Learning Forum

[peteroznewman]

Frank,

Use a Body-Body General Joint in the System model.  One end is scoped to the hole in the lug, the other end is scoped to the feature that has a pin through that lug hole. To represent the pin without modeling the pin in the System model, leave the Joint rotational DOF parallel to the pin Free. Since the System model has many lugs of the same shape, but oriented in many different directions, create a local coordinate system at each lug. Align the local X axis to the normal of the base and the the local Z axis normal to the face of the lug. Use each local coodinate system to define the Joint Csys and for force output from the joint. In that way, sorting the forces in the X, Y and Z direction means you can apply the maximum force in the correct directions to the Detailed model.

I assume the structure sees cyclic loading, which means the materials are subject to fatigue failure. Fatigue failure is dependent on the stress amplitude and the number of cycles. The stress amplitude depends on the radius of the fillet at the interior corners. A lug machined out of a solid block of material has uniform material properties so you can use the stress on the face of the fillet to evaluate the cycles to failure for that material.

A lug welded to a base plate does not have uniform material properties. Weld material is full of tiny cracks so its fatigue strength is much lower than the parent metal it connects. Look up a weld design standard for your country to learn how to design a welded joint.

Weld beads are often left as welded, which creates geometry with many stress risers where the angle changes suddenly from the weld face to the plate face it is joined to. To eliminate the stress risers, the weld bead has to be ground down to create the fillet radius.

Total plastic strain is used evaluate the elongation at break for a ductile material under a single load to failure. But if you have to design for fatigue of a welded joint, you will find you need to design for a lower stress than the yield strength of the parent metal.