Wood/plastic composite extrusion molding was implemented in order to produce a new material by combining the best properties of wood and plastics; the former is light and rigid, the latter is multifunctional and highly durable. In this study, we proposed a method in which melted plastic is tightly pressed into a cavity between a feeding wood plate and a die, and clarified the correlations among coating thickness, the length of the die, feeding speed and resin pressure. The appearance and adhesion strength of the coated resin were also investigated for each set of extrusion molding conditions. The result showed that the cross-sectional area of the coated resin strictly depends on the extrusion rate of the resin against wood plate feeding speed, while the resin pressure inside the mold cavity increases in proportion to the die length. This means that the resin pressure in the extrusion molding can be easily controlled regardless of coating thickness. Additionally, it was confirmed that the strength of adhesion between wood and plastics becomes sufficient, and even larger than that of wood itself if the resin pressure is set beyond a certain value.
The consideration of plastic anisotropy is useful in carrying out more precise simulation of bulk forming as well as of sheet forming. We have tried a small-cube compression test to determine the anisotropic coefficients F, G, H, L, M, and N of Hill's quadratic criterion (1948). A cubic specimen was cut out of a bar, which had 1-mm-long edges and whose normal axis at the center of each surface is closely related to the original r-, θ-, or z-axis in cylindrical coordinates. The small cube was compressed in the specific direction under a well-lubricated condition, before the strain ratios of edges were measured to determine the anisotropic coefficients. For examples, an extruded bar of A6063 and a rolled bar of SUS430 in JIS indicated F/G/H/L/M/N values of 1.0/1.0/0.40/1.2/1.1/1.9 and 1.1/0.89/1.1/2.2/2.4/2.4, respectively. The results of the small-cube compression test were verified by FE analysis considering anisotropy. Furthermore, we applied the small-cube compression test to estimate the distribution of the anisotropic properties of the bar in the radial direction.
Scaled progressive dry deep-drawing test is conducted up to 300 times on the micro- and milli-scales, in which cups of 0.97 and 5.82mm diameters are produced with stainless steel foils of 0.05 and 0.3mm thicknesses, respectively. The experimental results show that the transition of maximum punch force in the repetition test has a different tendency for each scale and corresponds to the transition in the surface state of the tools and drawn cups. Although the strong adhesive wear is observed on the milliscale, there is little change in the surface state of tools and drawn cups on microscale. To investigate the wear behavior of work material on each scale, finite element analysis considering surface asperities is conducted. The distribution of wear volume at the die corner radius is evaluated with a semiempirical function of normal pressure and relative velocity between the blank and the die. The results show the low wear volume in the microscale process, due to the short sliding distance during the process. The progressive wear phenomena and the advantage of tool life in microforming are demonstrated.
A method of the determining the blocker shape of a type of park gear for automatic transmission was developed. In the method, four different basic shapes were first defined on the basis of the experience and knowledge of experts. Then, four parameters concerning the underfilling of the material into dies and die wear were evaluated by the finite element method. The proposed method was applied to the design of the blocker shape of an actual closed die forging of on idler and a gear part. The optimal blocker shape was successfully determined with fairly short calculation times. The optimal blocker shape of another single park gear was also successfully obtained by the proposed method.
Functionally graded cemented carbide (FGCC) models with a hardness distribution are fabricated by combining the powder layer compaction (PLC) technique and CNC milling. In the fabrication of the FGCC model, powders of cemented carbide (WC) with different Co contents are combined by compaction and then the resulting green compact is sintered. The hardness is confirmed to change smoothly around the interface of the WC samples with different Co contents in the sintered FGCC models. To control the hardness distribution of the sintered FGCC models, the influences of fabrication conditions on Co diffusion and movement during sintering are examined. Presintering at temperatures higher than 600 °C is found to be effective for suppressing Co diffusion and movement. Furthermore, residual stress in the sintered FGCC die model is estimated. When the inner layer is presintered at 1300 °C, a compressive residual stress is confirmed to be induced in the inner layer of the sintered FGCC die model.
Parts having a strength distribution were produced from tailor friction-welded billets consisting steel bars having different quenchabilities. JIS-SCr420 having high quenchability and JIS-S25C having low quenchability were joined by frictional welding. The tailor friction-welded billet was then forged, and the forged billet was quenched to induce a strength distribution. The formability of the tailored billet was examined from compression tests in compression in directions normal and parallel to the interface. For the 80% compressed tailored billets, no cracks were observed. In a tensile test of a specimen cut from the 80% compressed tailored billet in the parallel direction, the fracture occurred on the JIS-S25C side having a low flow stress, not at the interface. By annealing the tailored billet, inhomogeneous deformation around the interface was prevented. A shaft having a high strength flange and a connecting rod having high strength and machinability were produced by forging and quenching the tailored billet.
The authors proposed double-layer-type environmentally friendly lubricants, which were composed of an undercoat superior in adhering to a material and an overcoat superior in reducing the friction between the material and the die. The performance of these lubricants for cold forging was evaluated by the ring compression test, the combined forward rod-backward can extrusion-type friction test and the combined forward conical can-backward straight can extrusion-type friction test. The double-layer-type lubricants showed comparable friction characteristics and antisticking property to a conversion coating lubricant, when the film thickness and surface treatment before coating were improved. In a practical application by cold multistage forging, the double-layer-type lubricants showed a similar performance to a conversion coating lubricant.