Search

Multi-point die electromagnetic incremental forming is a novel forming method, which is aimed at large-sized sheet metal forming combining electromagnetic incremental forming with multi-point die. The multi-point die can form different curved surfaces without replacing the die; as a result, multi-point die electromagnetic incremental forming can form large-sized workpieces with different curved shapes. A finite element model of multi-point die electromagnetic incremental forming is established. The deformation process of large-sized workpieces is discussed during the first discharge of coil. The influence of multistep forming on the forming quality of sheet metals is explained. Simulation results are basically consistent with the experimental ones. The feasibility of this technology is verified through the experiment of multi-point electromagnetic incremental forming.

To refine the microstructure and improve the mechanical properties of AZ91D alloy by expendable pattern shell casting (EPSC), the mechanical vibration method was applied in the solidification process of the alloy. The effects of amplitude and pouring temperature on microstructure and mechanical properties of AZ91D magnesium alloy were studied. The results indicated that the mechanical vibration remarkably improved the sizes, morphologies and distributions of the primary α-Mg phase and β-Mg17Al12 phase, and the densification and tensile properties of the AZ91D alloy. With an increase in amplitude, the microstructures were gradually refined, resulting in a continuous increase in mechanical properties of the AZ91D alloy. While, with the increase of pouring temperature, the microstructures were continuously coarsened, leading to an obvious decrease of the mechanical properties. The tensile strength and yield strength of the AZ91D alloy with a vibration amplitude of 1.0 mm and a pouring temperature of 730 °C were 60% and 38% higher than those of the alloy without vibration, respectively.

The effect of pouring temperature on microstructure and bonding properties of the Mg/aluminised steel bimetallic castings prepared by the solid–liquid compound casting process was investigated in t...

Porous Al2O3 ceramic microspheres were prepared by a novel micro-droplet jetting rapid forming method using a polyvinyl alcohol (PVA) solution as a binder and a boric acid as a curing agent. The droplet jetting and slurry curing procedures are mainly responsible for the uniformity and production rate of the Al2O3 ceramic microspheres during this novel method. A slurry with a PVA content of 3 wt % and a solid loading of 45 vol % exhibited a high solid loading and a low viscosity, and it was suitable for the droplet jetting process. The curing process was determined by the cross-linking reaction between the boric acid and PVA, and the Al2O3 ceramic microsphere green bodies had a good and stable formability with a boric acid content of 10 wt %. The size of sintered Al2O3 ceramic microspheres with a good sphericity was precisely controlled in a small range. Furthermore, the sintering temperature had a significant effect on the performance of the Al2O3 ceramic microspheres. With a sintering temperature of 1400 °C for 3 h, the Al2O3 ceramic microspheres with a uniform microstructure were obtained, exhibiting superior performances that include a grain size below 5 μm, a sintered shrinkage of 6.67%, a relative density of 82.1%, an open porosity of 10.6% as well as a crush load of 76 N.

Modeling and simulation of the morphology evolution of immiscible polymer blends during injection molding is crucial for predicting and tailoring the products’ performance. This paper reviews the state-of-the-art progress in the multiscale modeling and simulation of injection molding of polymer blends. Technological development of the injection molding simulation on a macroscale was surveyed in detail. The aspects of various models for morphology evolution on a mesoscale during injection molding were discussed. The current scale-bridging strategies between macroscopic mold-filling flow and mesoscopic morphology evolution, as well as the pros and cons of the solutions, were analyzed and compared. Finally, a comprehensive summary of the above models is presented, along with the outlook for future research in this field.

The morphology of polymer blends plays a critical role in determining the properties of the blends and performance of resulting injection-molded parts. However, it is currently impossible to predict the morphology evolution during injection molding and the final micro-structure of the molded parts, as the existing models for the morphology evolution of polymer blends are still limited to a few simple flow fields. To fill this gap, this paper proposed a novel model for droplet morphology evolution during the mold filling process of polymer blends by coupling the models on macro- and meso-scales. The proposed model was verified by the injection molding experiment of PP/POE blends. The predicted curve of mold cavity pressure during filling process agreed precisely with the data of the corresponding pressure sensors. On the other hand, the model successfully tracked the moving trajectory and simulated morphology evolution of the droplets during the mold-filling process. After mold-filling ended, the simulation results of the final morphology of the droplets were consistent with the observations of the scanning electron microscope (SEM) experiment. Moreover, this study revealed the underlying mechanism of the droplet morphology evolution through the force analysis on the droplet. It is validated that the present model is a qualified tool for simulating the morphology evolution of polymer blends during injection molding and predicting the final microstructure of the products.

Tea waste biochar (TWBC) was prepared at 300℃, 500℃, and 700℃ under oxygen-limited atmosphere, and was characterized by elemental analysis, Brunauer-Emmett-Teller measurement, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. TWBC was then used to remove tetracycline from aqueous solution. The influences of solid-to-liquid ratio, pH, ionic types, and strength were investigated. The potential mechanism between tetracycline and TWBC was also explored. The results showed that the proper solid-to-liquid ratio was 4 g·L

This paper explores a compound forming method of the cylindrical drawing by using the servo press forming combined with the electromagnetic pulse-assisted incremental drawing. The method comprises four steps: the punch press pre-drawing, electromagnetic pulse-assisted incremental drawing, punch shaping, and the final continuous punch drawing. By applying the four steps sequentially, the good drawing performance was achieved, and the maximum drawing height was of 3.4 times compared with that of the conventional punch drawing process, without changing the diameter of the punch. During the electromagnetic pulse-assisted incremental drawing process, the drawing coils, the corner coils, and the upper and bottom auxiliary coils generate the electromagnetic pulse force to help achieve the drawing of the metal sheet. The electromagnetic pulse-assisted incremental drawing step and the punch press deforming step were alternately carried out. In the electromagnetic pulse drawing step, by applying a two-time discharge using 13 and 14 kV in turn, the height of the drawing was improved, and the thinning rate of sheet metal was reduced. The application of the servo press and the computer numerical control system in the electromagnetic pulse-assisted incremental drawing process can effectively improve the processing efficiency and provides technical basis for the intelligent control of the electromagnetic pulse-assisted incremental drawing process.

