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2024 Vol. 67, No. 3
Published: 2024-02-01

 
1 COVER
2024 Vol. 67 (3): 1-1 [Abstract] ( 4 ) HTMLNew PDF (1170 KB)  ( 4 )
6 CONTENTS
2024 Vol. 67 (3): 6-8 [Abstract] ( 2 ) HTMLNew PDF (426 KB)  ( 9 )
14 Research on Tungsten Micropore Machining Technology With Electrospark-Electrolytic Hybrid Energy Field
ZHANG Yan, CHEN Chao
DOI: 10.16080/j.issn1671-833x.2024.03.014

Tungsten has a series of excellent physical and chemical properties, which can meet the performance requirements of aerospace materials, and has been widely used in some key components of satellite, aircraft, aero-engine and other equipment. When traditional machining techniques are used to manufacture parts, the process is usually limited by heating at the interface between the part and the tool, elastic and plastic deformation, high tool wear rates, and changes in the material properties of the workpiece. The electric discharge machining (EDM) technology is one of the most effective machining technologies for conductive materials, but the reliability and efficiency of the existing EDM technology can not meet the machining requirements for the manufacture of tungsten small holes. A method of machining tungsten small holes in salt solution with certain conductivity by electrospark-electrolytic hybrid energy field is proposed. The mechanism of material removal during machining is analyzed. This method uses electrolytic action to generate hydrogen and form gas film at the tool electrical extremity, which promotes the rapid formation of plasma discharge channels between the two poles. The process optimization experiment was carried out to analyze the influence of different parameters on the machining characteristics. NaNO3 electrolyte with pulse width of 3 μs, pulse gap of 12 μs, peak current of 14.17 A and working liquid concentration of 18 g/L was used to obtain high efficiency and high quality tungsten holes.

2024 Vol. 67 (3): 14-22 [Abstract] ( 21 ) HTMLNew PDF (11821 KB)  ( 15 )
24 TLP Diffusion Welding and Joint Mechanical Property of GH3230 Superalloy Laminate Structure in Aero-Engine
QU Wenqing, ZHANG Sihan, Lü Yanlong, TENG Junfei, WANG Miao, YANG Wenjing, ZHUANG Hongshou
DOI: 10.16080/j.issn1671-833x.2024.03.024

With the increasing demand for higher thrust-weight ratio, the aero-engine hot-end components not only need the superalloy used for high temperature, but also need the structural configuration with higher cooling efficiency. In this paper, the new GH3230 superalloy porous laminated structure for cooling was TLP diffusion welded at the temperature of 1200 ℃ holding 4 h using the self-developed KNiCr–5 interlayer alloy. The welded quality and mechanical property of the laminated structure are tested. The results of ultrasonic testing show that, all the connection between the column structure and flat impingement plate of the laminated structure simulated sample is high quality and welded together, and no flaw is found. The homogeneous solid solution microstructure is formed in the welded seam zone, and no compound phase, crack and pore defect exist. The tension tests at room temperature and 950 ℃ high temperature reveal that all fractures happened at GH3230 superalloy base metals, when the tension loads were applied on column-to-base connection of laminated structure simulated samples and GH3230 superalloy rod-rod butt joints. The room/high temperature strength of weld seam are obviously higher than those of GH3230 superalloy base metal. The sample elongation at high temperature tension is over 52%, no macrocrack and microcrack existed in the weld seam after the thin plate welded joint was applied three-point bend to 90° angle, indicating the good plasticity of the weld seam. The excellent welded quality and property can provide the weld seam with the same heat conductivity and mechanical property as GH3230 superalloy base metal when the weld seam endure, high temperature load, avoid it becoming the bottleneck in the whole laminated structure.

2024 Vol. 67 (3): 24-29 [Abstract] ( 20 ) HTMLNew PDF (7860 KB)  ( 17 )
32 Model Prediction and Experimental Study on Deposition Width of Thin-Walled Parts Manufactured by Laser Deposition in Small Molten Pools
QIN Lanyun, LIN Pengxiang, YANG Guang, WANG Yushi, ZHOU Siyu
DOI: 10.16080/j.issn1671-833x.2024.03.032

The thermophysical process of laser deposition fabrication was combined with the geometric characteristics of thin-walled parts, a prediction model of deposition width was established based on the energy conservation relationship in the interlaminar deposition process. The model elaborates the relationship between deposition width and laser power, scanning speed, and powder feeding rate. Several groups of samples were prepared by Ti–6Al–4V (TC4) powder deposition to verify the prediction model. The results show that the model can accurately predict the deposition width of thin-walled parts under different process parameters, which improves the accuracy of experimental accuracy and efficiency. This results lays a theoretical foundation for the forming accuracy control of laser deposition manufacturing process in small molten pool.

