AVPRIN
AVPRIN, KEY, EFFNU
Specifies how principal and vector sums are to be calculated.
KEYAveraging key:
0
—
Average the component values from the elements at a common node, then calculate the principal or vector sum from the averaged components (default).
1
—
Calculate the principal or vector sum values on a per element basis, then average these values from the elements at a common node.
EFFNUEffective Poisson's ratio used for computing the von Mises equivalent strain (EQV). This command option is intended for use with line elements or in load case operations (LCOPER); the program automatically selects the most appropriate effective Poisson's ratio, as discussed below.
Notes
Selects the method of combining components for certain derived nodal results when two or more elements connect to a common node. The methods apply to the calculations of derived nodal principal stresses, principal strains, and vector sums for selects, sorts, and output (NSEL, NSORT, PRNSOL, PLNSOL, etc.). The calculation of these nodal results excludes beam and pipe elements.
This command also defines the effective Poisson's ratio (EFFNU) used for equivalent strain calculations. If
you use EFFNU, the default effective Poisson's
ratios shown below will be overridden for all elements by the EFFNU value. To return to the default settings, issue
the RESET command. The default value for EFFNU is:
Poisson's ratio as defined on the MP commands for EPEL and EPTH
0.5 for EPPL and EPCR
0.5 if the referenced material is hyperelastic
0.0 for line elements (includes beam, link, and pipe elements, as well as discrete elements), cyclic symmetry analysis, mode superposition analyses (with
MSUPkey= YES on the MXPAND command), and load case operations (LCOPER).For multistage analysis, a value of
EFFNUmust always be specified.
If EFFNU is specified, the calculation of
von Mises equivalent strain (EQV) is performed according to the
KEY setting. However, if EFFNU
is not specified, or if the AVPRIN command is not issued, the von
Mises equivalent strain is calculated using the average of the equivalent strains from
the elements at a common node (behavior of KEY =1)
irrespective of the value of the averaging KEY.
For a random vibration (PSD) analysis (for more details, see Review the Results in the Structural Analysis Guide):
Issuing either AVPRIN,0 or AVPRIN,1 calculates the principal stresses using the appropriate averaging method. They are then used to determine SEQV. The output will have non-zero values for the principal stresses.
If AVPRIN is not issued, the Segalman-Fulcher method is used to calculate SEQV. This method does not calculate principal stresses, but directly calculates SEQV from the component stresses; therefore, the output will have zero values for the principal stresses.
This command is also valid in POST26, where applicable.
See Combined Stresses and Strains in the Mechanical APDL Theory Reference for more information.