FATPARM

Bulk Data Entry Used to define parameters required for a Fatigue Analysis.

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
FATPARM ID TYPE MAXLFAT PSEUDO          
  STRESS COMBINE UCORRECT STRESSU PLASTIC SURFSTS      
  RAINFLOW RTYPE GATEREL            
  PRPLD CHK              
  MCORRECT MC1 MC2 MC3 MC4        
  CERTNTY SURVCERT              
  SPWLD METHOD CORRECT SURVCERT THCKCORR NANGLE      
  SMWLD METHOD CORRECT SURVCERT THCKCORR        
  FOS FOSTYPE              
  RNDPDF PDF1 PDF2 PDF3          
  RANDOM FACSREND SREND NBIN DS   STSUBID    
  SWEEP NE DF STSUBID          
  PSEUDO NPV NOISETHR MXHOTSPOT NACTDMG        
  NPLNCRT NPLN              

Definitions

Field Contents SI Unit Example
ID Each FATPARM card must have a unique ID. The FATPARM Subcase Information Entry may reference this identifier.

No default (Integer > 0)

 
TYPE Fatigue analysis type that is defined.
SN (Default)
Stress Life
EN
Strain Life
FOS
Factor of Safety Analysis 8
NSTRESS
Also supported for Stress Life for compatibility
 
MAXLFAT Controls the activation of Multiaxial Fatigue Analysis.
YES
NO (Default)
 
PSEUDO Flag which activates Pseudo Damage method for Fatigue Calculations. 16  
STRESS Indicates that parameters are to follow which define how the stress is used in fatigue calculation.  
COMBINE The sign on the Signed von Mises, Signed Tresca, Signed Max Shear is taken from the sign of the Abs Max Principal value.

For Stress Life, combined stress value is used; For Strain Life, combined strain value is used.

For Strain Life, shear strain components are engineering shear strain (two times tensor shear strain).
ABSMAXPR (Default)
Abs Max Principal - recommended for brittle materials
MAXPRINC
Max Principal
MINPRINC
Min Principal
VONMISES
von Mises
SGVON
Signed von Mises - recommended for ductile materials
TRESCA
Tresca
SGTRESCA
Signed Tresca
SGMAXSHR
Signed Max Shear
XNORMAL
X Normal
YNORMAL
Y Normal
ZNORMAL
Z Normal
XYSHEAR
X-Y Shear
YZSHEAR
Y-Z Shear
ZXSHEAR
Z-X Shear
 
UCORRECT Mean stress correction method for Uniaxial Fatigue Analysis. 5 6 7 15
Valid options for TYPE=SN:
NONE
GOODMAN (Default)
Goodman model
GERBER
Gerber model
GERBER2
Gerber model (negative mean stress is ignored)
SODERBE
Soderberg model
FKM
FKM Guidelines (all four Regimes)
FKM2
FKM Guidelines (only Regimes 2 and 3)
Valid options for TYPE=EN:
SWT (Default)
Smith-Watson-Topper model
MORROW
Morrow model
MORROW2
Morrow model (negative mean stress is ignored)
NONE
 
STRESSU FE analysis Stress Tensor Unit. The Unit is necessary because the SN/EN curve (MATFAT card) might be defined in different unit, and FEA stress needs to be converted before looking up the fatigue life for a given stress level on the SN curve. 9
MPA (Default)
PA
PSI
KSI
 
PLASTIC This parameter is only applicable for TYPE=EN.
NONE
NEUBER (Default)

For TYPE=SN, is not used.

 
SURFSTS Activation flag. If solid elements are defined in FATDEF, stress on the surface of the solid elements are used for damage assessment. For Multiaxial Fatigue Analysis, a membrane is created to calculate damage of the free surfaces in the model, and this is visible as an AUTO_SKIN component in the H3D file.
NO
Default for Uniaxial Fatigue Analysis
YES
Default for Multiaxial Fatigue Analysis
 
RAINFLOW Indicates that parameters required for Rainflow counting are to follow. This flag and its related parameters will be used only when the TYPE field is set to SN or EN.  
RTYPE Rainflow data type. 1
LOAD (Default)
Load-time history
STRESS
Stress-time history
 
GATEREL Relative fraction of maximum gate range. The reference value is the maximum range multiplied by GATEREL and used for gating out small disturbances or "noise" in the time series.

Default = 0.2 (0.0 ≤ Real < 1.0)

 
PRPL Flag that indicates proportional load treatment information is to follow.  
CHK Check Proportional Load.
Currently only applicable to a single load case in FATEVNT.
YES (Default)
NO
Even a single load case Multiaxial Fatigue Analysis will use Non-Proportional Load Fatigue Analysis.
 
