Abstract:

A synthetic method to calculate stress intensity factor KI by use of the data obtained in the experiment of three dimensional photoelasticity is developed in this paper. The process of this method may consist of essentially three phases. 1.curve fitting the data measured around a crack to the area required;2.analysing the results experiment and determining the "blunt" situation at the tip of crack;3.using Taylor series and extrapolating to obtain the stress intensity factor KI at the tip of crack. The method over-comes not only the measured deficiency of fringe information in the area but also the difficulty of measuring the accurate value of fringe at the tip of crack because of the "blunt" situation. A comparison of the results obtained by three methods of calculating the data of a typical experiment about a semicircle surface crack of a specimen shows that the synthetic method is the most accurate.

Key words: three dimensional crack, stress intensity factor, calculating method of photo-elastic experiment