Numerical investigation of compliance equations used in the R‐curve testing for clamped SE(T) specimens

This paper revisits a complicated analytical solution of the stress intensity factor K adopted in a newly published British standard BS 8571:2014 for clamped single edge notched tension (SENT) specimens. Comparison with existing numerical results of K shows that the analytical K solution in BS 8571 is correct only for the crack length to specimen width ratio a/W ≤ 0.6, but incorrect for a/W > 0.6. A reinvestigation is thus performed using the crack compliance method, and a corrected K solution is obtained for the BS 8571 clamped SENT specimens over the full range of a/W. On this basis, a simple closed‐form solution of K is obtained using the best curve fitting with an accuracy within 1% for crack sizes up to a/W = 0.98. Results show that the proposed closed‐form solution of K agrees well with the numerical results of K for the clamped SENT specimens.

Section: Discussion S O F T H E U S E O F K S O L U T I O N mentioning

confidence: 99%

Corrected stress intensity factor solution for a British standard single edge notched tension (SENT) specimen

Zhu

2015

“…Wang and Omiya suggest a CMOD‐based compliance equation with an effective elastic modulus. Huang and Zhou improve the accuracy of the compliance equation through modification factors.…”

Section: Introductionmentioning

confidence: 99%

A node release approach to estimate J‐R curve for single‐edge‐notched tension specimen under reversed loading

Liu

Qian

Wang

et al. 2019

This paper proposes a node release approach to estimate the fracture resistance curve, often known as the J‐R curve, for monotonic and cyclic fracture tests. The node release approach simulates the crack extension by releasing the constraints imposed on the node at the crack tip and estimates the J‐R curve by coupling the domain integral value with the corresponding crack extension. This proposed node release approach estimates closely the J‐R curve for SE(B) and SE(T) specimens subjected to monotonic loading. For SE(T) specimen under cyclic loading, this study implements the node release analysis in two approaches: (1) an equivalent monotonic analysis corresponding to the envelope of the cyclic load‐CMOD response and (2) a direct cyclic simulation. Both approaches lead to close estimations of the experimentally measured J‐R curve. The numerical analysis also confirms the path independence of the domain integral values in the direct cyclic simulation.

“…Although the BS 8571:2014 standard has already been published, it can be considered as still in its early development stage, hence prone to investigations and questioning of its procedures and methods. For example, Paredes and Huang and Zhou dwelled on the accuracy of current calculations of the plastic geometry η factor, and Huang and Zhou and Wang and Omiya on the compliance equations used for determining crack length for clamped SE(T) specimens.…”

Section: Introductionmentioning

confidence: 99%

Fracture toughness of high strength seamless pipe steel from SE(T) and SE(B) specimens evaluated by different standards

Filgueiras¹,

Menezes

Ipiña

et al. 2018

Recently released, BS 8571:2014 standard offers an alternative for the experimental determination of fracture toughness and resistance curves of metallic materials from SE(T) specimens. Similar in stress conditions and constraint to cracked tubes, specimens in SE(T) geometry should yield less conservative toughness values than conventional high‐constraint specimens, such as SE(B) geometry. However, the convention to determine the J‐integral fracture toughness proposed in the new BS standard is different from ASTM standards. In this work, SE(T) and SE(B) specimens of similar dimensions of a tough high‐strength seamless pipe steel were tested following the BS 8571:2014 and ASTM E1820‐16 standards, respectively. Because of the different standardized definitions, SE(T) specimens yield lower fracture toughness than SE(B) specimens, which could lead to more conservative results in structural integrity analysis. This investigation also suggests the introduction of the blunting line concept in the BS 8571:2014 standard in order to minimize this problem.