The Al/Mg bimetal was fabricated by using the lost foam casting method that is considered a near-net forming process, and the microstructure evolution of the Al/Mg bimetal from different cross section locations of the bimetal was investigated in the present work. An obvious interface layer generated in the middle of the aluminum and magnesium, which showed a variation for different cross section locations of the bimetal. The interface layer at the bottom cross section location had a maximum thickness, wherein a big gap was observed. The thicknesses of the interface layer gradually decreased from the bottom location to the top location. At the middle cross section location, the interface layer was uniform and compact. In contrast, the non-uniform interface layer was obtained at the top cross section location, and the partial location had no the interface layer. The interface layers at the bottom and middle locations consisted of three reaction layers including the Al12Mg17 + δ-Mg, the Al12Mg17 + Mg...

This paper discusses mechanical digital servo press control system and operating characteristics and adaptability to the hot forming requirements of high strength steel using the toggle mechanical presses [1-4]. A servo motor drive control strategy is made to adapt the stamping process. This paper describes results acquired by applying toggle mechanical servo press developed by author to the hot forming of high strength steel [5-7].

In order to solve the difficult problem of detection of pitch deviations of high-precision master gears, a new measuring instrument is developed. Detail description about measuring apparatus of pitch deviations developed for master gears was presented in the paper. Computer aided technology was used to deal with data collected by computer, and error analysis about the measuring apparatus was introduced, which affected measurement accuracy. The results confirm that the measuring apparatus is able to meet measurement requirement and improve efficiency through the measuring experiments on master gears of precision grade 2 and 1 with modulus 2 mm and 2.5 mm, respectively. And the uncertainties of single pitch deviation and total cumulative pitch deviation are 0.07and 0.26, respectively.

Due to the heterogeneity of metal distribution, it is challenging to identify the speciation, source and fate of metals in solid samples at micro scales. To overcome these challenges single particles of air pollution control residues were detected in situ by synchrotron microprobe after each step of chemical extraction and analyzed by multivariate statistical analysis. Results showed that Pb, Cu and Zn co-existed as acid soluble fractions during chemical extraction, regardless of their individual distribution as chlorides or oxides in the raw particles. Besides the forms of Fe2O3, MnO2 and FeCr2O4, Fe, Mn, Cr and Ni were closely associated with each other, mainly as reducible fractions. In addition, the two groups of metals had interrelations with the Si-containing insoluble matrix. The binding could not be directly detected by micro-X-ray diffraction (μ-XRD) and XRD, suggesting their partial existence as amorphous forms or in the solid solution. The combined method on single particles can effectively determine metallic multi-associations and various extraction behaviors that could not be identified by XRD, μ-XRD or X-ray absorption spectroscopy. The results are useful for further source identification and migration tracing of heavy metals.

The photoluminescent and electroluminescent characteristics of a blend polymer system consisting of a novel fluorene-carbazole copolymer (PFC) and poly(vinylcarbazole) (PVK) were investigated. Three OLED devices with the structures of indium-tin-oxide (ITO)/PVK:PFC/bathocuproine(BCP)/tris-(8-hydroxylquinoline)-aluminum (Alq3)/Mg∶Ag, indium-tin-oxide(ITO)/PFC/bathocuproine(BCP)/Alq3/Mg∶Ag and indium-tin-oxide(ITO)/PVK/ bathocuproine(BCP)/Alq3/Mg∶Ag respectively, were fabricated. The optoelectronic properties of the devices were measured. The results demonstrated that PVK in the blend system effectively restrained the formation of PFC excimers in solid films. Light emission of the device with blend system shifted with the variation of applied electric field, and variable color ranging from green to blue could be obtained. The luminance of blue light reached 1650cd/m2 when the drive voltage was higher than 7V. It was inferred that an energy transfer process from PVK to PFC might have occurred in this blend system.

Source characterization of heavy metals is prerequisite to assessing their potential contamination pathways and environmental risks, based on which pollution control and environmental remediation measures can be properly targeted. In the present study, recent progress in methodologies of source identification of heavy metals in solid waste are summarized. The key scientific concerns related to these methodologies based on the total contents, chemical speciation, isotopic composition, and single-particle signature are also discussed. Finally, prospective research with regard to source identification of heavy metals in solid waste is discussed according to current research conditions and progress.

Cracks frequently occur in conventional cylindrical deep drawing process due to the lower formability of aluminum alloy sheet at room temperature. Therefore, a new approach named electromagnetic pulse assisted progressive deep drawing is proposed in this paper. This method gains the radial electromagnetic force which helps to push the sheet metal in radial direction by placing the circular thrust coil upon and underneath the flange, while gaining the axial electromagnetic force by placing drawing coil in the bottom of the punch. The results shows that the placement of the radial thrust coil has significant effect on the sheet metal's state and distribution of stress-strain; In addition, the interaction of the axial drawing force and the radial thrusting force has great effect on the depth of the deep drawing cylindrical parts.