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2021 Vol. 64, No. 17
Published: 2021-09-01
FEATURE
FORUM
RESEARCH
C0NTENTS
COVER STORY
APPROACHING SCIENCE
 
       FEATURE
14 Microstructure and Tensile Properties of Hybrid Manufacturing TC4 Titanium Alloy
ZHU Yanyan, LI Chong,LIU Yuting, TIAN Xiangjun
DOI: 10.16080/j.issn1671-833x.2021.17.014
The hybrid manufacturing technique combining forging and selective laser melting techniques provides an effective approach for the manufacturing of complex integral titanium alloy component with high efficiency and low cost. The microstructure and properties controlling method of hybrid manufacturing titanium alloys is very important for the engineering application. The microstructure and mechanical properties of hybrid manufacturing TC4 samples of two typical process parameters with the layer thickness of 30μm and 60μm of selective laser melting were studied by means of metallographic and microscopic observation, room tensile testing and fractography observation. The results showed that the layer thickness has no effect on the microstructure and properties, however, larger layer thickness can increase the forming efficiency. The gradient microstructure in the bond zone of hybrid manufacturing TC4 is consist of the martensite structure in additive zone and equiaxed structure in substrate zone. There is no obvious heat affected zone in the forging substrate. The micro hardness of additive manufacturing zone is higher than that in the forging zone. The tensile properties of hybrid manufacturing TC4 can satisfy the requirement of the forging standard. The tensile strength of the bond zone is between the additive manufacturing zone and forging zone, but the elongation is equal to the additive manufacturing zone. Due to their different strength and ductility, it is concluded that a shear stress in the interface of gradient microstructure bond zone would form to adjust the deformation in this research. The fractography of the bonding zone tensile specimen is consist of quasi cleavage morphology in the additive manufacturing half zone and dimple morphology in the forging half zone.
2021 Vol. 64 (17): 14-20 [Abstract] ( 166 ) HTMLNew PDF (7269 KB)  ( 112 )
       COVER STORY
22 Research Progress on Electrically-Assisted Plastic Forming Technology of Titanium Alloy
LI Xifeng,CAO Xudong,WANG Bin,KONG Deli,LAN Xiaochen
DOI: 10.16080/j.issn1671-833x.2021.17.022
The research progress of electrically-assisted plastic forming process of titanium alloys is summarized. Electrically-assisted bending, electrically-assisted upsetting and electrically-assisted drawing are included. The electricallyassisted forming process of TC4 titanium alloy ring segment has also been developed recently. Under high current of 1500A (current density of 5.5A/mm2 ) and low voltage of 1.5V, the required forming temperature of about 600℃ can be obtained within 1min. The effect of pulse current on microstructure evolution of TC4 titanium alloy is very complicated. It can promote the transformation of β phase to α phase under certain circumstances and reduce its thermodynamic activation energy, which can also significantly reduce the anisotropy of TA15 and TA1 titanium alloy. The pulse current with appropriate frequency and density can repair some small cracks, dimples, voids, etc. The electroplasticity of titanium alloy mainly includes Joule heating effect and pure electroplastic effect. The existing research results draw inconsistent conclusions about pure electroplastic effect. Future research topics are also revealed.
2021 Vol. 64 (17): 22-30 [Abstract] ( 145 ) HTMLNew PDF (15123 KB)  ( 146 )
       FORUM
34 Superplastic Forming and Diffusion Bonding Process for Four-Sheet Air Rudder of TC31 Titanium Alloy
WU Yong, ZHOU Xianjun, WU Dipeng, TANG Guowei, CHEN Minghe
DOI: 10.16080/j.issn1671-833x.2021.17.034
In order to study the superplastic forming/diffusion bonding (SPF/DB) process of TC31 titanium alloy four-sheet air rudder, the high temperature tensile test, finite element simulation and air rudder experiment were conducted. The results indicated that the optimal deformation strain rate of TC31 titanium alloy at 920℃ was 0.001s–1, and the maximum elongation rate was 639%, which showed good superplastic ability. The ABAQUS simulation results showed that the maximum thinning occurred at the edge of the preset block, the maximum thinning rate was 67.5%, and the maximum strain of core plate was 1.04. The four-sheet TC31 SPF/DB air rudder part with no surface depression was prepared by experiment with 0.2MPa back pressure and step pressure loading method applied. The interface quality of core plate diffusion bonding was good under the diffusion parameters of 920℃/3MPa/2h, and the welding rate was 97%.
