FEMFAT

FEMFAT spotwelds are a particular realization type that conforms to the specifications outlined in the FEMFAT fatigue software.

Naming Conventions

This connector fits within the FEMFAT scheme to enable you to create a FEMFAT compatible spotweld within HyperMesh. Materials, properties, sets and systems are created with the appropriate names so it can be recognised when the model is read in FEMFAT.
Table 1. Nastran and OptiStruct
Item Name
Components FEMFAT_Spot_Inner_Nugget_Comp_(parent comp ID)
FEMFAT_Spot_Outer_Nugget_Comp_(parent comp ID)
FEMFAT_SPOT_BAR_Dia_xx(Diameter value)_Comp
Materials Inner_Nugget_Mat_(self ID) -151
Outer_Nugget_Mat_(self ID) - 152
Properties FEMFAT_Spot_Inner_Nugget_Comp_(parent comp ID)_Prop
FEMFAT_Spot_Outer_Nugget_Comp_(parent comp ID)_Prop
FEMFAT_SPOT_BAR_Dia_(Diameter value)_prop
System Collectors FEMFAT_Spot_Center_Node_(System ID)
FEMFAT_Spot_Inner_Nugget_Nodes_(System ID) - 115
FEMFAT_Spot_Outer_Nugget_Nodes_(System ID) - 120
FEMFAT_Spot_Outer_Nugget2_Nodes_(System ID) – 125
Table 2. Abaqus
Item Name
Components FEMFAT_Spot_Inner_Nugget_Comp_(parent comp ID)
FEMFAT_Spot_Outer_Nugget_Comp_(parent comp ID)
FEMFAT_SPOT_BAR_Dia_xx(Diameter value)_Comp
Materials MAT(self ID)
MAT(self ID)
Properties FEMFAT_Spot_Inner_Nugget_Comp_(parent comp ID)_Prop
FEMFAT_Spot_Outer_Nugget_Comp_(parent comp ID)_Prop
FEMFAT_SPOT_BAR_Dia_xx(Diameter value)_prop
Sets MAT151 (ELSET which contains elements which has MAT151)
MAT152 (ELSET which contains elements which has MAT152)
C115 (NSET contains nodes assigned to coordinate system 115)
C120 (NSET contains nodes assigned to coordinate system 120)
C350 (NSET contains nodes assigned to coordinate system 350)
System Collector C_(System ID)
C_(System ID)
C_(System ID)

Material

Materials adhere to the following rules:
  1. The material ID created for inner and outer nuggets should be based on the interpretation of the base material.
    Note: If base material E > 150,000 N/mm2, then the material is considered as steel. In this case, follow these rules:
    • Inner Nugget Material ID should be 151
    • Outer Nugget Material ID should be 152
    Note: If base material E < 150,000 N/mm2, then the material is considered as aluminum. In this case, follow these rules:
    • Inner Nugget Material ID should be 154
    • Outer Nugget Material ID should be 155
  2. Inner Nugget should have mat ID = 151/154. Young's modulus of Mat 151/154 is calculated as 40 * Base sheets young's modulus.
  3. Outer Nugget should have mat ID = 152/155. Young's modulus of Mat 152/155 is equal to the surrounding sheet.
  4. Beam element is assigned Mat ID =152.
  5. If Young’s modulus is different for links, then the average Young’s modulus is used.
  6. If mat ID already exists in the session, it will be reused.


Figure 1.

Property

Table 3. Shell Property
Profile Description
Nastran and OptiStruct PSHELL property with thickness derived from parent property.
Abaqus SHELLSECTION property with thickness derived from parent.
Table 4. Bar Property
Profile Description
Nastran and OptiStruct PBAR property is created and assigned a beam section (standard Rod section). The diameter of the rod should be the same as that of the FEMFAT weld diameter.
Abaqus BEAMGENSECTION property is created and a generic beam section is assigned.

Diameter

Router = Input Diameter

Rinner = 0.58 * Input Diameter


Figure 2.

System ID

The System ID adheres to the following rules:
  1. If total dia < 2.5, the System ID = 300. If total dia > 9.9, the System ID = 300.
  2. If diameter is in range 2.5-9.99, then create system between 325-399.
  3. Simple approach would be 300 + (Dia *10).
  4. If Dia = 2.5, the System ID = 325. If Dia = 9.9, the System ID = 399.


Figure 3.