2023 Vol. 38, No. 2

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Strength and Failure
Analysis of the Size Effects on the Elastic Stress Concentration Factors at the Top of the Penetrating Notch in the Center of the Double-tension-plate
XUE Gang
2023, 38(2): 1-9.
[Abstract](159) [PDF 7098KB](112)
Abstract:
The stress fields at the top of the penetrating notch in the center of the double-tension-plate are analyzed with 350 sets of sizes by elastic finite element method. The functions of the normal stress concentration factor normal to the length-direction Ktσy, the first stress invariant concentration factor KtI1 and the Mises equivalent stress concentration factor i>Ktσ are built. The results indicate that all the elastic stress concentration factors increase with the increase of the ratio 2a/W of the length to the width of the notch as the parabolic function, and reduce exponentially with the decrease of the ratio r/a of the radius to half of the width of the notch.
Study on Crack Curvature Correction Method in Fatigue Crack Growth Rate Test
GAO Yuhao, WANG Jia, WU Zepeng, CHEN Pei, ZHAI Jianfei
2023, 38(2): 10-15.
[Abstract](343) [PDF 5886KB](76)
Abstract:
The fatigue crack length should be modified based on crack curvature correction according to the fatigue crack growth rate test standard. However, the specific correction method and calculation procedures are not given. Thus, two crack curvature correction methods are recommended in the paper, i.e. linear interpolation method and equal proportion method. The two curvature correction methods are compared by analyzing their correction principles combining with the experimental results. The results indicate that the modified da/dN-ΔK curve has an offset up to 15% toward to the low ΔK direction in the log-log coordinates system. When using da/dN-ΔK curve to conduct material selection and fatigue life evaluation, the modified da/dN-ΔK curve is safer than the unmodified. The difference between the da/dN-ΔK curves corrected by the two methods is not significant, and the maximum difference is about 2%.Both methods can be used as the curvature correction method in the fatigue crack growth rate test.
Welding
Experimental Measurement and Numerical Simulation of Residual Stress on Butt Welding Steel Plates
DING Penglong, CHEN Lei, HE Liang, YU Jun
2023, 38(2): 16-22.
[Abstract](162) [PDF 8103KB](93)
Abstract:
The welding residual stress of two welding steel plates is measured by the impact indentation method, and the residual stress distribution on the butt welding plate is simulated by the finite element method. The residual stress values by measurement and simulation are contrasted and analyzed. The two methods agree well with each other both on the stress value and distribution, The peak value of the residual stress by the actual measurement is 599 MPa, and that by the simulation is 597 MPa, indicating good applicability of the numerical simulation. The longitudinal residual tensile stress near the heat affected zone is larger than that of the horizontal residual compressive stress. In addition, the peak of the equivalent stress (Mises stress) is 792 MPa, higher than the yield stress at room temperature, showing the significant strain-strengthening phenomenon occurs to the material.
Microstructure and Properties of 10 mm Thick C-276 Alloy Plates by K-TIG Welding
ZHAO Fangfang, YANG Jichao, GUO Xiaohui, LI Ruiwu, MA Zhaowei
2023, 38(2): 23-26.
[Abstract](51) [PDF 4384KB](75)
Abstract:
The keyhole TIG (K-TIG) welding process is adopted to realize the single side welding and double side forming of 10 mm thick C-276 alloy plate. The weld cross section has no defects such as porosity, incomplete fusion and crack. The structure of the weld zone is mainly elongated columnar crystal and equiaxed crystal, and a small amount of precipitates are distributed at the grain boundary. The intergranular corrosion test is carried out by ASTM G28A method. The results show that the average corrosion rate of the weld is 4.418 mm/a, and its intergranular corrosion resistance of the weld is good. The average tensile strength of the joint is 735.5 MPa, and the fracture position is in the base metal. A large number of the fine equiaxial dimples are distributed on the tensile fracture surface, which is typical ductile fracture, and the joint has good toughness. No cracks are found by side bending test. The hardness values of the base metal, heat affected zone and weld seam of the joint have little difference, and the hardness of the joint is in good consistence.
Corrosion and Protection
Experimental Research on Erosion of 35CrMo Steel with Different Hardness in Sand Containing Fluid
LIU Chuangang, WANG Xiao, JU Shaodong, LIU Jingchao, ZENG Kai, JI Juxiang
2023, 38(2): 27-31.
