Digital Image Correlation Method Study of the Static Fracture Toughness and the Fracture Strength of a Thin-Sheet Alumin
- PDF / 766,106 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 51 Downloads / 220 Views
NOSTICS AND MECHANICAL TEST TECHNIQUES
Digital Image Correlation Method Study of the Static Fracture Toughness and the Fracture Strength of a Thin-Sheet Aluminum Alloy V. V. Avtaeva, * and N. O. Yakovleva a
All-Russia Institute of Aviation Materials, Moscow, 105005 Russia *e-mail: [email protected]
Received October 4, 2019; revised October 21, 2019; accepted November 24, 2019
Abstract—The fracture toughness of a thin-sheet V-1167RDTV aluminum alloy is investigated by digital image correlation method. The ways of correct estimation of the stress intensity coefficients obtained by calculating the displacement fields by the Williams equation are found. Buckling criteria are quantitatively determined, and a crack propagation resistance curve (R-curve) is plotted for static loading. Keywords: digital image correlation, fracture toughness, experimental mechanics, fracture mechanics, stress intensity factor, R-curve, buckling DOI: 10.1134/S0036029520100043
1. INTRODUCTION The orientation of the principles of aviation design to the concept of damage tolerance determined the need to know the critical characteristics of the material ability to resist the appearance and development of fatigue cracks during service load. However, the passport or certificate characteristics of structural materials [1] obtained under laboratory and fixed conditions of force action cannot completely take into account complex operational influences. When expensive bench tests are performed, the complex character of effects on structural materials is revealed in the form of early failure of structural elements. These differences from the results of calculations based on the experimental data of laboratory tests force designers to assign high safety factors. At the same time, to obtain information about the character of damage development in new materials [2, 3], experiments are still required; to substantiate and verify the strength calculations of a material for its rational use, it is necessary to numerically evaluate the characteristics describing the process of destruction at a high accuracy [4, 5]. In terms of fracture mechanics, the development of damages in which a dominant defect propagates (e.g., a main crack) is considered using a stress intensity factors (SIF) as the measure of elastic stresses at the crack tip [6, 7]. When fracture develops in a structure, it is necessary to take into account the inhomogeneity of the stress and strain fields due to a local change in the stiffness associated with the use of reinforcement or the presence of irregular zones.
To study mixed fracture according to mode I and II fracture models (normal crack opening, in-plane shear), researchers use the approach based on complex Muskhelishvili’s potentials and the potential developed by Williams for the case of a plane problem. In this case, the elastic field in the region of a crack propagation with the center of polar coordinates r and θ at the crack tip is calculated using the u and v displacement fields along Cartesian axes x and y, respectively, ∞
n2
Data Loading...