2024 Vol. 67 (3): 32-37 [Abstract] ( 14 ) HTMLNew PDF (7090 KB)  ( 14 )
38 Impact Properties of Porous Structures Formed by Laser Powder Bed Melting
YUE Xuezheng, LIANG Kunyi, LU Songhao, TANG Hulin
DOI: 10.16080/j.issn1671-833x.2024.03.038

Porous structures have been widely used in aerospace devices and biomedical instruments because of their good specific strength and energy absorption. The mechanical properties of porous structures largely depend on the deformation mechanism of structural units, so it is very important to fully understand the structural evolution of porous structures in the process of impact loading. In this paper, the 3D Voronoi technology was used to design the decahedron (Octa) with 80% and 90% porosity. The samples of porous aluminum alloy with two kinds of porosity were prepared by selective laser melting (SLM) forming technology. The drop hammer impact experiment was carried out to explore the energy absorption of porous structures with different porosity under the impact load. In the finite element simulation, X-ray transmission computed tomography (X-CT) was used to reconstruct the geometry model of the porous structure to explore the actual deformation mechanism and pore fracture mechanism of the porous result. The results show that the energy absorption of porous structures decreases with the increase of pores, and porous structures with high porosity are more likely to form multiple local dense regions in weaker locations. Meanwhile, the bending and yielding of cell walls generally occur during the collapse of pores, and the deformation is often propagated through the formation of several narrow collapse zones. In this paper, we have a new understanding of the deformation mechanism of Octa structures under impact load, which is of great significance to the impact resistance design and energy absorption evaluation of porous structures.

2024 Vol. 67 (3): 38-44,54 [Abstract] ( 8 ) HTMLNew PDF (15333 KB)  ( 9 )
45 Influence of Heat Treatment on Lattice Structures Properties Based on Selective Laser Melting
NIE Yunfei, TANG Qian, LI Kun, WANG Haoyu, WU Haibin, WANG Binsheng,QIN Changliang, YANG Zhen, SHI Jia
DOI: 10.16080/j.issn1671-833x.2024.03.045

Selective laser melting (SLM) technology is an ideal process for preparing complex lattice structures because of its unique forming principle. The effects of heat treatment on microstructure, mechanical properties, fracture mechanism and energy absorption characteristics of titanium alloy skeleton and sheet structure were analyzed by numerical simulation and experiment. The results show that the α + β phase is evenly distributed in titanium alloy after solution aging heat treatment, and the α' phase martensite gradually decreases and β phase increases with the increase of solution temperature. Under different heat treatment conditions, the compression strength of sheet structure is 1.81~2.17 times that of skeleton structure, and the stress of platform is 3.1 times that of the latter, but the elastic modulus of the two is similar. At the same time, the heat treatment process has little effect on the mechanical properties of the skeleton structure and great effect on the sheet structure. Both types of structures show the phenomenon of 45° diagonal shear fracture and fracture zone transfer. The energy absorption efficiency of the skeleton structure is much higher than that of the sheet structure, but the accumulated energy absorption amount is low. The heat treatment process does not improve the energy absorption performance of the measured structure.

2024 Vol. 67 (3): 45-54 [Abstract] ( 7 ) HTMLNew PDF (29192 KB)  ( 10 )
55 Effect of Hot Isostatic Pressing on Micro-Cracks and Microstructure of GH3230 Superalloy Fabricated by Selective Laser Melting
WANG Jihao, LIU Kaige, ZHANG Xuefeng, XIE Yinkai, LI Huaixue
DOI: 10.16080/j.issn1671-833x.2024.03.055

It was investigated that micro-cracks and microstructure characteristics of GH3230 superalloy fabricated by selective laser melting (SLM) before and after hot isostatic pressing (HIP) in order to reveal the SLM additive formability of GH3230 superalloy. The results show that there are many solidification micro-cracks in the SLM as-deposited GH3230 superalloy, and the micro-crack distribution is netlike along the XOY section and is threadlike along the ZOY section. Most of the solidification micro-cracks can be eliminated by HIP, and some longer micro-cracks are difficult to eliminate. There is elemental segregation phenomenon in as-deposited GH3230 superalloy fabricated by SLM, and exist a small amount of carbides along the boundary. After HIP, a large number of secondary carbides of MoWCr alloying elements are precipitated and the carbides along the boundary are larger than the intracrystalline precipitated ones. Micro-cracks easily reduce the XY direction tensile strength and elongation of as-deposited GH3230 fabricated by SLM and the XY direction tensile strength and elongation is greatly improved by HIP, and the effect mechanism was made a preliminary analysis.

