An Experimental Study of CTOD for Mode I/Mode II Stable Crack Growth in Thin 2024-T3 Aluminum Specimens

Abstract

An experimental study of crack tip opening displacement (CTOD) for Mode I/Mode II stable crack growth in thin sheet 2024-T3 aluminum has been conducted. To perform the experiments, an Arcan specimen and fixture was modified so that (1) slippage in the grips was eliminated, (2) large rotations of the fixture components were achievable and (3) bending stresses were minimized. Defining Θ to be the angle between the Mode I loading direction (perpendicular to the crack line) and the direction of applied loading, experimental results indicate that (a) for large amounts of crack extension, a ≥ 10 mm, the value of CTOD at 1 mm behind the crack tip appears to approach a constant value of 0.1 mm for all modes of loading, (b) the direction of crack extension varied with applied mixed mode loading, (c) Mode I crack extension is predominant for 0° ≤ Θ ≤ 60°, (d) Mode II crack extension is predominant for 75° ≤ θ ≤ 90° and (e) a transition zone exists for angles θ near 75°.

Discrete crack modelling of ductile fracture driven by non‐local softening plasticity

“…In the = 15 • case, this path has a downwards slope of −5 • , with no visible kinking. In the experiments, after a kink early in the growth process, this angle was approximately −7 • [39,40]. The kink near the start of the crack is believed to be due to a transition from mode-I dominated growth to mode-II, which is not captured by the present model.…”

“…In order to be able to compare the behaviour of the damage-fracture modelling with experiments, simulations have been done of the experiments performed by Amstutz et al [39,40] using modified Arcan specimens made of Aluminium alloy 2024-T3. The Arcan test [41] allows, by means of a special fixture, to load a test specimen at different angles , and thus to perform mixed mode fracture experiments.…”

A damage-based temperature-dependent model for ductile fracture with finite strains and configurational forces

“…In fact, one knows that in brittle fracture the two paths are clearly distinct (cf., e.g., Allaire et al 2011). However, for ductile fracture this is no more the case as laboratory experiments and numerical simulations show (Maccagno and Knott 1992;Amstutz et al 1995;James and Swenson 1999;Sutton et al 2000) (Fig. 12).…”

“…13 have been originally used for testing of composite specimens for stable tearing tests (Arcan et al 1978). We here refer to Sutton et al (2000) where experimental results by Amstutz et al (1995) have been reproduced with good qualitative agreement for 2024-T3 aluminum.…”

“…Let us remark that damage can be cast within purely elastic brittle fracture models but also plays a crucial role in the models designed for ductile materials such as metals, cf. Bažant (1976) or Amstutz et al (1995), Oliver (1995), Xue and Wierzbicki (2008). In fact, ductile fracture mechanisms under mixed mode I/II load show either shear, or microvoid coalescence behaviors (Maccagno and Knott 1992), with the latter here modeled by the introduction of ζ .…”