This paper describes the microstructure of Type 304 stainless steel after cyclic loading at room temperature under tension-torsion non-proportional strain paths. The degree of cyclic non-proportional hardening is correlated with changes in the dislocation substructure. Dislocation cells, dislocation bundles, twins and stacking faults are all observed. The type of microstructure formed and resultant stress response is dependent on the degree of non-proportional loading and strain range. Cyclic stress range was uniquely correlated with mean cell size.

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Abstract:Recently, a vacuum furnace for porcelain firing using high density and direct near infra-red rays was developed.A comparative study between the high density and direct near infra-red rays furnace and conventional porcelain firing furnace was made as follows using facial veneer type of porcelain fused cast crowns utilizing three types of alloys (Ni-Cr alloys, palladium alloys and gold alloys):repeated dynamic loading tests were made on crowns and shear bond strength tests using cylindrical rod specimens.Result of repeated dynamic loading tests: 1) Higher bond strength was obtained by firing in the direct near infra-red rays furnace than in conventional furnace.2) The bond strength of the gold alloys was the highest, and followed by that of palladium and Ni-Cr alloys.Results of shear bond strength tests: 1) Higher bond strength was obtained by firing in the direct near infra-red rays furnace.2) The bond strength of the gold alloys was the highest, and followed by that of Ni-Cr and palladium alloys. Result of SEM picture 1) Differences between firing methods were barely discernible in the opaque porcelain layers.2) Better bond strength of feldspar and quarts was observed in the deep part of the body of porcelain layers with direct near infra-red rays.

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