Vibration correlation technique for the estimation of real boundary conditions and buckling load of unstiffened plates and cylindrical shells

Applicability of the Vibration Correlation Technique for Estimation of the Buckling Load in Axial Compression of Cylindrical Isotropic Shells with and without Circular Cutouts

“…Figure 8(b) and Table 3). However, the modified VCT developed in [17] allows correlating reduction of the first natural frequency of an unstiffened cylindrical shell under axial compression to the buckling load when the buckling mode differs from the vibration one. In the following, we check the applicability of the modified VCT [17] to the unstiffened aluminium shells.…”

“…(Each of the two sets of shells mentioned was produced under the same conditions resulting in close imperfection signatures within a set, which allowed considering the shells as nominally identical within each set.) The respective plots are shown in Figure 12 together with a second-order fitting curve as stipulated by the modified VCT [17]. From the minimum of the approximating secondorder polynomial, the numerical value of the factor 2 characterizing the reduction of buckling load caused by shell imperfections was determined as 2 = 0.0609 for the set of Figure 12 these shells.…”

“…Applicability of VCT to unstiffened stainless steel cylinders was explored in [16] employing linear and quadratic fitting polynomials for vibration frequency squared as a function of axial load, with encouraging but inconclusive preliminary results. The VCT proposed by Souza et al [12,15] was applied to unstiffened cylindrical shells by Arbelo et al [17] using extensive numerical simulations. Negative values of the parameter 2 in (1) were obtained having no physical meaning, thus invalidating the approach [12,15] for unstiffened cylindrical shells.…”

“…Negative values of the parameter 2 in (1) were obtained having no physical meaning, thus invalidating the approach [12,15] for unstiffened cylindrical shells. However, it inspired a modification of VCT as follows [17]. It was proposed to approximate the (1 − ) 2 data as a second-order polynomial of 1 − 2 .…”

“…The modified VCT of Arbelo et al [17] has been extensively validated for thin-walled unstiffened cylindrical shells produced from carbon/epoxy [18][19][20], stainless steel [19], and aluminium [21] demonstrating its capacity of determining the axial bucking load via nondestructive tests. However, common applications from aerospace to civil structures require isotropic shell structures to be accommodated with local cutouts.…”