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Copyright of Journal of Nanchang University (Engineering & Technology) is the property of Nanchang University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Magnesium alloy usage in manufacturing engineering components resulting in weight reduction and as a consequence, reduction in fuel and energy consumption. Magnesium has a relatively low density and roughly 30% lighter than aluminum. However, magnesium is considered to be difficult to deform because of theHCP structure. In this present work, the effect of semi-solid forming temperature and heat treatment on mechanical properties of Mg-Al-Zn were investigated. Mg-Al-Zn ingot was machined into a billet and formed with three different temperatures and underwent T4 heat-treatment process. To determine the mechanical properties and microstructure of the magnesium alloy, tensile and hardness test were performed and the result indicates that the highest average maximum tensile stress was achieved at 209 MPa at 530ºC after forming with T4 heat treatment and highest hardness value was at 21.44 HRB at 560ºC. On the other hand, effect of the forming temperature gives impact to the evolution of the microstructure from large grain size (as-cast) to the smaller grains size (0.00797mm2) forming at 560°C. This relate to the extensive dynamic recrystallization (DRX) occurs during forming and Mg-Al-Zn was sensitive with heat either direct or indirect heating method.

Background/aims: The appropriate heating temperature for the fabrication of mouthguards using ethylene vinyl acetate sheets is reported to be 80-120°C. However, the measurement side of the heating temperature has not been determined. The aim of this study was to investigate the influence of the measurement side of the heating temperature when fabricating mouthguards.Materials and Methods: Mouthguard sheets of 3.8 mm ethylene vinyl acetate were vacuum-formed on working models until the sheet was heated to 120°C. The sheet temperature was measured at the upper side and the lower side. The thickness of the mouthguard was measured at the labial surface of the central incisor, and the buccal and occlusal surfaces of the first molar. The fit of the mouthguard was examined at the central incisor and the first molar by measuring the distance between the mouthguard and the cervical margin of the working model. Differences in the thickness and fit of the mouthguards were analyzed by two-way analysis of variance.Results: Mouthguard thickness varied among the measured regions of the central incisors and first molars (P < .01). The thicknesses at the labial surface of the central incisor and buccal surface of the first molar were larger when the sheet temperature measured at the lower side was 120°C compared to when the sheet temperature measured at the upper side was 120°C (P < .01). The fit of the mouthguard was better when the sheet temperature measured at the lower side was 120°C (P < .05).Conclusions: The sheet temperature should be measured at the lower side of the sheet and it should be 120°C for fabricating mouthguards. [ABSTRACT FROM AUTHOR]

The present work focuses on creating a better understanding of the possibility of forming specific geometric structures from plywood and subsequently develops an improved equation for representing the spring-back phenomenon during the thermoforming process of veneer plywood. Primarily, the formation of multiple bends and their interactions, have been studied with a four-point bending rig. Real-time strains were measured using strain gauges and a kinematic analysis of the macroscopic deformation was carried out through grid strain analysis. It was followed by a geometric conformance study, results of which showed 0.45% deviation from the desired profile angle. Subsequently, a new empirical equation was formulated based on the experimental results using an open-source software, named Eureqa®, to find the change in sector angle after spring-back. The equation was validated by conducting experiments under different conditions and was found to perform well in the forming temperature range of 150–200°C and the pre-forming moisture content range of 20–27.3%. [ABSTRACT FROM AUTHOR]

Micro scale deformational behavior of metals is improved upon increasing the room temperature. Further, the drawbacks of micro forming caused by size effects are reduced significantly. In the current work, investigation on the material behavior of copper at elevated temperature ranging from room temperature to 200 ℃ is conducted. On the experimental part, a novel micro extrusion die set assembly has been developed along with temperature assistance, where the specimen is heated within the die assembly to study deformation behavior. When the forming temperature is raised, an enlargement of the forming limits is achieved along with a significant reduction in extrusion force. Further, the flow of material inside the die orifice was more uniform, and the micro pin showed a good replication of the die dimensions with homogeneous material deformation. During the increase of extrusion temperature and lubrication conditions (diamond-like carbon coating), the micro pin is more complete with higher dimensional accuracy and surface finish. The investigation on the influence of temperature showed that there is a reduction in microhardness of samples compared to the hardness of samples extruded at room temperature. However, there is a significant reduction of scattering due to homogenizing effect. [ABSTRACT FROM AUTHOR]

