Stress intensity factor and load-line displacement expressions for the round bar bend specimen

Underwood, J. H.

doi:10.1007/bf00012546

Cited by 3 publications

(1 citation statement)

References 9 publications

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“…The comparison with existing data showed good accuracy of the slice synthesis method [5] and the results were found useful by other scientists [6][7][8]. Encouraged by this situation, wide range compliance data for chevron-notched 3PB round bars are presented in this report.…”

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Wide range compliance of chevron-notched three-point bend round bars based on slice synthesis method

Wang¹

1995

Int J Fract

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The chevron-notched three-point bend (3PB) round bars ( Fig. 1) are useful for fracture toughness testing of brittle materials and this kind of specimen was recently recommended by the International Society for Rock Mechanics (ISRM) for testing Kto of rocks [1]. However, calibration work for its compliance is very limited, e.g. [2,3], and practical choosing of specimen parameters other than those specified by ISRM is impossible if costly calibration of experimental and numerical work is to be avoided.Recently, the author published some analytical results for the wide range compliance of edge-cracked 3PB round bars based on slice synthesis method [4]. The comparison with existing data showed good accuracy of the slice synthesis method [5] and the results were found useful by other scientists [6][7][8]. Encouraged by this situation, wide range compliance data for chevron-notched 3PB round bars are presented in this report.The detailed formulation was published in [9], and will not be repeated here. The basic idea of slice synthesis method is that the dimensionless compliance C (i.e. (8/P)DE, see Fig. 1, E is elastic modulus) is a synthesis of compliances of slices with a rectangular cross-section and straight-through crack Cij and C~ as follows 1 2 ~ '~tt I 2 tcLx At2 -2.., ~+ --2, 'where t, and t 2 are thicknesses for the slices shown in Fig. 1, respectively. The only difference in the present analysis as compared with (11) in [9] is the formula used for the calculation of Clj and C w The present formula is given belowwhere the first and second terms are deflection compliance caused by bend and shear deformation, respectively, for a 3PB strip without a crack, the third term Int Journ of Fracture @8

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Wide range compliance of chevron-notched three-point bend round bars based on slice synthesis method

Wang¹

1995

Int J Fract

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Wide range compliance of edge-cracked three-point bend round bars based on slice synthesis method

Wang

1992

Int J Fract

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Translaminar Fracture Toughness Test Methods and Results from Interlaboratory Tests of Carbon/Epoxy Laminates

Underwood

Kortschot

Lloyd

et al. 1995

Fracture Mechanics: 26th Volume

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Fracture tests were performed with carbon/polymer laminates and analyzed for the purpose of developing translaminar fracture toughness test and analysis procedures. Notched specimens were tested of two types of symmetrical layups — quasi-isotropic [0/45/90] and [0/90]; two carbon fiber/epoxy materials — a relatively brittle T300 fiber/976 epoxy and a tougher AS4 fiber/977-2 epoxy; two laminate thicknesses — 2 mm and 4 mm; and three specimen configurations — the standard three-point bend and compact configurations, and an extended compact specimen with arm-height to specimen-width ratio of 1.9. Stress and displacement expressions were obtained for the extended compact specimen, including those for stress intensity factor, K, and crack mouth opening displacement, V, in terms of relative notch length, a/W, and for a/W in terms of V. Relationships for the bending stresses that control self-similar and off-axis cracking for the extended compact specimen were derived. Damage was characterized in the tests, including that associated with arm breakage in the standard compact specimen and load-point damage in the bend specimen. Two types of notch-tip damage were characterized using radiography, that which extends perpendicular to the notch in predominantly 0‡ fiber layups, and that which occurs ahead of the notch in quasi-isotropic and 90‡ fiber layups. The applied K at maximum load, Kmax, determined in a way that took account of the effective crack growth up to the maximum load point, was used as a measure of fracture toughness. For deviations from the linear P-V plot corresponding to Δa/W ≤ 0.04, Kmax gave consistent measurements of fracture toughness. This criterion also excluded tests with damage of the type that violates the basic concept of fracture toughness measurement. Plots of Kmax vs δa/W showed increasing resistance to crack growth for quasi-isotropic layups and constant resistance to crack growth for predominantly 90‡ fiber layups.

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Stress intensity factor and load-line displacement expressions for the round bar bend specimen

Cited by 3 publications

References 9 publications

Wide range compliance of chevron-notched three-point bend round bars based on slice synthesis method

Wide range compliance of chevron-notched three-point bend round bars based on slice synthesis method

Wide range compliance of edge-cracked three-point bend round bars based on slice synthesis method

Translaminar Fracture Toughness Test Methods and Results from Interlaboratory Tests of Carbon/Epoxy Laminates

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