No abstract

Image-based deformation simulation of microstructures in metals is attracting attention; however, the data conversion processes from the images of microstructures into the geometric models for the deformation simulation are now inconvenient, and there is a possibility that it prevents diffusion of the image-based simulation. In order to solve the problem, we developed an interface geometric models for Crystal Plasticity Finite Element (CPFE) analysis. The interface incorporates several functions for data cleaning and coarse graining of the microstructures: functions to narrow down the limits of Eulerian angles presenting crystal orientations, integrate crystal grains with similar crystal orientations, eliminate small crystal grains, select representative crystal orientation in each crystal grain, and so on. The interface was applied to an orientation map of polycrystal microstructure in pure titanium, and the course-grained geometric models were successfully obtained. Image-based CPFE analysis was conducted using the geometric models with different number of finite elements. The numbers of crystal grains were assumed to be around 50 in any geometric models. A dislocation density dependent constitutive equation was employed and uniaxial tensile loading was applied to the geometric models by the forced displacement. The results showed that spatial distributions of stress, strain, and dislocation density were good agreement among geometric models with different number of elements in both elastic and plastic ranges while values of the strain and dislocation density showed quantitatively dependency of the number of elements on their distributions in the plastic ranges. These features indicate that the qualitatively similar results can be obtained using the developed interface on the condition that coarse graining of the microstructures does not occur even though the number of elements is changed.

No abstract

Inhomogeneous deformation of a single ¡-¢ colony in a Ti6Al4V alloy under uniaxial tensile conditions was numerically simulated using a crystal plasticity finite element (CPFE) method, and we predicted density changes in geometrically necessary dislocations (GNDs) depending on the vanadium concentration in the ¢ phase (V ¢ ). The geometric model for the CPFE analysis was obtained by converting data from electron back-scatter diffraction patterns into data for the geometric model for CPFE analysis, using a data conversion procedure previously developed by the authors. The results of the image-based crystal plasticity analysis indicated that smaller V ¢ induced greater stress in the ¡ phase and smaller stress in the ¢ phase close to the ¡-¢ interfaces in the initial stages of deformation because of the elastically softer ¢ phase with lower V ¢ . This resulted in greater strain gradients and greater GND density close to the interfaces in the initial stages of deformation within the single ¡-¢ colony when the ¢ phase plastically does not deform. [

No abstract

In this paper, we investigated changes in active slip systems of α-phase of Ti-6Al-4V alloy under a cyclic plastic loading using a crystal plasticity finite element method. In the analyses, a bicrystal model was employed, and the crystallographic orientations were set so as that prismatic <a> or basal slip system was the primary slip system in each grain. The results showed that there was a mechanism where the basal slip systems could reach the stage of activation under the cyclic plastic loading even though the condition was that the prismatic <a> slips initially operate. The reason for the activity changes was due to the changes in the incompatibility between the grains by the work hardening, and the effect of the incompatibility on activities of slip systems appeared even in the perpendicular arrangements of the grains to the loading direction.

No abstract

Plastic slip deformation in the vicinity of the tip of U-shaped notch in α phase titanium single crystal models subjected to cyclic tensile load is analysed by a crystal plasticity finite element method. Crystal orientation is defined so as that the basal plane is parallel to the specimen surface and a prismatic slip system operate as the primary one under tensile load. Results show that slip deformation develop in two thin strip shaped regions extending from the notch root during loading and these plastic shear strain does not diminish upon unloading.