Academics
Degrees:
M.S.
Civil & Environmental Engineering,
B.S.
Civil & Environmental Engineering,
Current Research:
DDSim: A next generation Damage and Durability
Simulator
Current
state-of-practice tools for life prediction of thermomechanically loaded
structural components are limited in some or all of the following capabilities:
geometry of and boundary conditions on the affected structural component,
automation of the analysis process, stochastics of the primary variables, and
physics of the damage evolution processes.
A
next generation damage and durability simulator, DDSim, addresses each of these
limitations with a hierarchical, multi-scale, ''search and simulate'' strategy.
This hierarchical strategy consists of three levels. Level I performs an
initial, reduced order, conservative screening to determine the most life
limiting locations for intrinsic material flaws. This is accomplished by using
the principle of superposition to combine stress fields from an uncracked
structure with analytical stress intensity factor solutions for internal,
surface and corner cracks to estimate the fatigue life of the structure. The
stress and temperature fields in the uncracked structure are computed by using
a finite element code and are transferred to Level I via the mesh and nodal
stress data. Hence, any finite element code capable of outputting such data can
be used. Next, a fatigue life prediction is made, assuming a crack originates
in the worst possible orientation, at every node in the finite element model. Initial
crack size can be specified deterministically or generated randomly, given a
statistical distribution, and run in a
It
is clear that in Level I the finite element model is not altered to include the
geometry of a crack. DDSim Level II, using the life predictions from Level I
and a user supplied range of life prediction values, alters the geometry of the
finite element model to include a crack (or cracks). Then, fully
three-dimensional, finite element based, crack growth simulations are performed
allowing arbitrarily shaped crack growth with automatic remeshing. These
simulations produce high fidelity life predictions for microstructurally large
fatigue cracks.
The
majority of a structure's fatigue life is consumed by crack nucleation: the
process of damage accumulation at the microstructural length scale leading to a
visually evident crack. In DDSim Level III a finite element model of a
representative volume of material is constructed, including accurate grain and
particle geometry and texture. This model is used to predict crack nucleation
at the location(s) of high interest as determined by the Level I and II
analyses. Hence, boundary conditions for the microstructural model are
determined from the field values of the continuum length scale model of Level
I. In turn, the cumulative damage in the microstructural model is used to
modify the constitutive parameters of the continuum model. This process is performed,
iteratively, until crack nucleation has occurred. The Level III multiscale
analysis can be performed in
DDSim's Life Prediction contour for a section of a
turbine disc under inertial loading.
Sponsored
by: NASA Cooperative Agreement NCC3-994, the
"Institute for Future Space Transport" University Research,
Engineering and Technology Institute, http://www.mae.ufl.edu/cuip/
M.S. Research:
Evaluation of surface cracks in welded components of nuclear reactor vessels
Sponsored
by: Hitachi Ltd.,
Papers & Presentations:
Emery,
J. M., Wawrzynek, P. A., Ingraffea, A. R., DDSim: A Next Generation Damage
and Durability Simulator, Invited presentation at ASME International
Mechanical Engineering Congress and Exposition (Materials and Structures for
Hypersonic Vehicles), Chicago, IL, November, 2006
Emery,
J., M., Wawrzynek, P., A., Ingraffea, A., R., "DDSim: A Next Generation Damage and
Durability Simulator", 11th International Conference on
Fracture,
Emery,
J., M.,
A
Quick Biographical Sketch
I
am a native Vermonter and prefer real maple syrup to squished-up corn; long
cold winters with plenty of snow to the heat of the desert; and smooth cool
running brooks full of trout to alligator infested swamps (no offense to anyone
who likes that stuff, it's just not for me). I was born on May 10, 1975,
the youngest member of a five person household, all of which are very dear to
me.
I,
like my father and my father's father, am an alumnus of
Shortly
after conferral of my undergraduate degree, I took my first job with Research
Engineers International as a technical analyst for their well known structural
analysis software STAAD.Pro. After about two years, I took a position as
a structural engineer with Behrent Engineering Company (BECO) a consulting firm
located near
In
the fall of 2001, I moved back to the northeast to pursue graduate studies at
Oh, and I fish...
