Automation of finite element analysis based on
a fully adaptive p-refinement procedure
can reduce the magnitude of discretization error
to the desired accuracy with minimum computational cost
and computer resources.
This study aims to 1) develop an efficient
p-refinement procedure with a non-uniform
p analysis capability for solving 2-D and 3-D
elastostatic mechanics problems, and 2) introduce a
stress error estimate.
An element-by-element algorithm that decides the
appropriate order for each element, where element
orders can range from 1 to 8, is described.
Global and element data structures that manage the complex
data generated during the refinement process are introduced.
These data structures are designed to match the concept of
object-oriented programming where data and functions are
managed and organized simultaneously.
The stress error indicator introduced is found to be more
reliable and to converge faster than the error indicator
measured in an energy norm called the residual method.
The use of the stress error indicator results in
approximately 20% fewer degrees of freedom than the
residual method. Agreement of the calculated stress error
values and the stress error indicator values confirms the
convergence of final stresses to the analyst. The error
order of the stress error estimate is postulated to be
one order higher than the error order of the error
estimate using the residual method. The mapping of a
curved boundary element in the working coordinate system
from a square-shape element in the natural coordinate
system results in a significant improvement in the
accuracy of stress results.
Numerical examples demonstrate that refinement using
non-uniform p analysis is superior to uniform
p analysis in the convergence rates of output
stresses or related terms. Non-uniform p analysis
uses approximately 50% to 80% less computational time than
uniform p analysis in solving the selected stress
concentration and stress intensity problems. More
importantly, the non-uniform p refinement procedure
scales the number of equations down by 1/2 to 3/4.
Therefore, a small scale computer can be used to solve
equation systems generated using high order
p-elements. In the calculation of the stress
intensity factor of a semi-elliptical surface crack in a
finite-thickness plate, non-uniform p analysis
used fewer degrees of freedom than a conventional
h-type element analysis found in the literature.
