Finite Element Analysis on the Vibration Mode of Composite Thin-walled
Box Beam with Double-cell Sections
Sun Shuangshuang
1,a
, Jia Fangwu
1,b
,Ren Yongsheng
2,c
1
College of Electro-mechanical Eng., Qingdao Univ. of Sci. & Tech., Qingdao 266061, China
2
School of Electro-mechanical Eng., Shandong Univ. of Sci. & Tech., Qingdao 266510, China
a
sunkira@sohu.com,
b
fangwu86@126.com,
c
renys@sdust.edu.cn
Keywords: Composite Thin-Walled Beam; Double-Cell Section; Modal Analysis; Finite Element
Abstract. The modal analysis of composite thin-walled box beams with double-cell sections is
carried out by the finite element software ANSYS. The finite element models are established first
for the double-cell composite thin-walled box beams, then the vibration modes of two box beams:
Circumferentially Uniform Stiffness (CUS) and Circumferentially Antisymmetric Stiffness (CAS)
are calculated and analyzed. The effects of length-width ratio and width-height ratio on the natural
frequency and the modal shape of the double-cell composite thin-walled box beams are discussed.
Introduction
Because of light weight, fatigue resistance and designability of strength and rigidity, composite
thin-walled beam structures have been widely used in the aerospace field and wind engineering
field [1]. At present, the research on composite thin-walled beams is mainly for single-cell box
beams and some achievements have been made in this aspect [2-4]. However, many engineering
structures like large wind turbine blades have characteristics of double-cell composite thin-walled
box beams. For this kind of composite beams, their dynamic problems are relatively hard to solve
due to the complexity of structures and the coupling between all kinds of deformations induced by
anisotropy of materials [5].
Based on our previous work [4,6], the vibration characteristics of two common double-cell
thin-walled box beams CUS and CAS will be further studied in this paper to consider the effects of
length-width ratio and width-height ratio on the natural frequency and the modal shape of both
double-cell thin-walled box beams by ANSYS 12.0. This research will provide some foundation for
the wide applications of these double-cell composite thin-walled box beams in engineering.
Theoretical basis for modal analysis
The finite element method is very effective in analyzing vibration characteristics of such
complex structures as thin-walled composite box beams with double-cell sections. The free
vibration equation of double-cell thin-walled composite beams can be written as:
0uKuCuM
=
+
+
(1)
Where, M, C and K are the total mass matrix, damping matrix and stiffness matrix.
u
,
u
and
u
are the total acceleration vector, speed vector and displacement vector of nodes.
As damping has little influence on frequency and vibration mode of structures, the generalized
eigenvalue equation of Eq. 1 is approximately expressed as:
0MK
i
2
i
=−
φω
(2)
Where, ω
i
and
i
φ
denote the i order natural frequency and vibration mode vector, respectively.
Advanced Materials Research Vol 569 (2012) pp 495-499 Online: 2012-09-28
© (2012) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/AMR.569.495
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans
Tech Publications, www.ttp.net. (ID: 132.174.254.159, Pennsylvania State University, University Park, USA-22/05/15,07:58:13)
