Showing papers by "Kamran Behdinan published in 2013"

Bridging Cell Multiscale Modeling of Nanoindentation at Finite Temperature

Abstract: This paper presents the simulation of nanoindentation in copper thin film using a multiscale finite element framework for modeling coupled continuum/atomistic systems at finite temperature. Seamless coupling between the atomistic and continuum domains is performed through bridging cells where the underlying atoms define the constitutive formulation for the cells with an overlapping local energy contribution accounting for the missing atomic interactions at the continuum/atomistic interface. The method implements a temperature dependent potential for finite temperature simulations avoiding the use of small timesteps. The results from the nanoindentation simulation are compared to a fully molecular dynamics simulation with respect to indenter load vs. displacement for various temperatures. Differences between multiscale and fully atomistic simulations were very small with the use of the multiscale modeling resulting in a significant reduction in simulation time showing the accuracy of the temperature dependent potential and proposed coupling scheme.

The Effects of Thermally Induced Residual Stress on the Fatigue Behaviour of Fibre Metal Laminates

Abstract: The focus of this study is the examination and modification of existing analytical models for the calculation of effective stress intensity factor range and prediction of fatigue crack growth rates in GLass REinforced (GLARE) fibre metal laminates (FMLs). The effects of tensile residual stress have been largely unconsidered by existing models and therefore a modified model for calculating effective stress intensity factor range as well as crack propagation rate has been proposed. This modification includes the detrimental tensile residual stresses induced in the aluminum layers as a result of the laminate curing process. A previous model developed with the implementation of the fibre bridging mechanism has also been modified to include residual stress. The results of the analysis agree well with the trends and magnitudes found in the literature, though due to a lack of available experimental data, a direct evaluation of the proposed modifications was not possible.

Enhance Derivative Design Considering Global Sensitivity of Design Parameters

Abstract: An engineering product design considers derivatives to reduce the life cycle cost and to increase the efficiency on operation when it has new demands. The proposed design process in this study obtains derivative designs based on sensitivity of design variable. The efficiency and accuracy of the derivative design process can be enhanced by implementing global sensitivity analysis. Sensitivity analysis sensors the design variables accordingly and variables with low sensitivity for objective function can be neglected, since computational effort and time is not necessary for a design with less priority. In this research, e-FAST method code for global sensitivity analysis module was developed and implemented on Multidisciplinary Design Optimization (MDO) problem. The wing design was considered for MDO problem that used aerodynamics and structural disciplines. The global sensitivity analysis method was applied to reduce the number of design variables and Collaborative Optimization (CO) was used as MDO method. This research shows the efficiency of reduction of dimensionality of complex MDO problem by using global sensitivity analysis. In addition, this result shows important design variables for design requirement to student when they solving design problem.