Cao, Xiao Wei Wang
Abstract: Meshing cylindrical surface always bears the alternating stress in the practical application. It will bring fatigue failure and fracture phenomena if the alternating stress is uncontroled, seriously affect the service life of the mechanical devices. The fatigue strength of the workpiece will be improved to boost the surface quality and surface strength and use the way of controling the workpiece surface residual stress brought by metal cutting to compressive stress. High-speed milling technology can greatly enhance the surface strength and surface quality of the workpiece surface, it can also change the cutting parameters to control the residual stress of the workpiece surface, so that it can greatly improve the fatigue strength of the workpiece.
82
Authors: Un Bong Baek, Jong Seo Park, In Hyun Chung, Seung Hoon Nahm, Young Hwa Ma, Yong Yun Lee
Abstract: The high cycle fatigue properties of two kinds of wrought Al 2519 alloys without and with scandium of 0.10% were investigated. The fatigue strength was determined at R = 0.1 under constant amplitude loading conditions in air. The alloy with scandium of 0.10% showed a little lower tensile yield strength and higher fatigue strength values. The fine grained Al-0.10Sc alloy exhibited a higher resistance against fatigue crack nucleation despite the lower yield stress in comparison to the coarse grained Al 2519 alloy. The results can be explained mainly with the microstructural differences between both alloys. This results are due to the presence of coherent Al3 (Sc, Zr) precipitates and a very fine subgrain structure.
2483
Authors: Un Bong Baek, Jong Seo Park, In Hyun Chung, Tae Won Park, Seung Hoon Nahm
Abstract: Al alloy is used extensively in several fields because specific strength is good and workability is superior. It is known that If Sc is added to Al alloy, strength is increased and re-crystallization temperature rises because microstructure becomes fine. The high cycle fatigue properties of four kinds of Al-Mg-Si alloys without and with only scandium of 0.20 % or with both scandium(Sc) of 0.20 % and zirconium(Zr) of 0.12% were investigated. The fatigue strength was determined at R = -1.0 under constant amplitude loading conditions in air. The alloy with scandium of 0.20 % showed a little higher fatigue strength values. The alloy with 0.20 % Sc and 0.12 % Zr showed highest tensile yield strength and highest fatigue strength. The fine grained Al 6061+0.20Sc+0.12Zr alloy exhibited a higher resistance against fatigue crack nucleation in comparison to the coarse grained Al 6061 alloy. The results can be explained mainly with the micro-structural differences among four alloys. This results are due to the presence of coherent Al3 (Sc, Zr) precipitates and a very fine sub-grain structure.
657
Authors: Jae Do Kwon, Sang Jin Cho, Yong Tak Bae
Abstract: The aged degradation of material is observed when heat-resisting steel is exposed for long periods of time at high temperatures. In the present study, the degraded 1Cr-0.5Mo steel that is used for long periods of time at high temperature(about 515°C) and artificially reheat-treated materials are prepared. These materials were used to study the effect of aged degradation on fretting fatigue behavior. Through this experiment, it is found that the fretting fatigue strength of reheat-treated 1Cr-0.5Mo steel is approximately 46 percent lower than that of the plain fatigue strength of the same material. Furthermore, the fretting fatigue strength of degraded 1Cr-0.5Mo steel was less than 53 percent of the same material™s plain fatigue strength. The maximum value of fatigue strength difference is observed as 57 percent between the fretting fatigue of degraded material and plain fatigue of reheat-treated material. These results can be used as basic data in a structural integrity evaluation of heat-resisting steel considering aged degradation effects.
1221
Authors: Fang Yu, Lie Ping Ye, Zhi Jun Dong
Abstract: Based on the theory of fatigue fracture of metals, quantitative analysis method was proposed for fatigue strength of cables of cable bridges and conclusions were reached through analysis of calculation formula: the analysis method of stress fatigue life was able to consider the section dimensions of the cables, plasticity of the material and stress ration caused by external loads and other factors which affect the fatigue life. This analysis theory was correct which took into consideration of relatively overall factors and was a better way to analyze the cable fatigue life. Meanwhile, the design of fatigue strength of bridge cables should adopt the theoretical fatigue limit represented by equivalent nominal stress amplitude as the design value of fatigue strength of cable. The theory represented by equivalent nominal stress amplitude considered the influence of stress ratio on fatigue life of cables caused by external loads. Compared with traditional method of fatigue strength estimate, with sufficient theory basis and overall consideration of factors, the results of this method were more reliable.
1214
Authors: Tsuyoshi Kubota, Hiroshi Yamagata
Abstract: The present requirements for the connecting rod are indicated and the fracture splitting (FS) technologies for constructing the big end boss are reviewed. Two possibilities of FS for a high strength Cr-Mo steel and Ti alloys were discussed. The carburized quench-temper FS connecting rod has a superior fatigue strength with a high dimensional accuracy at the big end boss. The possibility of using a titanium FS connecting rod was examined and proposed.
4850
Authors: Dong Ho Bae, N. Tomioka, J. Niisawa, H. Kitagawa
441
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