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Digital approaches for determination of fringe order and principal stress direction in photoelastic coatings are presented. The relationships between the intensity values and the fringe orders of two wavelengths, and relevant theory and explicit conditions for directly determining the principal stress angles in the range z/2 are derived. The scheme developed allows for the automatic determination of the fringe orders with or without zero-order fringes in the fringe patterns. Test results are reported.

Two base metals, a Cu–Si enriched type 304 stainless steel (containing 2–2·5 wt-% copper and 1–1·5 wt-% silicon) and a conventional type 304 stainless steel were welded using gas metal arc welding. The filler material was type 308L stainless steel and the shielding gas was a mixture of 98% argon and 2% oxygen. Inspection of the welds revealed that more δ ferrite was present when welding the Cu–Si enriched type 304 steels. Post-weld tensile strength and ductility were both lower in the Cu–Si enriched steel because copper and silicon formed low melting point compounds and tended to segregate to the grain boundaries. Ductility decreased and ferrite levels increased in both weldments as the heat input increased.

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