2021 Vol. 36, No. 4

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Materials Research
Pertinence of Material Constants in Paris Model for Fatigue Crack Propagation Rate of Metallic Materials
ZHANG Yajun, ZHANG Xinyao, ZHANG Yunhao
2021, 36(4): 1-8.
[Abstract](663) [FullText HTML] (136) [PDF 4185KB](69)
Abstract:
Fatigue crack propagation rate of metallic materials is an important index of mechanical property, which is employed for damage tolerance design and fatigue life assessment in engineering application. Paris model is the most popular expression for fatigue crack propagation rate, and the relation of fatigue crack propagation rate and stress intensity factor range at the crack front is believed to meet a power-function rule in the model. The model involves in two material constants of C and m. In this paper, based on some test data published in some literatures, the relationships between material constants of C and m in Paris model for fatigue crack propagation rate of metallic materials of alloy steels, copper alloy, titanium alloy and aluminum alloy were analyzed. The results indicated that the constants of C and m of different types of metallic materials satisfied good linear relationship, namely m=alnC+b, which was not affected by specimen sampling orientation, weld position, and test environment. Stress ratios had great influence on the linear relationship, especially when the stress ratio value was negative. The slopes of the linear models for different metallic materials were not equivalent and the influencing factors should be further researched systematically. The analyzing results would provide reference for fatigue design and application in engineering.
High Temperature Creep Properties and Microstructure of Ti-Al-Zr-Mo-Nb-Sn-Si Cast Titanium Alloy
LI Longteng, WANG Yang, LIU Xibo, YANG Xuedong
2021, 36(4): 9-13.
[Abstract](480) [PDF 9078KB](18)
Abstract:
The creep properties and microstructures of Ti-Al-Zr-Mo-Nb-Sn-Si cast titanium alloy at 600~750 ℃ were studied. The results showed that the creep residual elongations were less than 3% at 750 ℃/180 MPa/0.5 h and less than 0.4% at 600 ℃/400 MPa/0.5 h. The time before creep ruptures were more than 2 h and more than 14 h, respectively. The cast titanium aiioy had good creep resistance. There were fine particles in the high temperature creep fracture surface. After creep, the microstructure changed little in the plastic deformation zone, showing widmannstatten structure, and some grain boundaries disappeared and α lamellae became wider. After high temperature creep, dislocations increased obviously and entangled with precipitates.
Effect of Microtexture on the Stress Corrosion Property of Ti-6Al-3Nb-2Zr-1Mo Alloy
XU Yali, ZHANG Binbin, LU Xiaoyang
2021, 36(4): 14-22.
[Abstract](108) [PDF 14201KB](72)
Abstract:
The influence of microtexture on the stress corrosion cracking susceptibility and crack propagation path of a near alpha titanium alloy Ti-6 Al-3 Nb-2 Zr-1 Mo were investigated by the observation of the fracture surfaces and the crack propagating paths using EBSD method. The results showed that the morphologies of the microtexture zones were irregular thin lamellae which were nearly parallel to the rolling plane, with their longitudinal direction extending along the rolling direction, and that the grain orientation in the microtexture zones was their c-axis almost parallel to the transverse direction of the bulk plate. When the loading direction was almost parallel to the longitudinal directions of the microtexture zones, prismatic slip was easily activated in the grains of these zones, so as to decrease the stress concentration at crack tip as well as the stress corrosion cracking susceptibility. When the loading direction was almost perpendicular to the longitudinal directions of microtexture zones, prismatic slip and basal slip were hard to activate and that would lead to localized stress concentration and the formation of micro-cracks, raising the stress corrosion cracking susceptibility of the plate.
Effect of Preheating Temperature on Microstructure and Mechanical Properties of Aluminium-magnesium Alloy Thick Plate Welded Joint
LI Li, LIU Guoyuan, WANG Pengyun, LI Yaozong, CUI Yongjie, CHU Shaoqi, FENG Yan
2021, 36(4): 23-27.
