In the development of large vacuum chambers with openings into which branch pipes are installed there is the question of providing stability of the designs while optimizing metal content. Studies [1-3] on the stability of shells with openings have shown that openings with a profile that is not reinforced reduce the critical load of the design. The presence of an initial geometric irregularity in the zone adjoining the opening can result in the formation of localized stability loss (even for an opening of small diameter [1]). It is quite a complex task to carry out a theoretical calculation of the stress'--strain" state and stability of these designs. However, from experimental studies on models produced industrially it is possible to determine the effect of openings with installed branch pipes on the stress-strain state and stability of cylindrical shells.We can examine the results of experimental studies on the stability of large welded models of cylindrical shells with diametrically positioned cylindrical branch pipes. Cylindrical models made of 12Khl8N10T austeuite steel with R/H ratios of 133:1 and 200:1 (where R is the radius of the cylindrical shell, H is the wall thickness) were selected for the studies. The diameter of the main shell of the models was D = 2R = 800 ram. The shell was produced by stretch rolling followed by longitudinal seam welding. Two diametrically opposed openings of equal size were produced in the shells and cylindrical branch pipes closed at the ends with flat covers with ribbed reinforcement were installed and welded into the openings (Fig. 1). The diameter of the branch pipes was 0.6D, 0.8D, and 1D. The thickness h of the branch pipe was taken as equal to the thickness of the main shell. A rigid flange was fixed at one end of the main shell in order to support the model on a stand during the tests (Fig. 2). The main shell was closed at the other end by a fiat cover with ribbing.The stresses close to the branch pipes were recorded using KF 5P-3-100-A12 low basis resistance strain gauges and a MARS-1000 multichannel automated display system.The deviations from true geometric shape were recorded before the tests using a special instrument. The maximum relative ovalness was determined from the recorded results according to the following formula [4]
a-~ , I00 %, D~ § D~where Dma x and Dmi n are respectively the maximum and minimum diameters of the shells on measurement in two mutually perpendicular directions of a single cross section.The measurements showed that the main shells and branch pipes had deviations from true geometric shape that in individual cases exceeded the standard value [4]. These deviations occurred in adjoining zones of branch pipe and main shell. The deviations from linearity were 0.5-3.5 ram, and the relative ovalness of some models was higher than the standard permissible value (a = 0.5%) for stability designs.The models were subjected to hydraulic pressure and eva, cuation in stages (with the stresses recorded at each stage). The pressure during the tests was reco...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.