Welcome to the website of Dr Eann
Patterson
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Professor and Chair of Mechanical Engineering |
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Editor, Journal of Strain Analysis for
Engineering Design |
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http://www.journalofstrainanalysis.co.uk |
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Editor of the International Journal, Fatigue and Fracture of Engineering Materials and
Structures |
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Founding member of |
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Vice-chair of VAMAS technical working area on ‘Full-field optical methods for strain
measurements’ |
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Co-ordinator of EU FP5
project entitled ‘Standardisation Project for
Optical Techniques of Strain measurement (SPOTS) |
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Research interests in experimental mechanics with
applications in aerospace, biomechanics, and structural integrity (see 100+ peer-reviewed papers) |
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Contact details: |
email: eann@egr.msu.edu |
( + 1 517 353 9861 |
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Research Interests |
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Almost 250 publications
including more than 100 peer-reviewed
papers in the areas of Experimental Mechanics and Biomechanics. |
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Digital Photoelasticity
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Digital Photoelasticity
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Photoelasticity is virtually
the only available technique by which the complete three-dimensional state of
stress in a component can be determined by experiment. Until recently it has suffered two major
disadvantages, namely the resources required to manufacture an epoxy model of
the component, and the time required by a skilled photoelastician
to analyse the model. The first drawback is addressed in part by stereolithography (Curtis et al, 2003)
and the second by automated photoelasticity (Patterson,
2002). An innovative approach has
been taken to the use of phase-stepping in photoelasticity (Haake et al, 1993; Carazo-Alvarez, et al 1994; Barone & Patterson, 1996, Siegmann et al, 2005) and has led the development of
an automated system. Recent further innovations in this area include a new
polariscope which allows four phase-stepped images to be collected
simultaneously in transmission or reflection photoelasticity (Patterson
& Wang, 1998). These
principles are being incorporated into a new device, christened a poleidoscope (Lesniak
et al, 2004), which is being developed for commercial production in
collaboration with Stress Photonics
Inc. This technology has allowed
quantitative evaluation of stress magnitudes and directions in dynamic
photoelasticity. Recent work has
extended the applications of this technology into detailed fatigue studies on
crack closure (Pacey et al,
2005) and real-scale component evaluation (Patterson et al, 2006), integrated
photoelasticity (Tomlinson & Patterson, 2002),
and fibre pull-out in composites (Zhao et al, 2005 & 2006). The integration of photoelasticity with thermoelasticity
(Greene & Patterson, 2006) has allowed
individual principal stresses to be obtained independently for each point in
field of view (Greene et al, 2007). |
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Photoelastic
fringe pattern in a crane-hook (top) & intensity map for phase-stepped
photoelastic pattern (bottom). |
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Thermoelastic Stress Analysis
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Thermoelastic Stress
Analysis
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Significant contributions have
been made to the development of thermoelasticity (Barone & Patterson, 1996
& 1998).
Independently photoelasticity supplies the difference in principal
stresses, and thermoelasticity supplies the sum of
the principal stresses. A number of
separation methods exist for each technique but they all require some prior
knowledge of the stress distribution and many involve integration through the
data which leads to large accumulated errors (Haake et al, 1996).
The advent of full-field automated photoelasticity has allowed
combined thermo-photo-elasticity to be achieved for the first time for a full
field of data. This work has led to
the development of novel instrument of achieving simultaneous thermo- and
photo-elastic measurements. New methods have been developed for analysing
cracks in components using thermoelasticity (Tomlinson et al, 1997), by extending a novel technique
in photoelasticity (Nurse & Patterson, 1993)
based on Muskhelishvili's approach. These developments are allowing real-time
monitoring of crack growth (Diaz et al, 2004) as well as
providing new insights into crack closure (Patterson
et al, 2006). A significant new development is the integration of concepts
from moiré (Heredia-Ortiz & Patterson, 2003) with thermography to produce a new technique of the
experimental stress analysis, known as thermal moiré. This technique is non-destructive and
non-contacting, can be applied to real components subjected to service loads
and allows in-plane and out-of-plane surface strains to be determined. The integration of photoelasticity with thermoelasticity (Greene &
Patterson, 2006) has allowed individual principal stresses to be obtained
independently for each point in field of view (Greene
et al, 2007). |
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Thermoelastic images from a fatigue crack (top) and a bicycle front fork (bottom) obtained from a Deltatherm system |
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Engineering Applications
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Engineering Applications
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Early applications of the photoelastic
research were in threaded connections (Kenny &
Patterson, 1985, 1986 & 1987).
