Page 191 - Using ANSYS for Finite Element Analysis Dynamic, Probabilistic, Design and Heat Transfer Analysis

178 • using ansys for finite eLement anaLysis
performed. The initial data points from the random design calculations can
serve as starting points to feed the optimization methods.

5.2.3.1 Single Loop Analysis Tool

This is a simple and very direct tool for understanding design space. It is
not necessary but it may be useful to compute values of state variables or
the objective function. The design variables are all explicitly defined by
the user. A single loop is equivalent to one complete FEA. At the beginning
of each iteration, the user defines design variable values, X=X = design
*
variables defined by the user, and executes a single loop or iteration. If
either state variables or the objective function are defined, corresponding
state variable and objective function values will result.

5.2.3.2 Random Tool

Multiple loops are performed, with random design variable values at each
loop. This design tool will fill the design variable vector with randomly
generated values for each iteration. Each random design iteration is equiv-
alent to one complete analysis loop. A maximum number of loops and a
desired number of feasible loops can be specified. This tool is useful for
studying the overall design space, and for establishing feasible design sets
for subsequent optimization analysis. Random iterations continue until
either one of the following conditions is satisfied:

n�� = N r
r

n =� N f
f
Where:
n = number of random iterations performed per each execution
r
n = total number of feasible design sets (including feasible sets from
f
previous executions)
N = maximum number of iterations
r
N = desired number of feasible design sets.
f

5.2.3.3 Sweep Tool

The sweep tool is used to scan global design space that is centered on a
user-defined, reference design set. Upon execution, a sweep is made in