Direct observation of elastic and plastic strain fields during ductile tearing of a ferritic steel
Direct observation of elastic and plastic strain fields during ductile tearing of a ferritic steel
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直接观察铁素体钢延性撕裂过程中的弹性和塑性应变场
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
T. Connolley
中科院分区：
文献类型：
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作者：
H. Coules;G. Horne;M. Peel;S. Oliver;D. V. Gelderen;T. Connolley
Residual and thermal stresses have a considerable effect on the process of brittle fracture. In addition to this, the effect of these stresses on elastic-plastic fracture is known to be significant. This is accounted for in structural integrity assessment methodologies such as R6 Rev 4 and BS 7910:2013 by introducing factors representing the interaction between primary and secondary stresses (those that do and do not contribute towards plastic collapse, respectively). The initiation of ductile tearing in a ferritic pressure vessel steel was studied experimentally. Energy-dispersive X-ray diffraction was used to determine lattice strains in the vicinity of a crack tip in modified compact tension specimens at incremental loading steps until the initiation of ductile tearing. The X-ray diffraction measurements allowed the stress field to be evaluated with a high spatial resolution. At the same time, the pattern of total strain at the surface of the specimen was observed using digital image correlation. Prior to the experiment, two samples were subjected to localised out-of-plane compression ahead of the crack tip to introduce a residual stress field and hence significant crack loading in the absence of external load. Stress and strain field data for cracked specimens, with and without a pre-existing residual stress field, indicated significant differences in the development of plastic strain up to the point of tearing initiation. It is shown that this can only be explained when both residual stress and prior material hardening are taken into account.
