PSI - Issue 5

Amal ben Ahmed et al. / Procedia Structural Integrity 5 (2017) 524–530 Amal ben Ahmed et al. / Structural Integrity Procedia 00 (2017) 000 – 000

526

3

3. Computational Engineering Approach

3.1. FE modeling

A three-dimensional finite element analysis using ABAQUS commercial software was implemented to determine the fatigue response of A356-T6 aluminum alloy.TheRVE model used to determine the stress distribution in the vicinity of the defect is a cube containing hemi-spherical pore. Due to symmetry of the problem only ¼ of the numerical specimen is considered. Boundary conditions and symmetries are implemented as shown in fig.1.In order to compute the high stress distribution in the vicinity of the defect, a very fine structured mesh has been modeled in this region. The non-linear isotropic/kinematic hardening model is considered to describe the material behavior. This plasticity model is capable to characterize the material behavior during cyclic loading considering the Baushinger effect, mean stress relaxation, ratcheting and cyclic hardening.

Fig. 1. Finite Element model: Load and Boundary conditions: (a) tension loading (b) torsion loading Experimental investigations [IbenHouriya et al. (2015), M.J. Roy et al. (2011) and M. Roy et al. (2012)] have revealed that the fatigue crack propagation mechanism occurs in the Highest Loaded Plane (HLP). Therefore, will be determined along this critical plane, for different defect sizes ( √ ) and various load conditions (tension / torsion). 3.2. Stress distribution analysis In the HLP, numerical simulations showed that is almost constant for an arc centered on the defect and it can be interpolated as follow: = { −1 −1 ( ( 1 ) 4 + 1) Under fully reserved tension (4) −1 −1 ( ( 1 ) 5 + 1) Under fully reserved torsion (5)