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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Interim Director 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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2008 |
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PATTERSON, E.A., WHELAN, P., ‘Optical signatures of
small nanoparticles in a conventional microscope’ Small, DOI:
10.1002/smll.200800703. |
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PATTERSON, E.A., WHELAN, P., ‘Tracking
nanoparticles in an optical microscope using caustics’, Nanotechnology, 19(10):105502. |
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LOPEZ-CRESPO, P., CAMAS-PEÑA, D.,
GONZALEZ-HERRARA, A., YATES, J.R., PATTERSON, E.A., ZAPATERO, J., ‘Numerical
and experimental analysis of crack closure’, Key Engineering Materials,
385-387:369-372. |
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LOPEZ-CRESPO, P., SHTERENLIKHT, A., PATTERSON,
E.A., YATES, J.R., WITHERS, P.J., ‘Fatigue crack monitoring using image
correlation’, Key Engineering Materials, 385-387:341-344. |
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WHELAN, M.P., ALBRECHT, D., HACK, E., PATTERSON, E.A.,
‘Calibration of a speckle interferometry full-field strain measurement
system’, Strain, 44(2):180-190. |
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CHRISTOPHER, C.J., JAMES, M.N., PATTERSON, E.A.,
TEE, K.F., ‘A quantitative evaluation
of fatigue crack shielding forces using photoelasticity’, Engng. Fract.
Mechanics, 75(14):4190-4199. |
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ROWLANDS, R.E., PATTERSON, E.A., ‘Determining
principal stresses thermoelastically’, J. Strain Analysis, DOI: 10.1243/03093247JSA358. |
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LOPEZ-CRESPO, P., BURGUETE, R.L., PATTERSON,
E.A., SHTERENLIKHT, A., WITHERS, P.J., AND YATES, J.R., ‘A study of a crack
at a fastener hole by image correlation’, Experimental Mechanics, DOI
10.1007/s11340-008-9161-1. |
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BACKMAN, D.,
M LIAO, M., L CRICHLOW, L., M YANISHEVSKY, M., AND PATTERSON, E.A., ‘The use of digital image
correlation in a parametric study on the effect of edge distance and thickness
on residual strains after hole cold expansion’. J. Strain Analysis, 43, DOI
10.1243/03093247JSA448. |
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LOPEZ-CRESPO, P., SHTERENLIKHT, A., PATTERSON,
E.A., WITHERS, P.J., AND YATES, J.R., ‘The stress intensity of mixed mode
cracks determined by digital image correlation’, J. Strain Analysis, 43, DOI
10.1243/03093247JSA419. |
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2007 |
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PATTERSON, E.A., BRAILLY, P., BURGUETE, R.L.,
HACK, E., SIEBERT, T., WHELAN, M., ‘A challenge for high performance full-field
strain measurement systems’, Strain,
43(3):167-180 |
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TEE K.F., C J CHRISTOPHER, C.J., JAMES, M.N.,
PATTERSON, E.A., ‘New Insights into Plasticity-Induced Crack Tip Shielding
via Mathematical Modelling and Full Field Photoelasticity’, Key Engineering Materials, 345-346
pp. 199-204. |
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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) 051013 |
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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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CHRISTOPHER, C.J., JAMES, M.N., PATTERSON, E.A.,
TEE, K.F., ‘Towards a new model of crack tip stress fields’, IJ Fracture, 148
(4): 361-371. |
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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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