Objectives This article discusses the evaluation of the effectiveness of three-layer pipes of a symmetric and asymmetric structure. For this, the stress-strain state of three-layer pipes of different materials under the influence of internal pressure is investigated. Pipeline structures today occupy important positions in the infrastructures of many countries. Trunk structures affect the economy, industry. Every year, new safety requirements are added to the reliability indicators of these structures.Method The calculation is carried out by numerical methods, namely using the finite element method (FEM), implemented in the LIRA PC.Result The calculation of the pipes is performed, on the load from the transported medium, applied to the inner contour of the pipe. Moreover, for three-layer pipes of all variants, Nx tensile stresses along the generatrix, Ny ring tensile stresses and Txy shear stresses in the xy plane were determined. Isopoles of tensile and shear stresses are given.Conclusion The numerical results showed that the use of less deforming material as a material for the manufacture of asymmetric bearing layers leads to a redistribution of stresses in the bearing layers and aggregate, and this must be taken into account when designing three-layer pipes.

Objectives. In this research, we set out to explore the possibility of increasing the resistance of three-layered panels with a pyramid filler filled with fibrous material to dynamic loads. Although issues associated with dynamic impact, penetration of solid bodies and breaking of solid barriers have always been of interest, particularly in military affairs, they are increasingly attracting the attention of researchers investigating various industrial problems.Method. A calculation was performed using the finite element method (FEM), which is widely used in various areas including construction. The possibility of calculating the movement of a solid body in fibrous material using the FEM, namely using the LIRA-SAPR software, was considered.Results. From the constructed models, it can be seen how the striker moves inside the fibrous material. Therefore, using the SC LIRA-SAPR allows the work of the filler to be assessed while a solid body moves inside it. The results of the calculation of striker movement in fibrous material depending on the speed of the body (striker) and the density of the filler (fibre) are shown in figures.Conclusion. The conducted numerical studies showed that a discrepancy between the calculation results for a three-layered structure under dynamic loads using the FEM and analytical dependencies was about 10%.