arXiv subjects

Amir Mehdi Dehrouyeh-Semnani

Publications and source records attributed to Amir Mehdi Dehrouyeh-Semnani.

3 recordsLinked to original sources

arXiv2024

A quaternion-based mathematical model for geometrically exact dynamic analysis of cantilevered pipe conveying fluid

For the first time, the development of the nonlinear geometrically exact governing equations and corresponding boundary conditions of hanging cantilevered flexible pipes conveying fluid in the framework of the quaternion system is undertaken. Additionally, the linear model is derived from the nonlinear one for the stability analysis. The linear and nonlinear mathematical formulations based on the geometrically exact rotation-based model are also extracted from the current model. The obtained integro-partial differential-algebraic equations are converted to a set of ordinary differential algebraic equations via the Galerkin discretization technique, and the resulting equations are numerically solved to determine the self-excited oscillation behavior of the system in the post-flutter region. The critical flow velocities, time traces, bifurcation diagrams, phase planes, and deformed configurations are compared with those reported based on the geometrically exact rotation-based model. The comparative studies divulge that the present model can successfully capture the stability and dynamic characteristics of the system. An interesting feature of the current ordinary differential-algebraic equations is that their coefficients are time-independent, unlike those of geometrically exact rotation-based equations in the Galerkin form. The results show this feature leads to a remarkable decrease in the computational cost, although the number of equations increases and the nonlinearity becomes stronger. The challenging issues with the numerical solution utilized in this study are also discussed.

physics.flu-dyn↗

arXiv2022

Nonlinear geometrically exact dynamics of fluid-conveying cantilevered hard magnetic soft pipe with uniform and nonuniform magnetizations

It is generally acknowledged that a hanging cantilevered pipe conveying fluid becomes unstable by flutter-type instability at a critical flow velocity; moreover, the pipe undergoes periodic self-excited oscillations in the post-flutter region. Additionally, the critical flow velocity increases when the magnetized pipe is exposed to an actuating parallel magnetic field. The question arises as to whether the actuating magnetic field leads to lessening the oscillation amplitude of the system in the post-flutter region. To answer the question, the nonlinear responses of a fluid-conveying cantilevered hard magnetic soft pipe with uniform and nonuniform magnetizations under an actuating parallel magnetic field are examined. In the case of the nonuniform magnetization, the mass density and elastic modulus of the pipe in addition to its residual magnetic flux density vary along its length. The mathematical formulation is constructed via a nonlinear geometrically exact model and is solved by employing the Galerkin technique in conjunction with the Runge-Kutta finite difference scheme. The numerical results are then analyzed to reveal the role of magnetization in the magneto-hydro-elastic responses of the system in the absence and presence of magnetic field.

cond-mat.soft↗

arXiv2020

On bifurcation behavior of hard magnetic soft cantilevers

Hard magnetic materials belong to a novel class of soft active materials with the capability of quick, large, and complex deformation via applying an external actuation. They have an extensive range of potential applications in soft robots, biomedical devices, and stretchable electronics, etc. Recently, investigation on the experimental and theoretical nonlinear mechanics of hard magnetic soft cantilevers has received notable considerations. In the available analyses, the most attention was paid to the non-bifurcation-type nonlinear mechanics of the system, and bifurcation was considered for a specific case. In the current study, the general trend of bifurcation-type nonlinear mechanics of hard magnetic soft cantilevers is introduced and the effective parameters on the occurrence of bifurcation are identified. Additionally, new trajectories due to the bifurcation and the corresponding workspace are presented. Eventually, a comprehensive comparative study between the new trajectories and workspace with those reported in the prior studies is carried out.

cond-mat.soft↗