Abstract
A double cantilever beam geometry has been chosen in order to investigate the importance of the higher-order terms of the Williams’ power expansion for the crack path estimation. The crack propagation has been tested experimentally on a brittle polymethylmethacrylate (PMMA) specimen and although the mode I loading conditions were applied, the crack kinked from its original plane immediately and propagated towards the bottom side of the specimen. It has been shown that this phenomenon is connected to the magnitude and sign of the T-stress and to the level of the constraint generally. In this work, the influence of the third and higher terms of the Williams’ series on the crack propagation is investigated. The generalized form of the well-known maximum tangential stress fracture criterion for determination of the crack propagation angle has been tested and discussed. The observed differences in the crack trajectory of different specimens have been found to be related to the magnitude of the higher-order terms of the stress tensor components at the crack tip.
Highlights
A s one of the important types of material failure, brittle fracture has been widely taken into consideration by researchers, trying to propose precise failure prediction criteria for different brittle and quasi-brittle materials such as rocks, concretes, ceramics and polymers
Among the studied geometries in their research, application of only the first stress term in Williams’ series expansion for fracture prediction of Tapered Double Cantilever Beam (TDCB) specimens made of Harsin marble rock resulted in 47% difference with the Average Strain Energy Density (ASED) results obtained by considering all stress terms in a control volume around the crack tip for the same specimen
The reason is that when the crack propagation in the DCB specimen with W = 30 mm was investigated, no deviation from the original crack plane was observed, i.e. the crack propagates in the original direction regardless the distance of the crack tip where the criterion is applied as well as the number of the Williams’ expansion (WE) terms considered
Summary
A s one of the important types of material failure, brittle fracture has been widely taken into consideration by researchers, trying to propose precise failure prediction criteria for different brittle and quasi-brittle materials such as rocks, concretes, ceramics and polymers. This paper shall show differences between the well-known one-parameter fracture mechanics concept and the multiparameter one Whereas the former one uses the stress intensity factor (SIF) as the single-controlling parameter for assessment of the fracture response of the specimen/structure [10], the latter one is based on the approximation of the stress/displacement crack-tip field by means of the Williams’ expansion (WE) [11], i.e. an infinite power series originally derived for a homogeneous elastic isotropic cracked body subjected to an arbitrary remote loading. Ayatollahi et al [22] proposed two fracture criteria based on strain energy density to take into account the effect of first non-singular term of stress in WE According to their results higher accuracy of the fracture load prediction can be obtained by use of two parameter fracture criteria. The results obtained from the numerical analysis are compared to the experimental ones
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