[Abstract](113) [PDF 5933KB](92)
Abstract:
The erosion experiments of 35CrMo steel with three different hardness and five different impact speeds are carried out, and the weight loss and eroded surface morphology studied and analyzed. The influences of speed and hardness on erosion wear rate of 35CrMo steel are analyzed, and the equation of erosion wear rate with speed and hardness fitted. The experimental results show that the erosion wear rate of 35CrMo steel increases rapidly with the increase of speed, with a power relation of 2.55~2.66, and decreases linearly with the increase of hardness. Hardness and speed have independent effects on the erosion wear rate of 35CrMo steel, and there is no significant coherence.
Effect of Solution and Aging Treatment on Corrosion Resistance of HDR Duplex Stainless Steel
LIU Xin, HU Yulong, LIU Nian, SU Xiaohong, CHEN Shan
2023, 38(2): 32-37.
[Abstract](70) [PDF 6621KB](73)
Abstract:
In order to improve the corrosion resistance of marine duplex stainless steel in sea water environment, the HDR duplex stainless steel is treated by the solid solution and aging treatment, and the 3D microscope, Vickers hardness tester, scanning electron microscope, energy spectrometer and other instruments are used to analyze the microstructure, chemical compositions, hardness, and corrosion resistance. The corrosion resistance of the steel in 3.5% NaCl solution is studied, and the most suitable solution temperature determined. The results show that σphase is precipitated when the specimen is aged when the solid solution temperature is between 1 050 and 1 150 ℃ and the hardness of the specimen is promoted. When the solid solution temperature is 1 100 ℃, the specimen exhibits best pitting corrosion resistance. When the solid solution temperature is between 1 050 and 1 150℃, the aging treatment weakens the corrosion resistance of HDR duplex stainless steel.
Mechanical Properties and Corrosion Behavior of B4Cp/7050Al Aluminum Matrix Composites
XIE Bin, WANG Desheng, WANG Pengyun, XIE Shufeng
2023, 38(2): 38-43.
[Abstract](46) [PDF 9356KB](11)
Abstract:
In order to explore the mechanical and corrosion properties of the high strength and high modulus aluminum matrix composites, the aluminum matrix composites with reinforcing phase of 17% and 20% of volume fraction are prepared by powder metallurgy. The corrosion research results show that the corrosion of the aluminum matrix composites is closely related to the matrix. The exfoliation corrosion and electrochemical corrosion of the composites are less sensitive than those of the matrix. The addition of reinforcing phase deteriorates the intergranular corrosion and salt spray corrosion of the materials.
Test and Analysis
Microstructure and Mechanical Properties of Annealed CoFeNiCrMnBx High Entropy Alloy
HOU Lili, GUO Qiang, YAO Yuhong, LIU Jiangnan
2023, 38(2): 44-48.
[Abstract](90) [PDF 7493KB](19)
Abstract:
CoFeNiCrMnB<i>x high entropy alloy is prepared by vacuum arc melting furnace and annealed. The results show that when the CoFeNiCrMnB0.15 and CoFeNiCrMnB0.20 alloys are annealed at 1 100 ℃ for 20 hours, their interdendritic structures are granular Cr2B phase, and that the granular Cr2B phase increases with the increase of B content. The yield strength and tensile strength of CoFeNiCrMnB0.20 alloy are 496 MPa and 890 MPa, which are 104.0% and 79.4% higher than those of the as cast CoFeNiCrMn alloy.
Effect of Surface Quality of Titanium Plate on the Interface between Titanium and Steel Plates
LI Ya, JIANG Xiaobo, WANG Zibo, ZHANG Shaolun, ZHOU Zhijun, WANG Shujun
2023, 38(2): 49-52,62.
[Abstract](49) [PDF 6289KB](10)
Abstract:
To find out the reasons for the delamination, broken edge and folds of the Ti plate, the bonding strength of the explosive welding Ti-steel clad plate is tested, and the surface quality of the Ti plate is analyzed. The results shows that the metallurgical defect of Ti ingot, broken edge and heterogeneous oxidation layer contribute to the weak bonding of the clad plates. Then, the suitable measures for the quality control and surface treatment of the Ti plate are put forward.
Process Research
Study on Channel Structure Optimization of Printed Circuit Heat Exchanger
SHI Xinxin, YAN Dong, WANG Wei, HAN Linju, ZHANG Shuaifei
2023, 38(2): 53-56.
