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fatigue behavior of Unbonded Partially Prestressed Concrete Beams with Flexure

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China Ocean Engineering 1997年第2期12卷 225-234页

作者： Song, YP Che, HM Yi, W SW JIAOTONG UNIV DEPT BRIDGE ENGNXIAN 610031PEOPLES R CHINA

A study on fatigue behavior of unbonded partially prestressed concrete beams is presented. Model tests have been carried out in static loading and cyclic compressive loading on 15 beams with flexure. The ratios of the lower limit to the upper limit of fatigue load are 0.5 and 0.3 respectively, and the frequencies of cyclic loading are 8 Hz and 4.5 Hz respectively. The experimental results of the strains of the concrete and steel bars, the deflection of test beams, and the crack width of normal section are analyzed. According to statistics and analysis of test results, the corresponding calculation models are developed and presented.

关键词： fatigue behavior unbonded partially prestressed concrete beam

Ultra-high cycle fatigue behavior of high strength steel with carbide-free bainite/martensite complex microstructure

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International Journal of Minerals,Metallurgy and Materials 2009年第3期16卷 285-292页

作者： Xue-xia Xu Yang Yu Wen-long Cui Bing-zhe Bai Jia-lin Gu Laboratory of Advanced Materials Department of Materials Science and Engineering Tsirtghua University Beijing 100084 China

The ultra-high cycle fatigue behavior of a novel high strength steel with carbide-free bainite/martensite （CFB/M） complex microstructure was studied. The ultra-high cycle fatigue properties were measured by ultrasonic fatigue testing equipment at a frequency of 20 kHz. It is found that there is no horizontal part in the S-N curve and fatigue fracture occurs when the life of specimens exceeds 10^7 cycles. In addition, the origination of fatigue cracks tends to transfer from the surface to interior of specimens as the fatigue cycle exceeds 10^7, and the fatigue crack originations of many specimens are not induced by inclusions, but by some kind of ＂soft structure＂. It is shown that the studied high strength steel performs good ultra-high cycle fatigue properties. The ultra-high fatigue mechanism was discussed and it is suggested that specific CFB/M complex microstructure of the studied steel contributes to its superior properties.

关键词： high strength steel ultra-high cycle fatigue bainite martensite fatigue behavior

Relationship between the fatigue behavior and grain structures of an as-extruded Mg-6.2%Zn-0.6%Zr(in wt.%)alloy

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Journal of Materials Science & Technology 2023年第18期149卷 119-126页

作者： B.J.Wang D.K.Xu C.L.Jiang L.Y.Sheng E.H.Han School of Environmental and Chemical Engineering Shenyang Ligong UniversityShenyang 110159China Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Binzhou Institute of Technology Binzhou 256606China Shandong Key Laboratory of Advanced Aluminium Materials and Technology Binzhou 256606China Shenzhen Institute Shenzhen Key Lab Human Tissue Regenerate&RepairPeking UniversityShenzhen 518057China

Through investigating the tension-tension fatigue behavior of an as-extruded Mg-6.2 wt.%Zn-0.6 wt.%Zr(ZK60)alloy,it revealed that the determined fatigue strength at 107 cycles was quite sensitive to the grain *** them,the fine grain structure had the highest fatigue strength of 130 MPa,whereas the typical“bi-modal”grain structure had the lowest fatigue strength of 110 *** analysis demon-strated that for the fine grain structure,fatigue cracks preferentially nucleated at grain *** the“bi-modal”and coarse grain structures,the fatigue crack initiation was dominated by the cracking along slip bands.

