TABDMP1

Bulk Data Entry Defines modal damping as a tabular function of natural frequency.

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
TABDMP1 TID TYPE   FLAT          
  f1 g1 f2 g2 f3 g3 f4 g4  
  f5 g5 etc. etc. etc. etc. etc. etc.  

Example

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
TABDMP1 2                
  2.5 0.01057 2.6 0.1362 ENDT        

Definitions

Field Contents SI Unit Example
TID Table identification number.

No default (Integer > 0)

 
TYPE Damping units type.
G (Default)
CRIT
Q
 
FLAT Specifies the handling method for y-values outside the specified range of x-values in the table.
= 0 (Default)
If an x-value input is outside the range of x-values specified on the Table, the corresponding y-value look up is performed using linear extrapolation from the two start or two end points.
= 1
If an x-value input is outside the range of x-values specified on the Table, the corresponding y-value is equal to the start or end point, respectively.
 
fi Natural frequency value in cycles per unit time. Must be specified in either ascending or descending order, but not both.

May be ignored by placing SKIP in either of the two fields used for that entry.

No default (Real ≥ 0.0)

 
gi Damping value.

May be ignored by placing SKIP in either of the two fields used for that entry.

No default (Real)

 

Comments

  1. Modal damping tables must be selected in the Subcase Information section, using the SDAMPING entry. This form of damping is supported in modal transient, modal frequency response, and modal complex eigenvalue analyses.
  2. A METHOD statement must be present in the SUBCASE.
  3. For example, in Figure 1 discontinuities are allowed only between points f 2 MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOzamaaBa aaleaacaaIYaaabeaaaaa@37C9@ through f 7 MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOzamaaBa aaleaacaaIYaaabeaaaaa@37C9@ . Also, if g MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOzaaaa@36E1@ is evaluated at a discontinuity, then the average value of g MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOzaaaa@36E1@ is used. In Figure 1, the value of g MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOzaaaa@36E1@ at f = f 3 MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOzaiabg2 da9iaadAgadaWgaaWcbaGaaG4maaqabaaaaa@39BB@ is g=( g 3 + g 4 )/2 MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4zaiabg2 da9maabmaabaGaam4zamaaBaaaleaacaaIZaaabeaakiabgUcaRiaa dEgadaWgaaWcbaGaaGinaaqabaaakiaawIcacaGLPaaacaGGVaGaaG Omaaaa@3F81@ .
  4. At least one continuation entry must be specified.
  5. The end of the table is indicated by the existence of ENDT in either of the two fields following the last entry. An error is detected if any continuations follow the entry containing the end-of-table flag ENDT.
  6. For FLAT=0 (default), TABDMP1 uses the algorithm:
    (1)
    g = g T ( f ) MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4zaiabg2 da9iaadEgacaWGubWaaeWaaeaacaWGMbaacaGLOaGaayzkaaaaaa@3C21@
    Where,
    f MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOzaaaa@36E1@
    Input to the table
    g MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOzaaaa@36E1@
    is returned
    The table look-up g T ( f ) MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4zaiaads fadaqadaqaaiaadAgaaiaawIcacaGLPaaaaaa@3A2F@ is performed using linear interpolation within the table and linear extrapolation outside the table using the two starting or end points (Figure 1). No warning messages are issued if table data is input incorrectly.


    Figure 1. Example of Table Extrapolation and Discontinuity

    For FLAT=1, the same algorithm as FLAT=0 is used, except that values outside the range are not extrapolated. The corresponding start or end point y-values are used for all y-values outside the range.

  7. The KDAMP option, on the PARAM card, may be used to switch between viscous and structural damping. Viscous is the default and is used when PARAM, KDAMP is not present.
    KDAMP
    Results
    1 (Default)
    B matrix
    -1
    ( 1 + i g ) K MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaeWaaeaaca aIXaGaey4kaSIaamyAaiaadEgaaiaawIcacaGLPaaacaWGlbaaaa@3BC6@ matrix
  8. If TYPE is G or blank, the damping values gi are in units of equivalent viscous dampers as:(2)
    b i = g i ω i k i MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOyamaaBa aaleaacaWGPbaabeaakiabg2da9maalaaabaGaam4zamaaBaaaleaa caWGPbaabeaaaOqaaiabeM8a3naaBaaaleaacaWGPbaabeaaaaGcca WGRbWaaSbaaSqaaiaadMgaaeqaaaaa@4023@

    If TYPE is CRIT, the damping values gi are in units of fraction of critical damping C / C 0 MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbwvMCKf MBHbqefqvATv2CG4uz3bIuV1wyUbqedmvETj2BSbqefm0B1jxALjhi ov2DaebbnrfifHhDYfgasaacH8srps0lbbf9q8WrFfeuY=Hhbbf9v8 qqaqFr0xc9pk0xbba9q8WqFfea0=yr0RYxir=Jbba9q8aq0=yq=He9 q8qqQ8frFve9Fve9Ff0dmeaacaGacmGadaWaaiqacaabaiaafaaake aacaWGdbGaai4laiaadoeadaWgaaWcbaGaaGimaaqabaaaaa@3C00@ .

    If TYPE is Q, the damping values gi are in the units of amplification or quality factor, Q. These constants are related by the following equations:(3)
    C / C 0 = g / 2
    (4)
    Q = { 1 / ( 2 C / C 0 ) 1 / g
  9. To achieve identical displacements in Modal frequency response or Modal transient analyses when the SDAMPING Bulk Data Entry is used instead of PARAM, G, the steps described here can be followed:
    • The TYPE field in the TABDMP1 Bulk Data Entry should be set to CRIT. This TABDMP1 Bulk Data Entry is referenced by the SDAMPING Subcase Information Entry.
    • Set the damping value (field gi) in the TABDMP1 Bulk Data Entry equal to half of the value of PARAM, G (set the constant value to C / C 0 MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbwvMCKf MBHbqefqvATv2CG4uz3bIuV1wyUbqedmvETj2BSbqefm0B1jxALjhi ov2DaebbnrfifHhDYfgasaacH8srps0lbbf9q8WrFfeuY=Hhbbf9v8 qqaqFr0xc9pk0xbba9q8WqFfea0=yr0RYxir=Jbba9q8aq0=yq=He9 q8qqQ8frFve9Fve9Ff0dmeaacaGacmGadaWaaiqacaabaiaafaaake aacaWGdbGaai4laiaadoeadaWgaaWcbaGaaGimaaqabaaaaa@3C00@ ).
    • Set PARAM, KDAMP,-1
  10. This card is represented as a load collector in HyperMesh.