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Principle of the Method of Caustics and its Application

Koji SHIMIZU
Kanto Gakuin University

Fundamental principle of the method of caustics is described and some applications of this technique on various problems at our laboratory are shown. When this technique is applied to the stress-frozen model in photoelasticity, there appears very different caustic patterns from those of usual one. Next, as an example of application on the dynamic fracture problem, analysis of fracture behavior of ceramic materials under dynamic loading at high temperatures is described. Moreover, special application of this principle on the method of ultrasonic caustics which is used to evaluate the defect size in the circular rods in water is shown.

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Fig.1 Principle of caustics method


Fig.2 Theoretical caustic pattern

  (a) KI=KII>0                                                                      (b)KI=KII<0

Fig.3 Theoretical caustic pattern for Mixed-mode for Mode I  ($B&K(J>0, $B&N(J=0) condition  ($B&K(J>0, $B&N(J=0)

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Fig.4 Schematic view of experimental apparatus of caustics method

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Fig.5 Caustic patternof stress-frozenmodel (PC, $B&K(J<0)


Fig.6 Caustic patterns under dynamic loading at high temperature (PSZ, 800$B!n(J, 106FPS)


Fig.7 Variations of dynamic KI and crack length a with time (PSZ, 800$B!n(J)

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Fig.8 Formation of ultrasonic caustic pattern (Aluminum, parallel ray,longitudinal wave)


Fig.9 Basic concept of ultrasonic caustics

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Last Updated July 15, 2001