The present work is focused on the hot deep drawing process for cylindrical 5083 aluminum alloy parts, by superimposing a thermal gradient between the blank center-flange region. The imprtance of application of forming processes at elevated temperatures, in improving the formability, has increasingly attracted attention in recent years. As a case study, the experimental and numerical tests were performed at three speeds (60, 200 and 378 mm min−1) from room temperature (RT) up to 0.9 melting point, inspired by the advent of extraordinary superplastic behavior of AA5083 in hot condition. In particular, the focus was on the effects of forming speed on punch load, thickness distribution, and earing behavior. Finite element simulations were run in order to investigate the limiting drawing ratio and temperature gradient. The tests highlight that by increasing the temperature, the number and the position of the ears are constant, while the height of ears decreases. Furthermore, limiting drawing ratio equal to 2.84 is reached at 550 °C. [ABSTRACT FROM AUTHOR]

The goal of the present work was to create a comprehensive guide to obtain 3-ply veneer laminates with a stable form. More precisely, a single curvature veebending test has been conducted on commercially available radiata pine (Pinus radiata D. Don) veneer plywood, in which the veneer was pre-softened in water. Within the framework of a parametric study, the spring-back and spring-forward of the 3-ply laminates was quantitatively evaluated. The variability and final contributions of each parameter was observed by a statistical data evaluation. The forming temperature and pre-forming moisture content were found to have the highest influences, while the experimental results could be satisfactorily simulated by calculations according to Taguchi. [ABSTRACT FROM AUTHOR]

In order to improve the formability of challenging materials, the innovative flame-heating integration into a spinning machine is proposed to apply new processing strategies for flame-assisted die-less shear and multi-pass metal spinning. The device mainly includes measurement system and control system. The calculating function of control system is designed to adjust the forming temperature according to the feedback of measurement system. TC4 and TA2 are used for shear spinning and multi-pass spinning to verify the feasibility and reliability of the system with the forming temperature 450 and 850 °C respectively. The temperature change during the process of spinning is recorded once a second by temperature sensors. Then the absolute values of mean relative deviations under two conditions are less than 5% by comparing measurement temperatures and preset temperatures. Furthermore, the result shows that the forming accuracy by adopting the system under two conditions is acceptable. [ABSTRACT FROM AUTHOR]

This paper investigated the influences of temperature and grain size on the deformability of pure copper in micro compression process. Based on the dislocation theory, a constitutive model was proposed taking into account the influences of forming temperature, Hall-Petch relationship and surface layer model. Vacuum heat treatment was employed to obtain various grain sizes of cylindrical workpieces, and then laser heating method was applied to heat workpieces during microforming process. Finite element (FE) simulation was also performed, with simulated values agreed well with the experimental results in terms of metal flow stress. Both the FE simulated and experimental results indicate that forming temperature and grain size have a significant influence on the accuracy of the produced product shape and metal flow behaviour in microforming due to the inhomogeneity within the deformed material. The mechanical behaviour of the material is found to be more sensitive to forming temperature when the workpieces are constituted of fine grains. [ABSTRACT FROM AUTHOR]

Temperature is the main effective process parameter in the warm deep drawing (WDD) process to improve the formability of light-weight engineering materials, and this feature requires the accurate measurement and assessment of temperature for process stability. In this study, an evaluation of the WDD process was conducted according to the forming temperature curves (FTCs) characterized from work piece temperatures instead of tool temperatures, as usual. To achieve this goal, a special index material was developed to accurately obtain FTCs from the work piece material under closed and heated tool conditions. The differences of temperature on work piece material are required to define temperatures by curves. The characteristic behavior of these curves was investigated under non-isothermal WDD of AA 5754-O. In the experimentation stage, the process parameters, namely FTC, blank holder force and punch velocity, which assure successful deep drawability, were determined according to the failure-free cups by analyzing wrinkling and tearing conditions and minimum cup height parameters as output parameters. As the next step, optimum conditions were investigated by evaluating the cup volume and spring-back parameters. As a general conclusion, approximately 330°C in the flange-die radius region and 100°C in the cup wall-punch bottom region are the ideal optimum temperatures for the warm deep drawing process. [ABSTRACT FROM AUTHOR]

The stretching tests of the commercial AZ31 Mg alloy were conducted at 130 °C, 170 °C, 210 °C, at the forming speeds of 10 mm/min and 50 mm/min, respectively. The formability of AZ31 sheets at high temperature was evaluated by forming limit diagrams (FLD). The fracture morphologies were analyzed using a scanning electron microscope. The results show that the FLD of AZ31 Mg alloy is affected by the forming temperature, in another word, the formability increases with the increasing of the forming temperature. That may be because the non-basal slip system starts to move by thermal activation at high forming temperature. It is also demonstrated that the formability of the AZ31 Mg alloy is on the decline with the increasing of the forming speed. The slipping performs thoroughly to release the stress during the deformation if the forming speed decreases. In addition, the higher the forming temperature is, the more obvious the effect of the forming speed is. The forming temperature is the main dominating factor on the formability of AZ31 Mg alloy. [ABSTRACT FROM AUTHOR]

