Published Resources Details
Journal Article
- Title
- On teaching basic notions of elasticity, stiffness and buckling
- In
- Journal of the Institution of Engineers, Australia
- Imprint
- vol. 38, 1966, pp. 289-298
- Abstract
Without restriction as to system linearity, the notions of elasticity and stiffness are reviewed and differentiated in a general way. Stiffness is defined without reference to elasticity; and the existence of both a material factor and a geometrical factor in stiffness is elucidated. A simple geometrically non-linear, elastic-spring rig serves to illustrate these ideas, all of which are well documented but often not well understood nor often presented unambiguously at an elementary level. In introductory texts, the distinction between stiffness and elasticity is seldom drawn.
In a second rig employing a rubber bellows, concepts of zero arid negative stiffness are fully demonstrable, so introducing the fact of buckling as an instability. Higher modes of buckling occur as well. In a discussion of the energy changes associated with the instabilities and the post-buckling behaviour, the significance of dissipative effects, with which the rubber bellows is well endowed, becomes apparent.
A third rig enables the simple demonstration of the classical bifurcation type of buckling by the adaptation of an inverted, elastically-restrained pendulum. The significance of initial imperfections can be discovered quantitatively, and large-displacement post-buckling behaviour studied fully.
Throughout, stress is placed on an understanding of the role of stiffness as it changes with load or deformation configuration, this being the common basis of all forms of conservative elastic instability. Systems exhibiting bifurcation (Euler) buckling, finite-disturbance buckling, progressive snap-through buckling and oil-canning are all discussed and exemplified by the rigs. These several phenomena are never presented, in teaching, in an integrated fashion.