Enter the Mesh module.
From the Object field in the context bar, select Part and select a part from the list. This tool is available only for working on orphan mesh elements.
From the main menu bar, select .
Abaqus/CAE displays the Edit Mesh dialog box.
From the Category field, choose Mesh.
From the Method list, select Convert tri to tet.
From the buttons that appear in the prompt area, click Yes.
Abaqus/CAE converts the triangular mesh to a tetrahedral mesh.
After editing an orphan mesh, you should always verify node-, element-, and surface-based features such as section assignments, loads, and interactions to ensure that they are correctly applied to the modified mesh.