RESIDUAL STRESS ANALYSIS OF CONCRETE POWDER SAMPLE USING X-RAY DIFFRACTOMETER (XRD)

CIVIL ENGINEERING

The XRD technique for determining residual stresses in construction has been commonly utilized in the international scientific community for many years. Taking advantage of the concepts on which the technique is predicated, this study paper presents an advance within the latter utility by means of the laboratory calibration of the X-ray diffraction techniques in determining residual stresses. Using laboratory based or portable equipment, the XRD technique measures surface residual stresses by measuring the material's inter-atomic spacing. Laboratory X-rays have wavelengths of some order of angstroms (Å), which also has the same order of magnitude inter-atomic/inter-planar distances in polycrystalline solids. X-rays incoherence from a polycrystalline solid can critically interfere producing a diffracted beam. The angles at which the utmost diffracted intensities occur are measured. From these angles it's possible to get the inter-planar spacing (d), of the diffraction planes using Bragg’s law. If residual stresses subsist within the sample, then the (d) spacing would be distinct from that of an unstressed sample. This difference is proportional to the magnitude of residual stress present. Also bi-axial residual stresses are measured using XRD. The accuracy of those techniques is heavily dependent upon good surface preparation and grain size/texture which has been briefly discussed during this paper.

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