Later studies in this area include the effects of mean stress on the
fatigue life of bolts (Burguete
& Patterson, 1995), and the effects of eccentric loading on the
stress distribution in bolts (Burguete
& Patterson, 1995; Hobbs et al, 2000). These effects had both been largely ignored
in design codes but have been demonstrated to be significant as a result of
recent work with the Health and Safety Laboratory (Hobbs
et al, 2001). The theme of
fasteners has also been extended to include fastener holes (Nurse et al, 1994; Patterson
& Gungor, 1997) and stringers in aircraft (Nurse et al, 1995; Gungor et al, 1996) in work supported by British
Aerospace Airbus Ltd. Detailed studies
have been performed on the fracture mechanics (Burguete & Patterson, 1997) and contact mechanics
(Kenny et al, 1991; Burguete & Patterson, 2001) associated with the
fixings of turbine and compressor blades to discs in work supported by
Rolls-Royce plc and EPSRC, as well as fundamental studies in these areas (Patterson & Gungor, 1997)
which are important recurring themes in the application orientated studies. The expertise acquired in the
study of fasteners described above has been utilised
in the analysis of osseointegrated oral
prostheses. Analyses of these systems
have been performed including experimental work on the load distribution in
implants (Patterson et al 1995), and the fatigue
assessment (Patterson & Johns, 1992) including the
effects of clinical procedures (Burguete et al, 1994). |
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Strain field around a crack
growing from bottom to top from synchrotron data (top) and from
photoelasticity (bottom). |
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Computational Mechanics - Cardiac Prostheses
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Computational
Mechanics - Cardiac Prostheses
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Significant progress has been made in the development of design tools
for bioprosthetic heart valves (Huang
et al, 1990; Black et al, 1991; Patterson
et al,1996). These valves are made
from biological tissue mounted on a plastic frame. The tissue exhibits non-linear elastic behaviour and in this application undergoes large
deformations. In collaboration with Ove Arup & Partners, new finite element facilities
have been developed for LS-DYNA that include non-linear elastic shell and
brick elements (Chew et al, 1994). The first three-dimensional analysis of
such a valve (Black et al, 1991) demonstrated that
bending stresses were significant in these thin, membrane-like structures (Chew et al, 1997).
Subsequent work repeated this analysis but included temporal variations
so that the whole cardiac cycle could be studied( Patterson
et al, 1996; Thornton et al, 1997). Recent work has focussed
on realistic representation of the natural valve geometry, damage (Chew et al, 1999) and material anisotropy (Burriesci et al 1999).
Recent work has included the modeling of the opening mechanism of the
natural aortic valve (Howard et al, 2003) and the
integrated simulation of blood flow and material strain in the aortic valve
techniques for using fluid-solid interaction (Carmody et al, 2006) |
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Simulation
results using fluid-solid interaction for a prosthetic heart valve as it
closes. |
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List of peer-reviewed papers by date of
publication
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Research interests: Digital Photoelasticity, Thermoelasticity, Engineering Applications, Computational Cardiac
Mechanics |
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List of peer-reviewed papers by date of publication
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2007 |
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GREENE,
R.J., YATES, J.R., PATTERSON, E.A., 2007, Crack detection in rail using
infrared methods, Optical Engineering, 46(5) |
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PATTERSON, E.A., HACK, E., BRAILLY, P., BURGUETE,
R.L., SALEEM, Q., THORSTEN, S., TOMLINSON, R.A., WHELAN, M., ‘Calibration and
evaluation of optical systems for full-field strain measurement’, Optics and
Lasers in Engineering, 45(5):550-564. |
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PATTERSON, E.A., BRAILLY, P., BURGUETE, R.L., HACK,
E., SIEBERT, T., WHELAN, M., 2007, ‘A challenge for high performance
full-field strain measurement systems’, Strain, in press |
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2006 |
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ZHAO, F.M., |
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PATTERSON, E.A.,
DIAZ, F.A., YATES, J.R., ‘Observations on photo-emission and the process zone
of a fatigue crack’, Journal of ASTM International, J. Testing &
Evaluation, 3(6) paper id JAI13222. |
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2005 |
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PITERRESI, G., FOUND, M.S., PATTERSON, E.A., ‘An
investigation of the influence of macroscopic heterogeneity on the thermoelastic response of fibre reinforced plastics’, Comp. Sci.
& Tech. 65(2):269-280. |
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ZHAO, F.M.. MARTIN,
R.D.S., HAYES, S.A., PATTERSON, E.A., YOUNG, .R.J., JONES, F.R.,
‘Photoelastic analysis of matrix stresses around high modulus sapphire fibre by means of phase-stepped automated
polariscope’, Composites A: Applied Sci. &
Manu. 36(2):229-244. |
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HEREDIA ORTIZ, M,
PATTERSON, E.A., ‘Location and shape measurement using a portable fringe projection
system’, Experimental Mechanics, 45(3):197-204. |
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ZHAO, F.M. PATTERSON,
E.A.; JONES, F.R., ‘Phase-stepping photoelasticity for quantifying the
interfacial response in fibre composites at fibre-breaks’ Materials Science and Engineering A,
412(1-2):83-87. |
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2004 |
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ESTRADA
ESTRADA, J.R., PATTERSON, E.A., ‘Path dependency in
thermoelastic stress analysis’, Experimental Mechanics, 44(6):567-574. |
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PATTERSON,
E.A., OLDEN, E.J., ‘Optical analysis of crack tip stress fields: a
comparative study’, Fat & Fract. Engng. Mater. & Structures, 27(7):623-636. |
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JAMES,
M.N., HATTINGH, D.G., HUGHES, D.J., WEI, L.-W., PATTERSON, E.A., QUINTA DA FONSECA,
J., , ‘Synchrotron diffraction investigation of the distribution and
influence of residual stresses in fatigue’, Fat & Fract.
