To determine the maximum principal stress and normal and shear mode fracture energies for MO40 steel in an Abaqus XFEM analysis, you'll need to obtain these material properties through experimental testing (like fracture toughness and mixed-mode fracture tests) or literature review (material data sheets, research papers, or material databases). Once obtained, input these properties into Abaqus by defining a material with elastic properties, maximum principal stress criterion, and mixed-mode fracture energy as a function of mode mix ratio. Create a section, mesh the model with a fine mesh around the crack path, and define the XFEM analysis with crack initiation and damage evolution parameters. Remember to consider factors like uncertainty, temperature effects, and rate effects when interpreting results.