Abstract
The coupled Finite Fracture Mechanics (FFM) criteria are applied to investigate the ductile failure initiation at blunt U-notched and V-notched plates under mode I loading conditions. The FFM approaches are based on the simultaneous fulfillment of the energy balance and a stress requirement, and they involve two material properties, namely the fracture toughness and the tensile strength. Whereas the former property is obtained directly from experiments, the latter is estimated through the Equivalent Material Concept (EMC). FFM results are presented in terms of the apparent generalized fracture toughness and compared with experimental data already published in the literature related to two different aluminium alloys, Al 7075-T6 and Al 6061-T6, respectively. It is shown that FFM predictions can be accurate even under moderate or large scale yielding regimes.
Highlights
It is well-assessed that brittle fracture initiation in notched structures can be described accurately by combining a linear elastic fracture analysis with an internal material length l
To be more accurate for Al 7075-T6 U-notched plates, whilst average Finite Fracture Mechanics (FFM) provides the best results to be more accurate for Al 7075-T6 U-notched plates, whilst average FFM provides the best results for U-notched Al 6061-T6 plates: In this case, the discrepancy is less than 2.3%
In this work, in the spirit of the previous papers [12,16], the coupled FFM approaches proposed by in the spirit of the previous papers [12,16], the coupled FFM approaches proposed by Leguillon [5]
Summary
It is well-assessed that brittle fracture initiation in notched structures can be described accurately by combining a linear elastic fracture analysis with an internal material length l. Taylor [1] observed by fitting the value of σ0 through the simple point stress criterion that the ratio σ0 /σu approaches the unit value for ceramics, it is comprised between one and two for polymers, and can be sensibly larger (even up to eight) for metals In this latter case, it is difficult to refer to σ0 as a tensile strength, and some attempts to provide a clear physical/mechanics were recently put forward [7]. The above tests involved two aluminium alloys, Al 7075-T6 and Al 6061-T6, respectively: It was observed that Al 7075-T6 plates failed by moderate scale yielding, whereas Al 6061-T6 plates failed by large scale yielding In this case, stress criteria were exploited to match experimental data, but σ0 was evaluated through the Equivalent Material Concept (EMC) theory proposed by Torabi [15]. The coupled FFM approaches are based on the hypothesis of a finite crack extension l and assume the simultaneous fulfillment of two conditions [5,6]
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