Browsing by Subject "Cracks"

Now showing 1 - 4 of 4

Open Access
An animation system for fracturing of rigid objects
(Springer, Berlin, Heidelberg, 2005) Küçükyilmaz, Ayşe; Özgüç, Bülent
This paper describes a system for the animation of fracturing brittle objects. The system combines rigid body simulation methods with a constraint-based model to animate fracturing of arbitrary polyhedral shaped objects under impact. The objects are represented as sets of masses, where pairs of adjacent masses are connected via a distance-preserving linear constraint. Lagrange multipliers are used to compute the forces exerted by those constraints, where these forces determine how and where the object will break. However, a problem with existing systems is that the initial body models exhibit well-defined uniformity, which makes the generated animations unrealistic. This work introduces a method for generating more realistic cracks without any performance loss. This method is easy to implement and applicable on different models. © Springer-Verlag Berlin Heidelberg 2005.
Open Access
Development of a non-ordinary state-based peridynamics solver
(2019-09) Morasata, Rico
Damage prediction is crucial in the design process of engineering structures to ensure structural integrity. The limitations of empirical methods and the high costs associated with experimental analyses have prompted the development of numerical methods to predict the initiation and/or propagation of cracks under prescribed loading conditions. While various methods exist for failure prediction, their formulations rely on partial differential equations with spatial derivatives. As a result, these methods require special treatments in order to accurately capture the underlying failure mechanisms. To overcome these limitations, the peridynamic theory has been introduced as a novel, nonlocal continuum formulation. In contrast to the other methods, it is expressed as an integro-differential equation devoid of spatial derivatives, hence applicable to structural analyses involving discontinuities. This project aims to elaborate on the development of a solver based on a specific variant of the peridynamic formulation to investigate the behavior of two- and three-dimensional structures under certain loading conditions. The current code is developed to solve quasi-static problems related to damage initiation and propagation. In addition, it is aimed to show that peridynamics can capture local, hyperelastic deformations. The overall structure of the code is reviewed and the potential extensions of the current work are discussed.
Open Access
Microstructural association between mechanical behavior with bending fracture surfaces in Astaloy CrA sintered parts alloyed by Cu and C
(Elsevier Ltd, 2014) Khorsand H.; Ghaffari, M.; Ganjeh, E.
Application of powder metallurgy technique, a method presenting both economic and technical concepts for producing sintered parts, has been expanding in automobile and other engineering industries. Powder metallurgy parts usually possess residual porosity in their microstructures deteriorating mechanical performance. There have been many solutions to increasing of strength in these parts such as applying different heat treatment or adding alloying elements. It is well known that Fe-Cu-C is the one of main alloying system for both increasing the strength and decreasing cost of them. In this study, the microstructure, mechanical properties (transverse rapture strength and hardness), crack behavior and fracture modes of a low alloy Fe-Cr powder (Astaloy CrA) with different amount of copper (0, 1 and 2. wt.%) and carbon, in form of graphite (0.45, 0.6 and 0.8. wt.%) sintered at conventional condition have been investigated. Microstructural evolution showed adding copper and graphite as alloying elements could generate widespread of strength (857-1380. MPa) and hardness (170-295 HV5). Developing different phases in microstructure was the main reason for various mechanical properties. Crack coalescence phenomenon leads to fracturing with ductile (at sinter-necks) and brittle morphology. Micro-mechanism of fracture related to transparticle and interparticle crack propagation. © 2013 Elsevier Ltd.
Open Access
X-ray photoelectron spectroscopy for identification of morphological defects and disorders in graphene devices
(AIP Publishing, 2016) Aydogan, P.; Polat, E. O.; Kocabas, C.; Süzer, Şefik
The progress in the development of graphene devices is promising, and they are now considered as an option for the current Si-based electronics. However, the structural defects in graphene may strongly influence the local electronic and mechanical characteristics. Although there are well-established analytical characterization methods to analyze the chemical and physical parameters of this material, they remain incapable of fully understanding of the morphological disorders. In this study, x-ray photoelectron spectroscopy (XPS) with an external voltage bias across the sample is used for the characterization of morphological defects in large area of a few layers graphene in a chemically specific fashion. For the XPS measurements, an external +6 V bias applied between the two electrodes and areal analysis for three different elements, C1s, O1s, and Au4f, were performed. By monitoring the variations of the binding energy, the authors extract the voltage variations in the graphene layer which reveal information about the structural defects, cracks, impurities, and oxidation levels in graphene layer which are created purposely or not. Raman spectroscopy was also utilized to confirm some of the findings. This methodology the authors offer is simple but provides promising chemically specific electrical and morphological information.