Continuous vs.Discontinuous Crack Extension:Characterization of Ductile Tearing in Thin Plates
There are two alternative trends of thought concerning the mechanism of crack extension in an elastic-plastic material subjected to monotonically and slowly increasing tensile (Mode I) loading.The crack advances continuously,by infinitesimal growth steps,or discontinuously in finite growth steps.In this experimental study,slant cracks were extended in thin aluminium plates,depending on theirs geometry,with or without an intermittent attainment of the local instabilities displayed in test records.It means that the mechanism of ductile tearing in the test material may be changed simply by changing the specimen geometry.This observation is not in accord with the well-known energetic considerations that a mechanism of crack extension in a non-hardening or low-hardening elastic-plastic material must be only discontinuous.A wide consensus exists that a single-parameter characterization of crack extension is conceptually possible when fracture resistance is quantified by a critical,lower-limiting value ψc of the Crack Tip Opening Angle (CTOA-ψ).It is of scientific and practical interest to measure CTOA-ψ for slant cracks growing at different in-plane constraint states and in this way to clear up the above contradiction.In our specimens that were fractured under the highly constrained conditions of transverse plane strain,cracks were advancing in well-defined steps.The CTOA- ψ values related to different pairs of distinct fracture events strongly depend upon the choosing the neighboring pair.They were compared with the critical angles ψc determined with the use of ASTM/ ISO Standard test method and also with the CTOA- ψn values established from profiles of fully-developed cracks.
Crack extension Thin plates Thin-sheet aluminium Crack tip opening angle In-plane constraint
Volodymyr P. Naumenko
Department of Structural Integrity,G.S.Pisarenko Institute for Problems of Strength,Kyiv 01014,Ukraine
国际会议
北京
英文
1-10
2013-06-16（万方平台首次上网日期，不代表论文的发表时间）