Papers by Keyword: Constant Penetration Depth Method

Abstract: Three kinds of copper thin films were fabricated by RF-magnetron sputtering. The target power was selected to be 10 and 150 W to change the properties of the films. Thin glass sheet was used as a substrate. For the target power of 150 W, the deposition time was selected to be 7 and 40 min. The thickness was 0.6 μm and 2.9 μm, and the grain size measured was 243 nm and 450 nm, respectively. The grain size of thicker film was larger than that of thinner one. On the other hand, for the target power of 10 W, the thickness and grain size were 2.4 μm and 54 nm, respectively. The grain size depends on the target power. The residual stress distribution in the films was measured by X-ray method. Several methods such as the grazing incidence X-ray diffraction method, the constant penetration depth method and the conventional sin²ψ method were adopted. The measured weighted average stress increased with increasing depth. After taking the maximum value at about 0.3 μm from the surface, the value decreased with increasing depth. The stress distribution near the surface in the films deposited at 150 W was almost identical irrespective of thickness. On the other hand, for the target power of 10 W, the stress distribution shifted to compression side. The reason could be explained by the effect of the thermal residual stress. The real stress distribution was estimated by using the optimization technique. The stress took the maximum value at 0.5 μm from the surface, and was compressive near the substrate. .

Abstract: The compressive stress distribution below the specimen surface of a nanocrystalline medium carbon steel was investigated nondestructively by using high-energy X-rays from a synchrotron radiation source, SPring-8 (Super Photon ring-8 GeV) in the Japan Synchrotron Radiation Research Institute. A medium carbon steel plate was shot-peened with fine cast iron particles of the size of 50 μm. By using the monochromatic X-ray beam with three energy levels of 10, 30 and 72 keV, the stress values at the arbitrary depth were measured by the constant penetration depth method. The stress was calculated from the slope of the sin2ψ diagram. Measured stress corresponds to the weighted average associated with the attenuation of the X-rays in the material. The real stress distribution was estimated by using the optimization technique. The stress distribution was assumed by the third order polynomial in the near surface layer and the second order polynomial. The coefficients of the polynomials were determined by the conjugate gradient iteration. The predicted stress distribution agreed well with that measured by the conventional surface removal method.