Purohit, B
(2015)
Frequency analysis of non-uniform bolted beams.
Masters thesis, Indian Institute of Technology Hyderabad.
Abstract
Modal analysis of non-uniform bolted structures are of critical significance in modeling many complex
mechanical structures such as airplanes, missiles, ships, etc. The study of vibration is of foremost
importance when it comes to mechanical and aerospace applications. The vibration measurement is
a powerful but a sophisticated tool for designing mechanical structures. It helps to unravel critical
system dynamics and hence designing the model in a better way. The use of joints is important for
a mechanical structure as due to its compatibility and access. A seamless mechanical structure of
large dimensions is difficult to be made hence the use of joints is required. There are vast literatures
available related with the analytical as well as numerical modeling of bolted joint. The bolted joints
are classified on the basis of frictional force, extension of joint, loading, etc. There exist different
models like Iwan model, Bou-Wen model, etc for modeling of bolted joint. For our case we take
the bolted joint as a torsional spring with no damping effect. The use of torsional spring is inspired
by the mechanics of the studied structure. The torsional spring takes care of the moment that is
transferred at the joint and as there is no axial force acting at the joint the need of linear spring
is not required. However, most of the analytical model discuss about the modeling of first mode
of uniform structures with bolted joint. In this thesis, we present the modeling of single as well as
bolted non-uniform beams using approximate mode shapes for higher modes. To develop the model,
we first studied a simply supported beam using approximate mode shape method. The study is done
for obtaining higher modes of single non-uniform beams and then the work is extended for bolted
beams with three sections. The results are verified using numerical study. We present the study for
second and third vibrational modes as compared to previous works for first mode.
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