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Applications of High-Intensity Ultrasonics Based on Mechanical Effects
Published in Dale Ensminger, Leonard J. Bond, Ultrasonics, 2011
Dale Ensminger, Leonard J. Bond
Ultrasonic staking is another widely used application of the same equipment. Staking is a method of attaching plastics and metals (or other materials) by mechanically locking or enclosing the materials in plastic. A small protrusion is extended through a hole in the second material by a distance which is sufficient to form a suitable lock when staking is completed. The dimensions of protrusions (stud) and the mating hole form a slip fit. The end of the ultrasonic horn is contoured to the geometric design of the completed stake. The staking operation includes applying high ultrasonic amplitude under low clamping pressure to cause the plastic to flow and form a locking head at temperatures that are typically less than the melting point of the plastic. This process provides tight joints because there is no material spring-back as with cold heading, and it causes only minimal degradation of crystalline materials because the temperatures attained are less than the melting points of the materials.
Influence of rotational speed on the microstructure and mechanical performance of friction-riveted thermosetting composite joints
Published in Welding International, 2018
Natascha Zocoller Borba, Lucian Blaga, Jorge Fernandez dos Santos, Leonardo Bresciani Canto, Sergio de Traglia Amancio-Filho
These technological restrictions were the motivation for developing new joining technologies for multi-material structures. Solid-state techniques with generation of heat based on frictional energy such as friction spot joining (FSpJ) [4–6], friction-based injection clinching joining (F-ICJ) [7], friction staking [8] and friction riveting (FricRiveting) [9] are being employed successfully in the joining of thermoplastic components and/or fibre-reinforced thermoplastic composites and light metal alloys, such as titanium, aluminium and magnesium. The technical feasibility of friction riveting has already been investigated for hybrid joints of non-reinforced thermoplastics such as polycarbonate (PC) [10] and polyether-imide (PEI) [11] joined with rivets of aluminium alloy 2024-T3. Works have also been published concerning joints of glass-fibre reinforced PEI laminate (PEI-GF) [12], poly(ether-ether-ketone) reinforced with short carbon fibres (PEEK-CF) [13], joined with rivets of pure titanium and glass-fibre reinforced polyamide 6 (PA6-GF) joined to aluminium alloy 6056-T6 [14]. However, there has still been little research into the joining of complex systems such as thermosetting composites to metals by means of these processes. Amend et al. [15] applied a laser-based joining technique for joining thermosetting composites to thermoplastic composites, while Huang et al. [16] used a combination of gluing and plastic deformation for joining thin sheets of aluminium alloy A2017P to carbon-fibre reinforced epoxy resin.
Hybrid oxide brain-inspired neuromorphic devices for hardware implementation of artificial intelligence
Published in Science and Technology of Advanced Materials, 2021
Jingrui Wang, Xia Zhuge, Fei Zhuge
A SiO2/Ta2O5 heterojunction has been designed to control the rupture of Ag filaments [107]. The growth direction of the filaments is controlled by the SiO2 layer and the filament rupture is controlled by the ultrathin Ta2O5 layer. After the initial electroforming process, the subsequent formation/rupture of Ag filaments is confined in the Ta2O5 layer, thus leading to low operation voltages and high stability and uniformity of resistive switching. It has also been found that the staking sequence of different oxide layers has significant influence on resistive switching characteristics of oxide memristors based on metal filaments. As an example, Ag/SnO2/InGaZnOx/Pt and Ag/InGaZnOx/SnO2/Pt devices demonstrate typical bipolar and unipolar resistive switching, respectively [108]. The difference of the switching mode is attributed to different migration or diffusion rates of Ag ions in SnO2 and InGaZnOx. Compared to single layered SnO2 and InGaZnOx devices, both bilayered devices present low operation voltages, high ON/OFF ratios and excellent endurance and retention characteristics. It deserves mention that compared to unipolar operation mode, bipolar mode is preferable for synapse applications given better endurance performance [109]. The reason is explained as follows. If the device is RESET under a voltage bias with the same polarity as that during the SET process (unipolar mode), metal ions will gather again on the tip of the remaining filament resulting in an increase of the concentration of metal ions in the disconnected region. Therefore, the device cannot retain the OFF-state after repeated operations. In contrast, when the device is RESET under a voltage bias with the opposite polarity (bipolar mode), the RESET operation will promote the migration of metal ions away from the remaining filament, thus reducing the metal ion concentration in the disconnected region. In addition, a battery-like architecture of LiCoO2/SiOx/TiO2 has been proposed to mimic biorealistic synaptic behaviour [110]. LiCoO2, SiOx and TiO2 act as a resistive switching cathode layer, an electrolyte layer and an anode layer, respectively (Figure 3(a)). This device shows analog resistance modulation based on voltage-driven regulation of Li ion concentration in the cathode and anode layers. Synaptic plasticity including short-term potentiation/depression (STP/STD), long-term potentiation/depression (LTP/LTD) and spike-timing-dependent plasticity (STDP) is controlled by the Li ion concentration and its relaxation dynamics (Figure 3(b,c)).