Proposal for a new CTOD calculation formula

Kawabata, Tomoya; Tagawa, Tetsuya; Sakimoto, Takahiro; Kayamori, Yoichi; Ohata, Mitsuru; Yamashita, Yoichi; Tamura, Eiichi; Yoshinari, Hitoshi; Aihara, Shuji; Minami, Fumiyoshi; Mimura, Hiroshi; Hagihara, Yukito

doi:10.1016/j.engfracmech.2016.03.019

Cited by 44 publications

(28 citation statements)

References 5 publications

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“…Based on the results obtained from the silicone replicas and FE, it was found that the Japanese modification to the BS 7448‐1 and ISO 12165 equation, and the ASTM E1820 estimation are both recommended for determining CTOD for austenitic stainless steel and high strain hardening materials. The JWES CTOD equation for SENB specimens is given by

δ = K^{2} \frac{(1 - v^{2})}{m σ_{y s} E} + f ((),, B, \frac{σ_{y s}}{σ_{u t s}}) \frac{0.43 B_{o} V_{p}}{0.43 B_{o} + a_{0} + z}

where the correction factors are:

\begin{matrix} m = 4.9 - 3.5 (\frac{σ_{y s}}{σ_{u t s}}) \\ f (B) = 0.8 + 0.2 e x p \{- 0.019 (B - 25)\} \\ f (\frac{σ_{y s}}{σ_{u t s}}) = - 1.4 {((), \frac{σ_{y s}}{σ_{u t s}})}^{2} + 2.8 \frac{σ_{y s}}{σ_{u t s}} - 0.35 . \end{matrix}

…”

Section: Discussionmentioning

confidence: 99%

“…More recently Tagawa et al . and Kawabata et al . have used the silicone compound method to replicate the physical crack.…”

Section: Methodsmentioning

confidence: 99%

“…The FE method has often been applied to investigate fracture toughness estimation equations . A Geometrically and Materially Non‐linear Analysis (GMNA) FE model was used to predict CTOD in an SENB setup.…”

Section: Methodsmentioning

confidence: 99%

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Measurement and prediction of CTOD in austenitic stainless steel

Khor

Moore

Pisarski

et al. 2016

Fatigue Fract Eng Mat Struct

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A B S T R A C T Variation of Crack Tip Opening Displacement (CTOD) test values can have a significant effect on the Engineering Critical Assessment of a structure. This paper examines the development of CTOD with increasing load in an austenitic stainless steel. The silicone replication method giving variation of CTOD across the specimen thickness, and Digital Image Correlation (DIC) are compared to each other, and in turn to clip gauge measurements from tests. Results from Finite Element models are also presented. Estimations of CTOD from BS 7448-1, ISO 12135 and ASTM E1820, and a proposed modification from JWES are compared to the experimental data from the crack cast in silicone compound -assumed to be the actual CTOD. The DIC measurement showed consistency with crack replicas, and a formula is given to estimate CTOD using DIC. For high strain hardening austenitic stainless steel, both the JWES and ASTM E1820 estimations provide adequate accuracy for CTOD. N O M E N C L A T U R EA p = plastic area under P versus V p a 0 = initial crack length B = specimen thickness B 0 = remaining ligament, W À a 0 b = position on section as a ratio of B / 2 E = modulus of elasticity J = strain energy around the crack K = stress intensity factor K I = stress intensity factor in mode I loading m = plane strain function used in JWES m ASTM = function relating J to CTOD n = strain hardening exponent P = load r p = rotational factor for plastic hinge assumption V g = clip gauge opening displacement V p = plastic component of clip gauge opening displacement W = specimen width z = knife edge height δ = crack tip opening displacement (CTOD) δ 5 = direct CTOD measurement from two points at the specimen surface 5 mm apart, placed directly at the crack tip δ 5 DIC = δ 5 measured using the DIC technique δ SRC = CTOD measured on the silicone replicas δ FE = CTOD obtained from the FE model v = Poisson's ratio σ ys =0.2% proof strength at test temperature σ uts = ultimate tensile strength at test temperature σ y = flow stress at test temperature, (σ ys + σ uts ) / 2 ε = strain ɳ = geometrical based calibration function for J Correspondence: C. J. Brown.

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δ = K^{2} \frac{(1 - v^{2})}{m σ_{y s} E} + f ((),, B, \frac{σ_{y s}}{σ_{u t s}}) \frac{0.43 B_{o} V_{p}}{0.43 B_{o} + a_{0} + z}

where the correction factors are:

\begin{matrix} m = 4.9 - 3.5 (\frac{σ_{y s}}{σ_{u t s}}) \\ f (B) = 0.8 + 0.2 e x p \{- 0.019 (B - 25)\} \\ f (\frac{σ_{y s}}{σ_{u t s}}) = - 1.4 {((), \frac{σ_{y s}}{σ_{u t s}})}^{2} + 2.8 \frac{σ_{y s}}{σ_{u t s}} - 0.35 . \end{matrix}

…”

Section: Discussionmentioning

confidence: 99%

“…More recently Tagawa et al . and Kawabata et al . have used the silicone compound method to replicate the physical crack.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Measurement and prediction of CTOD in austenitic stainless steel

Khor

Moore

Pisarski

et al. 2016

Fatigue Fract Eng Mat Struct

View full text Add to dashboard Cite

show abstract

“…The elastic CTOD from WES 1108 was used as it was calibrated theoretically to account for the effects of strain hardening in the elastic loading region . The error in prediction of CTOD using Equation was investigated by normalising it to the CTOD from the models ( δ FE ), described as CTOD ERR.…”

Section: Discussionmentioning

confidence: 99%

“…The SEN(B) models were modelled under 3‐point bend loading and the apex of the crack face opening was identified as the hinge location. Findings from experimental work and finite element (FE) modelling shows that as the crack open due to loading, the effects of strain hardening due to plasticity cause the crack tip to deform away from the crack face plane . To account for the effects of crack tip blunting due to strain hardening, r p was extracted based on the intersection line extrapolated from the CMOD and CTOD to the symmetry line (Figure ).…”

Section: Methodsmentioning

confidence: 99%

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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