Buckling of Cylinders With Imperfect Length

Eighteen mild steel cylinders with the length-to-radius ratio, L/R ≈ 2.4 and with the radius-to-wall thickness ratio, R/t ≈ 185 were collapsed by axial compression. Cylinders had variable length at one end of sinusoidal profile. The magnitude of axial imperfection-to-wall thickness ratio, 2A/t, was varied between 0.05 and 1.0. Experimental results show that buckling strength strongly depends on the axial amplitude of imperfection. On average imperfect cylinders, with 2A/t = 1.0, are able to support 49% of experimental buckling load obtained for geometrically perfect model. The largest sensitivity of buckling strength was associated with small amplitude of imperfection in axial length. For example, for axial length imperfection amounting to 25% of wall thickness the buckling strength was reduced by 40%. It appears that the number of sinusoidal waves in the imperfection profile plays a secondary role, i.e., its role in reducing the buckling strength is not a dominant factor. The paper provides experimental details and comparisons with numerical results.