Kashi Nath Saha

Analytical Study on Elastic Limit Speed of Non-Uniform Rotating Disks Considering Thermal Effect on Elasticity Modulus

This study concerns the analysis of thermoelastic characteristics of non-uniform rotating disks subjected to thermal load including the effect of inertia force due to rotation of the disk. The solutions up to the elastic limit yield stress of the material are obtained under plane stress assumption by taking variation on total potential energy. The solution algorithm is implemented with the help of MATLAB computational simulation software. The analysis is carried out for various disk geometries and temperature distribution profiles. The effect of temperature on elasticity modulus is also investigated and some numerical results are presented and discussed in the form of limit angular speed under thermo-mechanical loading and reported in dimensionless form.

Growth of yield front in thermo-mechanically loaded non-uniform bars using an iterative variational method:

The aim of this study is to investigate the growth of yield front in post-elastic domain of a thermo-mechanically loaded non-uniform bar with clamped ends. The problem is solved through an extension of the variational method in post-elastic regime. It is assumed that yield stress is the only physical parameter dependent on temperature variation of the bar and all other material properties remain constant corresponding to the value at ambient temperature. The bar is axisymmetric, and during thermal loading, its plane cross sections remain plane maintaining axisymmetry. This analysis of the energy-based variational formulation is carried out by Galerkin’s principle, using a linear combination of sets of orthogonal coordinate functions which satisfy prescribed boundary conditions. The approximate solution additionally needs an iterative technique to find the growth in yield front for the type of prescribed temperature field. The solution algorithm is actualized with the assistance of MATLAB® computational simulation software. Uniform, linear and parabolic types of temperature distribution over the length of the bar are assumed, and some numerical results in dimensional form are presented and discussed for a clamped-clamped mild steel bar. The temperatures corresponding to onset of yielding and total collapse are considered as markers of yield limit and collapse loads. The temperatures and limit load factors for different bar geometries and temperature distributions are provided. The results reveal that the thermo-elasto-plastic deformation of clamped bar is significantly influenced by the effect of geometry parameters and by the nature of thermal load.

An approximate solution to the stress and deformation states of functionally graded rotating disks

The present work employs variational principle to investigate the stress and deformation states and estimate the limit angular speed of functionally graded high-speed rotating annular disks of constant thickness. Assuming a series approximation following Galerkin’s principle, the solution of the governing equation is obtained. In the present study, elasticity modulus and density of the disk material are taken as power function of radius with the gradient parameter ranging between 0.0 and 1.0. Results obtained from numerical solutions are validated with benchmark results and are found to be in good agreement. The results are reported in dimensional form and presented graphically. The results provide a substantial insight in understanding the behavior of FGM rotating disks with constant thickness and different gradient parameter. Furthermore, the stress and deformation state of the disk at constant angular speed and limit angular speed is investigated to explain the existence of optimum gradient parameters.