Investigations have revealed that size effect obviously affects forming quality and accuracy of micro parts. However, to find effective approaches that can reduce the influence of size effect is still a critical problem to be solved. Ultrasonic vibration has been widely used in industrial metal forming recently, and it has been proved that it is helpful for improving section quality compared with conventional blanking. In this study, micro-blanking process was carried out with a specially developed device. The square holes of copper foil T2 were investigated by analyzing the evolution of microstructure, crack initiation, quality of shearing surface, etc. Inhibition of crack initiation is found due to the softening effect in ultrasonic vibration assisted micro-blanking by analyzing section obtained under different ratios of blanking stroke to thickness (h/t), which increases the ratio of smooth zone. The analysis of microstructure in deformation area shows that a shearing deformation area becomes smaller, and radius of fillet decreases. Surface roughness of smooth zone decreases with ultrasonic vibration due to polishing effect. Compared with traditional micro-blanking, this compound plastic forming technology applying ultrasonic vibration on the punch can improve the section surface quality by increasing the ratio of smooth zone, and decreasing the surface roughness and fillet radius. The experimental outcomes reveal the mechanism of shearing deformation behavior during ultrasonic vibration assisted micro-blanking process of copper foil and the findings confirm that ultrasonic vibration can be regarded as a way to improve the forming quality of micro-blanking.

Size effects on plastic deformation behaviors in uniaxial micro tension of pure nickel fine wires were investigated experimentally, including flow stress and inhomogeneous deformation behaviors. It is found that with the increase of grain size or the decrease of number of grains across the diameter, the flow stress decreases and inhomogeneous deformation degree increases. When there are less than 9.3 grains across the diameter, the flow stress decreases quickly with the increase of grain size. Then, the flow stress size effect in micro tension of fine wires is revealed by a proposed model by introducing the grain boundary size factor. These results also indicate that both the fracture strain and stress decrease with the increase of grain size. When there are less than 14.7 grains across the diameter, both the fracture strain and stress decrease quickly. This indicates that the inhomogeneous deformation degree in micro tension increases with the decrease of the number of grains across the diameter. The fracture topography tends to be more and more irregular with the decrease of the number of grains across the diameter. Then, the formation mechanism of irregular fracture topography was analyzed considering the inhomogeneous distribution of microstructure when there are a few grains across the diameter.

•Erecting a comprehensive emergy frame evaluating bio-hydrogen-tech industrialization.•Realizing the numerical calculation of the comprehensive efficiency evaluation model.•Distinguishing human-capital, policy-aid and resource-structure in the business case.•Fermentative-organic-wastewater bio-hydrogen is more sustainable.Focusing on the incompatible measurement of the environment property, resources property and economy property, the article aims to make a generalized environment-resource-economy analysis of the processes and to present an overview of different biohydrogen production technologies from the standpoint of the mass production and the whole commercialization chain. One part of the model is the emergy comprehensive efficiency index calculation model, the other is the ternary diagram of structure coefficient for emergy input. The model is used to the organic wastewater of the biohydrogen industrialization demonstration project, and then compared with other biohydrogen and typical renewable energy production technologies. The outputs indicate that the industrialization efficiency of biohydrogen production is available. After the application case of demonstration project, the exploratory work enlightens the similar literature from several aspects. Firstly, the efficiency evaluation model supplies a scientific judgment foundation stone for future laboratory research. Secondly, it provides an alternative theoretical logic to optimize the operation and decision-making of the industrialization and commercialization of the new technologies. Thirdly, it provides a new perspective and quantitative calculation method to effectively integrate that the components comprehensive efficiency of biohydrogen technology change with the different technology processes.

•Uniaxial compression of cylinders with fewer grains across thickness was conducted.•Hall–Petch law is not valid for specimen with fewer grains across thickness.•Competition of free and non-free boundary effects leads to flow stress size effect.•The proposed model is suitable for analysis of size effects in micro compression.Uniaxial compression tests were carried out on pure nickel polycrystals with constant thickness (t) of 1.0 mm and various grain sizes (d). Experimental results show that flow stress does not decrease with grain size continuously according to Hall–Petch law. For specimens with fewer grains across the thickness (t/d less than about 9), the Hall–Petch law is not valid anymore and even an inverse Hall–Petch effect occurs as the t/d ratio decreases from 6.2 to 3.5. The size effects on flow stress were analyzed considering boundary conditions, including free surfaces and constrained external boundaries. Then a model considering both free surface weakening and external boundary strengthening effects was proposed. The competition of free surface weakening and external boundary strengthening effects results in the flow stress size effects in micro-compression. There is a good agreement between the experimental and analytical results.

With the miniaturization of parts, dimensions of parts have obvious effects on friction in microforming processes when liquid lubricants are applied. To eliminate size effects of friction, diamond-like carbon (DLC) film was deposited on the surface of female die and blank holder for its superior tribological characteristics. Strip drawing tests were carried out on conditions of different lubricants, and tribological behaviors of DLC film at female die surface were evaluated using punch load. The results reveal that the specimen dimensions and surface topography of specimen have a little effect on tribological behaviors of DLC film than castor oil. DLC film shows lower coefficient of friction (COF) in large deformation and small dimension. With the increasing of test times, wear of DLC film occurs. Raman spectra indicates that the ratio between integrated intensities of D and G peaks (ID/IG) increases with the increasing of tests times, which means that graphitization of DLC film occurs for the rise of temperature induced by the friction at contact surface. The interesting thing is that H content increases with the times of tests especially for high contact load, which is evaluated by the ratio of the slope m of fitted linear background to the intensity of the G peak (m/IG). The increase of H content means that the number of free hydrogen atoms becomes larger for the breakage of CH bonds induced by the friction work. The graphitization and breakage of CH bonds may have an obvious effect on the tribological behaviors of DLC film in microforming.Highlights► Decreasing of dimension and surface polishing have a little effect on its tribological behaviors of DLC film. ► Graphitization of DLC film becomes more clearly with the increasing of test times. ► A model is developed to analyze the graphitization of DLC film by calculate the friction work. ► DLC coating still contains a certain amount of free hydrogen atoms.

In microscale deformation, the magnitudes of specimen and grain sizes are usually identical, and size-dependent phenomena of deformation behavior occur, namely, size effects. In this study, size effects in microcylindrical compression were investigated experimentally. It was found that, with the increase of grain size and decrease of specimen size, flow stress decreases and inhomogeneous material flow increases. These size effects tend to be more distinct with miniaturization. Thereafter, a modified model considering orientation distribution of surface grains and continuity between surface grains and inner grains is developed to model size effects in microforming. Through finite element simulation, the effects of specimen size, grain size, and orientation of surface grains on the flow stress and inhomogeneous deformation were analyzed. There is a good agreement between experimental and simulation results.

With the miniaturization of the parts, the size effects occur in microforming processes. To investigate the effect of die cavity dimension on the microforming ability of the billets, the coining tests have been carried out with pure aluminum using groove width from 40 to 120 μm at the temperature of 400 °C. The experimental results show that the microforming ability decreases with the increasing of ratio L/b when the ratio L/b is less than 0.5, and the microforming ability increases with increasing of the ratio L/b when the ratio L/b is larger than 0.5. These phenomena might be analyzed from the viewpoint of multi-grain structure of billet. Following that, the isothermal microforming processes of microgears are carried out, and the successful manufacture of the microgears indicates that the billet can fill a very small die cavity completely.