Estimating fracture toughness from small specimens

Stark, H.L.; Ibrahim, Raafat N

doi:10.1016/0013-7944(86)90253-5

Cited by 59 publications

(18 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Cylindrical samples with annular cracks exhibit numerous advantages when compared with the standard specimens recommended by the ASTM E399 Standard Test Method for Linear‐Elastic Plane‐Strain Fracture Toughness K Ic of Metallic Materials : (1) they are easy to machine and thus cheaper; (2) they need less amount of material to guarantee the plane strain condition because their circular geometry increases the constraint, thereby assuring a plane strain state with independence of their size; and (3) the annular crack does not end in a plane stress region. These specimens also exhibit some disadvantages, such as the frequent appearance of fatigue non‐symmetric crack advance, thus producing eccentricity of the circular ligament in relation to the bar axis. This phenomenon may be caused by slight non‐symmetries regarding the sample, the grips or the testing machine, as well as non‐uniform material properties, residual stress effects, etc.…”

Section: Introductionmentioning

confidence: 99%

Crack tip field in eccentric circumferentially cracked round bar (CCRB) under tensile loading

Toribio

González

Matos

2018

Fatigue Fract Eng Mat Struct

View full text Add to dashboard Cite

In this paper, the stress intensity factor (SIF) is computed in a circumferentially cracked round bar (CCRB) subjected to applied tensile load or to imposed axial displacement, considering that the resistant ligament is circular and exhibits certain eccentricity in relation to the cylinder axis. The computation was performed by means of the finite element method, using a 3‐dimensional model and the J‐integral, the analyzed variables being the diameter and the eccentricity of the circular ligament. Results show that the SIF value is higher at the deepest point of the crack. For a given ligament diameter, an increase of ligament eccentricity (in relation to the bar axis) raises the difference between the SIF values at those points of the crack associated with the maximum and minimum depth. Furthermore, the maximum SIF value is higher for applied tensile load than for imposed axial displacement, mainly for high eccentricities and small diameters of the ligament, as a consequence of a greater rotation of the bar.

show abstract

Section: Introductionmentioning

confidence: 99%

Crack tip field in eccentric circumferentially cracked round bar (CCRB) under tensile loading

Toribio

González

Matos

2018

Fatigue Fract Eng Mat Struct

View full text Add to dashboard Cite

show abstract

“…A precrack of about 300 #m depth was thus made at the bottom of the notch using a tempered 30 #m-thick razor blade. This rapid and easy method allows good control of the precrack eccentricity (< 100 #m, as required according to Stark and Ibrahim [1]) and induces a minimum strain-hardening at the tip of the precrack. Very deep precracks can be obtained in this way.…”

Section: Precracking Of the Rodsmentioning

confidence: 99%

“…This geometry also presents several advantages well reassessed recently in the literature [1,2,3,4,5] and attracting the attention of many researchers especially for the characterization of fracture toughness when only small size specimens are available [3]. Indeed the triaxial stress state at the tip of a circumferential crack in a bar is close to plane strain even for a small rod diameter.…”

Section: Introductionmentioning

confidence: 99%

“…The stress intensity factor K of an axisymmetrical crack in a cylinder can be evaluated using [6] I~: P ~4fTra°Pe° (1-~ -RO 3 (R°) 2 (R°) 3 (R°~4~ 27rR~V w0 2--~w0+8 ~00 -0.363 ~00 +0"731k~oo/ ]' (1) where P is the applied load and all the other geometrical parameters are defined on Figure 1. The '0' indice refers to the initial value of the parameters.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Critical assessment of the application of the J-integral and CTOD concepts to circumferentially cracked copper bars

Pardoen

Delannay

1996

Int J Fract

View full text Add to dashboard Cite

The aim of this work is to explore experimentally the validity of the concepts of J-integral and crack tip opening displacement for characterizing the stress and strain state at the tip of an axisymmetrical crack in a bar undergoing large plastic strain before crack extension. The tests are made on extruded copper round bars presenting a very high ductility. Three different analytical formulations of the J-integral proposed in the literature for circumferentially cracked bars are compared at initiation of cracking. The limit between shallow crack and deep crack geometries is experimentally demonstrated. It is found that, in neither of these geometries, J and ~CTOD are dominant. However, the ratio Jc/~c is constant for deep cracks, which suggests an alternative fracture criterion consisting in postulating the dissipation of an average critical energy per unit volume until crack extension.

show abstract

“…The idea of CCB as alternative fracture mechanics samples is not new. Notched cracked bar have been used by Stark and Ibrahim [1], Ibrahim and Stark [2][3], and Lam and Ibrahim [4]. Devaux et al [5] used axisymmetric cracked bar to determine local approach fracture parameters to compare with CT data.…”

mentioning

confidence: 99%

Use of Circumferentially Cracked Bar sample for CTOD fracture toughness determination in the upper shelf regime

Gentile

Persechino

Bonora

et al. 2014

Frattura Ed Integrità Strutturale

View full text Add to dashboard Cite

ABSTRACT. In this work, the use of circumferentially cracked bar (CCB) sample to determine material fracture toughness in the upper shelf regime for carbon steels has been investigated. Since high fracture toughness materials are known to exhibit extensive crack tip blunting before ductile crack initiation, accurate specimen design is required to provide realistic fracture toughness measurement. Here, a CCB was designed to have similar loss of constraint as for SENT sample. Continuum damage mechanics was used to predict the occurrence of ductile crack initiation and propagation. Finite element analysis was performed to predict specimen response and to compare computed J-integral crack driving force with measured CTOD. Finally, experimental tests were performed on X65 carbon steel and the measured critical CTOD was compared with available fracture data obtained with SENT.

show abstract

Estimating fracture toughness from small specimens

Cited by 59 publications

References 1 publication

Crack tip field in eccentric circumferentially cracked round bar (CCRB) under tensile loading

Crack tip field in eccentric circumferentially cracked round bar (CCRB) under tensile loading

Critical assessment of the application of the J-integral and CTOD concepts to circumferentially cracked copper bars

Use of Circumferentially Cracked Bar sample for CTOD fracture toughness determination in the upper shelf regime

Contact Info

Product

Resources

About