Abstract
The authors were concerned with the factors which influence high-amplitude acoustic emission during ductile crack extension in quenched and tempered low-alloy steels. A systematic approach was adopted to isolate the effects of compositional variables, microstructural variables, and strength level. Experimental steels were used to avoid the effects of uncontrolled changes in composition and manufacturing process which are inevitable when comparing steels which have been produced commercially. The effect on acoustic emission of the following variables was evaluated: 0·2% proof stress, carbon content, sulphur content, and sulphide morphology. It appears that proof stress is the most important factor governing the amount of high-amplitude acoustic emission generated as the result of ductile cracking in steels; a secondary influence is exerted by the sulphur content in steels which contain elongated manganese sulphide inclusions. The results indicated that very low levels of high-amplitude acoustic emission would be expected during the ductile cracking of steels with proof stress levels below about 1000 N mm−2.
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