2024 Vol. 67 (3): 55-61 [Abstract] ( 8 ) HTMLNew PDF (20646 KB)  ( 7 )
62 Research on Acquisition Strategy of Space Tube Forming Process
SONG Chaoyang, WU Jianjun, WU Wei, XU Xinliang, LIU Long, YU Zhongping
DOI: 10.16080/j.issn1671-833x.2024.03.062

Based on the free bending forming principle of spatial tube fittings, the formed tube fittings are divided into stable section and transition section, and the forming process of the two sections are analyzed respectively to obtain the free bending forming process strategy of spatial tube fittings. For the stable section, the mapping relationship between the bottom circle radius and pitch of the space spiral tube and the bending die offset and the clamp torsion speed is analyzed, and the forming process parameters of the space spiral tube are predicted by BP neural network. Through the test, it is found that the maximum relative error between the predicted value of the bending die offset and the numerical simulation test is 1.08%, and the maximum relative error between the predicted value of the clamp torsion speed and the numerical simulation test is 3.4%; For the transition section, the effects of the bending die offset and the loading mode of clamp torsion on the forming of spatial tube fittings are studied by orthogonal design experiment. It is obtained that the loading time of bending die and clamp in the transition section is 0.9 s. Combined with the above analysis, the acquisition strategy of tube free bending process based on primary equivalent approximation and secondary optimization is established, and its feasibility and effectiveness are verified by an example.

2024 Vol. 67 (3): 62-74 [Abstract] ( 10 ) HTMLNew PDF (12077 KB)  ( 14 )
75 Accuracy Test Method of Laser Tracker Measurement Based on Linear Trajectory
DOI: 10.16080/j.issn1671-833x.2024.03.075

Laser tracker measurement technology is widely used in assembling, manufacturing and other fields. For the study of the laser tracker measurement accuracy, a set of coordinate measurement accuracy testing system is developed, which can realize synchronous trigger of motor motion control, grating scale acquisition and laser tracker measurement through multi-axis motion controller based on the data collected by grating scale. The repeated positioning accuracy of the system and the synchronous trigger coordinate measurement accuracy of the laser tracker are tested respectively. The results show that the system repeated positioning error is between [–4.0 μm, 4.0 μm]. When the distance between three laser trackers and the target mirror in the tangential direction is [2.7 m, 3.4 m], the coordinate measurement error varies with the velocity between [–23 μm, 988 μm]. When the distance between laser tracker and the target mirror in the radial direction is [1.5 m, 3.8 m], the coordinate measurement error varies with velocity between [5 μm, 915 μm].

2024 Vol. 67 (3): 75-82,114 [Abstract] ( 22 ) HTMLNew PDF (5115 KB)  ( 14 )
83 Identification of PTFE Inclusion and Rich Resin Defects in CFRP Composites by Ultrasonic Testing
FU Dongxin, LIN Li, ZHANG Shuning, LUO Zhongbing
DOI: 10.16080/j.issn1671-833x.2024.03.083

The fabrication and identification of different inclusions are difficult in carbon fiber reinforced polymer (CFRP) laminates. In this paper, ultrasonic testing of inclusions, including artificial delaminations with Polytetrafluoroethylene (PTFE) and rich resin regions are studied by numerical simulation and experiment. Firstly, an ultrasonic reflection finite element model of multidirectional laminate considering elastic anisotropy of CFRP layers is established, and the time-domain signals of A-scan obtained by simulation and experiment are compared to prove the validity of the model. Then, PTFE inclusion with a width of 6 mm and thicknesses of 0.03– 0.40 mm and rich resin defects with thickness of 0.03– 0.85 mm are preset inside the CFRP laminate. The ultrasonic A-scan time-domain waveform of the defects is obtained by simulation, and the influences of the two kinds of defects thickness changes on the maximum amplitude and the kurtosis factor of ultrasonic signals are analyzed and compared. The results show that with increasing defect thickness, the maximum amplitude and kurtosis factor of defect signals both show a trend of first increasing, then decreasing and finally stabilizing. However, the maximum amplitude of rich resin defects is lower than that of PTFE inclusion, and the variation trend of rich resin defects kurtosis factor with thickness lags behind that of PTFE inclusion.

