Principle And Methods Of Measuring Non-Destructively Residual Stresses Of Beryllium With X-Ray

Beryllium is a light metal. It is broadly used in nuclear energy, aviation and aerospace industry because of its excellent properties such as low density, high specific strength, specific heat capacity and good heat conductivity. As a structural material, there exist residual stresses in it to a different extent while it is processing. In many cases the residual stresses have a harmful influence upon Beryllium and its products when they are in use. Because beryllium and its products are used in the relative special fields, it is quite difficult to measure their residual stresses in non-destructive way by comparison with thegeneral structural material------iron and steel. It has been rarely reported for the studyabout the measurement of the residual stresses. The measurement of residual stresses by X-ray diffraction is a mature technique. Since beryllium is a light element material, it has little absorption to X-ray beam, lead to a higher penetration depth. Many of X-ray stress analyzer at present are designed for heavy element materials such as iron and steel. So it is very important how to make the present analyzer apply to non-destructive measurement of beryllium's residual stress by altering measuring technique and evaluating method.The present X-ray residual stress techniques are systematically analyzed in this paper. To aim at the shortcoming of these techniques and AST2001 X-ray stress analyzer of USA when used in determination of the residual stress of weldments made of beryllium and the item processed by hot isostatic pressing, X-ray computer tomography applied to measurement of beryllium's three-demensional residual stress with depth resolution is first presented on the basis of higher penetrating capacity of X-ray in beryllium. This method can non-destructively measure beryllium's three-demensional residual stress with depth resolution and calculating the stress free lattice spacing, d0, of the material in test. The evaluating result is controlled by three self control mechanism, that is linear correlation coefficient, R, Poisson's ratio, v, and the error estimators, and is high reliable. According to the equilibrium conditions of the linear elasticity theory and the surface boundary conditions, X-ray residual stress integral transform method is first presented. From the developed model function of the residual stress components varied with depth, beryllium's three-dimensional residual stress with depth resolution can be determined only by one characteristic X-ray. This method can avoid the irradiated point displacement due to changing the target when different characteristic X-ray used and has more improved than multi-wavelength method. The measuring precision has beenincreased by this method. The X-ray computer tomography measuring system used to determine the residual stresses of beryllium and its products is designed. In this system X-ray multi-rotating-variables control system can control the measuring device where the tested workpiece is placed on it and which can provide four motive freedom. When the tapered slit is installed on ASTX2001 X-ray stress analyzer, it can effectively restrained the incoming reflecting beam that can enter the X-ray stress analyzer's detector without the tapered slit at non-tested point. The point on every measuring can be restricted within 0.4mm. The residual stresses within the workpiece are measured by X-ray computer tomograpy in the way of point by point, surface by surface and layer by layer. This system extends the applying scope of ASTX2001 X-ray stress analyzer. It makes the analyzer can not only determine the residual stresses of heavy element materials such as iron and steel, but also non-destructively measure light element materials such beryllium when the tapered slit is mounted on ASTX2001 X-ray stress analyzer.Computer programs for X-ray residual stress computer tomography and X-ray residual stress integral transform method are designed in this paper. X-ray residual stress computer tomography is verified with the experimental data of ber...