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2021 Vol. 64, No. 10
Published: 2021-05-15
FEATURE
FORUM
RESEARCH
C0NTENTS
COVER STORY
APPROACHING SCIENCE
 
       FEATURE
14 Temperature Distribution of Ceramic Top-Coat in Thermal Barrier Coatings Via Delamination Crack Shape and Size
DONG Hui,ZHOU Panhu,ZHOU Yong,HAN Yan,WANG Heyu,HUA Wanchao
DOI: 10.16080/j.issn1671-833x.2021.10.014
The finite element simulation was used to characterize the relationship between different crack shapes in the thermal barrier coating ceramic top-coat and the shape and size of bright spots on the coating surface. The results show that when the crack length is less than 1mm, the shape effect of the crack has no obvious effect on the surface temperature distribution and size of coating ceramic top-coat. When the crack length exceeds 1mm, the shape of the bright spot on the surface of the ceramic top-coat gradually follows the shape of the internal delamination crack, and the larger the crack edge effect (the smaller the angle), the more the shape change of the bright spot on the ceramic top-coat surface above it tends to the shape of the internal delamination crack. Different shape crack size and area have different effects on the maximum temperature of the ceramic top-coat above the crack. With the increase of crack size and area, the maximum temperature of the ceramic top-coat above the three shape cracks increases. When the crack size exceeds 0.5mm, the difference of surface temperature of the three cracks gradually increases, and the increase of surface temperature of cylindrical crack is the most significant. Therefore, the size of the bright spot on the surface of the ceramic top-coat can reflect the actual size of the internal crack, and the relationship between the bright spot size and the internal crack size is not affected by the crack shape, location and other factors.
2021 Vol. 64 (10): 14-18 [Abstract] ( 88 ) HTMLNew PDF (3090 KB)  ( 154 )
       COVER STORY
20 Development of CNC Technology and Its Role in Intelligent Manufacturing
WANG Miao,ZHANG Zhenming,LI Long,XIE Yun
DOI: 10.16080/j.issn1671-833x.2021.10.020
At present, the rapid development of intelligent manufacturing industry makes the openness and intellectualization of numerical control technology more obvious, and our country pays more attention to numerical control technology, which will effectively promote the automation and intellectualization of industrial manufacturing in our country. The paper summarized the development status and development trend of CNC technology in China, analyzed the existing gap between the domestic CNC technology and intelligent manufacturing development level and the international advanced technology. The development of CNC technology is the embodiment of a country’s manufacturing capability and level, combining big data and artificial intelligence, CNC technology has become an important cornerstone of intelligent manufacturing. The innovation and breakthrough of numerical control technology has become an important guarantee for the completion of intelligent manufacturing engineering.
2021 Vol. 64 (10): 20-26 [Abstract] ( 151 ) HTMLNew PDF (1496 KB)  ( 551 )
       FORUM
30 Dissimilar Friction Stir Welding Between Polymers and Aluminum Alloys
MENG Xiangchen,CAO Bingqi,LI Yulong,GU Chen,WAN Long,HUANG Yongxian
DOI: 10.16080/j.issn1671-833x.2021.10.030
The heterogeneous structures between polymers/polymer matrix composites and aluminum alloys can fulfill the desired requirements in structural properties and lightweight design. Friction stir welding (FSW) is a solid state welding technique characterized by low temperature and severe plastic deformation, which cannot be influenced by crystal structures, physical and chemical properties FSW can realize high-quality joining between polymers and aluminum alloys. Aiming at welding parameter optimization, joint formation, defect types and causes, strength improvement and so on, the current progress of FSW between polymers and aluminum alloys was reviewed. Meanwhile the future outlooks and engineering application were further prospected.
2021 Vol. 64 (10): 30-40 [Abstract] ( 58 ) HTMLNew PDF (8367 KB)  ( 43 )
41 Study of Materials Flow on Non-Keyhole Friction Stir Welding
LI Dengchang, YUE Yumei,JI Shude,CHAI Peng,SHANG Zhen
DOI: 10.16080/j.issn1671-833x.2021.10.041
The non-keyhole friction stir welding was used to attain the weld without keyhole in the weld end. A model of material flow was established by the fluent software. The material flow behavior during non-keyhole friction stir welding was obtained by the numerical simulation and was verified by the cross section morphology. The experimental results about cross-section morphology show that the stir zone (SZ) is approximately drum-shaped, the thermo-mechanically affected zone is banded and distributed on both SZ sides and under the SZ, and the heat-affected zone presents a basin shape. The numerical simulation results show that the maximum flow velocity of the material is located at the outer side of the sleeve, the material inside the sleeve flows downward under the action of centrifugal force generated by high-speed rotation. Increasing rotation velocity of tool and decreasing the welding speed can expand the high-speed flow area of the material, which is conducive to reducing the height of the kissing bond line at the root. The experimental results well agrees with numerical simulation results.
