Mechanical APDL Structural Analysis Guide

Undamped Modal --- --- No ( 1 ) --- ---

Yes Yes Yes ( 1 ) Yes Yes

Mode Superposition

Harmonic

Mode Superposition Yes Yes Yes ( 1 ) Yes ---

Transient

Spectrum

SPRS,MPRS Yes Yes Yes ( 1 ) Yes ---

PSD Yes Yes Yes ( 1 ) Yes ---

DDAM Yes ( 3 ) Yes ( 3 ) Yes ( 3 ) Yes ( 3 ) Yes ( 3 )

1. MP,DMPR specifies an effective material damping ratio. Specify it in the modal analysis (and expand the
   modes,MXPAND,,,,YES) for use in subsequent spectrum and mode-superposition analyses.


2. The material dependent damping (MP,DMPR) and the mode dependent damping (MDAMP) cannot be
   cumulated. Use only one method.


3. In DDAM analyses, damping input is not used when calculating mode coefficients; however, damping
   may be used in the mode-combination procedure. Refer to Combination of Modes in the Mechanical
   APDL Theory Reference for more information.

Table 1.3: Damping for Damped Modal and QRDAMP Mode Superposition Analyses

Damping Ratio Structural Damping

Element

Damping

( 1 )

Rayleigh Damping

Material

Depend-

ent

Global

Mode De-

Global pendent

Material

Depend-

ent

Global

DMPRAT MDAMP DMPSTR MP,DMPR

COM-

BIN14,

MP,BETD

and

MP,ALPD

ALPHAD

and

BETAD

MAT-

RIX27, ...

Yes Yes Yes --- --- Yes ( 3 ) Yes ( 3 )

Damped

Modal

(DAMP or

QRDAMP)

Yes ( 2 ) Yes ( 2 ) Yes Yes Yes Yes Yes

QRDAMP

Mode Su-

perposi-

tion Har-

monic

Yes ( 2 ) Yes ( 2 ) Yes Yes Yes --- ---

QRDAMP

Mode Su-

perposi-

tion Tran-

sient

1. Includes superelement damping matrix


2. ALPHAD,BETAD,MP,ALPD, and MP,BETD damping must be applied in the QR Damped modal analysis
   portion of the mode-superposition analysis.

Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information

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