Key Engineering Materials Vol. 661

Abstract: Based on materials, different punch radii (0.3, 0.35, 0.4, 0.45, and 0.5 mm), two sets of diameter-diameter ratio 1.(.167, 1.25, 1.33, 1.4167, and 1.5) and 2.(1.6, 1.45, 1.33, 1.231, and 1.143), and two sets of depth ratio 1.(1.3, 1.4, 1.5, 1.6, and 1.7) and 2.(2.14, 1.875, 1.67, 1.5, and 1.36) are used for the stamping processes to analyze the simulation and experimental difference in copper sheet-metal (C1100) miniature layered cups. Prandtl-Reuss flow rule is integrated with finite deformation theory and Updated Lagrangian Formulation (ULF) to establish the incremental elastic-plastic deformation Finite Element Method in Coulomb’s Friction Law for simulating the miniature layered cup process. Generalized r_min algorithm is utilized in the forming process for dealing with elastic-plastic behaviors and die contact. From the simulation data, the relationship among deformation history, punch load, and punch stroke, the stress-strain distribution, and the distribution of the thinnest thickness by different punch radii are acquired.

Abstract: The study investigated the effect of grain size on the micro deep drawing of SUS304 stainless steel squares. Three stainless steel sheets with different thicknesses of 0.05 mm, 0.1 mm and 0.2 mm were treated by annealing processes at 1100 °C in which the holding times were varied in order to adjust the grain size. The sheets were used in the micro deep drawing processes for producing the square cups with 3 mm side length and 1.8 mm height. According to the design rules from references, the dimensions of the blank were determined to reduce the variation on the rim height of the square cup. The results showed that two peak values appeared on the load curves and the as-received sheet with the smallest grain size led to the largest load. Moreover, the cases of the as-received sheet with smaller grains had smoother surface textures than those of the annealed sheets with larger grains.

Abstract: The objective of this study is to establish three analytical models including the Upper Bound Method (UBM), the Slab Method (SM), and the Finite Element Method (FEM) for the rotating compression of bonded double-layer clad cylinder. As for the prediction of bulging deformation, apart from the FEM simulation, the other hybrid method can combine the UBM with an elliptical curve-fitting method for predicting compression force and bulging deformation. Meanwhile, the compression force and bulging deformation between analyses and experiment are compared to validate the correctness of the models. These models established can be offered to the reference of metal forming industries.

Abstract: The aim of this research is to investigate the effect of grain size on the mechanical properties and deformability of titanium alloy in equal channel and cross-sectional reduction channel angular pressing process. Specimens made of grade 2 titanium alloy with diameter 5 mm are annealed to temperature of 500 °C to 1000 °C resulting in different initial grain sizes, thus underwent tensile test for obtaining mechanical properties. Molds for both processes are designed to carry out serve plastic deformation. Finite element models are created and simulated the deformation behavior according to the mechanical properties of tensile test. Experimental results show that small α-phase grain starts to form in 700 °C homogenization treatment and its grain size increases as an increasing of annealing temperature. The β-phase microstructure precipitates resulting in brittle behavior in 850 °C annealing treatment. Simulation result show that squeeze load of ECAP is larger than 100 ton but it can be reduced when exit angle of channel is larger than entrance. Outer corner of ECAP with 90 ̊ generate lower squeeze pressure than that of 40 ̊.

Abstract: Because of being in possession of shape memory effect and superelasticity, Ni-Ti shape memory alloys have earned more intense gaze on the next generation applications. Conventionally, Ni-Ti shape memory alloys are manufactured by hot forming and constraint aging, which need a capital-intensive investment. To have a cost benefit getting rid of plenty of die sets, this study is aimed to form Ni-Ti shape memory alloys at room temperature and to age them at elevated temperature without any die sets. In this study, starting with solution treatments at various temperatures, which served as annealing process, Ni-rich Ni-Ti shape memory alloy wires were bent by V-shaped punches in different curvatures at room temperature. Subsequently, the wires were aged at different temperatures to have shape memory effect. As a result, springback was found after withdrawing the bending punch and further after the aging treatment as well. A higher solution treatment temperature or a smaller bending radius leads to a smaller springback, while a higher aging treatment temperature made a larger springback. This springback may be compensated by bending the wires in further larger curvatures to keep the shape accuracy as designed. To explore the shape memory effect, a reverse bending test was performed. It shows that all bent wires after aging had a shape recovery rate above 96.3% on average.