关键词： Mg alloys Grain structure Cyclic slips fatigue behavior Crack initiation

Experimental and numerical investigations on fatigue behavior of aluminum alloy 7050-T7451 single lap four-bolted joints

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Journal of Materials Science & Technology 2018年第7期34卷 1205-1213页

作者： Xiaomei Liu Hao Cui Shangzhou Zhang Haipo Liu Gaofeng Liu Shujun Li School of Fmvironmental and Materials Engineering Yantai University Yantai 264005 China Oriental Bluesky Titanium Technology Co. LTD. Yantai 264005 China Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

The fatigue behavior of aluminum alloy 7050-T7451 single lap four-bolted joints was studied by high- frequency fatigue test and finite element （FE） methods. The fatigue test results showed that a better enhancement of fatigue life was achieved for the joints with highlocked bolts by employing the combinations of cold expansion, interference fit, and clamping force. The fractography revealed that fatigue cracks propagated tortuously; more fatigue micro-cliffs, tearing ridges, lamellar structure were observed, and fatigue striation spacing was simultaneously reduced. The evaluation of residual stress conducted by FE methods confirmed the experimental results and locations of fatigue crack initiation. The extension of fatigue lives can be attributed to the evolution of fatigue damage and effect of beneficial compressive residual stresses around the hole, resulting in the delay of crack initiation, crack deflection, and plasticityinduced crack closure.2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.

关键词： 7050 aluminum alloy Bolted joint fatigue behavior Finite element analysis Residual stress

Thermal shock fatigue behavior of TiC/Al_2O_3 composite ceramics

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Rare Metals 2008年第3期27卷 308-314页

作者： SI Tingzhi LIU Ning ZHANG Qing＇ an YOU Xianqing School of Materials Science and Engineering Anhui University of Technolog3 Ma ＇anshan 243002 China School of Materials Science and Engineering Hefei University＇ of Technology Hefei 230009 China

The thermal shock fatigue behaviors of pure hot-pressed alumina and 30 wt.% TiC/Al2O3 composites were studied. The effect of TiC and Al2O3 starting particle size on the mechanical properties of the composites was discussed. Indentation-quench test was conducted to evaluate the effect of thermal fatigue temperature difference （ΔT） and number of thermal cycles （Ⅳ） on fatigue crack growth （Δa）. The mechanical properties and thermal fatigue resistance of TiC/Al203 composites are remarkably improved by the addition of TiC. The thermal shock fatigue of monolithic alumina and TiC/Al2O3 composites is due to a ＂true＂ cycling effect （thermal fatigue）. Crack deflection and bridging are the predominant reasons for the improvement of thermal shock fatigue resistance of the composites.

关键词： ceramic matrix composites TiC/Al2O3 composites thermal shock fatigue fatigue behavior fatigue resistance

Surface integrity and fatigue behavior when turning γ-TiAl alloy with optimized PVD-coated carbide inserts

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Chinese Journal of Aeronautics 2018年第4期31卷 826-836页

作者： Changfeng YAO Jiannan LIN Daoxia WU Junxue REN The Key Laboratory of Contemporary Design and Integrated Manufacturing Technology Ministry of EducationNorthwestern Polytechnical University

This paper presents a comprehensive investigation on the effects of tool and turning parameters on surface integrity and fatigue behavior in turning c-Ti Al alloy. The wear of inserts surface, cutting forces, and surface roughness were studied to optimize PVD-coated carbide *** topography, residual stresses, microhardness, and microstructure were analyzed to characterize the surfaces layer under different turning parameters. Surface integrity and fatigue life tests of c-Ti Al alloy were conducted under turning and turning-polishing processes. The results show that compared to CNMG120412-MF4, CNMG120408-SM is more suitable because it obtained low cutting force, surface roughness, and tool wear. With increasing the cutting speed and depth, the depths of the compressive residual stress layer, hardening layer, and plastic deformation layer increased. For turning and turning-polishing specimens, the compressive residual stress was relaxed by less than 20%–30% after 10^7 cycles. The fatigue life of a turning-polishing specimen with Ra= 0.15 mm has increased 3 times from that of a turning specimen with Ra= 0.43 mm.

