Table 1: Comparison of analytical approximations with the exact one for buckling loads.

(a) (b) (c) (d)

20°1.01541.0152 (0.0197)1.0155 (0.0098)1.0155 (0.0098)
40°1.06371.0609 (0.2632)1.0648 (0.1034)1.0647 (0.0940)
60°1.15171.1371 (1.2677)1.1567 (0.4341)1.1576 (0.5123)
80°1.29391.2437 (3.8797)1.3056 (0.9042)1.3164 (1.7389)
100°1.51841.3808 (9.0622)1.5318 (0.8825)1.5890 (4.6496)
120°1.88481.5483 (17.8534)1.8615 (1.2362)2.0821 (10.4680)

Number inside the bracket ( ) is the % relative error computed.
(a)Results by the exact theory [12].
(b)Results by the HPM truncated to the first order.
(c)Results by the HPM truncated to the second order.
(d)Results by the SAA.