This paper reports the synthesis of a new printable ABS–MWCNT composite filament, for use in fused deposition modeling (FDM), using an extrusion technique. Acrylonitrile butadiene styrene (ABS) and multi-walled carbon nanotubes (MWCNTs) were the initial materials used for fabricating the filaments. The MWCNTs were dispersed in ABS resin, then extruded through a single-shaft extruder in filament form, with MWCNT contents of 0.5%, 1%, 1.5%, 2%, 3% or 4% by weight. After extrusion, the diameter of the filaments was about 1.75 mm, making them appropriate for FDM. The as-synthesized filaments were then used in FDM to print out samples, on which tensile tests and other analyses were carried out. The results demonstrate that the sample with 2% MWCNTs had the highest strength value, 44.57 MPa, comprising a 42% increase over that of the pure ABS sample. The morphology and dispersion of MWCNTs in the composite were observed by field emission scanning electron microscopy (FESEM), demonstrating the uniform distribution of MWCNTs in the ABS matrix. The thermal behavior results indicated no significant change in the ABS structure; however, the melt flow index of the filaments decreased with an increase in the MWCNT content.

In this study, the effect of bow shape on resistance acting on a hull in regular head waves was investigated by applying a commercial Computational Fluid Dynamics (CFD) code. For this purpose, the hydrodynamic performance as well as the resistance of ships with blunt and bulbous bows were simulated. By analyzing the obtained CFD simulation results, the effects of the bow shape on the hydrodynamic performance and resistance of the ships were found. A new bulbous bow shape with drastically reduced added resistance acting on the hull in waves is proposed. Finally, the obtained CFD results for the hydrodynamic performance of ships are presented.

Motorbike shock absorbers made with a closed die employ a tube-forming process that is more sensitive than that of a solid billet, because the tube is usually too thin-walled to conserve material. During tube forming, defects such as folding and cracking occur due to unstable tube forming and abnormal material flow. It is therefore essential to understand the relationship between the appearance of defects and the number of forming steps to optimize technological parameters. Based on both finite element method (FEM) simulations and microstructural observations, we demonstrate the important role of the number and methodology of the forming steps on the material flow, defects, and metal fiber anisotropy of motorbike shock absorbers formed from a thin-walled tube. We find limits of the thickness and height ratios of the tube that must be held in order to avoid defects. Our study provides an important guide to workpiece and processing design that can improve the forming quality of products using tube forming.

Single-point incremental forming (SPIF) has drawn much attention recently due to its flexibility in making parts for rapid prototypes and small samples. Several studies have pointed out the benefits of using ultrasonic vibration (UV) in SPIF experimentally. This study verifies the effect of UV in reducing the forming forces by performing numerical simulations. In addition, the effect of several process parameters, including tool diameters, rotational speeds, step sizes, and ultrasonic vibration amplitudes, is investigated in detail. It is found that an increase in the tool rotational speed and vibrating amplitude decreases forming forces, whereas an increase in the vertical step size increases forming forces.

Forming complex sheet products using hydrostatic forming technology is currently a focus of the majority of forming processes. However, in order to increase stability during the forming process, it is necessary to identify and analyze the dependency of the forming pressure and the quality of a product on input parameters. For the purpose of modeling the forming pressure, this paper presents empirical research on the product of a cylindrical cup made of various materials, including carbon steel (DC04), copper (CDA260), and stainless steel (SUS 304) with different thicknesses (0.8 mm, 1.0 mm, and 1.2 mm), under a defined range of binder pressures. The regression method is selected to formulate an equation that shows the relationship between the input parameters, including the materials (ultimate strength and yield stress), workpiece thickness, binder pressure and the output parameter, and the formation of fluid pressure. The mathematical equation allows us to determine the extent of the effect of each input on the forming pressure. The experimental results can be used for the easier planning and forecasting of the process and product quality in hydrostatic forming.

The effect of plastic deformation upon the grain structure and mechanical properties of Al-Cu-Mg-Mn alloy tubes under upsetting was investigated. It was found that plastic deformation techniques such as cold upsetting can overcome the disadvantages of the cutting process, such as the anisotropy of the original material, no grain structure, and not high mechanical properties, while also improving the mechanical properties of the product in local plastic deformation zones by changing the grain and fiber structure of the material. This article presents the results of our research and evaluates the increase of material durability in the tubes’ deformation zones compared with the initial state. In this study Al-Cu-Mg-Mn alloy material had been cutting with turn machine and plastic deformation by upsetting. Microstructures and hardness variations of cut surfaces that are obtained with different processes have been investigated.