I suggest you create two curved surfaces offset from the large tube to cut the pad and small tube on one edge of the weld fillet and two ellipsoidal offset surfaces from the pad edge and small tube to cut the large tube and pad on the other edge of the weld fillet. You will need another ellipsoidal surface on the side face of the pad to cut the large tube. That will deliver many new solid bodies that have very simple topology of each body for the mesher to mesh. Use Shared Topology to connect the mesh across the multiple solids that used to be a single solid for the pad and two tubes. You can then use Bonded Contact to glue the weld fillet faces to each simple body that is touching it.