Influence of test parameters on the measurement of the essential work of fracture of zinc sheets

Abstract

The Essential Work of Fracture (EWF) concept is used to characterize the fracture of thin plates of a zinc alloy. The consistency and applicability of the EWF approach are discussed. The successive stages of the fracture process were studied: the evolution of the shape of the crack tip was observed with a scanning electron microscope, the shape of the plastic zone and the evolution of necking in the ligament ahead of the crack tip were measured using a laser profilometer and the onset of cracking in the ligament was detected by means of a TV camera coupled with acoustic emission recording. The influence of both test parameters and material parameters on the Essential Work of Fracture (w~) and on the CTOD (~c) are elucidated. The effects of specimen geometry, deformation rate, texture and grain size are especially investigated. The main advantages and drawbacks of the EWF method are highlighted. Nomenclature ant = Slope of/~m~x against l, /3 = Shape factor, tic = Crack-tip opening displacement, ~, = Factor (= w~/(a~. 6c)), Fm~x = Maximum load, l = Ligament length, t : Thickness of the plates. u : Displacement. rp = Extent of the plastic zone. W = Width of the plates. Wtot = Total work of fracture. W~ = Essential work of fracture. Wp = Non essential work of fracture.'//)tot = Specific total work of fracture. w~ = Specific essential work of fracture. wp = Specific non essential work of fracture. dy = Ultimate elongation.

Fracture Resistance of Advanced High-Strength Steel Sheets for Automotive Applications

“…Then, w e can be determined by linear extrapolation to zero ligament length. w e has shown to be a suitable parameter to describe the crack propagation resistance of thin ductile sheets, including polymers, [40][41][42] metals, [43][44][45][46][47] and AHSS. [9,14,15,34,35,[48][49][50][51][52] It is important to point out that the plane stress fracture toughness of thin ductile sheets has an important contribution from necking and, therefore, the measured w e cannot be considered an intrinsic material property but a material constant for the given sheet thickness.…”

Fracture toughness examination of dual‐phase and interstitial free steel using essential work of fracture method

“…One of the fundamental hypotheses of EWF methodology is that fracture happens after the complete yielding of the specimen. Several researchers 19,22,24 have divided the total energy consumed by the sample W f into two entities, which are the work of crack initiation w i and the work of crack propagation. According to Y.W.…”

“…Some of the notable research work on the EWF method is mentioned here. [19][20][21][22] Several attempts 19,23 have been made to compare specific EWF w e with J IC . However, J IC is defined at the initial stage of crack growth, and w e is defined over entire crack growth.…”

Evaluación del trabajo esencial de fractura en chapa de un acero de alta resistencia de fase dual

“…Sin embargo su uso está muy extendido, particularmente, en la determinación de la tenacidad en films poliméricos [11][12][13] . En metales, ha sido utilizado para caracterizar diferentes chapas metálicas de aleaciones de zinc [6] , aleaciones de aluminio [14] , bronce y latón [8] , aceros de baja aleación [5 y 7] y, recientemente, en aceros TRIP [15] . La metodología desarrollada por Cotterell y Reddel en 1977 [5] propone que el trabajo necesario para hacer avanzar una grieta en un material dúctil se puede separar en dos contribuciones: la energía correspondiente al trabajo de deformación plástica en el frente de la grieta y la energía consumida por todos los procesos microscópicos que causan la fractura.…”

“…Es en este sentido que se considera un trabajo esencial, siendo por la forma en la que está definido, una manera de aproximar el valor de J c . Esta metodología se ha aplicado anteriormente para caracterizar chapas de acero, aleaciones de aluminio, bronces y latones [6][7][8] . Los buenos resultados conseguidos permiten postular su uso para aceros AHSS como herramienta de caracterización de su tenacidad a fractura.…”