Trajectory Strategy Effects on the Material Characteristics in the WAAM Technique.

The wire Arc Additive Manufacturing (WAAM) technique has evolved into a cutting-edge 3D printing technique. This study surveys the influences of trajectory on the characteristics of low-carbon steel samples generated by the WAAM technique. The results show that the grains in the WAAM samples are isotropic, with grain size numbers ranging from 7 to 12. Strategy 3, with a spiral trajectory, has the smallest grain size, while strategy 2, with a lean zigzag trajectory, has the largest. The variations in grain size are caused by differences in heat input and output during the printing process. The WAAM samples achieve a significantly higher UTS value than the original wire, demonstrating the WAAM technique's benefit. Strategy 3, with a spiral trajectory, achieves the highest UTS value, 616.5 MPa, 24% higher than the original wire. The UTS values of strategy 1 (horizontal zigzag trajectory) and strategy 4 (curve zigzag trajectory) are comparable. WAAM samples have significantly higher elongation values than the original wire, with only 22% elongation. The sample with the highest elongation value, 47.2%, was produced by strategy 3. Strategy 2 has an elongation value of 37.9%. The value of elongation is proportional to the value of UTS. WAAM samples have average elastic modulus values of 95.8 GPa, 173.3 GPa, 92.2 GPa, and 83.9 GPa, corresponding to strategies 1, 2, 3, and 4. Only a strategy 2 sample has a similar elastic modulus value to the original wire. All samples have dimples on the fracture surface, indicating that the WAAM samples are ductile. These fracture surfaces' equiaxial shape corresponds to the original microstructure's equiaxial shape. The results provide the optimal trajectory for the WAAM products is the spiral trajectory, while the lean zigzag trajectory gains only modest characteristics.

Improving the Melt Flow Length of Acrylonitrile Butadiene Styrene in Thin-Wall Injection Molding by External Induction Heating with the Assistance of a Rotation Device.

In injection molding, the temperature control of the dynamic mold is an excellent method for improving the melt flow length, especially of thin-wall products. In this study, the heating efficiency of a novel heating strategy based on induction heating was estimated. With the use of this heating strategy, a molding cycle time similar to the traditional injection molding process could be maintained. In addition, this strategy makes it easier to carry out the heating step due to the separation of the heating position and the mold structure as well as allowing the ease of magnetic control. The results show that, with an initial mold temperature of 30 °C and a gap (G) between the heating surface and the inductor coil of 5 mm, the magnetic heating process can heat the plate to 290 °C within 5 s. However, with a gap of 15 mm, it took up to 8 s to reach 270 °C. According to the measurement results, when the mold heating time during the molding process increased from 0 to 5 s, the flow length increased significantly from 71.5 to 168.1 mm, and the filling percentage of the thin-wall product also increased from 10.2% to 100%. In general, the application of external induction heating (Ex-IH) during the molding cycle resulted in improved melt flow length with minimal increase in the total cycle time, which remained similar to that of the traditional case.

Thermal and Mechanical Behavior of Hybrid Polymer Nanocomposite Reinforced with Graphene Nanoplatelets.

In the present investigation, we successfully fabricate a hybrid polymer nanocomposite containing epoxy/polyester blend resin and graphene nanoplatelets (GNPs) by a novel technique. A high intensity ultrasonicator is used to obtain a homogeneous mixture of epoxy/polyester resin and graphene nanoplatelets. This mixture is then mixed with a hardener using a high-speed mechanical stirrer. The trapped air and reaction volatiles are removed from the mixture using high vacuum. The hot press casting method is used to make the nanocomposite specimens. Tensile tests, dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) are performed on neat, 0.2 wt %, 0.5 wt %, 1 wt %, 1.5 wt % and 2 wt % GNP-reinforced epoxy/polyester blend resin to investigate the reinforcement effect on the thermal and mechanical properties of the nanocomposites. The results of this research indicate that the tensile strength of the novel nanocomposite material increases to 86.8% with the addition of a ratio of graphene nanoplatelets as low as 0.2 wt %. DMA results indicate that the 1 wt % GNP-reinforced epoxy/polyester nanocomposite possesses the highest storage modulus and glass transition temperature (Tg), as compared to neat epoxy/polyester or the other nanocomposite specimens. In addition, TGA results verify thethermal stability of the experimental specimens, regardless of the weight percentage of GNPs.