Influence of surface hardening by laser irradiation on the loss factor of cast iron
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Influence of surface hardening by laser irradiation on the loss factor of cast iron Hiromasa Adachi, Yoshihiko Masuo, and Teruo Hasegawa Nagoya Municipal Industrial Research Institute, 3-4-41 Rokuban, Atsuta-ku, Nagoya 456, Japan (Received 7 February 1997; accepted 10 July 1997)
Surface hardening by laser irradiation was examined regarding the loss factor, which is the parameter of the vibration-damping characteristics, for flake graphite cast irons and spherical graphite cast irons. The surface of the samples was quenched by changing speed of beam, gas pressure, and beam frequency. It was found that the depth of the hardening region was from 0.12 mm to 1.11 mm, and the hardness of the boundary between the hardening and the nonhardening regions changed suddenly. It was confirmed that the loss factor of the laser hardened specimens increased considerably as compared with that of the as-cast specimens. The internal friction at the vicinity of the boundary between the hardening and the nonhardening regions may be responsible for this result.
I. INTRODUCTION
II. EXPERIMENTAL
Making materials light, thin, short, and small, was suitable for reinforcing noise and vibration regulations, which promoted the development of vibration-damping materials for many manufacturers, and in particular, car manufacturers. Some of the materials are restricted type composite steel sheets, which are two-layer structures pasted and sprayed with rubber or plastic on steel sheets, and other materials are nonrestricted type composite steel sheets, which are three-layer structures sandwiched in a very thin rubber or viscoelastic material by two layers of steels. The former is damped because of viscoelastic hysterics by elongation deformation of the viscoelastic material, and the latter is damped because of viscoelastic hysterics by shear deformation of the viscoelastic material. However, at points such as the properties to be processed, application temperature, etc., the use range is limited only by using the viscoelastic material together, and there are many cases that do not fill the design demand. Accordingly, metal materials of high strength need to have high vibration-damping characteristics.1–3 Surface hardening by laser irradiation is applied positively for car manufacturers in the U.S., and contributes to improvements of quality and productivity as well as friction and wear characteristics. In other countries in the 1980s, examination was advanced mainly for iron and steels, mainly related to cars, and surface hardening by laser irradiation has only escaped recently from the study stage; by this time we expected practical use and have begun to need it, but there are almost no data about vibration-damping characteristics available.4–7 In this study, surface hardening by laser irradiation was examined regarding the loss factor, which is the parameter of the vibration-damping characteristics, for flake graphite cast irons and spherical graphite cast irons.
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