The default material used for Mechanical is Structural Steel. We need to change it to the new material we defined earlier (Bone). In the outline window, expand Geometry and highlight Solid Body 1. The bone model will now be highlighted in green, meaning it is being selected. Right below the outline window you will see "Details of Solid Body 1". Expand Material, and change the assignment to Bone. The material properties we defined for Bone will now be assigned to the bone model.