In this study, we attempted to manufacture wood-based products of arbitrary shapes and high strengths by allowing the cryptomeria to flow and harden in a metal mold without using a binder. Experimental results show that the wood has good liquidity owing to the maintenance of its moisture using the metal mold that remains sealed in a hot press. The good product along the metal mold shape was obtained under the following processing conditions : a molding pressure of 60-160 MPa, a molding temperature of 140-180°C and a moisture content of 10-50%. Moreover, the molding pressure that can be molded decreases at a high temperature and a high moisture content. The density of the obtained good product is 1.36 g/cm3, and the average Vickers hardness is 29.4HV0.1. In addition, the product obtained at a molding temperature of 160°C and a sealing time of 90 min does not facilitate shape recovery even if it boils with water for 30 min.
A new plastic joining method for fixing bars with a hot-forged plate was proposed, in which steel bars maintained at room temperature are directly indented into a high-temperature steel plate, as reported in a previous paper. To examine the validity of the developed plastic joining method, the optimum conditions of the plastic joining method are investigated using an SCM435 steel bar and an A5052 aluminium plate on a mechanical or AC servo-controlled press. It is possible to indent the bar to the plate without the buckling or plastic deformation of the bar at room temperature, and the attained shear bonding stress of the bar–plate is approximately 70% of the shear strength of the plate material. The bonding mechanism of the proposed plastic joining method is discussed from the viewpoints of plate seizure and mechanical clamping associated with the process.
This study deals with experimental and geometrical analyses of a cylindrical surface finishing process using a diamond burnishing tool. Roller burnishing techniques are applied to the surface finishing of aluminum alloy or stainless steel parts. However, they are not applicable to hardened work materials such as high-carbon-chromium- bearing steel. Diamond burnishing tools, instead of the roller tools, are used to finish such hardened materials. Certain practical burnishing tests were carried out under several machining conditions considering burnishing load, feed rate and diverse preliminary processes using an NC. lathe. From the experimental results, the effect of surface texture on and the estimation of a dimensional change in burnishing are clarified and performed, respectively.
Suitable tool path conditions for incremental tube burring with a bar tool are determined to obtain a uniform wall thickness distribution at the edge of a branched tube by an explicit finite element simulation. In the determination, an aluminum alloy tube, A5083-O, of 400 mm diameter and 6.0 mm wall thickness and a bar tool of 65 mm diameter are modeled. In this study, the second stage of incremental tube burring process is focused on, which is the crucial burring stage predominating the feasibility of burring process and product quality. As to the rocking condition of a bar tool at this stage, it is found that decreasing rocking angle by 5 degrees per cycle is suitable for preventing fracture and achieving high product accuracy. In addition, the simulation results show that an initial rocking angle of 45 degrees is effective in decreasing burring torque and wall thickness reduction ratio at the edge part of branched tube. This reveals that simulation is valid as a design tool for the process optimization of this multistage incremental forming.
Branched tubes are an important component of the piping system. A new incremental burring process for manufacturing branched tubes is developed to enhance the formability, product quality and process flexibility of large branched tubes. A significantly crucial process history using a bar tool is proposed suitably on the basis of features of conventional forming processes. Concerning incremental burring processes, proper forming conditions were decided using FE simulation, as previously reported. In this study, to put a new burring method to practical use, a large branched pipe is studied. In the experiment, the following branched tubes are used: A5083-O, SUS304 and SS400 with diameters of 300 and 400 mm and wall thicknesses of 3.0, 4.0 and 6.0mm. The equipment is remodeled to achieve new processes and a bar tool with diameter of 65 mm is used. The method consists of three stages. The history of thickness reduction ratio distribution is almost the same as that in the analysis. Moreover, the thickness reduction ratio distribution at the edges of the branched tubes is hardly affected by the materials and thicknesses of the work. The results show that branched tube can be burred under a cold condition and its use can flexibly reduce the die cost related to the diameter of the branched tube with a bar tool.
A hot shear spinning process of cast aluminum alloy parts with an inclined roller was developed to improve the formability of the cast aluminum. Hot shear spinning has the function of eliminating dendrites and shrinkage cavities in cast aluminum alloys. The backward metal flow in the slope region of a blank was prevented by reducing wall thickness perpendicularly to the mandrel by means of the inclined roller, and thus the wall thickness does not return after passing the gap between the roller and mandrel. As the roller angle increased, the thickness return ratio decreased, and the ratio was almost zero above 30°. The surface crack length in the corner region of the spun blank was reduced by the use of an inclined roller. The elongation of the spun blank with the inclined roller was larger than that with a noninclined roller, whereas the tensile strength was smaller owing to the reduction in redundant deformation. In addition, the inclined rollers were effective in forming the step region of the blank.