Sharif Digital Repository

In this study, a multi-scale model is proposed to assess softening kinetics and microstructural changes during isothermal annealing within an aluminum alloy. In the first stage, an elastic-plastic finite element analysis is performed for computing the distributions of effective plastic strain and stress while the stored energy after cold rolling is defined based on the predicted data and then utilized for generation of the initial conditions in the microstructural analysis. In the next stage, an algorithm based on cellular automata coupled with a first order rate equation is used to determine the progress of softening behavior at elevated temperatures while both recrystallization and... 

In this paper, a new disk type variable reluctance (DTVR) resolver is introduced. The proposed resolver works based on the sinusoidal variation of the coupling area between stator and rotor. An analytical model based on winding function theory is proposed for the performance analysis of the sensor. Then, the influence of stator slot shape, radial and peripheral slot width, pole numbers, and slot skewing and harmonic injection into the rotor couture on the accuracy of the proposed resolver is examined. The 3-D time stepping finite element method is used to show the effect of optimizations. Finally, the prototypes of the two-pole, four-pole, and eight-pole DTVR resolvers are constructed and... 

Switched Reluctance Motors (SRMs) possess both simple structure and high speed operation, but they suffer from considerable vibration and acoustic noise. The significant vibration and acoustic noise reduction techniques are categorized in two groups: Drive based methods and geometrical design based group. The main challenge in both groups is reducing the acoustic noise and vibration without significant deterioration in other performance characteristics of the motor such as average torque and efficiency. In this paper a novel multi-stage SRM with skewed poles is proposed to significantly reduce vibration and acoustic noise in almost constant average torque and even higher efficiency. Design... 

Shape is a key factor in influencing mechanical responses of bones. Considered to be smart viscoelastic and inhomogeneous materials, bones are stimulated to change shape (model and remodel) when they experience changes in the compressive strain distribution. Using reverse engineering techniques via computer-aided design (CAD) is crucial to create a virtual environment to investigate the significance of shape in biomechanical engineering. Nonetheless, data are lacking to quantify the accuracy of generated models and to address errors in finite element analysis (FEA). In the present study, reverse engineering through extrapolating cross-sectional slices was used to reconstruct the diaphysis of... 

This work aimed to evaluate trunk muscle forces, internal loads and stability margin under some simulated standing postures, with and without external loads, using a nonlinear finite element model of the T1-S1 spine with realistic nonlinear load-displacement properties. A novel kinematics-based algorithm was applied that exploited a set of spinal sagittal rotations, initially calculated to minimize balancing moments, to solve the redundant active-passive system. The loads consisted of upper body gravity distributed along the spine with or without 200 N held in the hands, either in the front of the body or on the sides. Nonlinear and linear stability/perturbation analyses at deformed,... 

Variable reluctance resolver (VR-Resolver) is a robust electromagnetic sensor that provides position information for closed-loop control systems of permanent magnet synchronous motors (PMSMs). For specific motion control applications, an outer rotor structure is presented for the VR-Resolver in this article with a nonoverlapping tooth-coil windings configuration to simplify the manufacturing process. The study on the structure of the proposed position sensor is carried out, followed by the description of the working principle. The presented outer rotor VR-Resolver is simulated and its performance is investigated in detail with the aid of transient finite-element analysis (TFEA). Sensitivity...