# PFATSPW

Bulk Data Entry Defines properties for Spot Weld Fatigue Analysis.

## Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
PFATSPW ID SPTFAIL ALPHA HEXA_D TREF TREF_N SF

## Definitions

Field Contents SI Unit Example
ID Each PFATSPW card must have a unique ID. This ID may be referenced from a FATDEF definition.

No default (Integer > 0)

SPTFAIL Damage assessment option type.
SHEET (Default)
Only assess sheet damage at the spot weld location.
NUGGET
Only assess nugget damage at the spot weld location.
ALL
Assess both sheet and nugget damage at the spot weld location.
AUTO
Automatically assess damage based on the following condition, if:
$D<\alpha \sqrt{T}$
assess nugget damage at the spot weld location
$D\ge \alpha \sqrt{T}$
assess sheet damage at the spot weld location

Where, $D$ is the diameter of the weld connector, α is set using the ALPHA field, and T is the thickness of the shell.

ALPHA The value of α used to determine the AUTO option on the SPTFAIL field.

Default = 3.5 (Real > 0.0)

HEXA_D Effective diameter of the spot weld that is generated using Hexahedron (CHEXA) elements.

Default = See Comment 1 (Real ≥ 0.0)

TREF Reference thickness for thickness effect consideration. 2

Default = 25.0 (Real > 0.0)

TREF_N Exponent for the thickness effect consideration. 2

Default = 0.2 (Real ≥ 0.0)

SF Stress scale factor. 3

Default = 1.0 (Real > 0.0)

2. TREF is used to define the reference thickness for thickness effect consideration. If the thickness of a shell (T) is greater than the specified value (TREF), and the THCKCORR field on the FATPARM entry is set to YES, then the thickness effect is included by increasing the stress ( ${\sigma }_{ij}$ ) based on: (1)
${\sigma }_{\mathit{ij}}={\sigma }_{\mathit{ij}}{\left(\frac{T}{\mathit{TREF}}\right)}^{\mathit{TREF}_N}$
3. The stress ( ${\sigma }_{ij}$ ) can also be scaled directly using the Scale Factor field (SF) as: (2)
${\sigma }_{\mathit{ij}}={\sigma }_{\mathit{ij}}\left(\mathit{SF}\right)$