Note on the southwell method for estimating critical loads

Abstract

(a) Purpose of Note.--To draw attention to certain restrictions on the use of the 'Southwell plot' to estimate critical loads in cases differing in conditions from those which the method was first proposed. (b) Range of Note.--The effects on the 'Southwell plot' of variation of stress distribution, of elastic failure of the material and of other variation of critical stress, however it may be occasioned, is examined. (c) Conclusions. The 'Southwell plot' is strictly applicable only to deflections which go to infinity at a definite critical load. In other cases the plot usually over-estimates the buckling load; but the error should seldom be important.