Displacements and rotational factors in single edge notched bend specimens

Lin, I.-H.; Anderson, TL; deWit, R.; Dawes, M.G.

doi:10.1007/bf00942166

Cited by 27 publications

(12 citation statements)

References 3 publications

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“…In the calculation of the plastic component of CTOD, BS 7448‐1, ISO 12135, WES1108, early versions of ISO 12135, ASTM E1290‐93, and E1820‐01 assumed that the specimen flanges rotate about a stationary point within the uncracked ligament ahead of the crack tip, a distance equal to r p × B 0 , where r p is the rotational factor and B 0 is the remaining ligament ahead of the crack tip. This concept was introduced by Dawes in 1979, using a 2‐D plastic hinge model with assumptions of plane strain condition at the crack tip . Based on the argument that there is a tensile and compressive region ahead of the crack tip, the idea of a rotational hinge point had also been applied in the calculation of the crack tip opening angle (CTOA) …”

Section: The Concept Of Rigid Rotational Factor For the Determinationmentioning

confidence: 99%

“…The determination of the rotational factor is based on the geometrical analysis of a specimen under 3‐point bend loading. Consider a deformed SEN(B) specimen (Figure ), the distance of the rotational point from the crack mouth opening displacement (CMOD), H is defined in terms of rotational factor, r p ( W − a ) + a .…”

Section: The Concept Of Rigid Rotational Factor For the Determinationmentioning

confidence: 99%

“…Relating V p into δ p gives

δ_{pl} = \frac{r_{p} ((), W - a) V_{p}}{[r_{p} (W - a) + a + z]},

where δ pl is the plastic component of CTOD, where δ = δ el + δ pl . Anderson et al found that r p is insensitive to the specimen geometry for the same material .…”

Section: The Concept Of Rigid Rotational Factor For the Determinationmentioning

confidence: 99%

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A CTOD equation based on the rigid rotational factor with the consideration of crack tip blunting due to strain hardening for SEN(B)

Khor

2019

Fatigue Fract Eng Mat Struct

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Crack tip opening displacement (CTOD) from national and international standards was shown to give different values. This paper investigates the feasibility of CTOD determined based on the concept of rigid rotational factor in single‐edge notched bend (SENB) specimens. Based on validated modelling methods, finite element (FE) models were simulated for crack ratios 0.3 ≤ a0/W ≤ 0.7 and yield‐to‐tensile ratio 0.44 ≤ σys/σuts ≤ 0.98. This covers cases of shallow to deeply cracked specimens and a wide range of strain hardening properties. CTOD obtained from the FE models was used as the basis of a newly implemented strain hardening corrected rotational factor, which considers the effects of crack tip blunting due to strain hardening, rp sh. An improved equation considering strain hardening was implemented based on the rp sh. The equation gives accurate estimation of CTOD from the FE models compared with the equation from BS 7448‐1, ASTM E1820, and WES 1180.

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Section: The Concept Of Rigid Rotational Factor For the Determinationmentioning

confidence: 99%

Section: The Concept Of Rigid Rotational Factor For the Determinationmentioning

confidence: 99%

See 1 more Smart Citation

A CTOD equation based on the rigid rotational factor with the consideration of crack tip blunting due to strain hardening for SEN(B)

Khor

2019

Fatigue Fract Eng Mat Struct

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“…Especially below the general yield load, FGv, the method seems to be not very accurate, because "... if (F/Fcv) < 0.9 the re-values calculated are irregular and most of them are greater than 0.5" [17]. Beyond general yield most re-values lie between 0.4 and 0.5 [17][18][19]. They are increasing slightly with increasing %-values, probably due to crack extension.…”

Section: Three Experiments From Literaturementioning

confidence: 99%

“…Especially in 3-point bend specimens it is possible to determine experimentally the apparent (plastic or overall) rotational factor by recording simultaneously the clip-gauge displacement and the load-line displacement [17][18][19]. Especially below the general yield load, FGv, the method seems to be not very accurate, because "... if (F/Fcv) < 0.9 the re-values calculated are irregular and most of them are greater than 0.5" [17].…”

Section: Three Experiments From Literaturementioning

confidence: 99%

Plastic and overall rotational factors in bend- and CT-specimens

Kolednik

1989

Int J Fract

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A procedure for estimating theoretically the physical crack-tip-opening displacement (COD) for bend and CT-specimens is developed. The theory relies on the Irwin model of the plastic zone and on other well-known fracture mechanics relationships. Relationships between the physical COD and the conveniently measured crack mouth opening displacement are given in terms of rotational factors. Based on such theoretical considerations, on experimental results from literature, and on the authors experimental results it is concluded that the formula stated by the British Standard Test Method for measuring the critical COD overestimates the physical COD below general yield of the testpiece. An improved procedure for estimation of the physical COD is recommended.

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Fracture Toughness Testing Methods

Ebrahimi

2002

Characterization of Materials

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With increasing use of steel structures such as railroads, bridges and tanks in the nineteenth century, the number of casualties due to the catastrophic failure of such structures also increased, and hence, attention was drawn to the brittle fracture of steels. Fracture toughness is a measure of resistance to cracking in notched bodies. In general, during fracture toughness testing, the load‐versus‐displacement behavior of a pre‐cracked specimen is recorded. The load‐displacement curve depends on the size and geometry of the specimen as well as the loading mode. In practice, the goal of fracture toughness testing is to measure a single parameter (e.g., similar to yield strength) that is a material property and can be directly used in design. Fracture mechanics is a tool to translate the results of laboratory fracture toughness testing into engineering design. Depending on the material and the size and geometry of the specimen, different parameters can be evaluated. Stress intensity factor, K , is a parameter that describes the stress level as well as the stress distribution ahead of a crack. Crack driving force, G , is a measure of the elastic energy released per unit thickness of the specimen and per unit length of the crack. When extensive plastic deformation precedes crack initiation, the flow of energy to the crack tip can be evaluated using the J‐integral approach. The amount of strain at the crack tip, known as crack tip opening displacement, is another parameter that can be calculated from the fracture toughness testing results. To correlate the results of fracture toughness testing with a parameter that represents a material property, a fracture criterion needs to be established. Fracture toughness testing is a relatively expensive method in comparison to notched impact testing. There are many standard procedures established by ASTM where the reader can find the details of fracture toughness testing procedures. The purpose of this article is to summarize briefly various fracture toughness testing techniques and to provide the basic principles of fracture behavior and fracture mechanics necessary for understanding and selecting the proper testing technique. Emphasis will be placed on macroscopic standard testing techniques for metallic materials. Special techniques for mixed‐mode fracture, indentation fracture, crack arrest, creep fracture, and stress corrosion cracking as well as the atomistic concepts are not discussed here. Furthermore, the discussion is limited to elastically isotropic materials. There are mechanical testing methods that yield data related to the toughness of a material, but they do not provide an actual toughness value. For example Charpy V‐Notch impact testing and notched tensile testing measure the energy absorbed during fracture and the stress required for fracture, respectively. Such tests may be used for screening materials based on toughness. To conduct fracture toughness testing, a mechanical testing system, apparatus for measuring and recording load and displacement, as well as fixtures for holding the specimens, are required.

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Displacements and rotational factors in single edge notched bend specimens

Cited by 27 publications

References 3 publications

A CTOD equation based on the rigid rotational factor with the consideration of crack tip blunting due to strain hardening for SEN(B)

A CTOD equation based on the rigid rotational factor with the consideration of crack tip blunting due to strain hardening for SEN(B)

Plastic and overall rotational factors in bend- and CT-specimens

Fracture Toughness Testing Methods

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