# Uncertain dynamic responses of imprecisely defined arbitrary order fractionally damped beam subject to various loads

Diptiranjan Behera (Center for System Reliability and Safety, University of Electronic Science and Technology of China, Chengdu, China)
Hong-Zhong Huang (Center for System Reliability and Safety, University of Electronic Science and Technology of China, Chengdu, China)
Smita Tapaswini (College of Mathematics and Statistics, Chongqing University, Chongqing, China and Department of Mathematics, School of Applied Sciences, KIIT University, Bhubaneswar, India)

ISSN: 0264-4401

Publication date: 16 April 2018

## Abstract

### Purpose

Recently, fractional differential equations have been used to model various physical and engineering problems. One may need a reliable and efficient numerical technique for the solution of these types of differential equations, as sometimes it is not easy to get the analytical solution. However, in general, in the existing investigations, involved parameters and variables are defined exactly, whereas in actual practice it may contain uncertainty because of error in observations, maintenance induced error, etc. Therefore, the purpose of this paper is to find the dynamic response of fractionally damped beam approximately under fuzzy and interval uncertainty.

### Design/methodology/approach

Here, a semi analytical approach, variational iteration method (VIM), has been considered for the solution. A newly developed form of fuzzy numbers known as double parametric form has been applied to model the uncertainty involved in the system parameters and variables.

### Findings

VIM has been successfully implemented along with double parametric form of fuzzy number to find the uncertain dynamic responses of the fractionally damped beam. The advantage of this approach is that the solution can be written in power series or compact form. Also, this method converges rapidly to have the accurate solution. The uncertain responses subject to impulse and step loads have also been computed and the behaviours of the responses are analysed. Applying the double parametric form, it reduces the computational cost without separating the fuzzy equation into coupled differential equations as done in traditional approaches.

### Originality/value

Uncertain dynamic responses of fuzzy fractionally damped beam using the newly developed double parametric form of fuzzy numbers subject to unit step and impulse loads have been obtained. Gaussian fuzzy numbers are used to model the uncertainties. In the methodology using the alpha cut form, corresponding beam equation is first converted to an interval-based fuzzy equation. Next, it has been transformed to crisp form by applying double parametric form of fuzzy numbers. Finally, VIM has been applied to solve the same for the general fuzzy responses. Various numerical examples have been taken in to consideration.

## Keywords

#### Citation

Behera, D., Huang, H. and Tapaswini, S. (2018), "Uncertain dynamic responses of imprecisely defined arbitrary order fractionally damped beam subject to various loads", Engineering Computations, Vol. 35 No. 2, pp. 818-842. https://doi.org/10.1108/EC-04-2017-0134

### Publisher

:

Emerald Publishing Limited