| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2005: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2004: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Research Abstract |
In general, metals are usually hardened by plastic deformation under forces applied by various tools. Deformation processes are known as forging, rolling and extrusion. As the degree of plastic deformation increases, the strength of a structural or machine part usually increases. It is important when the load is heavy. On the other hand, the surface properties of the machine part is important same as properties of inside the materials. The surface treatments are usually used to improve the surface properties such as wear resistance and corrosion resistance. Plating, vapor deposition and thermal spraying are generally employed as the surface treatments. Shot peening is one of the surface treatments and it is defined as the process of cold working the surface of the structural or machine parts. This process is very useful for the improvement of the surface properties, especially fatigue strength. In this process, the material surface is collided repeatedly with many steel shots, making o
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verlapping indentations on the surface. The material undergoes large plastic deformation near the surface due to the collision of many shots. The plastic deformation is generated only in the material surface. Shot peening imparts compressive residual stresses on the surface, thus improving the fatigue life of the machine parts. Thus, shot peening is extensively used on automobile parts such as gears and springs in order to increase resistance to fatigue and stress corrosion failure.
In the present study, lining of the metal with foils using shot peening was investigated to improve the surface layer characteristics. In the shot peening experiment, a lot of foils set on the metal are pelted with hard particles traveling at a high velocity. These foils are bonded to the metal surface due to plastic deformation induced by the collision of the particles. The foils and the metal are heated to heighten the bondability because of the reduction of flow stress. In the experiment, a centrifugal shot peening machine with an electrical heater was employed. The metals are commercially carbon steel, pure copper and titanium alloys, and the foils are commercially aluminum, titanium and nickel. The effects of shot speed and the heating temperature on the bondability were examined. Bond strength was also evaluated by bending. Many foils were successfully bonded to the metal surface under an optimum condition. It was found that the present method is effective in improving of surface layer characteristics. Less
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