Abstract
La construcción de curvas J-R para un material dúctil, acorde con la Norma ASTM E1820-15 (2015), requiere de información del proceso de extensión estable de grieta. Según la Norma, la curva de resistencia puede ser obtenida de un ensayo con solo una probeta, en el cual el tamaño de grieta es medido simultáneamente con fuerza y desplazamiento por los métodos de cambios de flexibilidad, caída de potencial, y normalización. Basándose en los Formatos Común y Conciso, Donoso y Landes desarrollaron la “ley de crecimiento de grieta” y el “método del intercepto” como alternativas para obtener tamaños de grieta de un ensayo que exhibe extensión estable de grieta, pero del cual se dispone solo de datos fuerza-desplazamiento, y tamaños de grieta inicial y final. Ambos métodos alternativos se ven complementados por la construcción de una curva maestra, basada en estos Formatos, aplicada a probetas C(T) en las cuales los valores experimentales de extensión de grieta son insuficientes para producir una curva J-R válida.
Highlights
The evaluation of the fracture toughness of a material, as a measure of its resistance to crack extension, has been a relevant issue for the past five decades
The fracture toughness is often evaluated with ASTM E1820-15 (2015), both for the construction of the resistance, J-R curve, and for the evaluation of the initiation toughness JIc
The construction of J-R or J-Da curves for a ductile material per E1820 requires knowledge of the stable crack extension process
Summary
The evaluation of the fracture toughness of a material, as a measure of its resistance to crack extension, has been a relevant issue for the past five decades. As part of the construction of the resistance curve, E1820 requires a minimum number of J-Da points between the 0.15 and 1.5 mm exclusion lines Once this requirement has been met, a provisional value of the initiation fracture toughness, JQ, may be obtained as the intercept of the J-Da curve with the 0.2 mm offset line given by J = 2sy(Da – 0.2), where sy is the average of the yield and the ultimate tensile stress of the material. They pointed out that JQ may be estimated accurately by integrating to 99% of maximum load, without the need to construct a J-R curve In this context, Donoso and Landes (1994) and Donoso and Landes, (2001) developed methodologies that relate all three variables of a fracture toughness test: force P, displacement v, and crack size a. Since it is not simple to find information for pre-cracked C(T) specimens together with data collected from identical blunt notch specimens, the latter will be generated presently with the C&C Formats
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