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Hole-making for Carbon Fiber Reinforced Plastics (CFRP)/Ti-6Al-4 V stacks is crucial for the assembling strength of aircraft structure parts. This work carried out experimental work for helical milling (HM) of the stacks with sustainable cooling/lubrication (dry, MQL and cryogenic) conditions. Cutting forces and temperatures at the CFRP layer, Ti-6Al-4 V layer and the interface of stacks were obtained by a developed measuring system. The temperatures in CFRP machining at cryogenic condition varied from −167 °C to −94 °C, which were much lower than those at dry and MQL conditions. The maximum temperature near the interface of stacks for the ninth hole was higher than 240 °C due to heat conduction from Ti-6Al-4 V layer. The hole quality, hole diameter and tool wear mechanism at different cooling/lubrication conditions were presented and discussed. MQL condition generated mainly extrusion fracture for the fibers, due to the reduced friction effect compared with dry condition. MQL was helpful to reduce the feed mark at the hole surface of Ti-6Al-4 V alloy. The flank wear of cutting edge at MQL condition was better than those at dry and cryogenic conditions. Cryogenic cooling contributed to better CFRP surface with smaller delamination and hole entrance damage due to the increased resin strength and fiber brittleness. The damage near the entrance of CFRP were analyzed by the contact state of cutting edges and fibers. Additionally, hole diameters near the exit of CFPR layer were larger than other test positions. This work provided feasible processes for improving hole quality and tool life in hole-making of CFRP/Ti-6Al-4 V stacks.

Ti6Al4V alloy is the typical difficult-to-machine materials and often result in rapid tool wear, leading to poor machining quality in aircraft assembling. Compared to conventional helical milling, the ultrasonic assistant helical milling (UAHM) process has indicated its superior performance, however it is still a great challenge to improve the hole surface quality and accuracy. In addition, few studies has been conducted on the effect of different variables and cooling strategies on the hole-making performance in longitudinal-torsional ultrasonic assisted helical milling (LT-UAHM). This work mainly aims to investigate the surface finish and accuracy of the holes machined in LT-UAHM of Ti6Al4V alloy. The design approach of Taguchi experiment was employed to study how major variables such as the cutting speed, tangential feed, axial feed and the workpiece hardness influence the dimensional and geometrical tolerances and surface roughness. This paper also discussed the effect of three cooling strategies, i.e. dry condition, air coolant and minimum quantity lubrication (MQL) in LT-UAHM. Theoretical analysis demonstrated that the MQL coolant can be nebulized into hyper-fine droplets owing to the resonant cavitation phenomenon. Combined with the penetrating action caused by the separate-cutting principles of LT-UAHM, the cooling and lubrication performance of MQL was further enhanced. As a result, MQL&LT-UAHM had the most positive effect on circularity, cylindricity, nominal diameter and surface roughness, contributing to 34%, 32%, 39% and 40%, respectively. The second important machining factor was the cutting speed, contributing to 31%, 29%, 36% and 22%, respectively. The tangential feed and workpiece hardness have the negative effect on geometrical accuracy, respectively.

Helical milling (HM), axial ultrasonic vibration helical milling (A-UVHM) and longitudinal and torsional ultrasonic vibration helical milling (LT-UVHM) were developed for hole-making of Carbon Fiber Reinforced Plastic (CFRP) composites. Cutting trajectory, cutting speed, acceleration and effective rake angle of peripheral edge in HM and UVHM processes were modeled. Compared with HM, axial forces with UVHM processes were reduced by 9.0 %–35.7 %. The burrs at entrance and exit with UVHM were also reduced. In A-UVHM and LT-UVHM processes, an effect of shear with variable direction which is good to fracture fibers was presented, according to the relative movement of peripheral edge and fibers. Additionally, the variations of cutting speed and acceleration in A-UVHM and LT-UVHM are also helpful to fracture fibers, due to the wide range of speed and impact effect. Smooth surface with regular fiber fracture morphology and tiny fragments was generated in UVHM due to the effect of shear along variable direction. Compared with HM, the maximum effective rake angle of peripheral edge in UVHM was increased by 112.1 %–192.6 %, which is helpful to fracture fibers by sharper cutting edge.

Compared with conventional hole-making process, rotary ultrasonic machining (RUM) is commonly believed to improve the cutting performance, such as low cutting force, good hole quality, long tool life, and high material removal rate. However, this work proposes an interesting observation on hole-making process using longitude-torsional ultrasonic assisted helical milling (LT UAHM). Due to the special kinematic motion in LT UAHM, the trajectory of the cutting tool has complex characteristics which may generate a negative effect on machining performance. In this study, a comparative experiment between LT UAHM and conventional helical milling (HM) was carried out. The results showed that the axial cutting force is not always reduced, the machined hole quality is also not improved consistently in LT UAHM. To comprehend the cutting mechanism of LT UAHM incisively, a kinematic trajectory model was proposed. By the theoretical kinematic trajectory model, LT UAHM can generate the ultrasonic elliptical cutting in the process, and the phase shift is a critical factor that can affect the elliptical trajectory shape even the vibration cutting direction of the tool’s cutting edge. The equivalent cutting angle and direction of friction between the rake face and chip in processing change accordingly. As a result, the magnitude of cutting force and machined hole quality in terms of burr height in this process will be significantly affected.

