A Review of X-Ray Films for the Measurement of X-Ray Residual Stresses (Photographical Method)

Abstract

It is a matter of common knowledge that there are two ways, namely counter method and photo method, to measure X-ray residual stresses. it is a recent tendency that reinforcement of the counter method by a photographical method has been gradually prevailing at laboratories.At the same time, the manufactures of X-ray stress measuring apparatuses are trying to adapt the photo method every way.To cope with the above-mentioned situation, “Konishiroku”and“Fuji”, both Japanese typical makers of X-ray films that form the basis of the photo method, have made efforts to review X-ray films, and carried out sufficient testings on X-ray films for both industrial and medical uses.However, there are few data for X-ray area concerning the measurement of X-ray residual stresses. Therefore, our laboratory investigated in photo sensitivity, grain size, fixing time and the like, for five varieties of Types N, S, Y, RR, and R films, which are altogether the products of the“Konishiroku”, and carried out testings to determine the X-ray film best suited for the measurement of X-ray residual stresses.Putting their results together, Type N is superior to any other types in sensitivity and contrast, while it is very much inferior to any other types in grain size and fixing time.Type-S is inferior to Type N in sensitivity, and about equal in contrast, while the former is very much superior to the latter in grain size and fixing time.Type Y is shorter than any other types in fixing time, while it is equal to Type S and very much superior to Type N in grain size.Although Types RR and R are characterized as excellent in contrast in their maker's catalog, it has been proved that even when 30 minutes' exposure has been processed in such a condition as when it is used by us, they did not turn in the straight line area, so such films are not of any practical use.Therefore, it has been concluded that Type S is the best one for use in the measurement of X-ray residual stresses, because it is superior in contrast, grain size and fixing time, though it is a little inferior to the best Type N in sensitivity.Furthermore, in the process of these tests, has been ascertained again the efficiency of X-ray filter, that was reported in the special issue of the Society Journal last year, concerning X-ray stress measurement as mentioned below.According the to the characteristic density curve of X-ray film shown when the X-ray filter is not used, the density of diffraction line becomes high in a short time, while the density of the background becomes high. Therefore, the value of the density of diffraction line minus the background density namely the effective density decreases.However, in the case of the characteristic curve of X-ray film with the use of the X-ray filter, the density of diffraction line does not become so high in a short time. But as the density of background does not become high, even if the exposure time becomes longer, the latter is superior to the former in the effective density and contrast.As a result, it has been made clear that the efficiency of such an X-ray filter is to be greatly enhanced by setting it before the X-ray film, so as to absorb the diffused reflection of X-ray besides making the characteristic X-ray, unicolorous which is the main purpose of this filter.