[Abstract](63) [PDF 5256KB](15)
Abstract:
The printed circuit heat exchanger (PCHE) is welded by diffusion welding, but the existence of the heat exchange flow channel causes the interruption of the transmission of welding pressure along the heat exchange plate, resulting in the non-welding in the middle of the flow channel. In order to improve the welding quality, the optimization of the runner structure is carried out. The research results show that increasing the chamfer of the rectangular runner is beneficial to improve the welding quality. Dislocation of the hot and cold runners (to place the lower runner aid plate in the middle of the upper runner) can also change the axial stress distribution between the plates to improve the welding quality.
Influence of Spraying Angle on the Properties of Plasma Sprayed AT13 Ceramic Coatings
SU Xuanbo, LI Longbo, WEI Daling, XIE Shufeng
2023, 38(2): 57-62.
[Abstract](66) [PDF 8668KB](12)
Abstract:
Micro-and nano-Al2O3-13%TiO2 coatings are sprayed by using the APS system. The influences of the spray angle on the increased thickness of a single pass, coating microstructure, hardness and bonding strength are studied. The results show that with the decrease of the spraying angle, the increased thickness of a single pass and binding strength decrease, that the porosities of the two coatings increase, and that the hardness does not change significantly. When the spray angle is 90°, the two coatings are in good condition, and the increased thickness of a single pass of the nano-Al2O3-13%TiO2 coating is 21.5% higher than that of the micro-Al2O3-13%TiO2 coating. When the spray angle is 45°, the increased thickness of a single pass and bonding strength of the former are 47% and 42.1% higher than those of the latter. When the spray angle is 30°, the microAl2O3-13%TiO2 coating has serious defects, and the nano-Al2O3-13%TiO2 coating also has large pores. The hardness of the micro-Al2O3-13%TiO2 coating is slightly higher than that of nano-Al2O3-13%TiO2.
Design and Research of High Pressure Large Volume Carbon Fiber Fully Wound Cylinder
WANG Geng, SUN Yongwei, DENG Xin
2023, 38(2): 63-66,83.
[Abstract](63) [PDF 2829KB](13)
Abstract:
At present, high pressure and large volume carbon fiber fully wound gas cylinders above 450 L (hereinafter referred to as type III gas cylinders) are still in the research stage in China, and there is no current national standard. We carry out the design research of the 45 MPa and 500 L type III gas cylinder. According to the grid theory, the safety design of carbon fiber winding layer should be done under blasting pressure. It is analyzed the stress of aluminum liner and winding layer under the working condition of the high pressure large volume type III gas cylinder. And the liner design of this type of gas cylinder is completed on the premise of ensuring that the joint surface doesn't fail. Under the limit pressure of blasting of the type III gas cylinder, the winding shell can be regarded as an orthotropic thin-walled shell structure. When the internal strain displacement relationship of the shell is same, we check and calculate the strength of the liner to ensure its safety.
Nonmetallic Material
Design and Research of the Intelligent Grinding System of the Marine Composite Structure
QIAO Baobao, CHEN Runhua, LING Jie, ZHANG Xiaomei, LI Xiang
2023, 38(2): 67-75.
[Abstract](65) [PDF 12685KB](8)
Abstract:
The characteristics and problems of the large-scale integrated molding marine composite components are analyzed, and the latest application status at home and abroad is explained. Based on the study above, the AGV composite robot intelligent grinding system is designed to solve the problems. The key technologies like the automatically generated grinding trajectoryof robot are introduced. Finally, the system is tested physically. The grinding efficiency is improved by more than 10 times compared with that of the manual grinding, the grinding mechanical roughness reaches 0.63 μm, and the linear precision reaches 0.5 mm, which can fully meet the practical use requirements of the marine composite components. The development of a high-performance AGV composite robot intelligent grinding system can not only improve the grinding quality and efficiency of the large-scale integrated molding marine composite components, but also provide an effective research platform for realizing other processing processes for the large-scale marine composite components, thus laying the foundation for the subsequent digital, clustered and pulsed production of the same type of products.
Preparation and Foaming Properties of PMMA Nano-cellular Foam
YU Ni, ZHANG Yi, PENG Weikai, LUO Hao
2023, 38(2): 76-83.
[Abstract](48) [PDF 12027KB](16)
Abstract:
PMMA with high adsorption capacity for supercritical carbon dioxide is selected as the matrix material and foamed by supercritical CO2 foaming technology. The influences of saturation and foaming stage parameters and CO2 adsorption capacity on the structure parameters of the PMMA foam are studied. The results reveal both the low-temperature and high-pressure can increase the adsorption capacity of CO2, and that the mass fraction of CO2 in PMMA increases from 21.59% to 35.72%.After the PMMA with CO2 of 35.72% is foamed at 40 ℃ for 30 s, we can obtain the PMMA nano-cellular foam with the uniform cell size of 35.9 nm and cell density of 1.57×1 015.
