The Theory of Critical Distances applied to multiscale toughening mechanisms

Taylor, David

doi:10.1016/j.engfracmech.2019.02.012

Cited by 35 publications

(84 citation statements)

References 42 publications

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“…The analysis concludes with the observation of the fracture surfaces and micromechanisms observed in the different specimens (SEM) [ 14 , 16 , 27 , 28 ].…”

Section: Methodsmentioning

confidence: 99%

Analysis of Notch Effect in 3D-Printed ABS Fracture Specimens Containing U-Notches

et al. 2020

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In this paper a fracture assessment in additive manufactured acrylonitrile butadiene styrene (ABS) fracture specimens containing U-notches is performed. We performed 33 fracture tests and 9 tensile tests, combining five different notch radii (0 mm, 0.25 mm, 0.50 mm, 1 mm and 2 mm) and three different raster orientations: 0/90, 30/−60 and 45/−45. The theory of critical distances (TCD) was then used in the analysis of fracture test results, obtaining additional validation of this theoretical framework. Different versions of TCD provided suitable results contrasting with the experimental tests performed. Moreover, the fracture mechanisms were evaluated using scanning electron microscopy in order to establish relationships with the behaviour observed. It was demonstrated that 3D-printed ABS material presents a clear notch effect, and also that the TCD, through both the point method and the line method, captured the physics of the notch effect in 3D-printed ABS. Finally, it was observed that the change in the fracture mechanisms when introducing a finite notch radius was limited to a narrow band behind the original defect, which appeared in cracked specimens but not in notched specimens.

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“…The analysis concludes with the observation of the fracture surfaces and micromechanisms observed in the different specimens (SEM) [ 14 , 16 , 27 , 28 ].…”

Section: Methodsmentioning

confidence: 99%

Analysis of Notch Effect in 3D-Printed ABS Fracture Specimens Containing U-Notches

et al. 2020

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“…The TCD performs the static assessment by making use of the linear-elastic stress fields damaging the material in the vicinity of the crack initiation locations. [2][3][4] From a practical point of view, the in-field usage of the TCD is based on an effective stress, σ eff , whose calculation involves a material-dependent length scale parameter. According to the way it is defined, σ eff quantifies the extent of damage associated with the entire linear-elastic stress field acting on the material within a finite size domain.…”

Section: Tcd Overviewmentioning

confidence: 99%

“…While the effective stress can be determined according to different strategies, 5 certainly the Point Method (PM) represents the simplest way to use the TCD. 2 The PM is expressed mathematically as follows (Figure 1):…”

Section: Tcd Overviewmentioning

confidence: 99%

“…Using the stress field in the vicinity of the notch, other methods can be defined. Considering the average stress instead of the stress function (2), for instance, leads to the well-known Line Method 2 :…”

Section: Tcd Overviewmentioning

confidence: 99%

“…The Theory of Critical Distances (TCD) 2 is an approach falling in this category. It uses a constant known as the critical distance, L. Normally, the value of L is determined by conducting experiments on specimens containing different types of stress concentrators-for example, notches having different sharpness-and fitting predictions to the data.…”

Section: Introductionmentioning

confidence: 99%

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The application of the Theory of Critical Distances to nonhomogeneous materials

Marșavina

Sapora

Susmel

et al. 2023

Fatigue Fract Eng Mat Struct

Self Cite

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The Theory of Critical Distances (TCD) has undoubtedly represented a breakthrough in the brittle failure assessment of engineering materials containing defects, crack, or notches. The basic idea on which the simplest formulation of the TCD is based is to evaluate an effective stress at a characteristic distance from the tip of the defect/crack/notch and compare it with an inherent fracture strength. Is the critical distance related to the material (micro) structure? Whereas a correlation was already proved for homogeneous materials, the current attention to nonhomogeneous ones has brought the question back to the fore. The goal of the present work is therefore twofold: (i) to extend the use of the TCD, through the simple yet effective Point Method (PM), for the static failure assessment of inhomogeneous materials, such as cellular, biological, and additively manufactured (AM) materials; and (ii) to look for a correlation between critical distance and internal (micro) structure.

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Application of the Theory of Critical Distances for the Fracture Assessment of a Notched Limestone Subjected to Different Temperatures and Mixed Mode with Predominant Mode I Loading Conditions

2021

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This work aims to assess the fracture of U-notched limestone samples subjected to mixed mode I+II loading conditions with a predominant mode I influence, both at room temperature and at 250ºC. This analysis is based on the use of the Theory of the Critical Distances, and more specifically on the use of the Line Method, considering both an analytical and a numerical approach for the definition of the stress fields. An experimental campaign of almost 400 three-point bending tests has been performed as a basis for the fracture assessment of the limestone, using Single Edge Notched Bend (SENB) specimens with notch radii varying from 0.15 mm up to 15 mm, different temperature conditions and variable loading positions. The Theory of Critical Distances has successfully been applied to study the experimental results. The analytical and numerical stress fields for pure mode I fracture assessments provide similar accurate results both at 23ºC and 250ºC. Similarly, the mixed mode (I+II) fracture assessments allow the critical distance (𝐿𝐿) to be characterised for different mode mixities (𝑀𝑀 𝑒𝑒 ), using the stress field around the notch tip obtained from the numerical models. Comparing the values of the critical distance against the mode mixity in isolation, a slight decrease of 𝐿𝐿 is observed as it approaches pure mode I conditions (𝑀𝑀 𝑒𝑒 = 1). However, if the results are analysed separately for each notch radius, 𝐿𝐿 seems to be relatively constant with 𝑀𝑀 𝑒𝑒 . In parallel, a certain influence of the notch radius on the critical distance is appreciated, which shows an increment both at 23ºC and 250ºC.

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The Theory of Critical Distances applied to multiscale toughening mechanisms

Cited by 35 publications

References 42 publications

Analysis of Notch Effect in 3D-Printed ABS Fracture Specimens Containing U-Notches

Analysis of Notch Effect in 3D-Printed ABS Fracture Specimens Containing U-Notches

The application of the Theory of Critical Distances to nonhomogeneous materials

Application of the Theory of Critical Distances for the Fracture Assessment of a Notched Limestone Subjected to Different Temperatures and Mixed Mode with Predominant Mode I Loading Conditions

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