UNDERSTANDING IMPERFECTION-SENSITIVITY IN THE BUCKLING OF THIN-WALLEDSHELLS

The buckling of thin-walled shell structures under load is still imper fectly understood, in spite of much research over the past 50 years. I n this paper the author traces the history of the ideas which have bee n deployed in order to shed light on what is often referred to as 'imp erfection-sensitive' buckling behaviour of shells. The ideas, which re cur in various combinations, involve interaction of competing buckling modes, nonlinear behaviour, the growth of initial geometric imperfect ions under load and the alteration of the distribution of membrane str ess as imperfections grow. The author claims that there are strong gro unds for supposing that 'locked in' initial stresses on account of imp erfect initial geometry and the static indeterminacy of boundary condi tions of real shells have a pronounced effect on the buckling performa nce. This effect has been ignored in the past, and is the subject of a current experimental study.