In this paper, we describe certain mechanical properties, namely, Brinell hardness, Young's modulus and bending strength, of Japanese cedar densified using the newly developed rolling and fixation method (R&F Method) and compare them with the mechanical properties obtained using traditional press works with flat dies, that is, plane compression. The effect of the difference in deformation between the R&F Method and plane compression on the mechanical properties was examined under the fixation condition of a drying set (80°C×24hr). It was found that Brinell hardness was affected mainly by the unloading process of the R&F Method and that Young's modulus and bending strength were affected mainly by the shearing deformation of the R&F Method. Eternal fixation with a high-pressure steam (180°C×10min, 200°C×5min) had an effect on the recovery of the defects caused by the unloading process and shearing deformation. However, eternal fixation with a high- temperature dry air (180°C×20hr, 200°C×5hr) was not effective. We conclude that the eternal fixation of the R&F Method should be carried out with a high-pressure steam.
Combined extrusion forging is not used widely. The reason seems that it is impossible to predict the load and extruded length easily. It is considered that the extrusion load and extruded length are affected by the shape ratio of the billet (initial billet height (ho)⁄initial billet diameter (do)). In this study, the effect of the shape ratio of the billet on the extruded length was examined experimentally and by finite element simulation. The extruded length is affected by the shape ratio of the billet. In the case of a shape ratio of 1.5, the deformation is of the separate flow type. In the case of a shape ratio of 0.4, the deformation is of the shear flow type. The ratio of the forward extruded length to the backward extruded length (Lb'⁄Lf) decreases with an increase in the ratio of the reduction in area (Rb⁄Rf). Moreover, in the billet with a large height compared with the diameter, the relationship between extruded length and stroke changed in a certain stroke. When the diameter and height of the billet were decided on the basis of the size of the product, the method predicted both the forward and backward extruded lengths.
The work-hardening exponent n more or less shows strain dependence, which is directly obtainable from tensile load-elongation data in the uniform elongation range. The variation in n with strain is monotonic except for during the beginning of deformation and can be simply represented by a linear or parabolic function for most annealed or tempered metal sheets. Supposing that the n-ε relationship remains unchanged after the maximum load, the corresponding constitutive equation is easily determinable. When the load-elongation curve predicted by finite element analysis with the constitutive equation does not agree well with the experimental one, the parameters are optimized by the inverse analysis. Because the number of parameters is sufficient when using two at most, optimization is very easy. The proposed method has been applied to several metal sheets among which the work-hardening behavior differs markedly. The excellent agreement between the analytical and experimental load-elongation curves was obtained for all the materials, and it was verified that this method was simple and effective for estimating the stress-strain relationship in the post-uniform elongation range.
In the production of fasteners, the lubrication of wire films plays an important role in determining formability and die life. Zinc phosphate is one of the most popular lubricants for wires because of its high performance in terms of lubrication and cost. A one-liquid lubricant has been developed and an attempt has been made to apply it in place of conversion lubricants such as zinc phosphate. However, the performance of the one-liquid lubricant is generally unstable, thus; its improvement is strongly desired. The lubrication of wire films is enhanced by gluing powdered metal soap together at the time of drawing. Therefore, a tribosimulator at the side face of a testpiece is desired. Thus, we designed the shape via finite element (FE) simulation. This tribosimulator test was named the “flange header test”. In this test, forging load is increased at a point known as the lubrication limit. In addition, from the measurement of knockout load, the test enables us to evaluate the galling of a lubricant. Moreover, the test simulates the tendency to bring about die damage as in the case of mass production by continuous forging.
This paper proposes a theory of cold rolling that considers roll deformation into a noncircular profile, for the analysis of temper rolling or the rolling of thin hard strips. Although models of this kind were presented by Matsumoto & Uehori in 1988, and more recently by other authors, the computation often fails when there is a large “neutral zone”, where plastic deformation is not proceeding because of roll flattening near the neutral point. In this paper, the elastic deformation of the strip being rolled is considered in order to ensure that the computation is accurate and stable even for a reduction ratio as small as 0.1%. The formulation of the strip is similar to Orowan’s rolling theory, but is modified with elastic deformation. The computing time is instantaneous. The computed rolling force and forward slip are compared with experimental results of wet temper rolling. It was found that there may be such a case as the backward-slip zone disappears and the entry elastic zone merges with the neutral zone into an integrated neutral zone when the exit tension is large compared with the entry tension.
In this paper, we describe the electromagnetic bulging of a SUS304-O stainless steel sheet (0.15 mm thick) using a flat one-turn coil. The coil is made of one copper alloy plate and is 20mm wide. In the die forming, the forming region of the die is 12mm wide, 60mm long, and has a small meandering groove with a 0.6mm depth and a corner radius of 0.3mm. An electromagnetic force generated in an aluminum sheet (driver) used as a driving plate presses the SUS304-O sheet, and causes it to bulge into the groove. The bank energy required for inducing a bulging height of 0.43mm is 4.5 kJ, and the obtained workpiece has no significant wrinkles or curves. To investigate the bulging of the SUS304-O sheet, the magnetic flux density on the driver is calculated approximately using the assumption that it is a flat sheet. Because the flux density on the flat sheet consists of two components, the electromagnetic force also consists of two components. One of them is a bulging force in the die direction. The bulging force is essentially constant within 80% on the coil width of 20mm, and controls both the wrinkles and the curves of the workpiece during the bulging operation.