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Effect of shot peening coverage on fatigue limit in round bar of annealed medium carbon steel
Junji Sakamoto,이용성,정성균 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.9
Shot peening is an effective and economical technique for improving the fatigue strength of metallic components by inducing compressiveresidual stress and hardening the layer near the surface. The effect is generally evaluated by main two parameters: coverage andpeening intensity. However, the valuable coverage for improving the fatigue strength depends on the shape of the target material. In thisstudy, the effect of coverage on fatigue limit in round bar of annealed medium carbon steel was experimentally studied. The fatigue limitsfor shot peened round bar specimens with 140-2300% coverage increased 14-25% by comparing those for non-peened round bar specimens. The valuable range of coverage was 280-560% in the used material and shot peening condition for improving the fatigue limit inshort time. The result indicates that the valuable coverage of the round bar material is higher than full coverage to improve the fatiguelimit of the material due to the effect of incident angle on round bar, even though the degree depends on the materials and shot peeningconditions.
Mitsuru UESAKA,Atsushi FUKASAWA,Fumito SAKAMOTO,Haruyuki OGINO,Junji URAKAWA,Katsuhiro DOBASHI,Kazutaka TAKAO,Mitsuo AKEMOTO,Tomohiko YAMAMOTO,Toshinobu MIYOSHI,Toshiyasu HIGO 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.1
A Compton scattering X-ray source consisting of an X-band (11.424 GHz) electron linear accelerator (linac) and Q-switched Nd:YAG laser is currently under construction. Monochromatic hard X-rays are required for a variety of medical and biological applications. The new hard X-ray source produces monochromatic X-rays via collision between a 35-MeV multi-bunch (104 bunches in a 1 μs RF pulse) electron beam and 1.4 J/10 ns (532 nm) Nd:YAG laser beam. The linac uses an X-band 3.5-cell thermionic cathode RF gun and an alpha magnet as an injector. The thermionic cathode RF gun is the first of its kind and can generate a high current (2 μA) and a multi-bunch 2-MeV electron beam. To increase the efficiency of the X-ray yield, a laser pulse circulation system is adopted, that can increase the X-ray intensity by up to 50 times. This scheme can produce monochromatic tunable X-rays (10 40 keV) with intensities of 108 109 photons/sec. In addition, the X-ray energy can be changed rapidly over 40 ms by two different wavelength lasers (YAG fundamental (1064 nm), 2nd harmonic (532 nm)) and an optical switch. This quick energy change is very important for living specimens and is very difficult to achieve in light sources such as a large SR (Synchrotron Radiation) source. The system can be used for dual-energy X-ray CT and subtraction X-ray CT to determine the 3D distribution of the atomic number density and electron density, and specified atomic distribution, respectively. In this paper, we describe the details of the system, report on experiments on the X-band thermionic cathode RF gun, and discuss applications of monochromatic X-rays.?