MCORRECT Flag that indicates Multiaxial Mean Stress Correction information is to follow.  
MCi Mean Stress Correction to be used in Multiaxial Fatigue Analysis. Multiple mean stress correction models can be specified in the four MCi fields, the sequence is irrelevant.
Valid options for TYPE=SN:
GOODMAN (Default)
Goodman model
FINDLEY (Default)
Findley model
FKM
FKM Guidelines (all four Regimes)
Valid options for TYPE=EN:
SWT (Default)
Smith-Watson-Topper model
FS (Default)
Fatemi-Socie model
BM
Brown-Miller model
MORROW
Morrow model
 
CERTNTY Indicates that parameters that define certainties in fatigue analysis are to follow. This flag and the following parameter will be used only when the TYPE field is set to SN or EN.  
SURVCERT Certainty of survival based on the scatter of the SN curve. 4

Default = 0.5 (0.0 < Real < 1.0)

 
SPWLD Flag indicating that the following parameters are used for spot weld fatigue analysis.  
METHOD Spot weld fatigue analysis method.
RUPP (Default)
blank
 
UCORRECT Mean stress correction indicator for Uniaxial Fatigue Analysis.
NONE (Default)
FKM
FKM Guidelines (all four Regimes)
FKM2
FKM Guidelines (only Regimes 2 and 3)
 
SURVCERT Certainty of survival.

Default = SURVCERT value on CERTNTY continuation line (0.0 < Real < 1.0)

 
THCKCORR Thickness correction flag.
YES (Default)
NO
 
NANGLE Number of angles to be examined on the sheet and nugget.

Default = 20 (Integer > 0)

 
SMWLD Flag indicating that the following parameters are used for seam weld fatigue analysis.  
METHOD Seam weld fatigue analysis method.
VOLVO (Default)
Activates the Volvo method.
JNTLINE
Activates the Joint line method.
blank
 
UCORRECT Mean stress correction indicator for Uniaxial Fatigue Analysis.
NONE (Default)
FKM
FKM Guidelines (all four Regimes)
FKM2
FKM Guidelines (only Regimes 2 and 3)
 
SURVCERT Certainty of survival.

Default = SURVCERT value on CERTNTY continuation line (0.0 < Real < 1.0)

 
THCKCORR Thickness correction flag.
YES (Default)
NO
 
FOS Indicates that the following parameters are for Factor of Safety analysis (TYPE=FOS). This flag and following parameter will be used only when the TYPE field is set to FOS.  
FOSTYPE Used to select the Factor of safety analysis type.

Default = DANGVAN

 
RNDPDF Indicates Random Response Probability Density Function information is to follow. 12  
PDFi Random Response Probability Density Functions to be used in Random Response fatigue analysis. Multiple functions can be specified in the three PDFi fields, the sequence is irrelevant.
DIRLIK (Default)
LALANNE
NARROW
THREE
 
RANDOM Indicates that parameters for Random Response Fatigue are to follow. This flag and the following parameters will be used only when the LCID field references a Random Response Analysis Subcase.  
FACSREND Calculates the upper limit of the stress range (SREND). 10

Default = 8.0 (Real > 0.0 or blank)

 
SREND Used to directly specify the upper limit of the stress range.

Default = SREND based on FACSREND (Real > 0.0 or blank)

 
NBIN Calculates the width of the range of stress ranges for which the probability is calculated. 11

Default = 100 (Integer > 0 or blank)

 
DS Used to directly define the width of the stress ranges.

Default = DS based on NBIN (Real > 0.0 or blank)

 
STSUBID References the subcase ID of a Static Subcase to account for mean stress correction with any loading that leads to a mean stress different from zero.

Default = blank (Integer > 0 or blank)

 
SWEEP Flag indicating that options for Sweep Fatigue analysis are to follow. 13  
NF
Integer
Number of frequencies to be examined between the first and last frequency of the Frequency Response subcase.
NFREQ (Default)
NF is set equal to number of frequencies of the Frequency Response Subcase (based on FREQi entries).
 
DF Frequency increment from first to last frequency of the frequency response subcase. If DF is defined, NF is ignored. 14

Default = blank (Real)

 
STSUBID References the subcase ID of a Static Subcase to account for mean stress correction with any loading that leads to a mean stress different from zero.

Default = blank (Integer > 0 or blank)

 
PSEUDO Flag indicating options for Pseudo Damage method.

For additional information, refer to Pseudo Damage Method in the User Guide.

 
NPV Number of peak-valley pairs in approximated load histories.

For additional information, refer to Pseudo Damage Method in the User Guide.

Default = 3 (Integer)

 
NOISETHR Threshold for termination of an element cluster. An element cluster is allowed to continue expanding even if positive slopes are encountered between two elements, as long as the difference in pseudo damage between the two elements falls below NOISETHR. If the differences in pseudo damage at the cluster boundary is higher than NOISETHR, then the cluster expansion is terminated.

For additional information, refer to Pseudo Damage Method in the User Guide.

Default = 1.0E-8 (Real > 0.0)

 
MXHOTSPOT Number of hotspot clusters.

