To develop long-life welded bellows used under different pressure conditions, that is, atmospheric pressure and a high vacuum applied to the inside and outside of the welded bellows, respectively, finite-element simulations of the compression process of the welded bellows (Hastelloy C-22, 460mm in external diameter, 370mm in internal diameter, 0.475mm in thickness) with an inclined external edge are carried out. The results are as follows. The pressure difference opens the external section of the welded bellows up and down. The opening angle decreases as the angle of the inclined section increases. Therefore, the stress amplitude at the external edge during the compression process decreases as the angle of the inclined section increases. Welded bellows with an inclined external edge are made for a durability test and they do not break down during the test of 1,200,000 cycles.
In order to consider the application of the vacuum parts to the vacuum procedures in a joining process called surface-activated bonding (SAB), we conducted a SAB experiment at room temperature for the combinations of Al5N/SUS304, Al2N/SUS304, Al5N/SUS316 flange, and Al2N/SUS316 flange. We examined the influence of the cleaning state and the surface roughness on Al/SUS joining performance, as well as the bonding strength and the sealing characteristics of such joined samples. We have found the following. (1) Before joining, smooth surfaces of the Al5N and SUS304 samples were sputter cleaned using an argon fast atom beam (FAB) for 10 and 60 min, respectively, to completely remove surface oxide and organic materials. However, these samples can be joined even if the removal is imperfect. (2) When the FAB irradiation time was longer than 20min for Al5N and 30min for Al2N, the tensile pulling tests indicated bulk fractures in Al without an interface and that the bonding strength of the interface of the joined samples was higher than the Al strength. (3) Leak rates for Al5N/SUS316 and Al2N/SUS316 samples were 1.5 × 10-11 Pa · m3/s and 2.0 × 10-11 Pa · m3/s, respectively. These are within the permissible equivalent leakage of a large ultrahigh-vacuum (UHV) chamber. The leak test behavior with time for both samples indicated stable leak rates and sustainable sealing.
Uniaxial transverse compression tests on SUGI lumber (Japanese Ceder) are performed in a furnace that can maintain temperature and humidity uniformly, and the effects of parameters such as temperature, moisture content and strain rate on the stress-strain curve, which includes the unloading stage, are examined. As the factors used to evaluate lumber rolling characteristics, yield compressive stress, maximum compressive stress and recovery ratio in the unloading stage are selected from the compressive stress-strain curve. We investigate how these factors are affected by the above-mentioned parameters. For example, recovery ratio decreases in the case of lower moisture content and lower temperature. Approximate formulas of rolling load and torque containing the above-mentioned factors are introduced and the effects of the parameters on the rolling load and torque are discussed.
Damage to and fracture of dies of cold forward extrusion of a bolt part former was detected by use of a fractal property of acoustic emission (AE) during a practical manufacturing operation. Two conditions of lubrication, with and without vegetable oil, were employed. A fractal dimension m of AE amplitude was used to detect damage to and fracture of the die. The extrusion rate was set to 100 pcs./min. A decrease in m was observed after a certain number of repetitions of extrusion N under both conditions. Under the condition without vegetable oil, the die insert was completely ruptured by N = 2850. The m took a minimum value at N = 2807, and then increased. The progress of the defects on the surface of the workpiece showed good agreement with the change in m. Under the condition with vegetable oil, the die insert was completely ruptured by N = 11000. A decrease in m was observed at N = 9000. A fast overload fracture with a ratchet mark was mainly observed on the fractured surface of the die insert under the condition without vegetable oil. The region of stable crack propagation around the die radius was dominant under the condition of lubrication with vegetable oil.
