Extrusion components are used in many industrial systems, such as railroad vehicles and heat exchangers. The demand for components whose section and tube are not uniform is increasing, and there are several studies of nonuniform tubes. A typical extrusion study involves a tube with spiral projections on the inside wall. When the tubes are exchangers, such as in room air conditioners, they raise the heat exchange performance. If the exchanger tube are made of extruded aluminum, spiral projections formed on the inside wall can extend the limit of the exchanger. The exchanger tubes will become inexpensive and the productivity will be improved. We propose a new extrusion method for tubes with spiral projections on the inside wall in this study. The new extrusion method is suitable for mass production, and the setup spiral angle of projections is 30 degrees. The material flow of a billet is changed by the mandrel slots and the tubes with spiral projections on the inside wall are made. The extrusion conditions were experimentally discussed regarding the shape of circular tubes with spiral projections. We experimentally clarified the limit and characteristics of the extrusion of circular tubes with spiral projections on the inside wall in this study.
Recently, high-strength steels with over 1500 MPa in tensile strength have been manufactured by hot stamping. To decrease their coefficient of friction, the effects of die surface coating on such a parameter were investigated. The Five kinds of die coated with TiN, TiCN, CrN, TiAlN, and DLC-Si were used. The experimental tests were carried out under a dry condition using a simulation testing machine developed by the authors, and the coefficient of friction for a drawing stroke was measured. The coefficient of friction of the noncoated die increased abruptly with a stroke of 5 mm. On the other hand, the coefficients of friction of the hard-coated dies gradually increased by 10 mm. At a stroke of over 10 mm, the coefficients of friction of the noncoated and hard-coated dies finally approached 0.52. From the results of the surface analyses, the adhesion of aluminum on the die surface was observed.
Combining the Sachs deformation model with the dislocation theory, we can predict the stress-strain curve for both face centered cubic (FCC) and body centered cubic (BCC) single crystals generally. Residual dislocation densities are estimated from total amount of microscopic slip, considering cross-slipped dislocations and sessile dislocations. Stresses are calculated from estimated dislocation densities using the Bailey-Hirsch relationship. Finally, we showed a calculation example of the Sachs deformation model to explain low-angle boundary formation.
Intelligent actuators controlling their own stroke have contributed to robot system and factory automation. Usually, stroke is detected by using a sensor located on one end of the actuator and its construction is very complex. The space and the conditions for using the sensor are restricted because of its location. To solve this problem, a new kind of actuator was developed. This actuator's piston rod has magnetic scales made by irradiation with a laser beam. The scaling rod is robust and more accurate. However, irradiating with the laser incurs high cost because of the use of the expensive laser beam machine. Therefore, a new manufacturing process with plastic work is developed to improve productivity. In order to produce a one-body-type magnetic scale, we attempted martensitic transformation of steel by plastic deformation. Using a special austenite steel rod, a part of the surface was transformed into martensite by rotating a roll-die over the rod. The effect of crystal grain size on martensitic transformation was investigated. As a result, martensitic transformation was found to be more stable for finer grain. As magnetic scale became small through the grain refinement, the accuracy of stroke sensing became higher. We also discussed the possibility of fabricating a magnetic scale rod of a carbon steel.
A 3-stage stamping process including thickening of the bottom and flange corners of a cup with a flange was developed to improve the fatigue strength of the cup. A circular blank was drawn with conical punches in the 1st and 2nd stages, and the bottom and flange corners were thickened by flattening the conical bottom of the cup with a flange in the 3rd stage. Not only the bottom corner but also the flange corner of the cup was thickened by forming the flange corner in the latter half of the 3rd stage. The amounts of thickening at both corners were improved by the contact of the inclined portion between the two corners with the counter punch in the 3rd stage, i.e., thickening was concentrated around the two corners by preventing thickening of the inclined portion. A wheel disk formed by 6-stage stamping having the following 3 stages exhibited 15% and 10% thickening at the bottom and flange corners, respectively, and the bending rigidity was 1.7 times as large as that without thickening. It was found that the present stamping method is considerably effective in reducing the weight of parts and production cost.