Study on Preparation and Application of Epoxy Wear-Resistant Insulating Anticorrosive Coatings
ZHANG Lili, ZHANG Mingqi, CHEN Kaifeng, WANG Jingjing, ZHANG Xinyue, ZENG Dengfeng, SU Mengxing, LI Minghua
2023, 38(2): 84-90.
[Abstract](45) [PDF 6479KB](15)
Abstract:
The epoxy wear-resistant insulating anticorrosive coating is prepared by the laboratory simulation accelerating test with the bisphenol A resin and cardanol modified amine resin as the base material and alumina powder, silicon carbide, iron oxide red and other wear-resistant anticorrosive as fillers. The surface adhesion of the coating on carbon steel is more than 6 MPa. Under the condition of 750 g/1000 r, the abrasive weight loss of the coating surface is less than 30 mg. The coating has good insulation, the surface resistivity higher than 8.04×1010 Ω. After 1 000 h of salt spray test, the coating on the three plates has no blisters, rust and peeling off. The electrochemical impedance value test is carried out under the condition of 0.01 Hz low frequency impedance (|Z|0.01 Hz), and the electrochemical impedance value of the coating drops from 1.38×109 Ω·cm2 before the salt spray resistance test to above 8.11×107 Ω·cm2 after the test, showing that the coating has high impedance value and good protection performance. Besides, the coating is applied into the track anti-corrosion insulation protection of the test section of Jiaxing light rail, and the impedance value of the track with coating is 26.25 Ω·km while that of the track with no coating is 15 Ω·km, improving that coating has excellent insulation performance.
Review
Research Progress on Application of Surface Protection Technology in Maintenance of Warships
QIU Dianqiang, SU Xuanbo, WANG Zhe, WU Xiaoyu, XIE Shufeng
2023, 38(2): 91-96,108.
[Abstract](86) [PDF 8264KB](21)
Abstract:
Pneumatic, hydraulic devices, various valves and other motion components are widely used in almost all marine equipment, such as military and civilian ships, submarines, offshore platform. Sea water itself is a strong corrosive medium. The waves, tides and currents generate low-frequency reciprocating stress and impact on the metal components. In addition, marine microorganisms, adherent organisms and their metabolites all directly or indirectly accelerate the corrosion process. Compared with the land environment, the service life of the motion components in the marine environment is significantly reduced, which seriously endangers the service safety of marine equipment. Therefore, it is necessary to repair or replace the failed parts and protective coatings when the ship is regularly maintained. The economic, green and convenient surface protection technology has attracted much attention in shipyards. Here is introduced the application of surface protection technologies such as thermal spraying, laser cladding and chemical conversion in the field of ship maintenance at home and abroad in recent years, and put for ward several problems that need to be solved urgently in ship maintenance.
Research and Application Progress on Production of Anisotropic NdFeB Magnetic Powder by HDDR Process
YANG Jun, HUANG Dongya, WANG Yue, MO Manman, LIN Baichun, YANG Shu
2023, 38(2): 97-108.
[Abstract](96) [PDF 11975KB](29)
Abstract:
Hydrogenation-disproportionation-desorption-recombination (HDDR) process is an effective method to produce anisotropic NdFeB magnetic powders. The anisotropic bonded magnets prepared by HDDR process have excellent performance and light weight, which play an important role in improving the efficiency and reducing weight of micro-special motor. It has been industrialized and applied in automotive, drone and other fields. In order to improve the magnetic powder properties, the researchers are keeping investigating the HDDR process and the anisotropy mechanism. They optimize the grain boundary structure of the magnetic powders by using the grain boundary diffusion method to improve the coercivity and temperature stability of the magnetic powder, and apply the above achievements into the recycling of the waste sintered NdFeB to save rare earth resources. The magnetic property of the HDDR anisotropic magnetic powders is better than that of the isotropic magnetic powders, but the deformation plasticity comes after. The researchers attempt to take the HDDR magnetic powders as precursor material to fabricate hot deformation magnets to improve their performances. The effect of grain refinement of the HDDR process provides a new research approach for improving the coercivity of the sintered NdFeB magnets, however, until now, no ideal result has been obtained. In this paper, the development of HDDR process and its mechanism over the years are introduced, as well as its application in hot deformation magnets, sintered magnets and rare earth magnet recycling.

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