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In order to investigate the formability of the granular medium forming (GMF) based on the Mohr–Coulomb constitutive model with the tri-axial compression test of granular medium and the true stress–strain curves of TA1 titanium alloy from uniaxial tensile tests, the numerical simulation of TA1 titanium alloy sheet deep drawing with finite element method was performed, and the deep drawing tests were also carried out. Simulation analysis and test results show that the GMF process is suitable for titanium alloy sheets and can effectively improve the uniformity of the wall thickness of the formed parts, reduce the tendency of wrinkles, and improve the forming quality.

Hollow mesoporous nanospheres MoO

In order to investigate the formability of the granular medium forming (GMF), based on the Mohr-Coulomb constitutive model with the tri-axial compression test of granular medium and the true stress-strain curves of TA1 titanium alloy from uniaxial tensile tests, the numerical simulation of TA1 titanium alloy sheet deep drawing with finite element method was performed, and the deep drawing tests were also carried out. Simulation analysis and test results show that the GMF process is suitable for titanium alloy sheets, and can effectively improve the uniformity of the wall thickness of the formed parts, reduce the tendency of wrinkles and improve the forming quality.

Reinforced vermicular graphite cast irons were prepared by using aluminum precursor master alloy containing TiC-TiB2 nanoparticles. It was found that the vermicularity and amount of graphite increased by 15.0% and 16.6%, and grain size decreased by 32.9%. The yield strength, tensile strength and elongation were improved by 10.0%, 6.0% and 26.3% at a temperature of 20 °C, and 11.6%, 6.8% and 22.1% at a temperature of 150 °C. In addition, the wear volume loss was reduced by 18.0% by addition of the nanoparticles.

In order to predict the wrinkling of sheet metal under the influence of fluid pressure and temperature during warm/hot hydroforming, a numerical simulation model for sheet wrinkling prediction was established, taking into account through-thickness normal stress induced by fluid pressure. From simulations using linear and quadratic elements, respectively, it was found that the latter gave results that were much closer to experimental data. A novel experimental method based on an improved Yoshida Buckling Test (YBT) was proposed for testing the wrinkling properties of sheets under the through-thickness normal stress. A wrinkling coefficient suitable for predicting wrinkling was also presented. Based on the numerical simulations, an experimental validation of wrinkling performance was conducted. Ridge-height curves measured along the main diagonal tensile direction of the sheet were presented and showed that the wrinkling prediction criterion provided good discrimination. Furthermore, the wrinkling properties of several different materials were simulated to evaluate the accuracy of the prediction method, and the results revealed that the improved YBT gave good predictions for wrinkling in the conventional sheet metal forming process, while the prediction results for wrinkling in warm/hot sheet hydroforming were also accurate with the fluid pressure of zero.

Hollow mesoporous nanospheres MoO2/C are successfully constructed through metal chelating reaction between molybdenum acetylacetone and glycerol as well as the Kirkendall effect induced by diammonium hydrogen phosphate. MoO2 nanoparticles coupled by amorphous carbon are assembled to unique zigzag-like hollow mesoporous nanosphere with large specific surface area of 147.7 m2 g−1 and main pore size of 8.7 nm. The content of carbon is 9.1%. As anode material for lithium-ion batteries, the composite shows high specific capacity and excellent cycling performance. At 0.2 A g−1, average discharge capacity stabilizes at 1092 mAh g−1. At 1 A g−1 after 700 cycles, the discharge capacity still reaches 512 mAh g−1. Impressively, the composite preserves intact after 700 cycles. Even at 5 A g−1, the discharge capacity can reach 321 mAh g−1, exhibiting superior rate capability. Various kinetics analyses demonstrate that in electrochemical reaction, the proportion of the surface capacitive effect is higher, and the composite has relatively high diffusion coefficient of Li ions and fast faradic reaction kinetics. Excellent lithium storge performance is attributed to the synergistic effect of zigzag-like hollow mesoporous nanosphere and amorphous carbon, which improves reaction kinetics, structure stability and electronic conductivity of MoO2. The present work provides a new useful structure design strategy for advanced energy storage application of MoO2.

The current research investigated the microstructure and tensile properties of as-cast low carbon steels manipulated by TiC-TiB2 nanoparticles. It was found that the microstructure mainly contained blocky ferrite and pearlite. Widmanstatten structure consisting of acicular ferrite was also obtained in the matrix of unmodified low carbon steels. After introducing 0.01 wt% and 0.02 wt% TiC-TiB2 nanoparticles, the formation of widmanstatten structure was inhibited. The pearlite content increased from 26.3% to 36% and 36.7% respectively. The grain size reduced from 58.3 μm to 43.3 μm and 42.8 μm. For tensile properties, the yield strength, tensile strength and elongation of low carbon steels increased by 9.8%, 7.6%, 20.4% and 14.0%, 11.0% and 8.2%. The as-cast microstructure was refined since the nanoparticles act as heterogenous cores to promote the nucleation rate and hinder the growth of grains. The improved strength could be associated with the fine-grain, thermal-mismatch and dispersion strengthening mechanisms, and the improved ductility could be associated with the fine microstructure and scattering effects of nanoparticles.

