If the nodal forces are to be imported for a FEMFAT spot (JSAE method) or FEMFAT weld(SSZ/MSZ method) analysis, the corresponding check box (see figure) must first be activated. This option prevents excessive memory use. Note: Node forces can currently be imported from NASTRAN op2, Abaqus otb and MEDINA bof.
GUI for the node forces in BASIC
GUI for the node forces in MAX
Generally speaking, FEMFAT spot gives you the option of using the available stress concept (nugget elements) or force concept (connectors) either separately or combined.
However, it should be mentioned that the stress concept should not be combined with the force concept within a single flange. The reason for this is that the stiffness varies between the two concepts.
Joints such as those with CWELD elements (force concept) are normally stiffer than FEMFAT element nuggets (stress concept). If a nugget is modeled next to a CWELD, this will result in the CWELD joint taking up more of the load flow, resulting in increased damage.
The damage of the nugget will thereby decrease. Because of this, the same type of joint should be used within large areas (entire flange length, vehicle area) if you want to combine the two concepts
FEMFAT has its own calculation concept for the assessment of joints. Therefore it is necessary to do a remeshing of the basic structure.
Following procedure is very helpful for the remeshing, in case the spot-diameter is chosen according to the sheet thickness or the diameter matrix in the spot database.
Step1: Definition of the center nodes and connecting elements. When there are failures it is very easy to correct them. Possible reasons may be double definition of CDHs.
Step 2: FEMFAT spot remeshing with mesh refinement.
Please note that after the remeshing the stress analysis has to be done once again.