LATIN-AMERICAN JOURNAL OF COMPUTING (LAJC), Vol XI, Issue 1, January - June 2024
Numerical Modeling For Fracture Mechanics
Problems Using The Open-source Fenics Platform
Caio César Prates Martins
Federal Institute of Espírito Santo
Vitória - Brazil
caiocp.martins@gmail.com
André Gustavo de Souza Galdino
Federal Institute of Espírito Sant
Vitória - Brazil
andre.galdino@ifes.edu.br
Brenda Resende Lemos
Federal Institute of Espírito Sant
Vitória - Brazil
brendarlemos2020@gmail.com
Jean Pierre de Oliveira Bone
Federal Institute of Espírito Santo
Guarapari - Brazil
jean.bone@ifes.edu.br
Rodolfo Giacomim Mendes de Andrade
Federal Institute of Espírito Santo
Vitória - Brazil
rodolfo.andrade@ifes.edu.br
Abstract— Fracture mechanics is the mechanical approach to
fracture processes, which emerged due to limitations in applying
traditional concepts of Mechanics of Materials to predict the
behavior of cracked materials. Analytical problem solutions with
this approach may be unattainable, so it is necessary to use
numerical modeling, such as the finite element method. However,
the use of more advanced software that solves engineering problems
numerically is limited by its high cost. FEniCS is an open-source
computational platform that solves partial differential equations by
the finite element method. Thus, from a tutorial for this
computational platform, this work proposes to reproduce a classic
problem of linear elastic fracture mechanics, based on the validation
of a comparison of a linear elastic problem with the commercial
software ANSYS ®. With the help of the provided tutorial, a code
was built to model a three-point bending test. Implemented with the
aid of Gmsh and Paraview, it was possible to obtain satisfactory
results and to show that FeniCS is a powerful and accessible tool for
solving fracture mechanics problems.
Keywords— Fracture Mechanics, Numerical Modeling,
FEniCS, Finite Elements
I. INTRODUCTION
The Finite Element Method (FEM) is an approach to
solving partial differential equations using numerical
techniques in which a continuous domain is discretized into
finite elements called mesh. With the advancement of
technology and, consequently, computational power, more
advanced engineering problems have become simpler to
solve. This is due to the fact that analytical solutions can be
complex and even unreachable, and the error achieved in
numerical solutions is considerably acceptable [1].
In general, the use of advanced FEM-based software
is restricted to companies and some teaching institutions, as it
is the case with ANSYS ® [2]. On the other hand, open-source
programs, such as the FEniCS Software [3], which is free, are
used more widely due to their availability and ease of access.
However, they tend not to have a graphical interface, unlike
commercial software, which makes the use of pre- and post-
processors essential for visualizing the solution. Even for a
simple computational solution approach, the development of
the finite element method can be complex, as it requires
knowledge about tensor and variational calculus in some
cases. The FEniCS [3] software, for example, uses these
principles and, based on programming knowledge and the
library itself, it is possible to solve partial differential
equations using a variational approach. Therefore, this work
proposes to present a numerical modeling of a linear elastic
problem and two of fracture mechanics, presenting a
preliminary comparison with ANSYS® for the linear elastic
problem.
A. Fracture Mechanics
Fracture mechanics is the mechanical approach to fracture
processes that emerged due to limitations applying traditional
concepts of Mechanics of Materials to predict the behavior of
materials in the presence of cracks. It was developed and
founded after the 2nd World War [4] and is widely used in
structural contexts in the areas of civil, mechanical, and
metallurgical engineering [5-7]. For materials with brittle
behavior, the linear elastic fracture mechanics (LEFM)
approach is used, while for materials with ductile behavior,
the elastoplastic fracture mechanics (EPFM) is used [4,8].
For example, in industry, a component may have such a
high cost that, depending on the conditions and its integrity,
it is more viable to have knowledge about fracture mechanics
and continue using it with cracks to perform an exchange,
which results in a complete pause of an operation. Alan
Arnold Griffith studied the behavior of an elliptical hole
when external stress is applied and established a
thermodynamic model for crack propagation [8]. Griffith
concluded that the strength of a material is not only linked to
chemical bonding parameters but also to the existing defects.
Therefore, it was realized that defects in the material are
factors that intensify the applied stress, making it susceptible
to exceeding the yield strength of the material and causing a
rupture, which is the basis of fracture mechanics [4]. With
this, a good characterization of the material must also have
experimental parameters of the LEFM, such as the fracture
toughness (K IC) and the critical energy release rate (Gc), for
example. Fracture toughness is independent of size, geometry,
and loading levels for a material with a given microstructure
and is the main obtained experimentally properties related to
fracture mechanics [8].
II. METODOLOGY
A. Numerical Modeling
The main concept addressed in the FEM is the
discretization of a continuous domain into finite geometric
elements, in addition to the use of polynomial interpolation to
determine the results in the region inside the elements [1].