Influence of macroscopic residual stress fields on fatigue crack growth measurement in SiC particulate reinforced 8090 aluminium alloy
作者:
KnowlesD. M.,
KingJ. E.,
期刊:
Materials Science and Technology
(Taylor Available online 1991)
卷期:
Volume 7,
issue 11
页码: 1015-1020
ISSN:0267-0836
年代: 1991
DOI:10.1179/mst.1991.7.11.1015
出版商: Taylor&Francis
数据来源: Taylor
摘要:
AbstractThe effect of residual stresses, induced by cold water quenching, on the morphology of fatigue crack fronts has been investigated in a powder metallurgy 8090 aluminium alloy, with and without reinforcement in the form of 20 wt-%SiC particles. Residual stress measurements reveal that the surface compressive stresses developed in these materials are significantly greater than in conventional metallurgy ingot 8090, because surface yielding occurs on quenching. The yield stresses of the powder route materials are greater than those of ingot produced 8090 and hence greater surface stresses can be maintained. In fatigue, severe crack front bowing is observed in the powder formed materials as a result of the reduction of the R ratio (minimum load/maximum load) by the compressive residual stresses at the sides of the specimen, causing premature crack closure and hence reducing the local driving force for fatigue crack growth∆Keff. This distortion of the crack fronts introduces large errors into measurements of crack growth rate and threshold values of∆K.MST/1370
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