Abstract
Acoustic emission (AE) testing has been carried out with uniaxial and biaxial (2:1 stress ratio) stressing of smooth samples of 21–6–9 and 304 stainless steel (SS). Uniaxial testing was done with simple tensile and compression samples as well as with the special biaxial specimens. Biaxial tensile stressing was accomplished with a specially designed specimen, which had been used previously to characterize AE in 7075 aluminium under biaxial stressing. Results were obtained for air-melt and for vacuum-melt samples of 21–6–9 SS. The air-melt samples contain considerably more inclusion particles than the vacuum-melt samples. For the 304 SS, ‘as received’ material was examined. To allow AE correlations with microstructure, extensive characterization of the 21–6–9 microstructure was carried out. Significant differences in AE occur in biaxially stressed specimens as compared to uniaxially stressed samples.
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