Default = 1% of the total number of elements of the entire model, or 2000, whichever is lower (Integer > 0)

 
NACTDMG Number of elements where the actual damage is calculated in a cluster.

Default = 20 (Integer > 0)

 
NPLNCRT Continuation line which indicates that critical plane calculation parameter for Multiaxial Fatigue analysis is to follow.  
NPLN Number of planes that damage is assessed on in Multiaxial fatigue analysis. The last two planes that are assessed are always 45 degrees and 135 degrees planes.

Default = 20 (8 < Integer < 92)

 

Comments

  1. RTYPE=LOAD is valid when there is only one static load case defined in an event. If the event contains multiple static load cases, RTYPE will automatically be set to STRESS because there will be stress super-positioning among different load cases; doing rainflow counting on load-time history could not deal with it.
  2. When RTYPE=LOAD, load-time history will be cycle counted using the rainflow cycle counting method. The cycle counting results (load Ranges and Means) will be scaled by combined FEA stress. Doing rainflow counting on load-time is much faster than doing it on stress-time (RTYPE=STRESS), especially when the load-time history is complex and contains a large number of time points, but it is less accurate.
  3. When RTYPE=STRESS, stress-time history will be cycle counted using the rainflow cycle counting method. The stress-time history has the same length as load-time, while each point of the stress time is the combined stress value where the stress tensor is FEA stress scaled by y point value of the corresponding load-time history.
  4. Certainty of Survival is based on the scatter of the SN/EN curve. It is used to modify the SN/EN curve according to the standard error parameter (SE) defined in fatigue property of material card (MATFAT). A higher reliability level requires a larger certainty of survival.
  5. UCORRECT=GERBER2 improves the GERBER method by ignoring the effect of negative mean stress.
  6. UCORRECT=MORROW2 improves the MORROW method by ignoring the effect of negative mean stress.
  7. UCORRECT=SODERBE is slightly different from GOODMAN, the mean stress is normalized by yield stress instead of ultimate tensile stress.(1)
    S e = S a ( 1 S m S y ) MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4uamaaBa aaleaacaWGLbaabeaakiabg2da9maalaaabaGaam4uamaaBaaaleaa caWGHbaabeaaaOqaamaabmaabaGaaGymaiabgkHiTmaalaaabaGaam 4uamaaBaaaleaacaWGTbaabeaaaOqaaiaadofadaWgaaWcbaGaamyE aaqabaaaaaGccaGLOaGaayzkaaaaaaaa@4245@
    Where,
    S e MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4uamaaBa aaleaacaWGLbaabeaaaaa@37E4@
    Equivalent stress amplitude
    S a MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4uamaaBa aaleaacaWGLbaabeaaaaa@37E4@
    Stress amplitude
    S m MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4uamaaBa aaleaacaWGLbaabeaaaaa@37E4@
    Mean stress
    S y MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4uamaaBa aaleaacaWGLbaabeaaaaa@37E4@
    Yield stress
  8. The STRESS, RAINFLOW and CERTNTY continuation lines are ignored in a factor of safety analysis (TYPE=FOS).
  9. If UNITS or DTI UNITS is present, the default value of STRESSU is determined by UNITS or DTI UNITS entry (UNITS entry takes precedence over DTI UNITS). If UNITS, DTI UNITS, and STRESSU are not provided, the default value of STRESSU is MPA. If UNITS or DTI UNITS issued.
  10. The Upper limit of the stress range is calculated as SREND = 2*RMS Stress*FACSREND. RMS stress is output from Random Response Subcase.
  11. The width of the stress ranges is calculated as DS=SREND/NBIN.
  12. Random Response Fatigue analysis is supported for both SN and EN Fatigue Analysis. For EN fatigue, currently Uniaxial fatigue and COMBINE=VONMISES are only supported.
  13. For Sine Sweep Fatigue:
    • Currently, only von Mises is supported for the COMBINE field.
    • Only Uniaxial Fatigue analysis is supported.
    • SN and EN for Solid and Shell elements are supported.
    • Weld Fatigue is not supported.
    • Only one FATLOAD is allowed on a FATEVNT entry
  14. If Frequency Response results are not available at a frequency calculated based on DF, then the Frequency Response results are interpolated from the nearest two results.
  15. The UCORRECT field is only applicable for Uniaxial Fatigue Analysis (Static, Transient, Random, and Sine Sweep Fatigue). It is not applicable in Multiaxial Fatigue Analysis. For Multiaxial Fatigue analysis, the MCORRECT continuation line is used for Mean Stress correction methods.
  16. The units for Elastic Modulus (E) and Rigidity Modulus (G) in the material data are obtained from the stress unit field (STRESSU) in the FATPARM card, in general. In the case of SN fatigue, the units for Elastic Modulus in the material data is obtained from the stress unit field (STRESSU) in the FATPARM card, when the critical distance is activated.
  17. This card is represented as a load collector in HyperMesh.