Narrow Results

Presented herein is a formulation for the buckling of a cylindrical shell subjected to external loads using an infinitesimal shell element defined in a convenient coordinate system. The governing equation in terms of the radial deflection is derived for the element by adopting an operator. The eighth order partial differential equation derived can be applied for cylindrical shells with various boundary conditions. For illustration, simply supported cylindrical shells subjected to axial compressive forces are studied using either a one-variable or a two-variable shape function. The critical stresses obtained for the buckling of cylindrical shells are compared with those by the finite element program SAP2000. The critical stress of the cylindrical shell is similar to that of the column, in that the critical stress decreases as the thickness ratio (the ratio of R/h) or the slenderness ratio increases. Good agreement has been obtained for most of the comparative cases, while the finite element results appear to be slightly higher for some cases.

This paper presents an investigation on the influence of stress gradient on the elastic critical stress of distortional buckling of cold-formed steel sections supporting wall sheeting or roof cladding in buildings. The critical stress of distortional buckling of cold-formed steel section beams subjected to a uniformly distributed transverse loading is calculated using the model proposed recently by Li and Chen. The sections investigated in the paper include channel, zed, and sigma sections. Numerical examples are provided that highlight the influence of stress gradient, section dimensions, and sheeting lateral restraints on the critical stress of distortional buckling.

The usual assumption of isotropy of the material is shown here to be one of the reasons for the observed disparity between the theoretical and experimental values of the critical stress for plastic buckling of plates and shells. When the effect of plastic anisotropy that commonly occurs in thin-walled structures is included in the theoretical framework, the predicted load at the point of bifurcation can be significantly lower than that corresponding to the isotropic material. The present paper is intended to demonstrate the influence of plastic anisotropy on the critical stress for the elastic/plastic buckling of rectangular plates under unidirectional compression. The results are presented graphically to indicate how the critical stress is lowered by the presence of plastic anisotropy that is characterized by an R- value less than unity.

A thermodynamic model for Ti-V binary alloy system was established based on two sublattice model to estimate the molar fraction, atom fraction of elements in carbonitrides. Precipitates were analyzed by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The results showed that The evolution of carbonitrides is (Ti_0.98V_0.02)(C_0.06N_0.94)→(V_xTi_1-x)(C_yN_1-y)→(Ti_0.55V_0.45)(C_0.23N_0.77), which is consistent with experimental results, in the temperature range from 950℃ to 900℃. While, R.A declined rapidly from 70.23% to 43.52% with the size of particles decreasing from 25 to 17nm and quantity increasing 8.4inds/μm² to 46inds/μm², respectively. In the temperature range from 900℃ to 850℃, R.A reduced unobviously from 43.52% to 31.5%. The critical stress, 88.79MPa, was equal to tensile strength at 825℃. Intergranular fracture was easy to occur with higher critical stress below 825℃.