Experimental Mechanics

, Volume 15, Issue 8, pp 303–310 | Cite as

Critique of Southwell plots with proposals for alternative methods

Paper examines those situations in which the Southwell plot works poorly and proposes alternative techniques for finding Pc
  • H. H. Spencer
  • A. C. Walker


The theory of the Southwell plot is outlined and its history traced. Examples are given in which the technique fails to give a straight line; these are classified into low-load and higher-load nonlinearities. It is shown that the former may be due to inherent zero errors in the deflection measurement and that this can cause serious errors in the apparent critical loadPc. A new approach involving “pivot points” is introduced and used to formulate plots which may help to linearize the data; an application to one of Karman's classical column tests is given.

For plates, use is made of a general post-critical equation of which Donnell's result for a simply supported square plate is a special case. A new graphical technique is proposed for findingPc for plates with small imperfections, and applied to example data from published test results. A more general numerical technique is also proposed and applied to results from a test during which the experimental boundary conditions were changing.


Boundary Condition Mechanical Engineer Fluid Dynamics Numerical Technique Column Test 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Society for Experimental Mechanics, Inc. 1975

Authors and Affiliations

  • H. H. Spencer
    • 1
  • A. C. Walker
    • 2
  1. 1.Applied Mechanics GroupHatfield PolytechnicEngland
  2. 2.University CollegeLondonEngland

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