[Abstract](58) [PDF 6712KB](11)
Abstract:
Mechanical properties, fracture morphology and metallographic structure of 50 mm thick 5383 aluminum-magnesium alloy welded joints with different preheating temperatures were studied. The results showed that although it could be achieved good weld forming and excellent internal quality with lower preheating temperature, the mechanical properties were relatively lower. Analysis results showed that low preheating temperature led to low temperature of welding pool, so lots of FeMn rich phases in aluminum alloy could not melt completely. The remaining FeMn rich phase segregated, which caused the deterioration of local plasticity and strength of welded joints.
Study on Annealing Process of Large Size Copper Nickel Alloy Tube
ZHAN Yao, ZHANG Yi, WANG Zhihua, GAO Zhenxuan
2021, 36(4): 28-33.
[Abstract](186) [PDF 7093KB](11)
Abstract:
The annealing process of copper nickel alloy seamless pipe was studied. Six typical copper nickel alloy seamless tubes were selected and produced by drawing. The annealing test was carried out according to the proposed annealing test scheme. After annealing, samples were taken for performance test. By testing tensile strength, yield strength and elongation, as well as Bush hardness and Rockwell hardness, and carrying out metallographic test, that whether the microstructure change from processed state to single-phase recrystallized α structure was observed. When the annealing temperature was less than or equal to 700 ℃, it was impossible to obtain single-phase α structure with complete recrystallization. When the annealing temperature was higher than 730 ℃, the grains would grow continuously. Annealing holding time less than or equal to 30 minutes could not achieve all recrystallization, and more than 40 minutes could make the grain continue to grow. The optimal annealing process for seamless copper nickel alloy pipe was holding at(720±10) ℃ for 40 minutes.
Effect of Molecular Structure of Solution Polymerized Styrene Butadiene Rubber on Acoustic Properties
ZHANG Cong, WANG Wenfei
2021, 36(4): 34-38.
[Abstract](31) [PDF 4412KB](6)
Abstract:
Styrene butadiene rubber(SBR) is one of the commonly used underwater sound absorption rubber. Here were studied the effects of styrene content and polarizability of SSBR molecular structure on its sound absorption properties. The results of sound absorption test showed that the sound-absorbing performance changed little with the increase of test pressure. The sound absorption performance of SSBR with lower styrene content was poor under various test pressures. With the increase of styrene content in the chain, the sound absorption performance was obviously improved. Polarization modification of SSBR could effectively improve its sound absorption under pressure. When the mass fraction of polarizing group reached 10%, the sound absorption performance was obviously improved.
Study on the Variation Relationship of Anticorrosive Coating Viscosity with Temperature
HAN Yue, LIU Hongyu, WANG Jiani, SHI Meihui, GUAN Shuai, KANG Xin
2021, 36(4): 39-43.
[Abstract](38) [PDF 901KB](10)
Abstract:
Four methods of viscosity determination of coatings and relevant national standards were introduced. Temperature, the key factor affecting the viscosity of coatings, was studied by means of Stomer viscometer. The results showed that temperature had a great influence on the viscosity of coatings, and that with the increase of temperature, the viscosities of the four coatings decreased linearly.
Material Application
Study on Stress Corrosion Cracking Behavior of T Profiles of 7055 Aluminum Alloy
TENG Kui, LUO Xianfu, LI Hongping, CHA Xiaoqin
2021, 36(4): 44-50.
