The additive manufacturing technology (AM) enables the design of complicated topology optimized parts. Due to the optimization the overall stress level in the parts increase and therefor the requirements to the quality rise. Defects in a highly loaded cross section of the part can lead to failure or a significantly reduced lifetime. With the knowledge that it is almost impossible to avoid internal defects during the manufacturing process it is necessary to cover the effect of the defects. Computer Tomography (CT) as a non-destructive testing method provides all necessary information of the defects and geometrical deviations. Combining the defect data of the CT-scan with a structural-mechanical simulation facilitates to cover the effect of defects. Defects in critical areas of the part will act as a stress concentration in the cross section and will directly influence the lifetime and performance of the part. To validate the defects a Finite Element (FE) calculation is necessary. The classical FE calculation method requires a geometry followed volume mesh of the defects. Therefor the CT data needs to be exported and meshed in a FE program, this step will lead to a loss of accuracy due to the export process. Furthermore, the creation of a geometry followed volume mesh with small defects and complicated surfaces can be difficult. Calculate directly on the CT data without a mesh export is the most accurate way to validate the stresses around a pore. The Immersed Boundary Method (IBM) uses a non-geometry followed hexahedral voxel grid to discretize the part. This step replaces the difficult creation of the volume mesh. With this method the stresses around the defects can be calculated in an efficient way. The traditional validation workflow is based on a CAD-based simulation, that does not include the internal or external deviations and defects of the part. Combining the CAD and CT results enables a new dimension in the validation process. With the submodeling method the CAD-based displacements are used as new boundary conditions for the CT-based simulation. A scan of the complete part or a scan of a region of the part can be used. By combining the CAD and CT based simulation results, the effect of the defects of additive manufactured parts can be evaluated with more information than only using the perfect defect free CAD model.