Theoretical Study of Sound Insulation Simulations (About Attaching Effect of Sound Absorbing Material and Consideration of Sound Insulation Performance by Height of Origami Core)

We have developed a new truss core panel by origami forming to get the higher aspect ratio than that by multi-stage press molding. Our object is to apply the new origami truss core to the train floor. Whether or not this goal can be achieved depends on whether this new origami truss core with a high aspect ratio has excellent sound insulation characteristics. Therefore, as a development of the analysis technology by FEM which accurately estimates the sound insulation characteristics, at first, the relation between the aspect ratio and the sound insulation performance is discussed in the flat plate with one core. So far, sound insulation simulations using FEM did not match with theory of the mass law. However, this can be achieved by setting the end of the transmitted side to be a nonreflective boundary. In this paper, to generalize this method, it is determined theoretically that the sound pressures from the FEM can be separated accurately into the sound pressures of the forward and backward waves from Helmholtz’s equation. Then, the sound insulation characteristics of a flat plate obtained using the proposed theoretical method and the conventional method are compared while assuming that the flat plate is a rigid body. In addition, the validity of the proposed method is confirmed by evaluating the effect of attaching a sound absorbing material to the plate. Furthermore, application of the proposed method to a flat plate with a truss core and an examination of whether a high aspect ratio is advantageous for sound insulation are also presented.

Nanocellulose Bulk Material Prepared by Steam Treatment and Hot Press Molding: Material Processing and Machining Test

Nanocellulose (NC) has been spotlighted as a new building block of future materials since it has many advantages, such as being lightweight and environment-friendly and having high mechanical properties and heat resistance. However, the use of NC requires an upscale manufacturing process to maintain its advantageous properties. Herein, the process of assembling NC into a macro-scale bulk material was developed through a combination of steam treatment and hot press molding. The steam treatment was applied to an NC paste to energize the hydroxyl groups in the cellulose, followed by two stages of hot press molding, which helped in the self-assembly of NC without adhesives. Cellulose nanocrystals were used as the NC, and circular disk shape specimens were prepared. The mechanical properties of the prepared bulk material were higher than typical engineering plastics. In addition, an end mill machining test of the NC bulk material showed its machinability. This paper showed the processing feasibility of NC bulk material, which can substitute plastics.

Effect of the Propionylation Method on the Deformability under Thermal Pressure of Block-Shaped Wood

Converting wood waste into thermoplastic materials is an attractive means of increasing its utilization because complex three-dimensional molded products can easily be obtained by press molding wood with thermoplasticity. Chemical modification, especially esterification, is a promising method for imparting thermoplasticity to wood. In this study, we produced multiple propionylated wood specimens using several propionylation methods and elucidated the factors affecting the deformability of the wood. Regardless of the method, all of the propionylated wood samples showed deformability in the tangential direction. However, in the longitudinal direction, not only the degree of propionylation but also the propionylation method had a significant influence on the deformability. The flow in the tangential direction occurred under a relatively low pressure, whereas the flow in the longitudinal direction occurred under higher pressure. The chemical composition and motility of each sample were evaluated using solid-state NMR measurements. With some propionylation methods, decomposition of the cellulose main chain occurred during the reaction, which had a dominant effect on the deformability of the wood in the longitudinal direction. These results indicate that the deformability of wood can be controlled by the appropriate selection of a propionylation method and its treatment conditions.

Effect of calcium carbonate filler and alkali treatment on physical and elastic properties of jute mat reinforced polyester resin composites

Polyester resin-jute mat reinforced composites with different wt% of calcium carbonate (CaCO3) filler were fabricated using a simple cold press molding method. The effects of CaCO3 filler and alkali (NaOH) treatment on various physical and elastic properties were evaluated. Water absorption (WA) increases with the increase of soaking time and load. The maximum WA was observed for 5 wt% addition of CaCO3 and for more CaCO3, WA decreases. The ultimate tensile strength (UTS) and flexural strength (FS) decreases with the addition of CaCO3 for 0.5 wt% NaOH treated composites but for 5 wt% NaOH treated composites UTS and FS increases with the addition of CaCO3 filler. The optimum filler addition is about 5 wt% CaCO3. With the addition of CaCO3, tangent modulus increases for 0.5 wt% NaOH treated composites and for 5 wt% NaOH treated composites it increases up to a maximum value and then decreases. The effect of load on tensile and flexural properties is also discussed. Bangladesh Journal of Physics, 26(2), 61-68, December 2019