The cutting load in the vicinity of the tip of the blade is important for evaluating scissors. Thus, the relationship between the cutting position and the cutting load was investigated. As a result, it is understood that the cutting load increases rapidly in the vicinity of the tip of the blade. This is a phenomenon which could not be explained on the basis of the length of the torque arm. Then, the clearance when the fiber was cut was measured. As a result, it is understood that the clearance when the fiber was cut grows to be positive at the position where the cutting load grows. Moreover, the deformation of the blade measured at the same time indicates that the blade is transformed at this moment. The cutting load increases with due to the increase in clearance. The following two points are suggested as reasons for this observation. One is an increase in the load brought about by an increase in the contact force of the blade due to the transformation of the blade. Another is an increase in the load brought about by the change in the sectional area of fiber due to an increase in the clearance.
In this paper, we describe form rolling of microgrooves (herringbone grooves) on the surface of cylindrical metal specimens used for fluid dynamic bearings. A new reciprocating form rolling machine for the form rolling of microgrooves on metal shafts is deigned and constructed. The materials used are austenitic stainless steel SUS303 and aluminum alloy 6061 with a diameter of 10 mm. The gap between a couple of flat dies is set in the resolution of micrometers. Form rolling performance is checked for two types of die combination : in one type, the upper die has a flat surface and the lower die has herringbone grooves on its surface (flat/corrugated dies); in the other type, both upper and lower die surfaces have herringbone grooves (corrugated/corrugated dies). The depth of grooves does not become uniform in the circumferential direction when using the former die combination, while the latter die combination is effective in producing uniform microgrooves 10 μm deep. It is also found that burrs generated at the tip of projections can be restrained by making the bottom shape of grooves round. Finite element simulation results for the form rolling of microgrooves are in qualitative agreement with the experimental observations.
We have investigated efficient iterative methods for solving a large sparse system of linear equations in elastic-plastic finite element analysis applying the multigrid (MG) method. In this study, we extend this method to the shell structure. For a combination of shell elements and an iterative solver such as an ordinary conjugate gradient (CG) method, it is well known that convergency tends to degrade. The MG method, which we adopt here, is combined with the CG method. This finite element system including the solid-degenerated shell element displays greatly improved convergency. Furthermore we also adapt it to the contact problem. In the latter half of this paper, we show numerical results for plate bending and V-bending analyses. In a series of plate bending analyses, our new solver requires less computing time than the direct solver does, for a fairly large-scale model. For the largest model, which has about 380,000 degrees of freedom, the direct solver is not applicable due to the insufficient memory capacity of the computer (PC) used in this research, whereas our new solver is able to obtain a converged solution. The new solver has obvious advantages in computing time and memory usage over the standard direct solvers.
The use of magnesium and its alloys, which have excellent vibration damping properties, as materials for parts of acoustic equipment, such as the diaphragm used in speakers or tweeters, is now being considered. However, a foil of 50-100μm thickness is required for acoustic equipment, and it is considered difficult to press such a foil made of magnesium and its alloys into the desired shapes. In particular, magnesium foil, which must be processed through warm forming, is expected to be more difficult to form than other metal foils. In this study, we initially used an AZ31 magnesium alloy foil and a pure magnesium foil, which has a higher vibration damping property than an alloy foil, to evaluate the formability in the warm forming of these foils using two press forming methods: stretch forming and deep drawing. Next, on the basis of the examination results, we proposed two forming methods for the manufacture of a dome-shaped diaphragm for a tweeter and succeeded in forming a diaphragm made of pure magnesium foil using these methods.
In this paper, we describe a seam welding technique for aluminum sheets with a gap (before welding) and its experimental results. When an impulse current from an energy-storing capacitor bank passes through a flat one-turn coil, a high-density magnetic flux is suddenly generated inside the coil. Eddy currents are induced in the overlapping parts of two aluminum sheets (1 mm thick each) placed inside the coil. The two parts are strongly pressed simultaneously by applying an electromagnetic force, leading to their collision. If the movement velocity of these parts is high, both their surfaces should be clarified by the effect of the collision known as explosive welding, and then joined by both the electromagnetic force applied and the joule heat generated in them. The bank energy required for welding 5×50 mm2 area becomes less than 1 kJ by generating a gap between the two aluminum sheets.