Engng. Mater. & Structures, 27(7):609-622. |
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DIAZ, F.A., PATTERSON, E.A., TOMLINSON, R.A.,
YATES, J.R., , ‘Measuring stress intensity factors during fatigue crack
growth using thermoelasticity’, Fat & Fract. Engng. Mater. & Structures 27(7):571-584. |
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DIAZ, F.A., YATES, J.R., PATTERSON, E.A., ‘Some improvements
in the analysis of fatigue cracks using thermoelasticity’,
Int. J. Fatigue, 26(4):365-376. |
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LESNIAK, J.R., ZHANG, S.J., PATTERSON, E.A. , ‘The
design and evaluation of the poleidoscope: a novel digital polariscope,’ Experimental Mechanics, 44(2):128-135. |
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2003 |
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CURTIS, J. D., HEREDIA-ORTIZ, M., PATTERSON, E.A., ‘On the industrial applications of
moiré and fringe projection techniques’, Strain, 39:1-6. GREENE, R.J., PATTERSON, E.A., ‘Integrating thermoelastic and numerical
stress methods for reliable analysis’, J. Strain Analysis, 38(4):1-10. PITARRESI, G., PATTERSON, E.A., 2003, ‘A review of the general theory
of thermoelastic stress analysis’, J. Strain Analysis, 38(5), 405-417. HEREDIA ORTIZ, M., PATTERSON, E. A., 2003, ‘Deformation
data from thermal marking’, Strain, 39:149-152. ZHAO, F., JAMES, M.N., PACEY, M.N., WEI, L-.W., PATTERSON,
E.A., 2003, ‘Characterisation of plasticity-induced
closure-crack flank contact force versus plastic enclave’, Engineering
Fracture Mechanics, 70(17):2473-2487. |
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2002 |
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PATTERSON, E. A., 2002, ‘Digital
photoelasticity: principles, practice and potential’, Strain, 38: 27-39. (Invited contribution). TOMLINSON, R. A., PATTERSON, E. A., 2002, ‘The use of
phase-stepping for the measurement of characteristic parameters in integrated
photoelasticity’, Experimental Mechanics, 42(1): 43-50. |
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2001 |
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BURGUETE, R. L., PATTERSON, E. A., ‘Comparison
of numerical and experimental analyses for contact problems under normal and
tangential loads’, Proc. Institution of Mechanical Engineering, Part G, J.
Aerospace Engng., 215 (9): 113-123. PATTERSON, E. A., ‘Photoelasticity’, in Encyclopaedia
of Materials: Science and Technology, Elsevier Science Ltd. (Invited
contribution). |
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2000 |
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HOBBS, J. W., BURGUETE, R. L., HEYES, P.,
PATTERSON, E. A., ‘The effect of eccentric loading on the
fatigue performance of high tensile bolts’, Int. Jnl.
Fatigue, 22: 531-538. PACEY, M. N., HAAKE, S. J., PATTERSON, E. A., ‘A novel
instrument for automated principal strain separation in reflection
photoelasticity’, J. Testing & Evaluation, 28(4): 229-235. OLDEN, E. J., PATTERSON, E. A., ‘A rational decision making
model for experimental mechanics’, Experimental Techniques, 24(4): 26-32. HANDSCOMBE, R. D., PATTERSON, E. A., ‘The strategic mismatch
of industrial and university research’, Int. J. Manufacturing Technology and
Management, 2(7): 1013-1023. |
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1999 |
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PATTERSON,
E. A., WANG, Z. F., ‘Integration of spectral and phase-stepping methods in
photoelasticity’, Jnl. Strain Analysis, 34(1):
59-64. TOMLINSON,
R. A., PATTERSON, E. A., ‘On the feasibility of determining discrete
photoelastic parameters using the multi-load method’, Jnl.
Strain Anal., 34(4): 295-300. BARONE,
S., PATTERSON, E. A., ‘The development of simultaneous thermo- and photo-
elasticity for principal stress analysis’, Strain, 35(2): 57-66 (invited
review). PACEY,
M. N., WANG, X. Z., HAAKE, S. J., PATTERSON, E. A., ‘The application of
evolutionary and maximum entropy algorithms to photoelastic spectral
analysis’, Experimental Mechanics, 39(4): 265-273. TOMLINSON,
R. A., PATTERSON, E. A., ‘The effects of surface topography on the method of
caustics’, Experimental Mechanics, 39(4): 335-342. CHEW, G. G., HOWARD, I. C.,PATTERSON, E. A., ‘Simulation
of damage in a porcine prosthetic heart valve’, J. Medical Engng & Tech., 23(5): 178-189. BURRIESCI, G., HOWARD, I. C., PATTERSON, E. A., ‘Influence
of anisotropy on the mechanical behaviour of bioprosthetic heart valves’, J. Medical Engng. & Tech., 23(6): 203-215. CARAZO-ALVAREZ,
J. D., PATTERSON, E. A., ‘A general method for automated analysis of
caustics’, Optics & Lasers in Engng., 32:
95-110. |
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