Abstract: Material’s plastic deformation by hot forming processes can be used to make the materials generate dynamic recrystallization (DRX) and fine grains and accordingly products with more excellent mechanical properties, such as higher strength and larger elongation can be obtained. In this study, compression tests and water quenching are conducted to obtain the flow stress of the materials and the grain size after DRX. Through the regression analysis, prediction equations for the magnesium alloy microstructure were established. Simulations with different rolling parameters are conducted to find out the relationship between the DRX fractions or grain sizes of the rolled products and the rolling parameters. The simulation results show that rolling temperature of 400°C and thickness reduction of 50% are the optimal conditions. An average grain size of 0.204μm-0.206μm in the microstructure is obtained and the strength and formability of ZK60 magnesium alloys can be improved.

Abstract: Additive manufacturing processes and materials are described with respect to their ability to generate finished products. The accuracy of produced parts is seen as an important criterion for this technology to compete with subtractive or constant volume technologies. From the existing literature can be concluded process variation is high and part accuracy is not better then IT grade 9. The manufacturing process itself is complex and dependent on a number of machine, material and geometry parameters. A better understanding of the heat transfer within the product build environment will assist in the future to improve the process and therefore the resulting parts’ accuracy.

Abstract: The system in a package (SiP) including of a system on a chip (SoC) and a double-data-rate-three synchronous dynamic random access memory (DDR3 SDRAM) were studied with respect to the high-speed characteristics. The SiP was the multi-chip-module thin-profile fine-pitch ball grid array (MCM TFBGA) package with four-layer substrate. The high-speed 1600-Mbps data rate DDR3 signals were used in the signal integrity (SI) analysis. The SiP with low-cost silver (Ag) wires displayed a 500.18-ps aperture width in the eye diagram, which was successfully achieved signal integrity (SI) performance requirement. This work demonstrated the SiP with the Ag wires was the great potential solution for the advanced high-speed product applications.

Abstract: This study investigates how to improve the anti-adhesion issues between Silicon mold and nanostructures of hard polydimethylsiloxane (H-PDMS). A Silicon mold with different depths and widths was made using a focused ion beam (FIB). During the soft-lithography molding process, anti-adhesion layers were needed between the Silicon mold and H-PDMS samples to prevent the de-molding failure caused by the adhesion issues between the interfaces. This study adopts three methods to deposit anti-adhesion layers, such as liquid immersion, vapor deposition, and fluorine-doped diamond-like carbon (F-DLC) film. Perfluorooctyl-trichlorosilane (PFOTCS) was used as a mold-releasing agent for the liquid immersion and vapor deposition methods. The contact angles between each film were measured to determine the effect of anti-adhesion on the molding process. In addition, atomic force microscopy (AFM) was used to measure the adhesion force between the H-PDMS and anti-adhesion layers. The results show that the coatings of anti-adhesion layers are an effective approach to improve the formability of molding.

Abstract: The physic and dielectric properties of the polyetherimide/bamboo charcoal (PEI/BC) composites were studied by using bamboo charcoal as the conductive filler. The PEI/BC composites are fabricated using PEI, dispersant, solvents, and BC powder (BCP). The effects of the content of BCP on the physical and dielectric properties of PEI/BCP composites are studied in this research. Two different electric conductivity of BCP (BCP1 and BCP2) were used as the filler mixing with the polyetherimide, and the electric conductivity of BCP1 is higher than the BCP2. As the content of BCP1 and BCP2 increases from 10 to 70 wt%, the dielectric constants of PEI/BC1 and PEI/BC2 composites at 1 MHz increases from 5.06 to 19.73 and 4.7 to 18.9, respectively. All loss tangents of PEI/BC1 and PEI/BC2 composites are less than 0.04 at measured frequencies from 1 kHz to 1 MHz.