*5.1. Simulation Procedure*

Fatigue testing is simulated by doing (a) finite element elastic stress using the load in experimental fatigue testing and (b) fatigue life prediction using multi-axial strain-life approach using stress fields predicted in (a). The results of porosity from MAGMASoft are mapped to Finite Element Analysis (FEA) nodes using MAGMAlink. MAGMAlink allows user to import and export results to and from other softwares into and out of MAGMASoft. The translation and rotation features enable FEA mesh to accurately overlay the MAGMASoft model. FEA mesh is developed in ABAQUS prior to stress simulation. MAGMAlink provides the magnitude of nodal porosity which has to be integrated in ABAQUS. The node sets and nodal porosity data are included in the ABAQUS input file which contains all commands, boundary conditions, and properties required to run the stress simulation. A comparison of experimental and simulation results ensures competency of the model in predicting the fatigue life prediction.

The element type used for fatigue simulations is an eight-node linear brick element (C3D8R). The boundary conditions are set to replicate the actual testing conditions. The specimen is held fixed from one end and a uniformly distributed load, reflecting the actual loading condition for each specimen, is applied to the other end as shown in Figure 14a. Mesh sensitivity analysis confirmed a 1 mm node spacing suitable for all simulations. The resulting mesh is shown in Figure 14b. The finite element model developed with these specifications consist of 83,433 elements, 90,373 nodes and 345,546 variables.

**Figure 14.** (**a**) Boundary conditions and (**b**) Meshed specimen with 1 mm node spacing.

The simulation results are imported to Fe-safe software [15] which is used to predict lives of specimens. Tension and compression steps of fully reversed loading, i.e., R = 1 are taken into consideration while calculating the fatigue life. The material properties used for life prediction are summarized in Table 4. The inputs required by the software are material properties and loading cycle. Stress-strain conversion takes place within Fe-safe by utilizing the elastic modulus of pore-free steel. The recommended algorithm by Fe-safe for predicting fatigue life of steel is Brown–Miller algorithm with Morrow mean stress correction [15].


