 (3,379KB)
Simulating the Mechanics of Fretting Fatigue
Crack Growth 
Tom Curtin, John Baynham, and Sharon Mellings
The objectives of the following presentation
are to identify why fretting fatigue is important? And
to discover the following:
- Accuracy of predicted contact
stress
- Comparison of numerical and
analytical solution
- Fretting fatigue crack growth
simulation
- Computer model
- Predicted crack growth path
- Stress intensity factor solution
- Impact of crack growth on
edge of contact stress
- Extension of methodology to
real parts
(488KB)
Crack Growth Prediction Using FEM Data
Robert A Adey, John M. W. Baynham, Sharon Mellings,
Lie Zhang
As part of the engineering design process
engineers have to assess not only how well the design
satisfies the performance requirements but also how
durable the product will be over its life cycle. A major
cause of failure is the growth of cracks which grow
due to fatigue loadings to the point where the product
fails. This paper describes a new approach to predicting
crack growth which combines the best features of boundary
element and finite element technology.
(1,035KB)
Bidimensional
Stress Analysis and SIF's Assessment of a Cracked Aeronautic
Doubler-Skin Assembly by BEM and FEM
A. Apicella, E. Armentani, R. Citarella, G. Coppola,
R. Esposito
The riveted patch repair performance
of a cracked tension panel, with through-cracks initiated
on the most loaded holes, is simulated using a commerically
available Boundary Element code (BEASY) and Finite Element
code (ANSYS). A bi-dimensional stress analysis
on a single sided repair configuration is performed
by both methodologies, consequently the occurence of
out-of-plane bending and its impact on the through-thickness
SIF's (Stress Intensity Factors) variation is neglected.
(1,310KB)
Damage
Tolerance Analysis with Boundary Elements
Paul
R. Hearn
Hamilton Sundstrand utilizes the 3-D
fracture growth analysis capabilities in the commercial
boundary element software product, BEASY, to study crack
growth rates and directions in many of our aerospace
flight components. The outcome has been assessed to
be a significant improvement over previous, less sophisticated
methods used in fracture mechanics. BEASY enables these
fracture mechanics studies to be performed on the actual
3-D hardware, thereby, eliminating the need for crude
2-D approximations. This paper will discuss specific
study details, which include correlation/calibration
to test data as well as actual field data.
(970KB)
Fatigue
Life and Crack Growth Prediction
Robert
A Adey Benchmark, January 2004
As part of the
engineering design process engineers have to assess
not only how well the design satisfies the performance
requirements but also how durable the product will be
over its life cycle. A major cause of failure is the
growth of cracks which grow due to fatigue loadings
to the point where the product fails. This paper describes
a new approach to predicting crack growth which combines
the best features of boundary element and finite element
technology. The crack and the crack growth are simulated
using the boundary element model and the finite elements
are used to represent the remaining part of the structure.
Examples are presented showing how this can be applied
to an aerospace fitting.
(305KB)
Automatic Crack
Growth Prediction in Rails Using BEM
Sharon
Mellings, John Baynham, Robert A Adey
Durability
and damage tolerance calculations are typically based
on experimental data or analytical studies of simplified
cases. In this paper, a new numerical approach is described
which can be used with the full model loading to compute
the stress intensity factors and also to automatically
predict how cracks will propagate. The benefits of the
full numerical computation of the stress field are numerous,
accurate prediction of crack growth, improved stress
intensity data and more accurate prediction of life,
thus providing an accurate method for the forensic analysis
of failures.
(1,032KB)
Fatigue
Life and Crack Growth Prediction Using FEM Data
Robert A Adey, John M. W. Baynham, Sharon Mellings,
Tom Curtin MSCVPD, USA, October
2003
As part of the engineering design process
engineers have to assess not only how well the design
satisfies the performance requirements but also how
durable the product will be over its life cycle. A major
cause of failure is the growth of cracks which grow
due to fatigue loadings to the point where the product
fails. This paper describes a new approach to predicting
crack growth which combines the best features of boundary
element and finite element technology. The crack and
the crack growth are simulated using the boundary element
model (BEASY) and the finite element model (MSC NASTRAN)
are used to represent the remaining part of the structure.