2021 Vol. 64 (17): 34-40 [Abstract] ( 121 ) HTMLNew PDF (14603 KB)  ( 80 )
41 Study on Optimization of Process Parameters of Hydraulic Deep Drawing for Aluminum Alloy Box-Shaped Parts
MEN Xiangnan,Lü Xiuwen, XU Yong,XIA Liangliang, LI Xiaojun,ZHOU Xiong,CHEN Ming,ZHANG Shihong
DOI: 10.16080/j.issn1671-833x.2021.17.041
The key parameters of hydraulic deep drawing process for 2A16 aluminum alloy sheet were optimized by the combination of the response surface method and finite element simulation (FEM) to realize the high-efficient and precision forming of the aluminum alloy thin-walled box-shaped parts used in aviation. Three process parameters of blank fillet radius, blank holder force and hydraulic pressure were selected as optimization variables, and the maximum thinning rate of aluminum alloy box-shaped part was selected as optimization evaluation index. The experimental scheme was designed by central composite design method, and the experimental data were analyzed by response surface analysis software Design Expert 12. The second-order response model of the maximum thinning rate and the process parameters of the box-shaped part was established, and the optimal process parameters combination was obtained through this model. The results show that the optimal conditions of maximum thinning rate can be met when the blank holder force is 2.8MPa, the liquid pressure is 5.3MPa and the radius of the rounded corner of the blank is 100mm. By using the optimized combination of process parameters to carry out one-step hydroforming experiment, the box-shaped parts meeting the forming quality requirements can be obtained.
2021 Vol. 64 (17): 41-52 [Abstract] ( 119 ) HTMLNew PDF (19879 KB)  ( 139 )
53 Numerical Simulation and Optimization of Shot Peen Forming of Saddle-Shaped Integrally-Stiffened Panel
TIAN Shuo,GAO Guoqiang,ZHONG Lixin,CHEN Fulong,ZENG Yuansong,YANG Hui,SHANG Jianqin
DOI: 10.16080/j.issn1671-833x.2021.17.053
A simulation model for stress peen forming of saddle-shaped integrally-stiffened panels was established. Through a numerical simulation-based shot peen forming parameter planning process, the typical panel process plan was simulated and analyzed and an optimized process plan was obtained. The research results show that with the optimized process plan, the simulated deformation of the typical panel is basically consistent with the theoretical deformation. The maximum difference located at the 13th rib of the rear beam is only 3.7mm, which is 8.1mm less than the initial plan. The optimized test plan is used for the test. Compared with the simulated deformation, the differences of ribs 11–17 are less than 4mm. Compared with the theoretical deformation, the differences of ribs 11–17 are not more than 2.5mm, and the differences of ribs 12–16 are not more than 0.5mm. Therefore, the shot peening deformation simulation method is more accurate and the optimization plan is reasonable and feasible.
2021 Vol. 64 (17): 53-60/68 [Abstract] ( 88 ) HTMLNew PDF (3584 KB)  ( 175 )
61 Hot Stamping With Pre-Cooling Treatment for AA7055 High-Strength Aluminum Alloy Sheets
YUE Yuting, FENG Weijun,YANG Bing,LI Yongfeng, HE Ji
DOI: 10.16080/j.issn1671-833x.2021.17.061
For high-strength aluminum alloys at the solution temperature, it is difficult to achieve the best formability during the hot stamping and cold die quenching process (heat treatment, forming and in-die quenching, HFQ), and forming defects such as cracks would occur easily. To solve this problem, this paper introduces a pre-cooling treatment, which could cool the solid solution sheet to target temperature. In the quenching sensitivity temperature range, the mechanical properties of an AA7055 high-strength aluminum alloy sheet were tested under different pre-cooling temperatures after solid solution. It is found that the largest elongation and the best formability are obtained at pre-cooling temperature of 350℃. Taking structural parts with typical characteristics as an example, the HFQ process tests with different pre-cooling conditions and original sheet materials were carried out. It is found that the surface quality of the F–state sheet is better than that of the O–state one, and F-state sheet has better formability under the same process flow. The traditional HFQ comparative forming experiment was carried out on the F–state sheet, and the F–state sheet was severely broken without pre-cooling treatment. The uniaxial tensile tests were carried out on the typical positions of the well-formed parts. And it proves that the strength of the formed part is the lowest at the pre-cooling temperature of 350℃, which is near the nose tip temperature for quenching sensitivity. Taking into account the formability and strength, the pre-cooling temperature should be 400℃.
