Establishment of X-Ray Fractography as Failure Analysis Method

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1. X-ray diffraction observation of fracture surfaces yields useful information to analyze the causes of failure accidents of engineering structures. This experimental technique has been maned X-ray fractography. The following four X-ray parameters have been confirmed useful for determing the mode and mechanical conditions of fracture: residual stress, full width at half maximum (FWHM), diffraction pattern, and transformed phase.2. Computer image processing of diffraction patterns was use to determined the reversed yeild zone within the maximum yield zone on the fatigue fracture surface of mild steel. The distribution of FWHM is also useful for this determination of two kinds of zone.3. Although the residual stresses measured on fracture surfaces were tension in most cases, the compressive residual stresses were detected on the fatigue fracture under a high compressive mean stress and on the shear fracture surface made under mixed mode loading.4. The X-ray fractographic methods established for fatigue fracture in air at room temperature were found to be applicable to corrosion fatigue and high temperature fatigue. Quantitative analysis of creep fracture surface is left for a future study.5. The measured distribution of residual stresses beneath the fracture surface of alumina was usable for determining the depth of the plastic zone.6. The depth of the plastic zone beneath fracture surfaces measurd by X-ray methods is expressed by a fracture mechanics equation of the stress intensity factor and the material yield strength.7. X-ray fractographic techniques were successfully applied to fracture accidents in service of shaft, pin, bearing and high temperature materials.