2024 Vol. 67 (3): 83-88 [Abstract] ( 6 ) HTMLNew PDF (2626 KB)  ( 25 )
89 Stripping Failure Analysis and Assembly Process Optimization of Double-End Studs
FU Xuan, SUN Huibin, LIU Zicheng, XU Guangqing, TONG Hao
DOI: 10.16080/j.issn1671-833x.2024.03.089

In order to solve the problem of loosening and stripping of double-end studs on the intermediate casing of an aero-engine, the comprehensive failure analysis and troubleshooting were carried out from the aspects of installation strength, applied load and manufacturing defects. The main reason is that the decomposition torque of the self-locking nut is greater than the assembly torque of studs. Secondly, the high temperature of the cavity and the vibration of the engine will further aggravate the fatigue failure of the studs. And the assembly process of double-end studs based on the combination of temperature difference and vibration was proposed, where the stud was firstly heated, and then axial highfrequency vibration was added to the stud during the tightening process. Comparison tests and application experiments were performed. Results show that the average stripping failure rate of the double-end stud decreases from 21.6% to 3.2%, that is, the proposed assembly process can effectively improve the assembly quality of double-end studs, and increase the installation strength and stability of studs without damaging the quality of the thread teeth. The stripping failure of double-end studs is avoided effectively and the safety and reliability of aero-engine during test and flight are guaranteed.

2024 Vol. 67 (3): 89-95 [Abstract] ( 13 ) HTMLNew PDF (16393 KB)  ( 10 )
96 Study on Influence of Typical Manufacturing Defects in Autoclave Forming on Mechanical Properties of Composite
RONG Xiaoyuan, PAN Lijian, YUE Guangquan, LIU Jia, LIU Weiping, WANG Anwei
DOI: 10.16080/j.issn1671-833x.2024.03.096

By exploring the out-of-plane wrinkles and delamination defects easily generated during the autoclave forming process, out-of-plane wrinkle test pieces with different sizes and wrinkle layers and delamination test pieces with various sizes are prepared. Tensile, compression, short beam shear and three-point bending tests are carried out on the test pieces. Then the failure morphologies of the test pieces under test are compared and analyzed to explore the effects of outof-plane wrinkles and delamination on the comprehensive mechanical properties of the composites and failure mechanism. The results show that the tensile strength, compressive strength, interlaminar shear strength and flexural strength of the composites with out-of-plane wrinkles respectively decline by 47%, 77%, 23% and 49%, and the number of wrinkled layers of out-of-plane wrinkles has a more significant effect on the mechanical properties than the size; delamination can cause a significant decrease in the compressive strength, interlaminar shear strength and flexural strength of the composites which respectively decline by 24%, 38% and 15%, while it has little effect on the tensile strength.

2024 Vol. 67 (3): 96-105 [Abstract] ( 12 ) HTMLNew PDF (21227 KB)  ( 6 )
106 Research on MQL Parameter Optimization and Cutting Performance in Milling Titanium Alloy
RONG Jie, NIU Qiulin, GAO Hang, JING Lu, TANG Siwen, ZHANG Shenzhen3
DOI: 10.16080/j.issn1671-833x.2024.03.106

In the process of minimal quantity lubrication (MQL) milling, the machining craftwork parameters have a significant influence on the cooling and lubrication effect of tool-chip and tool-workpiece contact interface. In this paper, the influence of the air flow field disturbed by the high-speed rotation of the milling cutter on the MQL jet angle and the penetration mechanism of the cutting fluid under the influence of the cutting zone pressure are analyzed by finite element simulation. Then, the titanium alloy TC4 commonly used in aerospace is used as the workpiece material, and the oil-onwater (OoW) as lubricating medium. The influence of the three parameters of the injection angle, injection distance and lubricating oil flow rate of the minimal quantity lubrication system on the milling force of titanium alloy is investigated by orthogonal experiment. And the optimal process parameters of the oil-on-water minimal quantity lubrication (OoWMQL) system are as follows: the nozzle angle is 30°, the injection distance is 10 mm, and the lubricating oil flow rate is 135 mL/h. Then, the effects of cutting speed and feed per tooth on the cutting performance of titanium alloy in dry milling and waterbased minimum quantity lubrication (WMQL) milling were studied by using the optimal process parameters of OoWMQL milling force, while OoWMQL technology significantly reduces the milling force under all parameters, and the maximum reduction range is about 50%. In addition, the OoWMQL method can significantly reduce the surface roughness, inhibit the generation of surface defects such as tool marks and adhesive chips, and effectively improve the machinability of titanium alloy.

2024 Vol. 67 (3): 106-114 [Abstract] ( 14 ) HTMLNew PDF (30905 KB)  ( 23 )
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