Structural integrity of bone tissue plays an important role in daily activities of humans. However, traumatic incidents such as sports injuries, collisions and falls can cause bone fracture, servere pain and mobility loss. In addition, ageing and degenerative bone diseases such as osteoporosis can increase the risk of fracture [1]. As a composite-like material, a cortical bone tissue is capable...

The cracked Brazilian disc (CBD) specimen is widely used in order to determine mode-I/II and mixed-mode fracture toughness of a rock medium. In this study, the stress intensity factor (SIF) on the crack-tip in this specimen is calculated for various geometrical crack conditions using the extended-finite element method (X-FEM). This method is based upon the finite element method (FEM). In this m...

In this licentiate thesis the work done in the TURBO POWER project Influence of high temperature hold times on the fatigue life of nickel-based superalloys will be presented. The overall objective of this project is to develop and evaluate tools for designing against fatigue in gas turbine applications, with special focus on the nickel-based superalloy Inconel 718. Firstly, the constitutive beh...

This paper presents a meshless point collocation method for three-dimensional crack propagation. The meshless point collocation method is based on direct discretization of strong-form governing equations to achieve a truly meshless scheme that does not require mesh structures or a numerical integration procedure. These characteristics of the point collocation method enable the direction of an a...

Paris law constants are commonly obtained with a well established procedure based on standard specimens, notched and pre-cracked. Pre-cracking produces through cracks with stable shapes, nearly straight, similar during all propagation. However, in several situations specimens with corner and surface cracks are recommended. In these cases cracks having significant propagation will continuously m...

A series of molecular-dynamics simulations using a many-body interatomic potential has been performed to investigate the behavior under load of several ^001& and ^011& symmetrical tilt grain boundaries ~GB’s! in diamond. Cohesive energies, the work for fracture, maximum stresses and strains, and toughness as a function of GB type are evaluated. Results indicate that special short-period GB’s po...

Effect of thermal treatment on the fatigue crack propagation behavior of a new Ni-base superalloy Xingbo Liu a,*, ling Xu a, Ever Barbero a, Wei-Di Cao b, Richard L. Kennedy b a West Virginia University, Morgantown, WV 26506-6106, USA b Allvac, an AT! Technologies Company, Monroe, NC 28111-5030, USA Received 22 October 2006; received in revised form 23 March 2007; accepted 10 May 2007 The effec...

BACKGROUND Slow crack growth can be described in a v (crack velocity) versus KI (stress intensity factor) diagram. Slow crack growth in ceramics is attributed to corrosion assisted stress at the crack tip or at any pre-existing defect in the ceramic. The combined effect of high stresses at the crack tip and the presence of water or body fluid molecules (reducing surface energy at the crack tip)...

The aim of the present paper is to simulate the propagation of diffuse ultrasonic energy in concrete in the presence of a real crack. The numerical model is presented and validated by the comparison with experimental data from the literature. Unlike most of the studies which consider a crack as a notch, a realistic crack morphology exhibits partial contacts along its lips. These contacts are mo...

We propose a minimal nonlinear model of brittle crack propagation by considering only the motion of the crack-tip atom. The model captures many essential features of steady-state crack velocity and is in excellent quantitative agreement with many-body dynamical simulations. The model exhibits lattice-trapping. For loads just above this, the crack velocity rises sharply, reaching a limiting valu...