[Abstract](128) [PDF 7352KB](19)
Abstract:
The stress corrosion cracking(SCC) performance of 7055 aluminum alloy were investigated by using tensile testing, C-ring stress corrosion experiment, metallographic observation, scanning electron microscope and transmission electron microscope. The results show that longitudinal test specimen of 7055 aluminum alloy had higher tensile strength, yield strength, elongation and reduction of area than those of the transverse specimen. The cracking time of longitudinal C-ring specimens was longer than that of transverse specimens under intermediate immersion and constant temperature and humidity environment. The deformation grains were mainly elongated in the longitudinal section. The crack of the transverse sample grew along the longitudinal direction. Once the crack was formed, it grew rapidly along the elongated grain boundary, the crack was straight and the cracking time short. The grains of transverse section were equiaxial, and the crack of longitudinal sample grew along the transverse direction. In the process of crack growth, deflection along the grain boundary occurred, and the cracking time was long. The stress corrosion mechanism of 7055 alloy consisted of hydrogen embrittlement and electrochemical theory.
Introduction of Humidity Resistance Test Standards of Coatings
WANG Jiani, LIU Hongyu, HAN Yue, ZHEN Guanghao, SHI Meihui
2021, 36(4): 51-56.
[Abstract](264) [PDF 2510KB](12)
Abstract:
Humidity resistance test methods in GB standards, ISO standards and ASTM standards were introduced, and the test methods were summarized. Heat and humidity, condensation(in-cabinet exposure) and water fog were all in test atmosphere of high temperature and humidity, whose impetus for condensation was relatively smaller. While the temperature difference was large with the condensation(single-sided exposure), and the impetus for coating damage was large, so with the same test temperature, condensation was easier to happen. The condensation(single-sided exposure) was a preferred option when the humidity resistance result of coating, especially resistance performance to condensation, was urgently needed.
Study on and Preparation of Full Ocean Depth Buoyancy Materials
WANG Yueping, YANG Dongjie, MA Zhichao, PENG Xinling, HUANG Dongya, ZHENG Jingdong
2021, 36(4): 57-61.
[Abstract](149) [PDF 2035KB](15)
Abstract:
Full ocean depth buoyancy materials were prepared with glycidyl ether type epoxy resin, aromatic polyamine hardener and hollow glass bubbles. Here were investigated the influences of the volume fraction of hollow glass bubbles K1 on such performances as density, compressive strength, resistance to hydrostatic pressure and water absorption rate. The results showed that when the total volume fraction of the hollow glass bubbles in the full ocean depth buoyancy material was 66.7%, the introduction of appropriate amount of hollow glass bubbles K1 instead of HM42 could reduce the density of full ocean depth buoyancy material, the compressive strength was not less than 132 MPa, the resistance to hydrostatic pressure was not less than 150 MPa, and the water absorption rate was not higher than 0.2%. It's prospective to meet the safe usage of full ocean depth equipments.
Application Research on Vibration Isolation Performance of Rail Transit Fastener
DUAN Yongqi, LEI Pu, ZHAO Zhenping, XU Ning, CENG Fei
2021, 36(4): 62-66.
[Abstract](64) [PDF 5559KB](18)
Abstract:
According to the principle of vibration isolation, the structural and dynamic parameters were optimized on the basis of double-layer nonlinear fasteners, and the dynamic deformation, vibration and transmission characteristics of track system were tested respectively by selecting the lines with similar working conditions. The test results showed that the optimized double-layer nonlinear damping fastener could meet the safety requirements of track line. Compared with the original damping fastener, the vertical first-order frequency with the optimized fastener was reduced, the damping increased, and the Z-weighted acceleration total vibration level of the tunnel wall vibration was reduced by 1.7~2.2 dB, which proved that the optimized damping fastener had better vibration isolation effect.
Safety Performance Analysis of Upper Locking Double-layer Non-linear Turnout Fasteners on the Upper Depot
WANG Zhiqiang, LI Qiang, XIAO Yuchen
2021, 36(4): 67-71.
[Abstract](129) [PDF 3176KB](7)
Abstract:
The wheel-rail forces of 20 normal-operating trains passing through rails with upper locking double-layer non-linear turnout fasteners were tested on-site at the Metro and the data analyzed. The results showed when a train passed a double-layer non-linear turnout fastener, the maximum wheel load reduction rate was 0.14, the maximum derailment coefficient was 0.41, the average vertical force of the left and right wheels was 57.6 kN, and the average lateral force was 15.8 kN, which showed that the locking double-layer non-linear turnout fasteners on the upper part of the depot could fully meet the safety indicators of train operation.
