Shohei Kajikawa

Influence of Steaming and Boiling at 180 °C Plus on the Injectability of Bamboo Powder

In this study, we investigated changes in the injectability of bamboo powder and the Vickers hardness of compacted products resulting from differences in heat-treatment conditions such as steaming and boiling. We conducted injection tests and test fabrications of compacted products using bamboo powder treated under various conditions. From the injection tests of heat-treated bamboo powder, we found that injectability was improved by heat treatment. While bamboo powder steamed at 200 °C showed good injectability, boiling at 200 °C yielded better injectability. Vickers hardness tests conducted on compacted products showed that hardness was increased by heat treatment under appropriate conditions. In addition, we found that the heat-treatment condition required to increase the hardness of product was different from that needed to improve injectability.

Hot Press Moldability of Bamboo Powder without Additives

The hot press moldability of bamboo powder without additives was investigated in this study. Bamboo powder was hot pressed into self-bonded cylindrical moldings at temperatures of 160 to 200 oC and pressing times of 1 to 20 min at a punch surface pressure of 200 MPa. After pressing, the color, density and bending properties of the moldings were evaluated. The bending strength, bending elastic modulus and density were found to increase with an increase in temperature, and moldings having good mechanical properties were obtained at a temperature of 200 oC. With respect to the influence of hot pressing time on moldability, a maximum bending strength of 34 MPa was achieved for a time of 10 min at a temperature of 200 oC. In addition, we removed moldings from the mold after cooling to 100 oC or less in order to improve the surface texture and density of the moldings. The results showed a cooled molding had a good surface texture (resembling plastic) and a bending strength of 53 MPa.

Fabrication of Deep Cup with Flange by In-Plane Stretch Forming Applying Compressive Force in Thickness Direction

This paper presents a new stretch forming method that applies compressive force for forming a deep cup with a flange. In this method, a punch and a die having a hole are used, and the main parameters are the depth of the die hole, ddh, and the clearance between the punch and the die, c. The effect of ddh and c was investigated by using an aluminum blank of thickness 2 mm in an experiment and a finite element analysis (FEA). When ddh was too small, the material flow could not be controlled appropriately, and when ddh was too large, a local thinning occurred during initial stretching into the die hole. When c was set at large, the side wall thickness of the formed cup was uneven, but a deep cup could be obtained by setting c below a half of the blank thickness. As a result, a deep cup of height 8.3 mm and with a flange was formed successfully under the condition that ddh was 1.5 mm and c was 0.5 mm.

Stability of a Suppression Method of Dent and Spring-Back in Zigzag Bending of Sheet Metal/Plate

This paper focuses upon zigzag-shape bending for suppression of defects, including dent and springback. A series of finite element analyses was carried out in order to optimize the bending condition for suppression of these defects. As a result, it was clarified that a diagonal movement of the upper die was effective for suppression of dents while a rather vertical movement of the upper die was effective for suppression of springback. In order to suppress dent and springback at the same time, this paper proposes another method of bending method, whereby the upper die with special shape moves in a diagonal way. Moreover, the stability of the method against variation of tool dead position, which would be caused by elastic deformation of supporting members, was studied by FEM, followed by experimental verification.

Effect of Surface State of Die on Flow Rate of Steamed Bamboo Powder in Thermal Flow Test Using Capillary Rheometer

Thermal flow tests were performed on steamed bamboo powder using capillaries that were processed under different conditions in order to investigate the effect of the die surface state on the fluidity of the woody powder. The capillaries were processed by wire-cut electric discharge machining, reaming or drilling, and the arithmetic average roughness (Ra) varied from 0.5 to 2.5 μm. The bamboo powder was first steamed at 200 °C for 20 min, and its particle size was then controlled using different mesh screens. The thermal flow temperature was set at 200 °C. The results indicated that the flow behavior improved with increasing particle size. For the capillaries processed by WEDM, the flow rate for samples with particle sizes of 75~150 and 150~300 μm decreased with increasing Ra. On the other hand, when reaming or drilling was used to process the capillaries, the flow rate was almost independent of Ra, regardless of the particle size.

Effect of Heating at Oven-Dry State on Steam Treated Bamboo Powder Thermal Fluidity

In hot molding processes of woody material, it is important to understand the effect of oven-dry heating on the property of woody biomass material, such as thermal fluidity. In this study, thermal flow tests of untreated and steam treated bamboo powder were conducted to investigate the effects of heating at an oven-dry state on thermal fluidity. The test temperature was set to 200°C. Before the thermal flow test, powder was dry-heated in a capillary rheometer at 200°C with a variable heating time. Thermogravimetry was conducted to understand the thermal changes of the powder during an increasing temperature and constant temperature. Fluidity of untreated powder was improved with a short dry-heating but decreased with a long dry-heating. In contrast, steam treated powder fluidity was high compared to untreated one, but its fluidity did not improve from dry-heating. From these thermogravimetry results, the chemical changes associated with component volatilization relate with the thermal fluidity. Therefore, the decrease in fluidity from dry-heating occurred because fluidity related components escape from the powder through volatilization.

Hardness Property of Compacted Products Formed from Woody Powder Steamed at 130

New wood forming methods for improving the workability of wood, such as compaction molding or wood forging, have been developed in order to use wood biomass effectively. However, the improvement of the formability and mechanical properties of materials is desired for the practical realization of those wood forming methods. To improve the formability and mechanical properties of materials, it has been reported that steaming is effective. However, the effect of steaming at temperatures lower than 150-160 °C has not yet been investigated. In this study, we investigated the hardness of compacted products of woody powder steamed at 130 °C. Cedar, beech, bamboo and kenaf cores were used as materials, and these materials were steamed for various times. Next, the compaction molding of materials was attempted, and the Vickers hardness and density of the products were measured. The results show that the hardness was increased by steaming when beech, bamboo and kenaf cores were used. In addition, the hardness is proportionally changed with the density for most of the products. On the other hand, in the case of bamboo and kenaf cores, the hardness of products formed from air-dried materials changed, but density remained unchanged. Thus, it was considered that the effect of steaming was greater than that of the density for bamboo and kenaf cores. .

Displacement Behavior of Wood in Boss Forming Using Open-Die Wood Forging

Biomass materials such as wood are attracting renewed attention as alternative fuels in order to help resolve environmental resources caused by the use of fossil fuels. In this study, the possibility of products being processed from wood bulk was investigated by means of boss forming using open-die forging. Additionally, the difference in formability and deformation behavior during forging was investigated by changing the experimental conditions, such as the moisture content of the wood billets used, the forming pressure, and the forming temperature. The experimental results showed that wood had enough liquidity to be forged, and that two sudden and large increases in displacement occur during forging. Finally, the conditions governing these displacements were summarized from these results