On the influence of specimen geometry on the critical crack-tip-opening displacement

Kolednik, O.; Kutleša, Peter

doi:10.1016/0013-7944(89)90025-8

Cited by 16 publications

(4 citation statements)

References 17 publications

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“…[7] However, COD i increases near the side surface because of the loss of the out-of-plane constraint. [10] Here the local fracture toughness measurement can help to resolve the influence of specimen geometry and size on the fracture behavior. Even bigger is the advantage of the local fracture toughness measurement in inhomogeneous materials, since the different phases in the material will exhibit different local fracture initiation toughness, e.g.…”

Section: Measurement Of the Local Fracture Toughnessmentioning

confidence: 99%

The Characterization of Local Deformation and Fracture Properties – a Tool for Advanced Materials Design

Kolednik

2006

Adv Eng Mater

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Novel experimental techniques have been recently developed to measure local deformation and fracture properties. The techniques comprise quantitative fracture surface analysis and in‐situ loading experiments in combination with digital image analysis. Examples are presented, demonstrating how these methods can be used to investigate the damage evolution in materials, to improve tools for the numerical simulation, and for the design of more fracture resistant materials and components.

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Section: Measurement Of the Local Fracture Toughnessmentioning

confidence: 99%

The Characterization of Local Deformation and Fracture Properties – a Tool for Advanced Materials Design

Kolednik

2006

Adv Eng Mater

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“…5a, b). The radius py was measured as half of the opening of the crack lips near the tip of the crack in the unloaded specimen [22] with a microscope at • magnification. It turns out that py << d* for low and medium amplitudes of loading, i.e., the quantity Ae* can be found with the simplified relation [21] A e* = In 1 + red )"…”

Section: Case Of Given Strains Ae*mentioning

confidence: 99%

A unified model of initiation and growth of fatigue macrocracks. part 3. stage of growth of a macrocrack

Ostash¹,

Panasyuk²

1999

Mater Sci

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From a common viewpoint, fatigue fracture of materials is simulated by the process of initiation of an initial macrocrack of length a i = d* (d* is the constant of the material), which is successively (stepwise) repeated at the stage of its growth. As a result, the diagram "range of local stresses -period of initiation of an initial macrocrack" or "range of local strains -period of initiation of an initial macrocrack," which was determined for notched specimens, can be used for the construction of the diagram "growth rate of a macrocrack -range of the stress intensity factor" or "growth rate of a macrocrack -range of local strains," respectively, if the crack is presented as a sharp notch with effective rounded radius Peff = d* of the tip.For estimation of the endurance of a structural material, the endurance limits ~R and ~g of smooth and notched specimens, respectively, and the threshold of cyclic crack resistance Kth of specimens with a macrocrack are the most widespread characteristics. It often occurs that these characteristics correlate with other mechanical and physical parameters of materials in different ways. The reason for this lies in the fact that the characteristics are determined at various stages of fatigue fracture on the basis of fracture criteria for the limiting state of macro-or microvolumes of the material. At present, the opinion exists that the regularities of the processes of initiation and growth of a macrocrack are significantly different and, for this reason, are separately studied. To our mind, the process of fatigue of materials (the initiation of a macrocrack and its propagation) can be studied from a common viewpoint by using unified approaches and parameters and by interpreting the growth of a fatigue macrocrack as the stepwise repeated act of its initiation.In this context, it is worth noting the models of growth of fatigue cracks, which are based on the assumption that a crack can be regarded as a sharp notch [1, 2] with a rounded radius p = P* of the tip, where p* is the constant of the material [2]. The growth of a fatigue macrocrack is considered as a sequence of acts of its reinitiation in the vicinity of the tip of a sharp notch. This growth is described by the parameters that were found with smooth and notched specimens by using the well-known Neuber and Manson-Coffin approaches [1,2]. However, the parameter p* has no clear physical meaning, and methods for direct determination of its value are unknown up to now [2]. The problem of initiation of fatigue cracks was not considered in the works mentioned above.Let us postulate that the formation rate of the unit surface of a fatigue crack is a single-valued function of local strain both in the process of initiation of a macrocrack and in the course of its growth. From the viewpoint of the unified approach to initiation and propagation of fatigue macrocracks, investigations based on the above statement are of high priority. The structure of this function was established at the stage of growth of a macrocrack [3]. However, it w...

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“…There is, however, evidence that the variations of specimen geometries do not have much influence on CTODi and CTOAc. For ST37, direct CTODi measurements in [9] show that within certain ranges of geometry variations the CTODi value is quite constant. In [10] it was shown that for deeply notched bend type specimens the crack opening displacement at the growing crack tip (which is equivalent to CTOAc) measured in the central region of the specimen is unaffected by the specimen geometry.…”

Section: Numerical Analysesmentioning

confidence: 99%

A numerical study on the crack growth behavior of a low and a high strength steel

1996

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Geometry and size effects on the crack growth resistance curves in CT-specimens of a low and high strength material are numerically investigated. The fracture process is controlled by experimentally determined critical values of the crack tip opening displacement (CTODi) for crack growth initiation and the crack tip opening angle (CTOAc) for stable crack growth. The results show that for the low and the high strength material the geometry and size effects are different. This is mainly due to the fact that the load vs. load line displacement records are basically different for the two materials which results from the large difference in the scaled fracture toughness parameters, CTODI/¢0 and CTOAc/¢o, of the two materials.

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On the influence of specimen geometry on the critical crack-tip-opening displacement

Cited by 16 publications

References 17 publications

The Characterization of Local Deformation and Fracture Properties – a Tool for Advanced Materials Design

The Characterization of Local Deformation and Fracture Properties – a Tool for Advanced Materials Design

A unified model of initiation and growth of fatigue macrocracks. part 3. stage of growth of a macrocrack

A numerical study on the crack growth behavior of a low and a high strength steel

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