Welding Technology
Research on Microstructure and Properties of Ti700sr High-temperature Titanium Alloy TIG Welded Joint
MEI Wenjia, ZHANG Yunhao, GAO Fuyang, YAN Feihao, YU Wei, JIANG Peng, ZHU Lele, LIU Yinqi
2021, 36(4): 72-75.
[Abstract](175) [PDF 5939KB](10)
Abstract:
The welding of Ti700sr high-temperature titanium alloy plate was conducted with TIG technology, and the microstructure, hardness distribution and tensile properties of the welded joints were analyzed. It was confirmed that the joint was well formed after welding. The weld zone was composed of coarse columnar crystal and slender acicular α phase, the heated affected zone was composed of slender acicular α phase and residual β phase. The precipitation in HAZ was effectively controlled, and there was no obvious silicide precipitation on the phase boundary. In general, the hardness of HAZ was relatively higher and the hardness of weld low. The strength of the joint was about 903 MPa at room temperature and 397 MPa at 700 ℃. The strength of the weld was lower than that of the base metal.
Influence of GMAW-P Pulse Parameters on Welding Process and Weld Size
ZHANG Yu, XUE Gang, WU Yanming, HE Zhitao
2021, 36(4): 76-81.
[Abstract](115) [PDF 3386KB](8)
Abstract:
The influences of pulse current, pulse time, pulse frequency and other parameters on the weld formation and the stability of welding process were analyzed by using there-factor and three-level orthogonal test, combined with high-speed photography, welding electrical parameter acquisition, metallographic detection and other means. The results showed that among the three pulse parameters, the pulse frequency had a great effect on the penetration and welding stability, while the pulse current had a great effect on the weld width.
Current Status of Laser-arc Hybrid Welding Technology and Its Research Progress in the Field of Titanium Alloy
FU Chengxue, MA Zhaowei, LEI Xiaowei, LIU Jia, GAO Qi
2021, 36(4): 82-88.
[Abstract](308) [PDF 7529KB](47)
Abstract:
The principle, characteristics, classification, application and research progress of laser-arc hybrid welding technology and its application in titanium alloy were reviewed. The application status of the welding technology in shipbuilding, transportation and pipeline engineering was introduced. The engineering application of titanium alloy by laser-arc hybrid welding technology was prospected.
Review
Research Progress on Configuration Strengthening of Multi-phase and Multi-scale Aluminum based Composites
LIU Peng, XIE Bin, XIE Shufeng, WANG Pengyun
2021, 36(4): 89-93.
[Abstract](112) [PDF 5009KB](12)
Abstract:
The preparation of multi-phase and multi-scale aluminum based composites and the design ideas of its configuration compounding were briefly summarized from the aspect of configuration strengthening and toughening. The latest research results of improving the matching between strength and toughness of aluminum based composites by configuration compounding in recent years were listed. The way of industrialization of aluminum based composites with advanced configuration was prospected.
Experience Exchange
Guidance and Application of the New Version of ISO 12944 in the Long-term Anti-corrosion Design of the Steel Box Dirder of the Xiamen Second Eastern Passage
LIN Lihua
2021, 36(4): 94-100.
[Abstract](147) [PDF 788KB](8)
Abstract:
Here were introduced the main differences between the new version and the old version of the ISO 12944 series standards and at the meantime, was analyzed the environment characteristics that the steel box was in. According to the technical requirements of the new version of ISO 12944 Paints and varnishes — Corrosion protection of steel structures by protective paint systems, an environmentally friendly anti-corrosion coating system and its requirements for construction technology were recommended to ensure the long-term safety and reliable use of the steel box girder structure of the Xiamen Second East Passage Bridge.

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