Search

Tantalum is widely used in capacitor field in modern times. The tantalum shell of capacitor is usually obtained by deep drawing process, and adhesive wear of the shell is the main hidden danger during its deep drawing process. In this paper, ultrasonic vibration–assisted deep drawing technology is proposed to manufacture tantalum capacitor shell, in order to effectively control the adhesive wear of tantalum capacitor with the assistance of ultrasonic vibration energy. Influence of ultrasonic vibration on deep drawing force and surface forming accuracy of tantalum cup deep drawing is discussed by applying different amplitudes of ultrasonic vibration signals at different time periods. The results reveal that in the amplitude range of 3–7 μm, the amplitude of 5 μm has the best inhibition effect on adhesive wear during the deep drawing of tantalum cup, and the effect is especially obvious in the initial stage of the deep drawing process; the reduction of wearing can reach more than 22% comparing with the results without ultrasonic amplitude. [ABSTRACT FROM AUTHOR]

Advanced high-strength steel is widely used in automobile production and manufacturing, for its advantages of light weight, high strength, and good formability. Compared with common steel plate, higher forming forces are required during the stamping forming process of advanced high-strength steel plate due to its continuous strength improvement. The higher forming forces directly result in a sharp increase in the reactive force on the stamping die, which easily cause inevitable fatigue deformation and damage fracture. In view of the above problems, the stamping forming process of an advanced high-strength steel anti-collision beam part and the loading bearing condition of the stamping die were explored. On basis of the theory of topology optimization, the structure of the stamping die was optimized to obtain the qualified stamping parts and the lesser quality punch. A method based on the node contact force conversion was proposed, and the reactive force on the stamping die during the forming process was obtained to function as the load boundary condition of topology optimization. Geometric reconstruction of the stamping die was implemented referring to the topology optimization results. The final result reveals that the lightweight punch and the qualified stamping part without fatigue deformation can be efficiently achieved through topology optimization. [ABSTRACT FROM AUTHOR]

Amorphous alloys are considered as an ideal material for complex micro component fabrication due to their extraordinary mechanical properties and thermoplastic formability. However, the conventional theories and thermoplastic forming (TPF) methods for amorphous alloys require a lower loading rate and a higher pressure which extremely prolong the processing time and reduce the mold life. In this study, an efficient and low-cost TPF-based method is developed to fabricate the micro impeller by controlling flow states of amorphous supercooled liquid at different forming stages. Based on the finite element simulation results of the filling process and strain distribution, the new multistage forming method enables thin-walled blade fabrication without a significant "dead zone" by adjusting the velocity gradient of the flow front, thus reducing the pressure requirement. Also, the non-Newtonian flow region is proved to be an appropriate TPF window at high temperatures. To verify the validity of the multistage forming method, technological experiments undergoing different conditions were performed. Finally, the full-filled thin-walled blades with a width of 508 μm and surface roughness of 0.25 μm were prepared in about 50 s. This research demonstrates a new TPF-based method for the rapid fabrication of micro components with a high-aspect-ratio characteristic structure in an economic way. [ABSTRACT FROM AUTHOR]

Compared with traditional grinding, hard turning with ceramic tools has lots of advantages such as lower cost, higher productivity, better machining accuracy, and elimination of cutting fluids. However, the catastrophic fracture of ceramic tool frequently occurs in turning of hardened steel. Hence, there is a need to recognize the evolution of machinability aspects (cutting forces and tool wear) in the whole turning process. An orthogonal experiment was designed to investigate the evolution of cutting forces and tool failure mechanisms in intermittent turning of hardened 20CrMnTi steel with AlO-TiC ceramic tool. The effects of cutting parameters on cutting forces were analyzed by Taguchi method and analysis of variance (ANOVA) during different tool wear stages. The results revealed that the influence of cutting parameters on cutting forces gradually declined with the increased tool wear, and the contribution of depth of cut on cutting forces gradually increased. The optimal cutting parameters of cutting forces were calculated for different wear stages. In addition, the fracture modes and mechanisms of tool under different cutting conditions were investigated. The fatigue striations and fatigue beaches were observed at the fracture surface. The propagation paths and mechanisms of fatigue cracks were analyzed under different cutting speeds. The results indicated that the fracture area of tool was mainly affected by mechanical stress, while the depth of crack propagation was determined by thermal stress. [ABSTRACT FROM AUTHOR]

Micro-ultrasonic sheet-metal forming using molten plastic as a flexible punch is a new microforming technology useful for manufacturing micro-stamped thin sheet metals. In this paper, we researched how time parameters influenced the forming replication ability of microchannel forming. Our experimental results show that the forming replication ability of the method was improved by extending the ultrasonic action duration time and maintaining pressure time. An appropriate ultrasonic action duration time was determined by assessing the melting time of the plastic powder used as a flexible punch; an appropriate maintaining pressure time was determined by assessing the coagulation time of the molten plastic punch. When the ultrasonic action duration time was 0.5 s and the maintaining pressure time was 1.5 s, the forming replication ability of the microchannel reached 97 %. With further increases in the time parameters, the forming replication ability stopped rising, and the forming method produced parts with defects at a lower forming efficiency. Through these experiments, we obtained a set of optimal process parameters for microchannel formation. [ABSTRACT FROM AUTHOR]

Microdeep drawing has great potential in microsystem technologies, electron industries, new energy, etc. Microsquare cups with internal side length of 1 mm were formed in this study. The blank material was pure copper C1100 with a thickness of 50 μm which was annealed in vacuum condition at 573 and 723 K for 1 h, respectively. The experiments were conducted with an electronic universal testing machine. Three kinds of different lubrication conditions and blank holder force (BHF) were used, and the experimental velocity was 0.05 mm/s. The results showed that a microsquare cup with a limiting drawing ratio (LDR) of 1.89 was well formed. Compared to the as-received blank, the annealed blank decreased the drawing force and the earings and increased the LDR. The polyethylene (PE) film, which decreased the drawing force and increased the LDR, was much better than other lubrication conditions. The wrinkles decreased with the increase of the BHF under a specific value. [ABSTRACT FROM AUTHOR]

3D metal micro-mold fabricated through the micro double-staged laminated object manufacturing process is formed via stacking and fitting of multi-layer 2D micro structures. In this paper, it is suggested that micro-electric resistance slip welding technology be adopted to optimize the connection of micro structures in 3D metal micro-mold. Moreover, the deposition effect of tungsten electrode which was formed on the micro-mold surface and produced during micro-electric resistance slip welding is also studied. Firstly, the temperature field of electric resistance slip welding was simulated by ANSYS software and the maximum temperature in the slip welding area is 1,219 °C when the number of slip welding discharge is 160, which is far lower than the melting point of tungsten electrode material (3,410 °C). Hence, bulk tungsten will not shed during slip welding; however, the wear of the tungsten electrode will be deposited on the surface of the micro-mold in micro-particle shape. Secondly, the influence of slip welding discharge and surface roughness of tungsten electrode on tungsten deposition effect is studied and the study shows that: the content of tungsten within the slip welding area increases gradually as the number of slip welding discharge increases, and decreases gradually as surface roughness of tungsten electrodes increases. Finally, under 160 time's slip welding discharge and using tungsten electrodes (0.5-mm diameter and 0.12-μm surface roughness), the 3D metal micro-molds which contains 0.4 % tungsten in slip welding area and has a good quality surface was obtained. [ABSTRACT FROM AUTHOR]