Temperature dependence of the yield strength of aluminum thin films: Multiscale modeling approach

Abstract

Modeling deformation at elevated temperatures using discrete dislocation dynamics (DDD) is a recent area of high interest. However, the literature dedicated to this subject fails to address the variations of DDD parameters with temperature. This study aims to investigate the effect of temperature on the yield strength of aluminum thin films in two-dimensional DDD simulations. To this end, the temperature dependence of DDD parameters has been studied using molecular dynamics, three-dimensional DDD simulations, and the existing experimental results. Based on these calculations, we observed 18% decrease in the yield strength when temperature was increased from 100 K to 600 K. Discrete dislocation dynamics (DDD) is a powerful tool that has been successfully applied to simulate plastic deformation in crystalline materials specially at the micron and submicron scales in various modeling problems. In this method, the material is modeled as a continuous medium containing dislocations as the main plastic carriers, where evolution of dislocations is tracked. In the formulation of the DDD approach, it is assumed that the motion of a dislocation of unit length is governed by:where v is the dislocation velocity, m * is the effective mass, B is the drag coefficient, and F(t) is the driving force arising from externally applied stresses, image stresses, self-stress, interactions with other defects, and the lattice friction (Peierls stress). In this method, long range interactions between dislocations are calculated through theory of elasticity; short range interactions are determined based on local rules.DDD is implemented either in two-or three-dimensional frameworks. Three-dimensional DDD (3d DDD) includes dislocations in realistic geometries and many dislocation phenomena such as junction formation and cross-slip. 2d simulations include only infinitely long edge dislocations.In 2d approach, Frank-Read (FR) sources are represented by points; when the resolved shear stress exceeds a prescribed nucleation stress during a period of time, called nucleation time, the *

Temperature-controlled spatiotemporally modulated phononic crystal for achieving nonreciprocal acoustic wave propagation

“…From a temperature range of 0-1000 K, the Poisson ratio changes from 0.34 to 0.38, which is about a 10% increase. 20 This is overshadowed by the greater than 40% increase we see in Young's modulus from 600 to 100 K. Similarly, the mass density for aluminum varies approximately between 2725 and 2625 kg/m 3 in the temperature range under consideration, less than a 4% change, which is considered negligible for the purpose of this simulation. 21 The spatiotemporally periodic heating pattern applied to the top boundary was modeled as q 00 ¼ Qð1 þsgnðsin ðð2p=kÞx À 2pFtÞÞÞ, where k ¼ 2 lm is the spatial period and F ¼ 150 MHz is the frequency of the heating pattern, resulting in a translation speed of the pattern of v m ¼ 300 m/s, and sgn( ) denotes the signum function.…”

Design and Fabrication of a Kirigami-Inspired Electrothermal MEMS Scanner with Large Displacement

“…Micromachines 2020, 10, x 4 of 12 Table 1. Material selection of the electrothermal kirigami scanner [40][41][42][43][44][45].…”

Comparison of functionally graded and ungraded cylinder liners with finite element analysis

“…(1 − 2. ν Com ). B Com (7) By using equations ( 8) and ( 9), bulk modulus and shear modulus of aluminum and silicon were calculated (Table 2) To calculate the mechanical properties at different temperatures, Davoudi's study [14] was used, and Table 3 was formed. By using the equations ( 9) and ( 8), bulk modulus and modulus of elasticity of aluminum at 100 °C and 200 °C were calculated and presented in Table 4.…”