The automatic measurement is described for the relative retardation and principal axes in a photoelastic model. Also explained are the optical arrangement and method for the stress analysis of circular-polarized incident light. The data processing part of the system is composed of a CCD camera, a digital image-frame memory, and a personal computer. Therefore, the images produced by the combination of a quarter-wave plate and a polarizer are converted into digital images and are processed for each pixel. The results of an epoxy resin disk subjected to diametral compression show the usefulness of this method.

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This paper deals with the photoelastic stress investigation of shear stresses over the crosssections near the support of beams subjected to lateral force. In elementary theory, the shearing stress distributions of beams are independent of beam thickness and are wholly dependent on the shear forces. The shearing stress distributions, however, and the deformation obtained by the use of the elementary theory at the beam's boundary usually become incompatible with the actual boundary conditions. To remove this discrepancy, the effect of stress patterns near the support of beams must be considered. The results of the photoelastic experimental analysis are presented in terms of the two parameters, y/b and l/b. Comparison of the photoelastic experimental results show close agreement with those obtained from Filon's theory.

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When processing images with a computer for pattern understanding and other purposes, several problems are generally pointed out. Important ones among them are; (1) the difficulties in subsequent analysis and the accuracy of the result depend greatly on the quality of the input data, (2) large quantities of digitized data need to be dealt with, and (3) complex analysis and usually a long processing time are necessary. For these reasons, a highly efficient computer along with peripheral equipment is usually required. However, such high performance machines are not always available. This is particularly true in the case of the application of image processing to certain practical engineering fields. Thus, image processing techniques are not sufficiently utilized in practical engineering analysis in spite of its usefulness in visualization of phenomena. In this paper, the authors develop and construct an input/output system using a microcomputer for practical application to photoelastic fringe patterns in the field of strength of materials. This system can be easily operated by engineers not specialized in computer. It is applicable not only to interference fringe patterns but also to many other areas.

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When processing photoelastic fringes, there exist several problems such as how to reduce unwanted noise generated by various causes, and how to extract accurately necessary fringes. Using modern techniques for image processing, experimental data are pre-processed in several steps such as enhancing, sharpening and filtering. Then binary and thinning processes are performed. Finally broken portions of fringes are connected manually to obtain smooth fringe patterns. However, determination of the threshold values for the binary process and the connection of broken fringe portions still pose various problems. It is also difficult to construct all of the fringes over the whole image area. In this paper, we would like to express the brightness distribution of fringe patterns of both isochromatics and isoclinics by the spline smoothing method on a microcomputer. Using this method, brightness distribution over the whole area can be successfully smoothed, and the location of extreme points that correspond to the fringes can be easily extracted. We would like to establish the “structure driven image processing method, ”as a valuable improvement for the automatic extraction of photoelastic fringes.

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When analyzing stress distribution experimentally by the photoelastic method, fringe patterns may not be obtained over a whole area. It is necessary, for such cases, to reconstruct the fringe patterns by filling up the broken portions. Currently available techniques for this work are tedious and must be carried out by experts. This may be one of the reasons that the photoelastic method has not been accepted widely in industry. Various methods have been proposed to overcome this. Chief among them are; a hybrid analysis utilizing both numerical and experimental methods, and image processing of photoelastic fringe patterns. In the former, many problem still remain in comparing numerical results with experimental results. In the latter, not all of the procedures in such an analysis have been automated. This paper describes a newly developed algorithm for processing photoelastic fringe patterns on a microcomputer. Experimental data are represented by“smoothing spline functions. ”The locations of extreme points, fringes, and specimen contour are automatically extracted from these spline functions. In the smoothing process, breaks of fringe often occur over the region where the signal and noise ratio is small. Broken portions are reduced by superimposing several images on top of each other. The remaining broken portions, if exist, are automatically connected using locally applied planar curves.

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A new type of combination of three experimental and numerical computation procedures for two-dimensional stress analysis is presented, 1) photoelastic isochromatics (σ₁-σ₂), 2) digital computation of Laplace's equation ∇∇² (σ₁+σ₂) =0, 3) measurement of thickness change Δt= (σ₁+σ₂) νt/E of the model plate along the boundaries subjected to concentrated or distributed loads. The whole Laplace's field of (σ₁+σ₂) is computed by finite difference iterative harmonization procedure with the input boundary conditions obtained by the measurement of thickness change of the plate very accurately using a highly developed Digital Mu-Checker (M-311; Mitutoyo, up to the resolution of 0.0001mm). As the example, this procedure is applied to a circular disk under diametral concentrated loads. The results obtained are found to be satisfactory.

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In this paper, the photoelastic apparatuses are attached to the lathe and fed with the cutting tool concurrently. To prevent wear of the cutting tool the cutting speed was selected with 0.1m/min. After using the tool, the edge of the tool was scrutinized for wearing out. The condition of rake angle are α=0° with normal and restricted tool. The restricted tool was placed with 30° restricted angle of rake. This experiment was done after confirming the shape and size of the tool by using a profile projector. The analysis principle and calculation order by FEM is to divide orthogonal continuous material into quadrilateral element. The principal stress of the restricted and normal tool is maximum at the tip of tool, the shear stress is maximum after a certain distance from the tip. The result of FEM and photoelastic method shows that in the range of rapid decreasing normal stress of the tool edge, the shear stress is maintaining a certain value. And FEM value for stress analysis of tool face during cutting is in accordance with the result of photoelastic experiment well and the possibility of stress analysis of tool rake surface by theoretical analysis without trial was proved. Nomenclature

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Using the photoelastic technique of stress freezing, the rotating discs with a keyway are investigated under centrifugal forces. Disc models with keyways of various radius of curvatures of the corner are prepared. The preliminary experiment for rotating concentric circular ring is conducted in advance and the results are compared with the theoretical solutions. The stress concentration at the corner of the keyway is observed and the stress concentration factors are summarized with respect to the radius of curvature of the corner of the keyway. The optimum shape of the keyway will be deduced from the experimental results.

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