2021 Vol. 64 (17): 61-68 [Abstract] ( 105 ) HTMLNew PDF (9203 KB)  ( 73 )
       APPROACHING SCIENCE
70 Breaking Through Aeronautics and Astronautics Composite Key Mechanical Problems by Crossover and Integration of Science and Engineering
2021 Vol. 64 (17): 70-71 [Abstract] ( 75 ) HTMLNew PDF (770 KB)  ( 178 )
       RESEARCH
72 Effect of Selective Laser Melting Process Parameters on Forming Quality of Titanium Alloy Ti–6Al–4V
YUAN Meixia, HUA Ming, CHEN Xinyi, MENG Hao
DOI: 10.16080/j.issn1671-833x.2021.17.072
In order to explore the influence of selective laser melting (SLM) process parameters on the forming quality of products, the SLM forming experiment was carried out by using titanium alloy Ti–6Al–4V powder as raw material and taking the forming process parameters of point spacing, exposure time and line spacing as variables respectively. The surface morphology, flatness and straightness errors were collected and analyzed, the influence of forming parameters, such as point spacing, exposure time and scanning line spacing on forming quality is analyzed. The results show that the scanning point spacing, exposure time and line spacing are closely related to the surface micro geometry and geometric accuracy. With the increase of line spacing, the surface micro shape becomes rougher and the surface quality decreases, while the geometric accuracy error decreases and then increases with the increase of line spacing. In the exposure time of 80μs and point spacing of 40μm the geometric accuracy of the formed specimen is better than that of the exposure time of 60μs and point spacing of 30μm, and better than that of the exposure time of 100μs and point spacing of 50μm.
2021 Vol. 64 (17): 72-77 [Abstract] ( 101 ) HTMLNew PDF (32947 KB)  ( 121 )
78 Effect of Laser Shock Peening on Fretting Wear Behavior of TB6 Titanium Alloy
ZHANG Hao,SUN Zhiqiang,CAO Ziwen,LI Zhiqiang,ZHOU Wenlong,FU Xuesong
DOI: 10.16080/j.issn1671-833x.2021.17.078
The fretting wear behavior of TB6 titanium alloy before and after laser shock peening (LSP) was studied. The influence of displacement amplitude on friction coefficient and wear mechanism was analyzed. The surface integrity, friction morphology and wear volume of the original sample and the sample after LSP treatment were analyzed by X–ray diffraction, microhardness, laser confocal microscopy and scanning electron microscopy. The results show that after LSP treatment, the surface roughness (Ra) of TB6 increases from 0.203μm to 0.321μm. The surface microhardness increases from 322HV to 400HV. The residual compressive stress layer is introduced into the surface layer, and the maximum residual stress reaches –650MPa. In the fretting friction process, when the displacement amplitude is small (≤50μm), the adhesion appears on the friction surface of the sample, and the adhesion degree and friction coefficient increase after LSP. When the displacement amplitude is larger (≥75μm), pits appear on the friction surface of the sample. After LSP, the slope of the pits decreases, the friction coefficient and wear volume decrease, and the fatigue wear and abrasive wear are alleviated, which is helpful to improve the wear resistance of the material.
2021 Vol. 64 (17): 78-84/101 [Abstract] ( 82 ) HTMLNew PDF (26467 KB)  ( 77 )
85 Research on Scheduling Method of Complex Shell Part Manufacturing Shop Floor
FU Mei,XIE Huai,WANG Sunxin,SHEN Gaopan
DOI: 10.16080/j.issn1671-833x.2021.17.085
The shell part of the aero-engine fuel control system is with the production characteristics of specialized small flow shop, lean manufacturing, operation sequence flexibility, etc. To ensure that the shell parts are completed just in time, taking the earliness/tardiness cost as the optimization objective, a non-permutation flow shop scheduling model with operation sequence flexibility was constructed. An improved genetic algorithm with embedded two-segment encoding and three-stage decoding operators was proposed for scheduling model solution. The results of the practical production cases have verified the effectiveness of the proposed scheduling model and algorithm, in addressing the just-in-time production of complex shell parts. The proposed method also has the potential to be popularized to other shell parts manufacturing fields, such as automobile engines, decelerators, pumps, etc.
2021 Vol. 64 (17): 85-93 [Abstract] ( 115 ) HTMLNew PDF (1353 KB)  ( 257 )
94 Experimental Study on Ultrasonic Trepanning of Nomex Honeycomb Core
SUN Dingyi, KANG Renke, WANG Yidan, DONG Zhigang
DOI: 10.16080/j.issn1671-833x.2021.17.094
In order to solve the problems of complex machining and poor quality of the contour boundary along the axial direction in Nomex honeycomb core components, an ultrasonic trepanning method was proposed based on the trepanning process. The ultrasonic trepanning of Nomex honeycomb cores was carried out. Trepanning force measurement and incision quality observation tests were carried out under the tool spindle speed of 500–1500r/min and the feed speed of 1000–3000mm/min, respectively. The experimental results show that compared with the traditional trepanning process, the ultrasonic trepanning with the amplitude of 20μm can effectively reduce the trepanning force under the above machining parameters, with an average reduction of about 20%. The trepanning incision of Nomex honeycomb core processed by ultrasonic trepanning is smoother, more neat and without burrs than that of traditional trepanning. Combined with the experimental results, the relative motion relationship between the tool and the workpiece and the trepanning force during the ultrasonic trepanning process were further analyzed, and the reasons for the low trepanning force and good trepanning quality in ultrasonic trepanning process were theoretically explained.
2021 Vol. 64 (17): 94-101 [Abstract] ( 110 ) HTMLNew PDF (36033 KB)  ( 89 )
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