Summary The aim of this study was to assess the effects of power ultrasound-assisted (0, 400, 600, 800 and 1000 W, frequency of 20 kHz) cooking (80, 100, 120 min) on spiced beef. The results showed that power ultrasound could significantly increase the salt content (P 0.05). As for microstructure, the myofibrils of beef were ruptured by ultrasonic treatment along with the Z-lines leading to the muscle swelling. The results indicated that the application of ultrasound during cooking could effectively promote the penetration of salt, improve the water holding capacity and ameliorate the tenderness of spiced beef.

A fuel cell-electrolyzer series device with monoethanolamine (MEA) as fuel in the fuel cell and MEA-containing electrolyte in the electrolyzer is developed. The fuel cell stack directly powers the electrolyzer. As a result, MEA is degraded electrochemically in the anode sides of both fuel cell and electrolyzer, while high value-added H2 is produced in the cathode side of electrolyzer with a little supplied power or even without any. This work firstly screens out Au as the best-performing electrocatalyst for MEA electrooxidation. Following this, Au–Ni bimetals coated on nickel foam (Au–Ni@Ni foam) are prepared by the facile electrodeposition. An Au–Ni@Ni foam electrode with the optimized electrodeposition time of 30 min exerts a considerable area current of 27.2 mA cm−2, Au mass current of 58.1 A g−1 and onset potential of −0.44 V vs. Ag/AgCl in 1.0 mol L−1 KOH and 0.05 mol L−1 MEA. The electrochemical tests companied with the physico-chemical characterizations elucidate the monometallic-state Au, rather than its alloy-state, benefits the MEA electrooxidation. Tests finally show such fuel cell-electrolyzer series device equipped with Au–Ni@Ni foam anodes operates well in bench scale, which accordingly proves the device to be a tenable and smart strategy for simultaneous MEA degradation and resource recovery.

The aim of this study was to evaluate the effects of power ultrasound intensity (PUS, 2.39, 6.23, 11.32 and 20.96Wcm(-2)) and treatment time (30, 60, 90 and 120min) on the oxidation and structure of beef proteins during the brining procedure with 6% NaCl concentration. The investigation was conducted with an ultrasonic generator with the frequency of 20kHz and fresh beef at 48h after slaughter. Analysis of TBARS (Thiobarbituric acid reactive substances) contents showed that PUS treatment significantly increased the extent of lipid oxidation compared to static brining (P

For prolonging the shelf life of spiced beef during cold storage without destroying quality characteristics, ultrasonic-assisted cooking was applied in current study. Total viable count (TVC), the thiobarbituric acid reactive substances (TBARS), total volatile basic nitrogen (TVB-N), pH, texture profile, color and electronic nose data were determined. Results showed that ultrasonic-assisted cooking significantly decreased the TVC, TBARS and TVB-N values of spiced beef during cold storage. The decrease of pH, hardness and chewiness values and the time of flavor deterioration were slowed down during cold storage. As for color, ultrasound-assisted cooking delayed the decline of a* values but decreased the L* values during cold storage. In addition, hardness, chewiness and L* values showed a downward trend as the increase of ultrasonic power. These findings demonstrated that ultrasonic-assisted cooking was a potential way to maintain quality profiles and extend the shelf life of spiced beef.

Surface integrity of hole-making for Ti-6Al-4 V alloy is very important due to its application in aviation industry. Geometrical and mechanical behaviors of machined holes by helical milling (HM) and ultrasonic vibration helical milling (UVHM) were investigated. The textures of machined holes by the two processes were analyzed and the distances of adjacent textures were calculated according to the movement of peripheral edges. Due to the different surface geometrical textures, the hole-diameter error and surface roughness in UVHM are smaller than those of HM. A plastic deformation layer with thickness of 4–6 μm was observed by the distorted β phase in the cross-section of hole-surface in UVHM by SEM results. Compared with HM process, UVHM generates larger hardness at the subsurface of machined holes (20–200 μm) due to the material deformation caused by ultrasonic vibration. Compared with HM, the compressive residual stress of hole surface was increased larger than 63.5% by UVHM. The compressive stresses in UVHM are larger than 150 MPa at the depth less than 10 μm, which is consistent with the microstructure evolution caused by mechanical deformation.

In this investigation, samples were treated by ultrasonic probe (20 kHz) at an intensity of 25 W cm−2 for 20 or 40 min, followed by aging at 4 °C for 1, 3 and 7 d. Ultrasound treatment significantly increased myofibrillar fragmentation index (MFI) and decreased Warner-Bratzler shear force (WBSF) at 3 and 7 d of postmortem aging (P