To cut the cost of the laser powder bed fusion (LPBF) process, which is much higher than that of the traditional manufacturing process, an effective implementation of optimization analysis is needed. The study investigated the optimization of the LPBF Inconel 718 alloy with the Taguchi method and principal component analysis (PCA), covering four control factors at three levels in the manufacturing process. It focused on four mechanical properties, namely tensile strength, elongation, impact energy, and hardness. The results show that the highest tensile strength is obtainable at a laser power of 140 W, scanning speed of 800 mm/s, scanning pitch of 70 μm, and interlayer angle of 45 degrees. The optimal combination of process parameters for multiobjective optimization is just the same as that for single-objective optimization for tensile strength. The difference between the predicted and experimental average tensile strength is 1.2%, and the error of the predicted optimal strength index is 12.6%. The most important control factor for tensile strength and multiple responses is the angle between layers, with a contribution rate exceeding 90%. With a given volume energy density of the LPBF process, the higher the power and scanning speed, the higher the accumulated energy and the larger the amount of dendritic or cellular crystals formed.

This study investigates the influence of process conditions on the tensile properties of polyoxymethylene (POM) composites that contain three amounts of glass fiber-reinforcement (0 wt%, 15 wt% and 25 wt%). Four processing parameters - orientation of fiber, thickness of fiber layer, amount of fiber, and injection molding parameter were considered. The morphology of the fiber layer is observed by scanning electron microscopy (SEM), to elucidate the correlation between the orientation of the fibers and the mechanism of fracture of the bucking surface. The experimental results show that the maximum ultimate stress is obtained at a filling time of 1.5 s, a melt temperature of 215°C, a mold temperature of 75°C, and a packing pressure 75 MPa. SEM revealed that the composite contained two distinct layers. The fibers in the frozen layer were parallel to the melt flow, while the fiber was perpendicular to the melt flow in the core layer. The thickness of the frozen layer increased with the amount of fiber, increasing tensile strength. Additionally, fiber pullout and across-matrix cracking are the main fracture mechanisms of the frozen layer, whereas failure of the fiber-matrix interface is the major fracture mechanism in the core layer.

This study investigates the influences of two processing conditions on wear properties of Polyoxymethylene (POM) polymer, and further determines the optimal parameter setting for the injection molding process to achieve optimal wear quality. This study uses two experimental designs, including the conventional single factor design and Taguchi L₉ orthogonal design. Moreover, morphology of worn surfaces was analyzed by scanning electron microscopy (SEM). Analytic results confirm that combining the Taguchi experimental design with the analysis of variance (ANOVA) can link controlled parameters and targeted output, and rapidly predict the optimal parameter settings for various injection-molding conditions.

In this study, the optimal parameters of the vacuum brazing titanium alloy Ti-6Al-4V with TiCuNi filler (30 μm-thick metal foil) were investigated by the Taguchi method. The microstructures, microhardness, and fractographs of the titanium brazed joints produced by these optimal parameters were also analyzed. The results of this study demonstrate that for the best tensile strength, the optimal combination of process parameters is: 890 °C soaking temperature, 60 min soaking time, 975 °C brazing temperature, and 45 min brazing time. The tensile strength obtained by welding with the optimal parameters was found to be 1265 MPa. A small error of 0.24% between experimental and predicted values confirmed the validity of the combined optimized parameters. Finally, from the means of variance analysis (ANOVA), out of the four factors, the highest contribution to the optimal parameters was found to be the brazing time, accounting for 47.3%. The base material of vacuum brazing (VB) weldment is mainly composed of white granular α titanium, slender β titanium, and layered structures that are interlaced by α and β. The weld bead, composed of Ti-15Cu-15Ni, contains many slender needle-shaped Widmanstätten structures. This structure is associated with higher strength and lower ductility. The weld bead hardness of the vacuum brazed parts is higher than that of laser beam weldment and gas tungsten arc weldment. This study demonstrates the feasibility of the Taguchi method for obtaining the optimal process parameters of titanium vacuum brazed joints.

Tungsten inert gas welding and vacuum brazing butt joints of Al–Mg–Si alloy 6061 in the artificially aged condition T6 were studied. Constant amplitude and variable amplitude fatigue loading tests were performed. The experimental S-N curves were compared with the fatigue design curves recommended by the International Institute of Welding, British Standard, and Eurocode 9. Two mean stress correction methods, Goodman and Gerber, were evaluated. In terms of the size effect on the fatigue life, this article proposed an innovational thickness correction method based on the ratio of the ultimate tensile strengths of specimens with different thickness. For vacuum brazing components, the tensile strength–based thickness correction method was better than the thickness correction methods recommended by the International Institute of Welding and Eurocode 9.

This study investigates the influence of two process conditions on fiber orientations and tribological characteristics of POM/GF composites. The morphologies of fiber layers were observed to elucidate wear mechanisms, and the correlation between fiber orientation and fiber layer thickness. Experimental results indicate that there are three distinct layers from top surface to the core—a solidified layer, intermediate layer, and core layer. The tribological characteristics decreased as thickness of solidified layer decreased. Furthermore, minor grooving and debonded fibers were the major wear mechanisms for P-direction specimens. Severe cracks and cut fibers were the major wear mechanisms for AP-direction specimens.