Modern approaches to calculating the strength of green compacts by van der Waals forces (σ) are reviewed. Respective components (σ) are calculated and green tensile strength (σ) is experimentally determined for test powders of metals (Al, Zn, Cu, Ni, and Mo) and one nonmetal (FeSi). Comparison of σ/σ ratios shows that σ and σ are of one order for the atomized zinc powder, and σ is greater than σ for the atomized copper powder, though σ is greater than σ by two to three orders for most powders with irregular shape of particles. This difference can be attributed to the effect of shape and mechanical interlocking or seizure of particles when compacted. To predict the green strength, it is necessary to take into account both the shape of particles (or relative apparent density of the powder) and the forming temperature. [ABSTRACT FROM AUTHOR]

Abstract: In magnesium alloy sheet products have been attracting more and more attention in recent years because of their application potentials as coverings of portable electrical devices and automotive panels. However, magnesium alloy sheets are usually formed at temperatures between 250 and 400°C because of their poor plasticity at room temperature, which makes the tooling system quite complex and also the products cost expensive. A proper forming temperature range was determined. The effects of blank holding forces on the workpiece quality were analyzed by warm deep drawing of cups from magnesium alloy sheets. Therefore, appropriate process parameters were selected to avoid forming defects effectively. In the paper, a rigid blank holder was used to adjust blank holding forces. A special liquid lubricant PTFE was used on the tool surfaces. The conditions of process defects as flange wrinkling and ruptures were analyzed. Experiments were carried out to verify the computer simulation results. Efforts were made to optimize process parameters by analyzing the causes of defects in order to improve the Limit Drawing Ratio of magnesium alloy workpieces. Computer simulation with explicit finite element method was used to optimize the process parameters before carrying out the actual experiments. It is found that rolled magnesium alloy sheets have good deep drawing formability at a forming temperature range of 105–170°C with the limit drawing ratio up to 2.6. It is also necessary to control the time of heating blanks. The formability will be reduced severely by excessive heating duration. [Copyright &y& Elsevier]

Different synthesis routes can have different effects upon the properties of materials. In this paper, four different chemical methods: sol–gel acetate method, citric acid method, methanol method and oxalic acid method have been used to prepare BaTiO3 powders.With the help of differential thermal analysis (DTA), X-ray diffraction (XRD) and transmission electron microscope (TEM), the powder characterization has been compared. The results show that for acetate acid and methanol methods the particle size is smaller at 600 °C, but growth rate of particle for oxalic acid method is lowest.In order to find the different routes’ effects upon the sintering behavior, the powder prepared by different methods are pressed into pellets under 3 and 250 MPa, and then sintered at different temperatures. Among all the methods, the powder prepared by acetate acid and ethanol methods are easily to be pressed and higher density is easily to be obtained under 3 MPa, but they show less sensitive to the cold isostatic pressing (250 MPa) compared with oxalic acid and citric acid method. [Copyright &y& Elsevier]

Sustainable green manufacturing forms a critical aspect in the current times, where environmentally clean and renewable material, such as plywood, can be used not only for decorative purpose but also for producing particular profile sections. The goal of the present work is to minimise or eliminate the shape distortion through the spring-back or spring-forward (negative spring-back) phenomenon experienced by plywood during profile forming. Commercially acquired 3-ply laminates were used initially to investigate the influence of forming temperature and in-situ curing time while producing U-sections. Statistical analyses using Taguchi and full Factorial methods were employed for the design of experiments to find the ideal combination of the parameters providing minimal spring-back. Considering the structural integrity and the aesthetic aspect, the ideal values parameters were obtained as the forming temperature being 250 °C and the in-situ curing time being 80 s, giving a spring-back of 2.93°. The results were then applied to achieve sections with multiple 90° bends (top-hat sections) through a chemical-free process, giving an error of about 6% from the statistical study. They were also observed to experience significant spring-forward after curing. These led to the development of a modified forming technique where the top-hat profiles had negligible spring-back or spring-forward (≤ 1 0). • Profile sections of eco-friendly plywood can be successfully formed. • The parameters for chemical-free desirable forming of plywood are established. • U-channels and top-hat sections are formed successfully from plywood. • The change in sector angle is minimised (≤1°) through a novel forming technique. [ABSTRACT FROM AUTHOR]

Cylindrical deep drawing tests were performed on a fine-grain aluminium-magnesium alloy (5083-O) sheet at various forming speed (0.2~500 mm · min-1) and temperatures (298, 353, 423 and 453 K). It was found that limiting drawing ratio (LDR) is strongly affected by temperature while its value increases with decreasing forming speed independent of the test temperature. The LDR reaches minimum value at 353 K. It is associated with the maximum flow stress registered for this particular temperature and caused in turn by dynamic strain ageing. [ABSTRACT FROM AUTHOR]