Influence of Grooved Plate Cross-Sectional Shape on Bending Phenomena in Laser-Quenching Forming Process

This research proposes a method to achieve laser quenching and laser forming simultaneously. This technique uses a diode laser to produce thin steel sheet-assuming parts, such as springs and hinges. Energy and time are saved by combining the advantages of laser quenching, which has high input heat efficiency, and laser forming, which, unlike press molding, does not require metal molds. In this study, laser-quenching molding was performed for an entire thin steel plate, and the influence on warping was investigated. Furthermore, the proposed method was evaluated under repeated quenchings for different cross-sections of a workpiece. The results indicated that the technique prevented bending deformation during the next laser scan and reduced warping by increasing the second moment of area of the entire workpiece.

Investigation of the Tensile and Flexural Behavior of Polylactic Acid Based Jute Fiber Bio Composite

The main objective of this investigation is to reduce and eventually replace the use of non-biodegradable synthetic fiber. Bio composites have shown growth and has been used in the domestic sector, aerospace industry, circuit boards, and automotive applications over the past few years. Many types of natural fibres have been investigated to produce composite materials that are competitive with synthetic fibre composites. Jute is a natural fibre and is 100% bio-degradable and recyclable and thus environmentally friendly. Its properties include high tensile strength, low extensibility. This bio composite specimen has been fabricated with the help of hot press molding machine. The flexural and Tensile tests have been done according to the ASTM standards. The increasing awareness of global environmental and social concern and new environmental regulations have propelled the search for new composites that are compatible with the environment.

Mechanical Characteristics Testing of Biodegradable Ramie Fiber Reinforced Polylactic Acid (PLA) Fabricated with Hot-Press Molding

In this research, composite material was fabricated from both renewable resources and biodegradable materials: ramie woven fabric as reinforcement and 3D printed polylactic acid (PLA) filament as resin matrix. The laminate composites were produced using a film stacking method and processed using hot-press molding. The mechanical properties of woven ramie fabric, PLA matrix, and laminate composites were investigated. It is shown that the breaking force of the plain woven ramie fabric in the warp direction was greater than in the weft direction. Further, the tensile and impact properties of laminate at warp direction higher than weft direction when ramie fabric reinforcement is used. In addition, scanning electron microscopy examination of laminate composite showed good bonding between ramie fiber and PLA matrix. In summary, laminated composites based on polylactic acid and woven ramie fabric display good performance capability, which can use for the development of engineering applications.

Surface Remelting of Mold Inserts Made of NC11 Steel

In the study presented in this paper, the effect of a concentrated heat stream on geometry, microstructure, and hardness of superficial remeltings on NC11 steel is examined. The material is used for disposable mold inserts exposed to intensive abrasive wear in the course of the press-molding of hard aggregate stampings for refractory bricks. As a result of local remelting, the hardness of the steel surface increased and its microstructure was altered. Macro- and microstructure of the remelted areas was examined with the use of optical microscopy and measurements of remelting area geometry were carried out for different parameters of the remelting process. Hardness measurements were taken in the remelting area and in the heat-affected zone. The state of stress in the material before remelting and in the remelted area was also evaluated.

Driving Performance of Natural Fiber Gears Made Only from Bamboo Fibers Extracted with a Machining Center

Plastic gears are light and can be used without any lubricant, but they have low strength and an adverse effect on the environment. Therefore, a new gear that maintains these advantages while mitigating the disadvantages has been proposed. The development of sustainable and reproducible natural materials is desired to address these environmental problems. Therefore, in this study, a method was devised to extract high-quality and precise bamboo fibers using a machining center. Then, the hot press method was used to produce a novel spur gear made from only bamboo fibers, which is a green and organic machine element with a complicated shape. The present paper describes the characteristics of the proposed bamboo fiber gears, considering experimental results, including the hot press molding conditions, and the influence of fiber length on tooth bending strength, root strain, and vibration due to meshing teeth.