Initially, it was easy to spread Si and diamond mutually, and we assumed that a diffusion layer was formed due to a reaction of diffusion bonding and selected Si. We formed a diffusion couple after pressurization by the cold isostatic pressure (CIP) method using plates of Si and C (artificial graphite) to estimate a suitable temperature in the diffusion joining of Si with diamond, joining time, the what of SiC generated and by the reaction between the solids for which we used the hot isostatic pressure (HIP) method We analyzed the generation layer and reactivity, and determined the diffusion coefficient necessary to measure the generation speed of Si/C joining. We produced Si/diamond with a diffusion couple after having processed pressurization by the CIP method of powders of Si and diamond or plates of Si and diamond after determining a conditions. We spread, and joined the materials by the HIP method and evaluated diffusion mechanism and joining strength. As a result of analysis after HIP processing, SiC was generated from Si and a contact interface with diamond. Results of the measuring bonding strength using a tensile test showed that the tensile strength was 118.5 MPa under HIP processing of a temperature of 773 K and a holding time of 36.0 ks, while tensile strength was 170.7 MPa under HIP processing of 973 K and holding time of 36.0 ks.
The purpose of this study is to establish the thread rolling process of the bolt fastenings based on the double-screw mechanism. Two-roller die plunge feeding is employed as the rolling method due to its high processing precision. The roller dies used in this experiments have special grooves whose shape is almost a reverse projection of the double-screw thread. The pitch ratio of the course and fine threads of the double-screw bolts is set to be 2:1. The double-screw bolts can be rolled precisely in the same process as the single-screw bolts using these dies. The deformation behavior of the workpiece during rolling is examined and the formed material fills the grooves of the dies in each cross section very smoothly. The rolled double-screw bolts completely pass the very severe vibration loosening test based on NAS3354. The fatigue tensile strength of the rolled double-screw bolts is increased twofold that of the cutting double-screw bolts.
A novel processing method was proposed to enlarge the partial diameter in the middle of a round bar with a diameter of D0=10mm. This method is called the collar-forming processing method. In order to study the conditions under which this processing method can be applied to shafts with practical diameters of D0=25mm-40mm for general industrial machines, the processing experiments were carried out under various processing conditions, such as normalized axial-compressive stress σc/σy and bending angle θ. The results obtained are summarized as follows: the collar-forming process can be smoothly performed by selecting the initial interval L0 between zippers within the range of 32mm-62mm, according to both the size of D0 and the curvature radius ρ of the zipper ends; the cycle parameter N0, which is used to determine the necessary rotation number N for final collar size in a model equation, can be estimated from both (ρ, D0) and (θ, σc/σy); the deformation behaviors in the radial direction also depend on (ρ, D0) as well as (θ, σc/σy) and can be estimated from the function of ρ/D0 depending on bending angle θ; the necessary rotation number N has the tendency to increase with an increase in ω in the case of larger diameter.
We developed a fabrication technique for microdies made of titanium superplastic alloy. This technique consists of the following three processes: (1) microshapes are formed on Si substrates by a micromachining technique, (2) a functionally gradient layer of TiN/Ti is deposited on the Si base structures by sputtering, and (3) the Si base structures are imprinted with a Ti alloy using a vacuum hot press machine. In the third process, the functionally gradient layer is diffusion bonded to the Ti alloy simultaneously. In this technique, superplastic working of Ti alloy (SP700) is carried out to realize high precision forging at the microlevel. In addition, the functionally gradient layer of TiN/Ti is bonded over the Ti alloy to attain a surface roughness at the nanolevel. In this study, to satisfy these requirements of the Micro Electro-Mechanical Systems device, the working conditions such as working temperature, strain rate, final reduction in height of the Ti alloy specimen and thickness of the sputtered layer of TiN/Ti were optimised.
The deformation behavior of a magnesium alloy tube during press bending is investigated to clarify the effect of the difference between tensile and compressive stress-strain curves of magnesium alloy experimentally and theoretically. The bending experiments using a mandrel of wires are carried out at room temperature. An AZ31 magnesium alloy circular tube with 25mm outer diameter and 1.5mm wall thickness is used in the experiment. The unique deformation behavior of the AZ31 tube is discussed in detail and compared with the press bending deformation of a 6063-TD aluminum alloy tube. In the bending experiments, the AZ31 tube was able to be bent without wrinkling or splitting under the ratio of bending radius to outer diameter, R0/D0, of 3. A formula on the neutral surface position of a tube under pure bending is derived in this study. For an AZ31 tube having a low average flow stress and a low r-value in the compression range, the neutral surface position is predicted to move to the tensile side of the bend. The theoretical results are in good agreement with the experimental results. From these results, it is found that the high bendability of AZ31 is attributable to its unique deformation behavior with low average flow stress and a lower r-value in compression.
In sheet forming simulations using the finite-element method (FEM), the elastic deformation of tools during the forming process can play an important role, particularly when an accurate analysis is required to predict complex defects such as surface deflection due to the springback phenomenon. For an accurate springback simulation, a static explicit approach can be regarded as one of the most suitable methods. However, in most studies that have been made for FEM simulations coupled with deformable tools, a dynamic explicit approach has been applied; thus, accurate springback predictions have been rarely obtained. In this study, the authors propose an algorithm to deal with the contact between a sheet and deformable tools, which is specialized for coupling effects between nonlinear-elastoplastic and linear-elastic bodies in the framework of a static explicit time integration scheme. Stamping experiments on square cup deep drawing with a flexible blank holder were also conducted, and the results were compared with numerical ones. The results confirmed the ability of the coupled simulations with the proposed algorithm to predict the effect of tool elasticity on the behavior of the sheet.
An essential function of scissors is cutting a material efficiently. Sometimes it is said that the easiness of using and longevity of scissors are also important, in addition to their cutting efficiency, because they are hand tools. However, the importance of these characteristics are secondary and should come after the cutting efficiency. In this study, in evaluating hair-cutting scissors, the efficiency of cutting a string was investigated. It was carried out by changing various parameters of scissors. A nylon string was chosen to be the material to be cut. As a result, three parameters affecting the cutting load were found. They were the state of tightness of the screw, the edge angle and the sharpness of the edge tip. Next, their effects on the cutting load were investigated. The state of tightness of the screw affected the clearance at cutting. When the screw was loosened, the clearance and cutting load increased. On the other hand, when angle was changed, the direction of the power transmitted to the string changed. As for the sharpness of the edge tip, when the tip became dull, compression transformation was observed on the string. For this reason, extra power for the transformation was required.