Abstract:With the rapid development of micro‐electromechanical systems (MEMS), micro/nanoscale fabrication of 3D metallic structures with complex structures and multifunctions is becoming more and more important due to the recent trend of product miniaturization. As a promising micromanufacturing approach based on plastic deformation, micro/nanoforming shows the attractive advantages of high productivity, low cost, near‐net‐shape, and excellent mechanical properties, compared with other non‐silicon‐based micromanufactu… Show more
“…Both the experiment and numerical simulations shows a signi cant in uence of the size effect on the cracking character as the dimensions down to micro level. The forming limit curve shifts downwards with the decreasing thickness grain size ratio [9,10]. However, the deformation properties of ultra-thin sheet metal at high strain rate are different from that at quasi static strain rate.…”
This paper is concerned with Nakajima test and forming limit curve (FLC) of stainless 304 ultra-thin sheet metal in relation to the strain rate effect. The mechanical properties related to the micro structure of specimens are studied based on quasi static tension test. The forming limit curves are constructed by Nakajima tests with two different strain rates, quasi-static and high speed strain rate. Compared with the quasi-static FLC, the high speed FLC of the 304 ultra-thin metal sheet for all specimens with different thickness is lower through the entire region. The results confirm that the strain rates have a noticeably influence on the formability of ultra-thin sheet metal. The deformation and fracture behavior for high speed forming is discussed based on the previous study. The forming limit curves should be considered in the design in high speed ultra-thin sheet metal forming processes.
“…Both the experiment and numerical simulations shows a signi cant in uence of the size effect on the cracking character as the dimensions down to micro level. The forming limit curve shifts downwards with the decreasing thickness grain size ratio [9,10]. However, the deformation properties of ultra-thin sheet metal at high strain rate are different from that at quasi static strain rate.…”
This paper is concerned with Nakajima test and forming limit curve (FLC) of stainless 304 ultra-thin sheet metal in relation to the strain rate effect. The mechanical properties related to the micro structure of specimens are studied based on quasi static tension test. The forming limit curves are constructed by Nakajima tests with two different strain rates, quasi-static and high speed strain rate. Compared with the quasi-static FLC, the high speed FLC of the 304 ultra-thin metal sheet for all specimens with different thickness is lower through the entire region. The results confirm that the strain rates have a noticeably influence on the formability of ultra-thin sheet metal. The deformation and fracture behavior for high speed forming is discussed based on the previous study. The forming limit curves should be considered in the design in high speed ultra-thin sheet metal forming processes.
“…Therefore, the meso-/micro-forming, i.e., the plastic processing technology applied in the meso/micro-eld, has been serving as an effective fabrication method for the mass production of meso-/micro-scaled metallic parts [5,13]. Compared with other manufacturing processes, the meso-/micro-forming technology possesses outstanding advantages of quite high productivity rates and e ciency besides good product quality, low production cost, less material waste, net-shape or near-net-shape characteristics [14,15]. However, when the target parts are designed with multi-features or complex-structures, the production rate and e ciency of such technology are limited by the problems of feeding, transporting and picking up of billet and nal parts in forming process [16].…”
A progressive meso-/micro-forming process directly using continuous wire metals is firstly developed in this work and applied for efficiently making fork-shaped parts with irregular features, e.g., flat tines and cylindrical head. Meanwhile, both geometrical and microstructural size effects on the forming quality of fabricated parts are investigated. Therein, the brass CuZn35 wires with three diameters (0.4, 0.8 and 1.2 mm) and various grain sizes (30.9-159.2 µm) are prepared and employed as the experimental materials. The material flow behavior in this progressive meso-/micro-forming process is investigated by finite element simulations and the micro-scaled specimens are found to exhibit more uniform strain distributions. As for the dimensional accuracy, the absolute errors of the thickness and width of the final parts increase with grain size, while the errors of height and inner width are only related to the precision of the punch. The increasing surface roughness after the progressive meso-/micro-forming process decreases with enlarging specimens and refining grains. Cracks easier appear on the side surface of micro-scaled specimens and specimens with the larger grain size.
“…The sharp rise of Micro System Technology (MST) and Micro Electro Mechanical Systems (MEMS) has driven the current industrial development towards miniaturization even microminiaturization [1]. Compared with Micro-machining, Laser technology, LIGA technology and micro electro-discharge machining, metal plastic deformation has greater advantages in terms of cost control, processing efficiency and dimensional accuracy control [2,3], thus promoting the industrialization of micro-formed parts.…”
Ultrafine-grained (UFG) materials can effectively solve the problem of size effects and improve the mechanical properties due to its ultra-high strength. This paper is dedicated to analyzing the deformation behavior and microstructural evolution of UFG pure copper based on T-shape upsetting test. Experimental results demonstrate that: the edge radius and V-groove angle have significant effects on the rib height and aspect ratio λ during T-shape upsetting; while the surface roughness has little effect on the forming load in the first stage, but in the second stage the influence becomes significant. The dynamic recrystallization temperature of UFG pure copper is between 200 °C and 250 °C.
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