TWI Frequently asked question
by David Morgan
Buckling instability is defined as the large distortion that can occur in slender, structural members under compressive loading. Euler's formula gives the theoretical critical compressive load for buckling but only for very slenderstruts. The Rankine-Gordon method is more useful when dealing with real struts (see knowledge summary on buckling).
During welding, a large amount of heat is applied to a localised area of metal over a short period of time. The varying rates of cooling result in the formation of large residual stresses in and around the weld, and some associateddistortion. Both these effects may reduce the buckling resistance of the component:
- any substantial build-up of compressive residual stress will reduce the tolerable compressive structural stress by a proportionate amount.
- welding distortion that gives rise to out-of-plane deformation with respect to the plane of buckling will reduce the critical buckling load.
