Journal of Theoretical and Applied Mechanics, Sofia, Accepted Papers

ABSTRACT: In this research paper, we examined the effectiveness of repairing corroded marine structures using bonded composites through finite element analysis (FEM) to evaluate the J Integral. Our focus is to provide an overview of the behavior of a cracked and corroded plate repaired with a boron patch and bonded with (Araldite 2015). To obtain optimized results, we studied the effects of eight corrosion levels under different loading and temperature conditions. The selected temperatures were T = 80℃ and room temperature T = 25℃. The structure is under different mechanical loading of amplitude F = 220, 240, 260, 280, 300, 320, 340, 360 MPa.The analysis shows that increasing loading and corrosion levels result an increase in J Integral. The detachment of patches was evaluated under high loading (F = 360 MPa) for corrosion level a = 4.0 mm/year.

ABSTRACT: This paper investigates the response of a cracked rotor to varying angles between the crack front and the unbalanced force vector caused by changing centrifugal forces. A rotor with a switching crack is first mathematically represented, and then the response is generated using SIMULINK. At varied angles, the combined effect of crack and imbalance is observed. Maximum and minimum rotor deflection values are depicted on the orbit plots, and their difference with respect to the angles are noted. For various harmonics and vibration amplitudes, a full-spectrum Fast Fourier Transform (FFT) is conducted. Using FFT plots, the critical amplitude of vibrations for each variable angle is determined, and observations are given. This report finishes with some concluding remarks.

ABSTRACT: The effect of temperature-dependent viscosity on the onset of thermal convection in a viscoelastic fluid-saturating porous medium is studied for different cases of combination of rigid and dynamically free boundaries, Darcy-Brinkman-Oldroyd model is considered to investigate the rheological behaviour of the fluid. A necessary condition for the existence of overstability is derived, analytically. The values of critical Darcy-Rayleigh numbers for both stationary and oscillatory convection with linear and exponential viscosity variations (i.e. temperature-dependent viscosity) are computed numerically, using the Galerkin technique. The effects of rheological parameters, modified Darcy number, wave number and variable viscosity parameter on the stability of the system are computed numerically and depicted graphically for each case of combinations of boundary conditions. It is observed that the viscoelastic parameters; stress relaxation time and strain retardation time do not affect the onset of stationary convection, whereas the stress relaxation time has destabilizing effect and strain retardation time has stabilizing effect on the onset of oscillatory convection. It is also found that the temperature-dependent viscosity and modified Darcy number have a stabilizing effect on the onset of stationary as well as oscillatory convection for each case of boundary conditions.