关键词： fatigue behavior Microhardness Residual stress Surface roughness γ-TiAl alloy Tool wear

Influence of Grain Boundary on fatigue behavior of Ni-base Bicrystals

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Journal of Materials Science & Technology 2002年第1期18卷 69-72页

作者： Jiansong WAN, Zhufeng YUE, Xiaoliang GENG and Zhixian LUDepartment of Engineering Mechanics, Northwestern Polytechnical University, Xi’an 710072, China [ Manuscript received January 16, 2001, in revised form April 27, 2001] Dept. of Eng. Mech. Northwestern Polytech. Univ. Xi'an 710072 China

The influence of the grain boundary on the fatigue behavior was studied by two three-point-bending (TPB) specimens. One TPB specimen was named Bicrystal 1, whose pre-crack was along the grain boundary and the applied load paralleled to pre-crack direction, while the other TPB specimen was named Bicrystal 2, whose the pre-crack was perpendicular to the grain boundary and the applied load paralleled also to the pre-crack. It was found that the rate of the fatigue crack growth of Bicrystal 1 was about a tenfold higher than that of Bicrystal 2. The fatigue behavior of Bicrystal 2 specimens was dependent on the distance between the crack tip and grain boundary. The crack growth rate was highest when the crack tip was at a critical distance to the grain boundary, while the rate was the lowest when the crack tip reached grain boundary. After the crack was over the grain boundary, the crack growth rate increased. The crystallographic finite element method was applied to analyze the stress and strain structure ahead of the crack, in order to reveal the above characteristics of the fatigue behavior. It is the grain boundary-induced redistribution of stresses near the crack tip that induces the difference of fatigue behavior.

关键词： Bicrystals fatigue behavior Grain boundary Shielding effect

Improved fatigue behavior of Pipeline Steel Welded Joint by Surface Mechanical Attrition Treatment(SMAT)

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Journal of Materials Science & Technology 2009年第4期25卷 513-515页

作者： Yu Wang Min Huang Lei Zhou Zhixin Cong Huilin Gao School of Materials Science and Engineering Xi＇an University of Architecture and Technology Xi＇an 710055 China School of Materials Science and Engineering Xi＇an Shiyou University Xi＇an 710065 China Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenvang 110016 China

A pipeline steel X80 with welded joint was subjected to surface mechanical attrition treatment （SMAT）. After SMAT, a nanostructure surface layer with an average grain size of about 10 nm was formed in the treated sample, and the fatigue limit of the welded joint was elevated by about 13% relative to the untreated joints. In the low and the high amplitude stress regimes, both fatigue strength and fatigue life were enhanced. Formation of the nanostructured surface layer played more important role in the enhanced fatigue behavior than that of residual stress induced by the SMAT.

关键词： Surface mechanical attrition treatment (SMAT) Pipeline steel X80 Welded joint Surface nanocrystallization fatigue behavior

fatigue behavior of AZ31B magnesium alloy electron beam welded joint based on infrared thermography

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Transactions of Nonferrous Metals Society of China 2016年第10期26卷 2595-2602页

作者：杨宏伟崔泽琴王文先许并社许海鹰太原理工大学材料科学与工程学院太原030024 先进镁基材料山西省重点实验室太原030024 北京航空制造工程研究所北京100024

fatigue behavior of AZ31B magnesium alloy electron beam welded joint undergoing cyclic loading was investigated by infrared thermography. Temperature evolution throughout a fatigue process was presented and the mechanism of heat generationwas discussed. fatigue limit of the welded joint was predicted and the fatigue damage was also assessed based ontheevolution of the temperatureand hotspot zone on the specimen surfaceduring fatigue tests. The presented results show that infrared thermography can not onlyquicklypredict the fatigue behavior of the welded joint, but also qualitatively identify the evolution of fatigue damage in real time. It is found that the predicted fatigue limit agrees well with the conventionalS-Nexperimental results. The evolution of the temperatureand hotspot zone on the specimen surface can be an effectivefatigue damage indicatorfor effectiveevaluationof magnesium alloy electron beam welded joint.

关键词： magnesium alloy electron beam welded joint fatigue behavior infrared thermography