Título

COMPLIANCE SOLUTIONS INCLUDING 3-D AND SIDEGROOVE EFFECTS APPLICABLE TO CRACK SIZE ESTIMATION USING C(T), SE(B) AND CLAMPED SE(T) SPECIMENS

COMPLIANCE SOLUTIONS INCLUDING 3-D AND SIDEGROOVE EFFECTS APPLICABLE TO CRACK SIZE ESTIMATION USING C(T), SE(B) AND CLAMPED SE(T) SPECIMENS

Autoria

Moreira, Felipe Cavalheiro; Donato, Gustavo Henrique Bolognesi

DOI

10.5151/2594-5327-23094

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Resumo

Experiments regarding J-resistance curves and fatigue crack growth usually employ elastic compliance (C) techniques to estimate instantaneous crack size (a). This estimation derives from C using a dimensionless parameter (μ) which incorporates specimen’s thickness (B), elasticity (E) and compliance itself. Plane stress and plane strain solutions for μ are available: the work of Tada et al. from 1985, ASTM-E1820 and ASTM-E647 provide solutions for C(T), SE(B) and M(T) specimens, among others. Current challenges include: i) real specimens are in neither plane stress nor plane strain - modulus vary between E (plane stress) and E/(1-ν2) (plane strain); ii) furthermore, the existence of side-grooves affect specimen’s stiffness, leading to an “effective thickness” with deviations larger than 10% in crack size estimations following current practices, especially for shallow-cracked samples. As a step in this direction, this work investigates 3-D and side-groove effects on compliance solutions applicable to C(T), SE(B) and SE(T) specimens. Refined 3-D elastic FE-models provide Load-CMOD evolutions. Crack depths between a/W=0.1 and a/W=0.7 on 1/2T, 1T and 2T geometries with width to thickness ratio W/B=2 are investigated. Side-grooves of 5%, 10% and 20% are considered. The results include compliance solutions incorporating 3D and side-groove effects to provide accurate crack size estimation during laboratory fracture and FCG testing. The proposals were verified against current standardized solutions and deviations were strongly reduced.

 

Experiments regarding J-resistance curves and fatigue crack growth usually employ elastic compliance (C) techniques to estimate instantaneous crack size (a). This estimation derives from C using a dimensionless parameter (μ) which incorporates specimen’s thickness (B), elasticity (E) and compliance itself. Plane stress and plane strain solutions for μ are available: the work of Tada et al. from 1985, ASTM-E1820 and ASTM-E647 provide solutions for C(T), SE(B) and M(T) specimens, among others. Current challenges include: i) real specimens are in neither plane stress nor plane strain - modulus vary between E (plane stress) and E/(1-ν2) (plane strain); ii) furthermore, the existence of side-grooves affect specimen’s stiffness, leading to an “effective thickness” with deviations larger than 10% in crack size estimations following current practices, especially for shallow-cracked samples. As a step in this direction, this work investigates 3-D and side-groove effects on compliance solutions applicable to C(T), SE(B) and SE(T) specimens. Refined 3-D elastic FE-models provide Load-CMOD evolutions. Crack depths between a/W=0.1 and a/W=0.7 on 1/2T, 1T and 2T geometries with width to thickness ratio W/B=2 are investigated. Side-grooves of 5%, 10% and 20% are considered. The results include compliance solutions incorporating 3D and side-groove effects to provide accurate crack size estimation during laboratory fracture and FCG testing. The proposals were verified against current standardized solutions and deviations were strongly reduced.

Palavras-chave

Compliance solutions; 3D effects; Side-groove; Fracture specimens.

Compliance solutions; 3D effects; Side-groove; Fracture specimens.