(647KB)
Predicting
Residual Strength Using Fully Automatic Crack Growth
Sharon Mellings, John Baynham, Robert A Adey
The cost to industry of fracture was
recently estimated in a report of the US Department
of Commerce entitled "The economic effect of fracture
in the United States". In this report it estimated that
the cost of fracture was $119 billion dollars per year
(4% of gross national product). It further estimated
that approximately one third could be saved through
the use of current fracture control technology and a
further 25% could be saved through fracture related
research. Therefore the annual cost of fracture could
be halved by the application of better design tools
based on fracture mechanics technology.
(82KB)
Durability
prediction using automatic crack growth simulation in
stiffened panel structures
S. Mellings, J. Baynham, R A Adey, T Curtin
A new method is presented for automatically
predicting the growth of cracks in stiffened panel structures.
The procedure simplifies the modelling of stiffened
panels by allowing definition of beams and use of multiple
overlapping boundary element zones joined by connector
elements. Applications are presented to demonstrate
the effect of the stiffeners on crack growth.
(87KB)
Computational
And Experimental Fracture Analysis Of A Pin-Loaded Lug
Thomas J. Curtin, Robert A. Adey, Thomas R. Brussat
The structural fatigue failure of a common connecting
joint used to attach aircraft control surface components
was investigated. Fatigue testing and computer modeling
were used to determine the Mode I stress intensity factor
(K) solution for an aluminum lug with a single corner
crack. The lug was loaded through contact with a steel
pin restrained on one face only in order to simulate
a clevis.
(122KB)
MSD
residual strength assessment for a cracked joint
A. Apicella, R. Citarella, R. Esposito
The present work, realized in the context
of BRITE-EURAM (SMAAC) project, summarizes a numerical
procedure aimed to evaluation of the residual strength
of a cracked lap joint, based on the R-curve analysis
and plastic collapse prediction. The model adopted is
based on the use of the Dual Boundary Element Method,
implemented in the BEASY code, adopting a Linear Elastic.
Fracture Analysis for SIF’s evaluation. Experimental
collapse load was available, allowing a comparison with
numerical results aimed to validate the described procedure.
(72KB)
Multiple
Site Damage (MSD) crack growth: numerical evaluations
and experimental tests
C. Calì, R. Citarella,M. Perrella
This work is aimed to assess a numerical
procedure forMSD crack propagation simulation of 2D
pre-notched specimens (plates) undergoing a traction
fatigue load, as defined by a general load spectrum.
Experimental analyses on a fatigue machine were carried
out in order to validate the numerical results and to
provide the necessarymaterial fatigue data for the aluminiumplates.
The numerical analyses were performed using a commercial
code (BEASY) that is based on Dual Boundary ElementMethod.
(48KB)
Crack
propagation in Multi Site Damage conditions for a riveted
joint
A. Apicella, E. Armentani, C. Calì, R.
Citarella, A. Soprano
An MSD crack growth simulation is presented,
carried out by means of a Boundary Element code (BEASY),
for a two-dimensional analysis of a cracked butt-joint.
An equivalent 2D crack length is proposed for an approximated
2D analysis of a 3D problem (part elliptical crack front).
The aim of this work is to validate such assumptions
by comparing the numerical results with the experimental
data, obtained from a fatigue tested riveted butt-joint
of aluminum 2024 T3.
(63KB)
FEM-BEM
coupled methodology for cracked stiffened panels
C. Calì, R. Citarella, A. Soprano
A mixed methodology, involving both
BEM and FEM methods, applied on the same domain, is
a very effective tool in complex problems, because it
is possible to combine the advantages that both of them
offer. For example with FEM it is possible to better
face non-linear or anisotropic material problems, while
BEM is well-suited for crack problems by modeling only
the boundaries. In order to create the BEM super-element
stiffness matrix for a cracked domain we have adopted
a method based on Dual Boundary Element methodology
in which it is required to write the dual equation too.
(187KB)
Some
SIF’s evaluations by Dual BEM for 3D cracked plates
A. Apicella, R. Citarella, R. Esposito, A. Soprano
This work concerns a study on numerical
evaluation of linear elastic crack 3D problems with
linear and non-linear load conditions, using a Single-Domain
Boundary Element Method and in particular the Dual Boundary
Element Methodology (DBEM). The method, implemented
in a commercial code (BEASY), uses both the conventional
Displacement Integral Equation and the less commonly
used Traction Integral Equation and relies on the use
of discontinuous elements to model the cracks, whose
Stress Intensity Factors (SIF’s) are calculated
by means of the Crack Opening Displacement method (COD).
