An analysis of collapse mechanism of thin-walled circular tubes subjected to bending

TitleAn analysis of collapse mechanism of thin-walled circular tubes subjected to bending
Publication Typeวิทยานิพนธ์/Thesis
Year of Publication2011
AuthorsSomya Poonaya
DegreeDoctor of Philosophy -- Major in mechanical Engineering
InstitutionFaculty of Engineering, Ubon Ratchathani University
CityUbon Ratchathani
Call NumberTJ S697
KeywordsTube bending

Circular tubes have been widely used as structural members in many engineering
applications. Therefore, its collapse behavior has been studied for many decades, focusing on its
energy absorption characteristics and collapse mechanism. In order to predict the collapse
behavior of members, one could rely on the use of finite element codes or experiments. These
tools are helpful and high accuracy but are costly and require expensive running time. Therefore,
an approximate model of tubes collapse mechanism is an alternative approach especially for the
early step of design. This research is aimed to develop a closed-form solution to predict the
moment-rotation response of a circular tube subjected to pure bending. The model was derived
based on the principle of energy rate conservation. The collapse mechanism was divided into three
phases. New analytical model of ovalisation plateau in phase 2 was derived to determine the
ultimate moment. In phase 3, the Elchalakani et al.'s model [One of the well-established models]
was further developed to include the rate of energy dissipation on a rolling hinge in the
circumferential direction. The 3-D geometrical collapse mechanism was analyzed by adding the
oblique hinge lines along the longitudinal tube within the length of the plastically deformed zone.
Then, the rate of internal energy dissipation was calculated for each of the hinge lines which was
defined in term of velocity field. Inextensional deformation and perfect plastic material behavior
were assumed in the derivation of deformation energy rate. In order to validate the model
compare, the experiment was conducted with a number of tubes having various D/t ratios. In
addition, the computer simulation (finite element) of each specimen was also carried out. The
comparison of analytical, experimental and finite element results indicates that the model
proposed in this study agrees well with experiment and finite element. In addition, the proposed
model provides more accurate results compared to other studies.

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