Papers by Keyword: Area Detector

Abstract: The rotating-slit system was developed to overcome the measurement of internal stress using 2-dimensional detector. The diffraction spot trace method was proposed and examined to measure the internal stress of the material with coarse grains.

Abstract: Stress measurement on samples with texture and large grains is always a challenge. The diffraction peak intensity varies dramatically with different sample orientation. The macroscopic elasticity becomes anisotropic due to strong preferred orientation. The large grains may results in a big error in 2θ due to poor sampling statistics. The fitting results of the conventional sin²ψ method is extremely sensitive to texture and large grains. When stress is measured with a 2D detector, most of the above adverse effects can be minimized or eliminated. The data integration helps to smooth out rough diffraction profiles due to large grain size, texture, small sample area or weak diffraction. The large angular coverage and multiple diffraction rings can minimize the effect of the macroscopic anisotropy. The weighted least squares regression and intensity threshold can further reduce the effect of poor statistics associated with texture and large grains. Multiple {hkl} rings may be used to measure the stress to improve the statistics and minimize the elastic anisotropy effect.

Abstract: The two most important advances in two-dimensional x-ray diffraction (XRD²) are area detectors for collecting 2D diffraction patterns and algorithms in analyzing 2D diffraction patterns. The VÅNTEC-500 area detector represents the innovation in detector technology. The combination of its large active area, high sensitivity, high count rate, high resolution and low noise, makes it the technology of choice for many applications, including texture analysis. A 2D diffraction pattern contains information in a large solid angle which can be described by the diffraction intensity distribution in both 2θ and g directions. The texture information appears in a 2D diffraction pattern as intensity variation in g direction. The intensity variation represents the orientation distribution of the crystallites in a polycrystalline material. The diffraction vector orientation regarding to the sample orientation can be obtained by vector transformation from the laboratory space to the sample space. The fundamental equations for texture analysis are derived from the unit vector expression in the sample space.

Abstract: Two-dimensional x-ray diffraction is an ideal method for examining the residual stress and texture. The most dramatic development in two-dimensional x-ray diffractometry involves three critical devices, including x-ray sources, x-ray optics and detectors. The recent development in brilliant x-rays sources and high efficiency x-ray optics provided high intensity x-ray beam with the desired size and divergence. Correspondingly, the detector used in such a high performance system requires the capability to collect large two-dimensional images with high counting rate and high resolution. This paper introduces the diffraction vector approach in two-dimensional x-ray diffraction for stress and texture analysis, and an innovative large area detector based on the MikroGap™ technology.

Abstract: In this study, the authors investigated the application of the area detector type method for the purpose of evaluating residual stress in tools having a V-groove. The specimen used was a shot-peened forming rack. This alternative method uses a diffraction ring and single incidence X-ray to clarify precisely and effectively complex stresses and stresses in narrow parts of the tools such as the teeth on the surface of the rack. In addition, the authors evaluated stress gradients generated after shot peening using synchrotron radiation (SR).

Abstract: The influence of the peak determination method on the area detector type neutron stress measurement method was investigated. Two peak determination methods, the half value breadth method and the centroid method, were compared and discussed in this paper. Experiments and simulation studies were carried out respectively. The first experiment was conducted during the tensile stress test with a steel specimen having the thickness of 6mm, and the second experiment was conducted with steel specimens in the stress free state having the thickness between 1 mm to 20 mm. As a result of the experiments, it was found that the peak determination method has an affect on the area detector type neutron stress measurement. A numerical simulation study was also conducted and showed similar result as the experiments.

Abstract: In order to study the method of the neutron stress measurement using the cosα method, a numerical simulation study was performed and the result was compared with author's former experiment. The results of the simulation study agreed with those obtained in the previous experiment, which suggests the validity of the present method for neutron stress measurement.

Abstract: Starting from simple geometric considerations concerning directions and orientations, intelligent strategies for pole figure measurements were developed for the area detector. The amount and quality of texture information contained in measured or available data sets can be directly controlled. The texture approximation is done by the component method. The method does not have any restrictions concerning the grids of sample directions in the pole figures. An almost constant information depth can be obtained at a low angle of incidence of the primary beam for the study of thin surface layers.