Microcompression Behaviors of Single Crystals Simulated by Crystal Plasticity Finite Element Method
- PDF / 2,367,576 Bytes
- 7 Pages / 593.972 x 792 pts Page_size
- 70 Downloads / 219 Views
The early investigation of the materials ‘‘size effect’’ was mainly performed by mechanically testing (particularly, micro-compression testing) single-crystal micro-pillars, which were mechanically machined or electrochemically fabricated from bulk materials.[1–7] Since the microcompression test of single-crystal micro-pillars is different from the standardized compression test, which uses ‘bulk’ specimens, the crystal plasticity finite element method (CP-FEM) was frequently used for the parametric study of compressive deformation behavior of single-crystal micro-pillars.[4,8–13] Here, the bottom end of the single-crystal micro-pillar is intrinsically constrained in its lateral deformation. Thus, CP-FEM simulations aimed mostly at understanding the effect of bottom-end constraints, applied boundary conditions, and the sensitivity of the choice of constitutive models. In particular, these
JAE-HO JUNG, Graduate Student, KYUNG-MOX CHO, Professor, and YOON SUK CHOI, Associate Professor, are with the School of Materials Science & Engineering, Pusan National University, Busan 609-735, Korea. Contact email: [email protected] YOUNG-SANG NA, Senior Researcher, is with the Korea Institute of Materials Science, Changwon, Gyeongnam 642-831, Korea. DENNIS M. DIMIDUK, Consultant, is with BlueQuartz Software, LLC, 400 South Pioneer Blvd., Springboro, OH 45066. Manuscript submitted April 11, 2015. Article published online September 4, 2015 4834—VOLUME 46A, NOVEMBER 2015
simulations were mainly for the compressive deformation of single-slip-oriented micro-pillars. Even though the slip system kinematics and kinetics are incorporated in CP-FEM, FEM is still limited to a continuum representation of deformation, which lacks representing slip at the crystal defect scale and the discrete nature of slip intermittency in single crystals. In the present study, an effort was made to clarify how the CP-FEM predicts single-slip-dominated microcompression behaviors of single crystals under the different single-slip configurations (by varying the degree of primary slip-plane inclination). An elasto-viscoplasticity constitutive model was developed, based upon the combination of conventional slip system kinematics and kinetics equations, and used for the current simulations. Simulation results were analyzed as a function of primary slip-plane inclination angles and discussed. An elasto-viscoplasticity constitutive model used for the current CP-FEM simulation utilized a Power-law shear rate description a 1=m s ½1 c_ a ¼ c_ o a signðsa Þ: g^ Here, c_ a and g^a are the shear rate and slip resistance for the slip system a, respectively. Also, c_ o , sa and m are the reference shear rate, the resolved shear stress on the slip system a and the strain-rate sensitivity parameter, respectively. In Eq. [1], the slip resistance g^a was described by a Baily–Hirsch type flow stress description[15,16] modified to account for anisotropic slip system interactions: vffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi u 12 uX a ½2 Aab qb : g^ ¼ g^o þ glbt b¼1
Here, g^o , g, l, and b are t
Data Loading...
