Impact of structural shape distortion on its load-bearing capability

The article describes a distortion of thin-wall shells caused by transverse and longitudinal shrinkage of a structural material during formation of a joint weld. This phenomenon is typical for fuel tanks of launch vehicles, upper stages, propulsion systems of space vehicles and spacecraft and pressurized compartments, i.e. habitable, cargo, instrument compartments. The procedure of approximating the distorted shell shape is presented, and examples of calculation of stress-strain behavior of the shell with the geometry actually obtained in manufacturing are given. It is shown how drastically stresses vary in the area of shrinkage cavities as compared to stresses in the shell of a regular shape. Given are calculation results and experimental data on decrease of a load-bearing capability of the shells of high-strength materials, as well as many-fold reduction of service life of shells made of a high-ductile material under cyclic loading due to geometrical distortion. It is shown that the joint weld in conjunction with a modified geometry of the shell is the most vulnerable structural point in terms of strength. The highest dependence on the shrinkage cavities of high-strength materials is specified. Cases of development of rocket and space structures are provided.