2021 Vol. 64 (10): 41-46/63 [Abstract] ( 85 ) HTMLNew PDF (4514 KB)  ( 140 )
47 Effects of Post-Welding Heat Treatment on Microstructures and Properties of Dissimilar Steel Friction Stir Welded Joint
TANG Wenshen, YANG Xinqi, LI Shengli, LI Huijun
DOI: 10.16080/j.issn1671-833x.2021.10.047
The influences of post-welding heat treatment on the microstructures and properties of dissimilar steel friction stir welded joints for China low activation martensitic(CLAM) and 316L stainless steels have been investigated. It is found that the microstructure hardening tendency of the hardened martensite in the nugget of joint is obviously reduced by the post-welding heat treatment (PWHT), and which promotes the carbide to be precipitated again and transformed into a low carbon α phase. The weak site of the high temperature mechanical properties for dissimilar steel welded joint is transformed from the base metal to the further softening heat affected zone. The static recovery occurs in the nugget of 316L steel, and the property is slightly decreased. With the increase of post welding temperature, the phenomenon of interfacial carbon migration is intensified around the bonding-interface, the softened ferrite zone is formed around the interface at the side of CLAM steel and the chromium-rich carbide is formed around the interface at the side of 316L steel. When using the process of heating to 740℃ and holding for 2 hours, the dissimilar steel friction stir welded joint can obtain good strength and toughness matching, and the high temperature tensile strength reaches 97.5% of the welding state joint.
2021 Vol. 64 (10): 47-56 [Abstract] ( 69 ) HTMLNew PDF (25954 KB)  ( 40 )
64 Effect of Electric Pulse Treatment on Properties of Friction Stir Welded Joint of 2024-T4 Aluminum Alloy
XU Aijun,TANG Zejun,ZHANG Jintao,WAN Haifeng,WANG Zihan
DOI: 10.16080/j.issn1671–833x.2021.10.064
Electrical pulse treatment was carried out on 2024–T4 aluminum alloy friction stir welding (FSW) samples. The results show that the strength of the sample decreases obviously and the elongation increases obviously after the treatment. When the effective current density is 135A/mm2 , the tensile strength decreases by 25% and the elongation increases by 50%. The engineering stress-strain curve of the welding sample shows the zigzag fluctuation of PLC effect. After the aging treatment following by the electrical pulse treatment, the serrated fluctuation of tensile curve disappears. The elongation decreases slightly, while the strength increases. The material’s mechanical properties return to the FSW samples’ level. The tensile strength of the sample is 8% higher than that of the original joint after artificial reaging treatment, while the tensile strength is 4% higher than that of the original joint after natural reaging treatment. The microstructure shows that the grains are refined to different degrees in different areas of the joint after solution-treatment. The strengthening phase dissolves in the process of solution treatment, but re-precipitates in the process of reaging treatment. In addition, the volume and quantity of strengthening phase precipitated in nugget zone after artificial reaging treatment are larger in comparison to that after natural reaging treatment. The dissolution and precipitation of strengthening phase are the reasons for the change of mechanical properties and PLC effect of FSW samples after the reaging treatment following by solution treatment.
2021 Vol. 64 (10): 64-71 [Abstract] ( 46 ) HTMLNew PDF (32436 KB)  ( 70 )
       APPROACHING SCIENCE
72 Gathering Innovative Resources and Deeply Integrate Industry-University-Research and Application
2021 Vol. 64 (10): 72-73 [Abstract] ( 36 ) HTMLNew PDF (1292 KB)  ( 40 )
       RESEARCH
74 Research on Intelligent Matching Technology for Rivets to Control Interference
SHI Shuangjiang, CHEN Wenliang, WANG Ziyu
DOI: 10.16080/j.issn1671-833x.2021.10.074
Interference riveting is one of the key technologies in aircraft assembly. The control of riveting interference is very important to improve the fatigue life of riveted parts. Firstly, in order to control the interference accurately, the rivets were measured quickly based on machine vision. Secondly, the rivets were grouped by the equal tolerance and the group matching based on fruit fly optimization algorithm respectively. The matching rate and matching quality were used as evaluation indexes. Finally, an intelligent matching system for rivet and countersink based on fruit fly optimization algorithm was developed. Compared with the traditional equal tolerance zone grouping, the matching rate of the system is improved from 76.84% to 90.85%, and the matching quality of the system is improved from 0.8927 to 0.9096.