(148KB)
3D
Stress Intensity Factor evaluation by Dual BEM
A. Apicella, R. Citarella, A. Soprano
This work, realized in the context
of BRITE-EURAM (SMAAC) project, concerns a study on
numerical evaluation of linear elastic crack 3D problems,
using a Single-Domain Boundary Element Method and in
particular the Dual Boundary Element Methodology. The
method, implemented in a commercial code (BEASY), uses
both the conventional Displacement Integral Equation
and the less commonly used Traction Integral Equation
and relies on the use of discontinuous elements to model
the cracks. SIF’s on a circular quadrant crack
have been evaluated with reference to a two hole plate
undergoing different loading conditions.
(253KB)
Fully Automatic 3D Crack Growth with BEM
Sharon Mellings, John Baynham, Robert A Adey
In this paper, a new method is presented
for the automatic growth of edge cracks in three-dimensional
fracture analysis using BEM. The procedure described
overcomes the current problems with crack growth analysis
that currently has to be performed manually. Applications
are presented which demonstrate the effectiveness of
the technique.
(334KB)
Automatic 3D Crack Growth using BEASY
A.C. Neves, R.A. Adey, J.M.W. Baynham, S.M. Niku
This paper described an automatic procedure
for predicting crack growth in three dimensional structures
as well as calculating the stress intensity factors
at each crack increment. The procedure is implemented
in a general purpose engineering analysis system BEASY.
The system uses a dual boundary element technique to
simplify the modelling of the cracks and to provide
highly accurate stress intensity factors. Applications
are presented for single cracks and results compared
with analytical solutions.
(595KB)
Durability
Prediction Using Automatic Crack Growth Simulation
S. Mellings, J. Baynham, R.A. Adey, T. Curtin,
ICAF 2001
In this paper, a new method is presented
for the automatic growth of edge cracks in three-dimensional
fracture analysis using BEM. The procedure described
overcomes the current problems with crack growth analysis
that currently has to be performed manually. Applications
are presented which demonstrate the effectiveness of
the technique.
(986KB)
Mechanical
and thermal crack initiation along the seal edge of
cathode ray tube
C.Y. Cha, V. Lakshmanan, H. Betrabet, C.A. Brebbia,
R. Adey, S.Mellings, T. Curtin, BETECH
2001: 14th International Conference on Boundary Element
Technology
This article describes a thermal stress
boundary element analysis which was carried out to select
a mechanical device that would innovate the frit salvage
of cathode ray tubes (CRT). The panel and funnel of
a CRT are fritted at the seal edge. To reuse a CRT the
panel and funnel are separated by etching and then applied
a thermal shock. This procedure is known as frit salvage.
Current yield of the frit salvage success rate is about
61% which means that 39% of the components are lost
and cannot be reused. The financial burden can be reduced
if the salvage rate is improved through a better understanding
of the thermal shock mechanism.
(253KB)
Fully
Automatic 3D Crack Growth with BEM
Sharon Mellings, John Baynham, Robert A Adey
In this paper, a new method is presented
for the automatic growth of edge cracks in three-dimensional
fracture analysis using BEM. The procedure described
overcomes the current problems with crack growth analysis
that currently has to be performed manually. Applications
are presented which demonstrate the effectiveness of
the technique.
(272KB)
Simulation
of wheel-rail damage
Matthew Rudas, John Baynham, Robert A Adey,
COMPRAIL 2000 - 7th International Conference
on Computer Aided Design, Manufacture and Operation
in the Railway and other Advanced Mass Transit Systems
Wheel-Rail systems are inherently subject
to damage caused by the rolling contact and slip stick
behaviour between the wheel and the rail. Damage typically
manifests itself as wear or crack initiation and growth
in the rail. In order to accurately predict this phenomena
an accurate understanding of the contact mechanics and
crack behaviour is required. In this paper a methodology
based on BEM is presented which enables these type of
problems to be simulated. Two applications are presented.
In the first the wear of an auxiliary rail is predicted
and in the second the growth of a crack in the rail
due to the rolling contact is predicted.
(1,219KB)
Damage
Repair Simulation of a Tension Panel and Pressurized
Cylindrical Shell Using Adhesively Bonded Patches
Thomas
J Curtin and Robert A Adey
The bonded patch repair performance
of a cracked tension panel, and a pressurized cylindrical
shell with longitudinal through-crack, is simulated
using a commercially available boundary element code.
Three-dimensional, quadrilateral-shaped, reduced-quadratic
order, boundary elements are used to model the panel,
cylindrical shell, and repair patch. The adhesive layer
is modeled using a continuously distributed system of
linear springs. A special boundary element is used to
model the crack.
