三次元モアレ法に関する研究 : 高速三軸歪同時測定のモアレ新方式
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概要
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Studies of large plastic deformations of ductile materials under high speed dynamical load will, when adequately analysed, give fundamentals of fracture dynamics and thus will be the foundation for all metal workings. Experimental measurements of stress and strain distribution for this purpose could be made in many ways such as, by using mechanical or electrical strain gauges, photoelastic techniques, brittle coating methods, various grid or grating methods and so on. They all have their advantages and disadvantages respectively. However, effective representation to give both time and spatial distributions of displacements or deformations simultaneously on the actual material itself, under high speed range is not an easy matter. Experimental results on such high speed transient strain fields are therefore very few at this time. In this paper, Moire fringe techniques were applied for the high speed transient strain field analysis of the ductile metal test piece, and successful results were obtained. Moire fringe techniques are not new, but actual examples of their applications in such field are rare. In this experiment, dynamical load was given by a projectile shot from a specially designed gun type testing apparatus, and the phenomena were recorded by a multiflash high speed photography. According to its principle, Moire fringes show the distribution of displacements of deformations only on the surface (2-dimensionally) and therefore general display of 3-dimensional or 3-axial deformations has been impossible. Extending the ordinary Moire techniques, the author developed two unique new methods to measure distributions of transverse or vertical to the surface displacements directly on the specimen. High speed transient strainfield changes could now be analysed 3-dimensionally at the same time. These methods are to be called tentatively : a) V.O.I. Method, after the principle of illuminating through the original Moire pattern screen from Vertical or Oblique direction. (b V.O.O. Method, after the principle of Observing the deformation of the original Moire pattern printed on the surface from Vertical and Oblique directions. Details of the principles are shown in the main discussion of this paper. V.O.I. Method, using collimated or focused light, is to be used mostly in the laboratory for precise measurements on the specimens, while V.O.O. Method, could be used in open field for full scale tests because the limitation of the use of collimated or focused light and its transit through the master Moire pattern screen were both avoided. These methods are both expected to be used widely in the near future. By using these techniques to the full, high speed transient behaviours of annealed aluminum specimens in the vicinity of proceeding indentation of a hard steel wedge were examined and the results thus obtained were compared with the statical ones, and the difference between them were also discussed. Experimental results were analysed 2-dimensionally at the beginning and then treated 3-dimensionally by using the new methods. Accordingly, simultaneous measurements of high speed transient 3-axial displacements or deformations on the actual metal were achieved for the first time.
- 湘南工科大学の論文
- 1971-03-31