Laser-based powder bed fusion of polymers (PBF-LB/P) is one of the most promising next-generation manufacturing technologies because of its high design flexibility and support-free manufacturing capability. However, its productivity remains lower than that of conventional methods, and reducing the build time is a key challenge. This study aimed to accelerate the build process by reducing the number of layers through increasing the layer thickness and investigated the effects of powder bed optical properties on this approach. Accordingly, a highly transmissive powder bed was developed using a near-infrared laser and an optical absorber, which was compared with a conventional low-transmissive powder bed fusion process using a CO₂ laser. The heating behavior, melting state, and interlayer adhesion were evaluated for each layer thickness. Furthermore, transient heat-transfer simulations were conducted to quantify the influence of powder bed transmissivity on the thermal distribution during processing. The results indicate that, in a near-infrared laser-based fusion process, the powder bed maintains its mechanical properties up to a layer thickness of 200 μm, with deeper heating contributing to improved interlayer adhesion. These findings support the feasibility of increasing the layer thickness to enhance the productivity of PBF-LB/P without compromising part quality by appropriately designing the optical properties of the powder bed.
AZ31 magnesium alloy is a representative magnesium alloy with well-balanced mechanical properties and castability. However, AZ31 magnesium alloy also has the disadvantage of poor corrosion resistance due to its low aluminium content. In previous research, it is known that the corrosion mechanism is such that filamentous corrosion is generated and then changes to full-scale corrosion. However, the relationship between corrosion and bending properties has not been revealed. In this study, AZ31 magnesium alloy was immersed in salt water with a concentration of 5%, and three-point bending tests were conducted to confirm changes in bending stress and strain due to strength loss caused by corrosion. Then, investigated which parameters Ra and Rz, which are indicators of surface roughness, are related to the maximum bending stress of the fully corroded AZ31 magnesium alloy. As a result, when evaluating the relationship between maximum bending stress and corrosion, it was found that it is better to evaluate by Ra of the corroded surface rather than by Rz.
In recent years, efforts have been made in the agricultural field to improve crop quality and streamline agricultural management by collecting and visualizing various data on crop growth. In this study, we focus on the “spectrum of light” as information on sunlight that is essential for crop growth and aim to capture its functions. Specifically, a spectral sensor is used to measure the reflectance of light for each wavelength. Measurement data generally contains variations, making classification difficult using machine learning based on linear separation. In this study, we attempt classification using a nonlinear separation method capable of high-dimensional analysis and report its effectiveness. Crop growth varies depending on location, lushness, etc. Traditionally, this work relied mainly on experience and subjectivity, but by quantitatively evaluating the distribution and changes in the visible light band, farmers can visually grasp the growth status of crops and determine the optimal harvest time.
This study quantitatively analyzed rust-streak formation under controlled droplet supply and its relationship with the rust-removed surface profile of the substrate. A NaCl aqueous solution was dropped at a constant flow rate onto SPCC steel plates inclined at 70 degrees to observe the temporal development of the rust streak. Surface line profiles before and after the removal of red rust were measured, and profile changes were quantified relative to the initial surface. Rust layer height hrustx and rust-removed surface profile zr & lowast;x were determined, and their distributions and integrated values were compared. The rust width reached approximately 2.5-3.0 mm, comparable to the droplet diameter under the present conditions. Downstream, rust layer height increased with the extension of test duration, whereas the integrated profile of the rust-removed surface remained relatively small. Rust layer height and rust-removed surface profile were not directly related at each observation position L. These results suggest that rust streak formation within the tested parameter window involves not only locally formed rust but also rust carried from upstream by liquid flow, and indicate that visible rust morphology alone cannot adequately represent substrate-side profile changes under these specific conditions.
