In order to join the SPH to the lagrange, we need to ensure that sph is packed right to the edge of the domain. to do this, we need to use the edge packing option which is only available if the sph is created from a predef inside Autodyn. I.e. delete the SPH then go to PARTS>NEW and create a new sph. then, under the SPH menu create a new predef object in the shape of a cube which exactly fills the hole in the lagrange. Now you go to pack this part you will have the option of ‘edge packing’. You should then be able to join the two domains together as the SPH particles will go right to the edge of the domain and therefore be coincident with the Lagrange faces. If you wish to join SPH and lagrange then the lagrange part must be structured (i.e. created in AUTODYN) as SPH can not be joined to unstructured lagrange.