Finite Element Simulation of Shielding/Intensification Effects of Primary Inclusion Clusters in High Strength Steels Under Fatigue Loading

Abstract

The change of potency to nucleate cracks in high cycle fatigue (HCF) at a primary nonmetallic inclusion in a martensitic gear steel due to the existence of a neighboring inclu sion is computationally investigated using two-and three-dimensional elastoplastic finite element (FE) analyses. Fatigue indicator parameters (FIPs) are computed in the proxim ity of the inclusion and used to compare crack nucleation potency of various scenarios. The nonlocal average value of the maximum plastic shear strain amplitude is used in computing the FIP. Idealized spherical (cylindrical in 2D) inclusions with homogeneous linear elastic isotropic material properties are considered to be partially debonded, the worst case scenario for HCF crack nucleation as experimentally observed for similar sys tems (Furuya et alInclusion-matrix interfaces are simulated using a frictionless con tact penalty algorithm. The fully martensitic steel matrix is modeled as elastic-plastic with pure nonlinear kinematic hardening expressed in a hardening minus dynamic recov ery format. FE simulations suggest significant intensification o f plastic shear deformation and hence higher FIPs when the inclusion pair is aligned perpendicular to the uniaxial stress direction. Relative to the reference case with no neighboring inclusion, FIPs decrease considerably when the inclusion pair aligns with the applied loading direction. These findings shed light on the anisotropic HCF response of alloys with primary inclu sions arranged in clusters by virtue of the fracture of a larger inclusion during deforma tion processing. Materials design methodologies may also benefit from such cost-efficient parametric studies that explore the relative influence of microstructure attributes on the HCF properties and suggest strategies for improving HCF resistance of alloys.

Effects of Tube Processing on the Fatigue Life of Nitinol

“…Murakami's argument is corroborated by recent finiteelement simulations in which the effects of relative orientations of primary inclusion clusters in steels under fatigue loading were investigated by Salajegheh et al [29]. Their analyses showed a reduction of nucleation crack potency due to shielding of inclusion pairs when aligned with the applied loading direction.…”

A crystal plasticity-based study of the relationship between microstructure and ultra-high-cycle fatigue life in nickel titanium alloys

“…Two final studies of note are that of Przybyla et al [20] and Salajegheh et al [21]. Przybyla et al [20] used a 2D model to determine a strain-based damage parameter as a function of surface distance to a hard inclusion in the presence of an oxide layer, which this work will parallel albeit in 3D and without considering surface oxidation.…”

“…Przybyla et al [20] used a 2D model to determine a strain-based damage parameter as a function of surface distance to a hard inclusion in the presence of an oxide layer, which this work will parallel albeit in 3D and without considering surface oxidation. Salajegheh et al [21] studied the behavior of a strain-based damage parameter with respect to interaction and orientation between inclusions in 2D and orientation between inclusions in 3D; the present work will address similar inclusion interactions based on a NiTi specific microstructure. However, both Przybyla et al and Salajegheh et al used an isotopic phenomenological plasticity model rather than CP.…”

Multiscale Analysis of MnS Inclusion Distributions in High Strength Steel

“…For example, Salajegheh et al performed finite element analysis and showed that the effect of inclusion clusters on fatigue crack initiation decreases exponentially with increasing the inclusion spacing. 9) The COV d derived in the present study would be useful for expressing the degree of clustering and assessing its effect on fatigue. On the other hand, in order to predict the fatigue life by considering the effect of inclusions, several probabilistic models that take into account the distributions of inclusion size and shape have been proposed.…”

“…[4][5][6][7] Furthermore, more complex models that consider the arrangement of multiple inclusions are being examined. [8][9][10] Salajegheh et al have calculated fatigue indicator parameters using crystal plasticity simulations under different specimen sizes and inclusion sizes. 8) They have also examined stress shielding or intensifica-tion effects by changing the position of two neighboring inclusions.…”