(246KB)
Fatigue
Assessment of Welds on Piping on Jo-Bell Switches
Matthew Rudas, Richard Rudas, Robert Adey, Journal
of the Engineering Integrity Society
A large oil and gas facility was faced
with a major engineering evaluation when cracks were
discovered in welded pipe joints. The weld flaws were
located in the piping network used to connect a series
of process pressure vessel switches of the float and
chamber variety. Environmental fatigue loading of the
pipe joints by was a critical concern due to the potential
growth of the embedded weld cracks. Given the exorbitant
cost required to shut down the processing plant and
replace all the critical welded pipe connections, other
more cost-effective solutions were investigated with
the objective of developing a methodology to assess
the life of the process pressure vessel piping network
without requiring a costly shutdown of the facilities
refinery operation.
(502KB)
Fracture
Mechanics Analysis of Head Checks in Rails
Mathew Rudas, Robert Adey, International Railway
Journal
The vertical deflection of rolling
contact fatigue crack propagation can ultimately lead
to rail failure. Assessment of damaged rail sections
by computer modelling can give valuable information
on its remaining life and safe rolling-stock axle loads
and track speeds.
(113KB)
Fatigue
Crack Growth Simulation for Complex Three Dimensional
Geometry Loading
Second Joint NASA/FAA/DOD conference
on aging aircraft
(851KB)
Crack
growth analysis using BEASY
S.M. Niku, R.A. Adey
Catastrophic failure of engineering
structures is caused by cracks that extend beyond a
safe size. Cracks are present to some extent in all
structures and can lead to failure or decrease in structural
strength if they grow. This paper described an automatic
procedure for predicting the growth of cracks in two
dimensional structures and the key data for fracture
mechanics based design. The stress intensity factors.The
procedure is implemented in a general purpose engineering
analysis system BEASY.
(182KB)
Predicting
fatigue crack growth in complex components
A.C. Neves, S.M. Niku, R.A. Adey
Catastrophic failure of engineering
structures is caused by cracks that extend beyond a
safe size. Cracks are present to some extent in all
structures and can lead to failure or decrease in struc-tural
strength if they grow. This paper described an automatic
procedure for predicting the fatigue crack growth in
two and three dimensional structures and the key data
for fracture mechanics based design: the stress intensity
factors. The procedure is implemented in a general purpose
engineering analysis system BEASY.
(621KB)
Damage
tolerance analysis of a cracked attachment lug using
BEM
A. Apicella, S. Magliaro
A detailed 3D analysis using BEM (Bounday
Element Method) was performed to determine the stress
distribution and SIFs of a corner crack of the fuselage
to wing attachment lug of a medium range military transport
aircraft. The contact pin-lug has been studied with
non-linear contact analysis. Based on this study a crack
growth prediction has been performed with a proper analytical
model. For the above prediction, both - constant and
variable amplitude loads were considered. An experimental
correlation has been made for both crack growth and
final fracture of the component. As a result of the
present work it can be concluded the industrial feasibility
of fracture mechanics analyses using BEM.
(414KB)
Crack
analysis by Boundary Method
A. Elzein, R.A. Adey
A simple and efficient approach is
proposed for analysis of crack problems occurring in
mechanical components widely used in the aerospace industry.
A linear stress analysis of the cracked components is
performed using the engineering analysis system BEASY
based on the boundary element method, to derive accurate
predictions of the stress intensity factors corresponding
to either of the three modes KI, KII or KIII. With the
proposed approach, the user has to model only the surface
of the component, as opposed to its volume in finite
elements.
(201KB)
Application
of a Non-local Failure Criterion to a Crack in Heterogeneous
Media
Stefano Bavaglia and Sergei E Mikhailov
A plane problem is considered for an
infinite elastic medium with a circular elastic inclusion
and a crack reaching the interface. The Boundary Element
Method implemented in BEASY software package is used
to the stress field calculation. A modification of an
average stress non-local fracture criterion , is applied
in this work to predict the crack propagation and evaluate
the possibility of its further reflection, refraction
or interface delamination. The two criterion parameters
are obtained from classical tensile test and standard
fracture test results.
(476KB)
Frit
salvage innovation of cathode ray tube by initiating
to crack along the seal edge
C.Y. Cha,S.V. Iyer,V. Lakshmanan,C.A. Brebbia and
R.A. Adey |