To obtain the stress states of the sheet metal and understand the potential forming mechanism under the influences of fluid pressure and temperature during the warm hydroforming of 5A06-O aluminum alloy sheets, mechanics analysis was conducted for the warm hydromechanical deep drawing of a cylindrical cup, taking into account through-thickness normal stress induced by fluid pressure. By considering the additional stress during bending using a variable-stiffness pure bending model as equal to that determined using a bending moment model, the additional stress at the die corner during bending was solved. The force equilibrium equations for the cup near the die corner, which were classified by whether the blank contacted the die, were also established and the results were in good agreement with those obtained via the finite element method. Furthermore, mechanics analysis was also performed for the straight-wall region, and the results revealed that the error was slightly greater when the liquid pressure was used to approximately equal to through-thickness normal stress because the ratio of thickness to radius was not sufficiently large.

Confirmation of material properties is an important research area for determining metals deformation behavior. In order to research the effect of flow stress calculation on aluminum alloy sheet deformation behavior, warm sheet bulging test was carried out to obtain bulging height - pressure curves with different bulging heights and diameters in this study. Based on the bulging parts profile data measured by three coordinate measuring machine, the least square circle fitting radius were fitted. Existing theoretical models for radius of curvature and thickness were compared and best models were selected to obtain more accurate stress — strain curves by calculating the bulging flow stress. Combination model was used to calculate the bulging height — pressure curves obtained by bulging test and the stress-strain curves with different temperatures and pressure rates were obtained. A monotonous increasing function was resulted which is of great significance in the area of formability and deformation behavior of warm sheet hydroforming.

The formability can be improved in warm/hot sheet hydroforming due to two important factors of temperature and through thickness normal stress. An extension of the M-K model was presented in this paper with the liquid pressure induced through thickness normal stress taken into account. The through thickness normal stress was introduced by using the general form of the Hill48 criterion. The combined effect of temperature and through thickness normal stress on the increase of FLD0 is achieved by applying a proposed temperature dependent constitutive equation for 5A06 aluminum alloy (a Chinese designation of Al-Mg alloy, corresponding to the ASTM designation of 5056 aluminum alloy) into the M-K approach. The Newton–Raphson method is used in the numerical procedure and it is proved to be stable and correct. The yield loci show a significant dependence on temperature and through thickness normal stress. Both size shrinking caused by the elevated temperature and location shifting due to the increasing thickness normal stress of the yield loci are observed. Comparison of the experimental FLDs of AISI-1012 low carbon steel (an AISI designation of steel) at plane stress and room temperature, STKM-11A steel (a Japanese designation of Steel Tube Kozo Machine) for tube hydroforming at room temperature and 5A90 aluminum alloy (a Chinese designation of Al-Li alloy) at plane stress and elevated temperature with the theoretical results show good agreements. The effect of key parameters, such as inhomogeneity factor f0, n value, m value and initial thickness T0, grain size d, initial surface roughness R0, show a strong dependence on FLDs and increase of FLD0. The increase of FLD0 is formulized in a full quadratic form, which is a function of temperature and through thickness normal stress. The left quadrant of FLD was determined by the cylindrical warm hydromechanical cup deep drawing, which shows a good accordance with the predicted results by using the modified M-K model.

Warm/hot sheet bulging tests of 2A16-O aluminum alloy were conducted using elliptical bulging dies under various temperatures and pressure rates, in an effort to investigate the macroscopic and microscopic influence of the pressure rate on the formability and microstructural evolution of hydrobulging parts during warm/hot sheet hydroforming. The results revealed that the forming limit of the aluminum alloy was clearly influenced by the pressure rate as the temperature rose, wherein a lower pressure rate resulted in a higher forming limit. Metallographic observations and Energy Dispersive Spectrometer (EDS) analysis revealed no obvious influence of the pressure rate on the microstructure of hydrobulging parts after warm/hot sheet hydroforming. This study demonstrates that warm/hot sheet hydroforming of aluminum alloy may lead to an improved forming limit and inhibit microstructural degradation during processing.

The rate of fluid pressure variation is a crucial factor to indicate the forming speed and the pressure rate is applied to be one factor that can influence the deformation of material in warm sheet hydroforming. In this study, warm bulging test was conducted to obtain bulging pressure-height curves with different temperatures and pressure rates. Fitting the bulging pressure-equivalent strain curves obtained using bulging test with surface fitting method, the fitted equation of bulging pressure on equivalent strain and pressure rate was achieved, and the fitting result shows a good accordance with experimental and calculated values. Then, the relation between pressure rate and strain rate was obtained. The results of warm bulging test indicated that the deformation behavior of metal material is sensitive to pressure rate, which is of great significance for warm sheet hydroforming.

Lightweight materials, such as ultra-high strength steel, titanium alloys and aluminum alloys, are used widely in aerospace and automobile industries leading to increasing demands for advanced forming technologies. Recently many innovative sheet- and tube-forming methods have been proposed by researchers and R&D facilities around the word. These methods can greatly improve the formability of materials with low plasticity and can produce complex-shaped parts with good surface qualities. This review aims at providing an insight into the latest developments of particular sheet- or tubular-metal forming process and shows basic applications in modern industry.