Patent ID: 9645054
Date: 2017-05-09
CPC Classifications: B64C,G01M,G06F,Y02T

Claim:
1. A method for determining a knockdown factor (KDF) of load-carrying capacity of a cylindrical shell subjected to axial compression, the knockdown factor being used for calculating the load-carrying capacity of the cylindrical shell, and the cylindrical shell having no dimple, the method comprising: a) applying a first radial perturbation load to the cylindrical shell by using a load application device comprising T-rings attached to both bottom and top end of the cylindrical shell for forming a single dimple imperfection having an amplitude on the cylindrical shell; adjusting the amplitude of the single dimple imperfection and calculating load-carrying capacities of the cylindrical shell under the single dimple imperfection to obtain a relationship between the first radial perturbation load and a sensitivity to load-carrying capacity, and determining a rational perturbation load range, where a maximum imperfection amplitude corresponding to a maximum perturbation load N b) then simultaneously applying three radial perturbation loads on three load positions of the cylindrical shell by using the load application device for forming three dimple imperfections on the cylindrical shell, wherein the three dimple imperfections form a regular triangle; defining a distance between a circumcenter and a vertex of the regular triangle as l, varying the distance l from zero, calculating corresponding buckling loads, and drawing a curve representing a relationship between the buckling loads and the distance l; defining a distance corresponding to a minimum buckling load as an effective distance l where, L is an axial height of the cylindrical shell, R is a radius of the cylindrical shell; setting l to be equal to l c) in design of experiment, performing sampling by using the amplitudes of the radial perturbation loads N, n d) calculating a combination of radial perturbation loads that is adapted to form a worst imperfection for the cylindrical shell by using an optimization formulation which is expressed as follows: where, N calculating the knockdown factor (KDF) via a formula: where, P