X線による応力測定法に関する研究

Abstract

Recently, the experimental procedure of X-ray stress measurement has been notably improved because of improvement of the equipment for use as well as of revision of theoretical background. However, there are a few problems that want further investigations. One of them is the question whether the stress values obtained from the measurement of a state of stress by using different lattice plane coincide or not. This problem of diffraction plane dependence has been discussed to some extent up to date, but its real feature is still in the vague. Consequently, considering from the stand point of engineering application, it is important to determine the most favourable diffraction plane for the measurement of stress through the use of characteristic X-ray. In order to clear up the problem, the author performed the following experiments. Two sorts of materials were used in this experiment, one being annealed specimens of 0.07% carbon steel and the other a plastically extended specimens of 0.13% cabon steel plate. All specimens were etched before subjecting to X-ray photography. The characteristic X-ray ofCoKα1, CrKα1 and FeKα1 were radiated to the specimen surface through double pin hole of 1 mm in dia. and stresses were measured by adopting the diffractions from (310), (211) and (220) atomic planes. Since it is important in stress measurement to have an accurate measure of the distance between film and specimen surface for each exposure of film, the standard substance was used and both diffraction lines of standard substance and objective materials were taken on the same film.Intensity distribution curve was taken from each pattern by using an automatic recording type microphotometer. The distance between peak position of intensity of diffraction from standard material and specimen was measured from these curves. This process led us to very easy detection of the peak of X-ray diffraction and also to exact measurement of length on the film. Stress determination was practiced by employing so-called sin2 φ method.Two series of experiments were carried out as follows;(A) A special miniature bending testing machine was used and surface stress on specimensof annealed 0.07% carbon steel was measured by X-ray at several stages of bending within elastic range. The mechanical stress and the value of X-ray stress which was obtained from each lattice planes were compared.(B) Experiments were made concerning the diffraction plane dependence in the measurement of residual stress that was produced by plastic deformation. Annealed 0.13% carbon steel specimens were stretched beyond yield point. At several stages of loading the load was removed and the surface residual stresses were measured using (310), (211) and (220) atomic planes obtained by CoKα1, CrKα1 and FeKα1 radiation, respectively. On the other hand, well known corrosion method for measurement of residual stress was adopted, in order to correlate the results with the residual stress determined by X-ray method.The conclusion of the present study is as follows;(1) As far as mechanically applied stress is concerned, the stress value determined by means of X-ray agrees very well with the mechanical stress. This coincidence gives us a proof of high accuracy of the X-ray stress measurement.(2) Concerned with the determination of residual stress produced by plastic deformation by means of X-ray, it was confirmed that the values of residual stress obtained from measurement on the diffraction lines of (310) atomic plane by CoKα1 and (211) atomic plane by CrKα1 radiation were close to each other, but the values due to (220) plane by FeKα1 radiation is likely to disagree from these measurements.kn-abstract=