m.h. abolbashari

In this paper, the reliability based design optimization of columns under buckling load is investigated using evolutionary structural optimization. To determine the reliability index, the Hasofer-Lind method is employed and results are compared with the Monte Carlo method. The standard response surface method with central composite design is used to estimate the limit state function. An optimization algorithm for optimal design of columns against buckling with different cross-sections and boundary conditions is presented while keeping the column weight constant.The Taguchi method is used to provide the most suitable levels of the design variables. Then by introducing reliability constraints into the algorithm, the optimized shape of the column under buckling load based on reliability is obtained. Optimized design obtained from Deterministic Optimization (DO) and Reliability Based Design Optimization (RBDO) are compared. Numerical examples show that maximum buckling load capacity is increased compared to the initial uniform design and also RBDO model is more reliable than DO.

This study aims at investigation the effects of material distribution and thermal boundary condition on stress field of FGM rotating hollow disk. For this purpose, three different problems with four distribution functions for material properties and three different thermal boundary conditions have been applied. Young’s modulus, density, and coefficient of thermal expansion distributions are defined as functions of the radius, and Poisson's ratio is assumed uniformly because it has equal value in two considered materials. The first, with assumption of elastic perfectly plastic behavior for material, disk plastic area rate with linear, power, exponential, and logarithmic material property distributions at three different temperature boundary conditions is studied and the best distribution for minimizing plastic area is detected. In the following with the assumption of constant rotational speed, thermal boundary conditions and external and internal radius of the disc, by utilizing criterion Von-Mises stress and the Taguchi method, the distribution of material properties for minimizing the maximum Von-Mises stress in each of the thermal boundary conditions is introduced. Finally, the sensitivity of Von Mises stress subject to the rotational speed, thermal boundary conditions, and material properties of the inner and outer radii is investigated by utilizing the Taguchi method. It’s concluded that the sensitivity of maximum Von-Mises stress to temperature distribution is more than to material distribution and rotating speed.