2021 Vol. 64 (10): 74-79/85 [Abstract] ( 60 ) HTMLNew PDF (2812 KB)  ( 137 )
80 Experimental Investigation on Discharge States Characteristics of EDM
HOU Shaojie, BAI Jicheng, LIU Xiaomeng, LIU Huan
DOI: 10.16080/j.issn1671-833x.2021.10.080
The machining quality is influenced significantly by the gap discharge states in electrical discharge machining (EDM). In order to avoid abnormal discharges such as arc, the discharge states needed to be identified by the discharge state detection system according to different discharge characteristics. In order to solve this problem, the single pulse discharge method was used to explore the different characteristics of spark discharge and arc discharge. Under different experimental conditions, the two kinds of discharge voltage waveforms were respectively transformed by fast fourier transformation (FFT). It is found that the frequency amplitude of spark discharge is significantly different from that of arc discharge in the lower frequency range. Therefore, the average frequency amplitude of 0–5MHz frequency range was taken as the research object to study the influence of different variables on it. The experimental results show that the open-circuit voltage and pulse duration have little effect on the average frequency amplitude of the two discharge states, while the electrode materials and workpiece materials have great influence on them. The average frequency amplitude of the spark discharge state is higher than that of the arc discharge, –30dB can be used as the threshold to distinguish the spark discharge and the arc discharge.
2021 Vol. 64 (10): 80-85 [Abstract] ( 95 ) HTMLNew PDF (2459 KB)  ( 194 )
86 Research on Built-in Method of Intelligent Processing Equipment in Discrete Manufacturing Workshop
SHEN Xiaoyu, TANG Dunbing, ZHANG Zequn, ZHENG Du, GUAN Chencheng
DOI: 10.16080/j.issn1671-833x.2021.10.086
With the advent of Industry 4.0, the continuous integration of internet of things (IoT) technology and manufacturing technology, the processing equipment and manufacturing systems in the manufacturing workshop are more closely connected, and higher requirements are placed on the interconnection between equipments. In traditional manufacturing plants, processing equipment exists only as independent individuals in manufacturing systems. The lack of interactive negotiation between the processing equipment and other equipment in the manufacturing system, which results in the equipment cannot adjust the processing process in time. To this end, combined with the IoT manufacturing technology theory, the method of constructing intelligent processing equipment for physical resources in the workshop is studied. Taking the processing equipment in the discrete manufacturing workshop as an object, an adaptation layer for different types of system equipment is constructed. Based on this, the intelligent analysis layer of the device is established, so that the device can select tasks by analyzing the environmental information and its own state information. At the same time, it defines the external interaction mode of the device, overcomes the independence of the traditional device, and enables the interaction between the devices. Finally, the construction results are applied to the processing equipment of the actual CNC system, which proves the feasibility of the construction method and improves the dynamic performance of the entire manufacturing system.
2021 Vol. 64 (10): 86-94/101 [Abstract] ( 67 ) HTMLNew PDF (6684 KB)  ( 183 )
95 Microstructure and Mechanical Properties of TiBw/TA15 Composite Sheet
WANG Fuxin,FU Mingjie,QIAN Jianhang, ZENG Yuansong,HAN Xiuquan
DOI: 10.16080/j.issn1671-833x.2021.10.095
TiB whisker reinforced titanium matrix composite has a wide range of potential applications in aircraft skin, frame beam and other components due to its excellent high temperature performance. The effect of rolling deformation on the microstructure and properties of TiBw/TA15 composite was studied. The microstructure of TiBw/TA15 composite sheets was analyzed by OM and SEM. It was found that the microstructure of TiBw/TA15 composite sheet is fine, and TiB whiskers are uniformed distributed. But the micro cracks formed by the deformation of TiBw phase are obviously observed. By analyzing the mechanical properties, it was found that the tensile strength of TiBw/TA15 composite sheet is 10% higher than that of the slab at room temperature and 600-650℃. The tensile strain at room temperature increases from 4.8% to 8% after rolling deformation. The high temperature endurance property of TiBw/ TA15 composite sheets is similar with that of the slab. While rolling deformation has little effect on the high temperature durability.
2021 Vol. 64 (10): 95-101 [Abstract] ( 55 ) HTMLNew PDF (8216 KB)  ( 43 )
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