LHC Seminar

Why and when might thin-walled structures get unstable ?(Examples not only from the world of accelerators)

by Blazej Skoczen (CERN/LHC)

30-7-00 (CERN)



Thin-walled structures are omnipresent in our everyday life. Typical examples are that of soda cans, egg shells, car bodies, roof panels or aircraft wings. In the world of accelerators, vacuum chambers, thermal shields and bellows belong to the same group of thin-walled objects. What conditions have to be satisfied in order to provoke buckling? What are the forms of instability of thin shells? How does the process of buckling start and what is its dynamics? When does the plastic deformation occur and what are the consequences for the post-buckling forms? What is the effect of material defects (micro-voids, micro-cracks) on mechanical instability of structures? Finally, how do the structures buckle at cryogenic temperatures? These and other questions will be addressed in the presentation where a new approach to coupling of fatigue and buckling shall be explained. Also, an application of this idea to design of the LHC mechanical compensation systems against buckling will be presented.