Abstract
This paper provides a complete overview of the applicability of the Equivalent Material Concept in conjunction with the Average Strain Energy Density criterion, to provide predictions of fracture loads in structural materials containing U-notches. The Average Strain Density Criterion (ASED) has a linear-elastic nature, so in principle, it does not provide satisfactory predictions of fracture loads in those materials with nonlinear behaviour. However, the Equivalent Material Concept (EMC) is able to transform a physically nonlinear material into an equivalent linear-elastic one and, therefore, the combination of the ASED criterion with the EMC (EMC–ASED criterion) should provide good predictions of fracture loads in physically nonlinear materials. The EMC–ASED criterion is here applied to different types of materials (polymers, composites and metals) with different grades of nonlinearity, showing the accuracy of the corresponding fracture load predictions and revealing qualitatively the limitations of the methodology. It is shown how the EMC–ASED criterion provides good predictions of fracture loads in nonlinear materials as long as the nonlinear behaviour is mainly limited to the tensile behaviour, and how the accuracy decreases when the nonlinear behaviour is extended to the material behaviour in the presence of defects.
Highlights
In the 1970s, Sih [1] presented the Strain Energy Density factor (S) as the product of the StrainEnergy Density by a certain distance
As stated in [2], the Average Strain Energy Density (ASED) criterion is based on the quantification of the Strain Energy Density averaged over a control volume defined at the notch tip
The ASED criterion is a relatively simple failure criterion that may be applied to linear-elastic materials and has been widely validated in a significant number of brittle and quasi-brittle structural materials (e.g., [4,7,8])
Summary
Energy Density by a certain distance (from the point of singularity). Lazzarin and co-authors (e.g., [2,3,4,5]) proposed the Average Strain Energy Density (ASED) criterion as a combination of Sih’s model with the concept of elementary structural volume suggested by Neuber [6]. As stated in [2], the (local) ASED criterion is based on the quantification of the Strain Energy Density averaged over a control volume defined at the notch tip. The ASED approach is based on the idea that failure occurs when the mean value of the elastic strain energy (W) referred to a volume (or an area, in plane problems) is equal to a critical value (Wc ) [2], which is a material property. The ASED criterion is a relatively simple failure criterion that may be applied to linear-elastic materials and has been widely validated in a significant number of brittle and quasi-brittle structural materials (e.g., [4,7,8]).
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