Consideration of nonlinear properties of new structural materials

In recent years, new structural materials (composite and polymer materials, non-ferrous alloys) are widely used in mechanical engineering. For example, in the production of high-pressure vessels, in order to lighten the design, a thin-walled aluminum alloy liner is installed in a strong carbon fiber shell. However, such materials are among the physically nonlinear ones, when, even with minor deformations, there are significant deviations from the Hooke's law. Therefore, the development of methods to account for this effect and assessment of its impact on the stress-strain state of the design is an actual problem. In this paper, the authors justify the possibility of using the finite element method for nonlinear relationship between stresses and strains. They propose to approximate a real deformation diagram by a cubic parabola. As a result, the calculation data are obtained in the form similar to the linear theory of the finite element method.