Explore the vast range of titles available.

The paper considers the problem of creating and operating products of reusable space-rocket hardware, in particular with respect to ensuring the integrity of structural elements and safe return to Earth under aerodynamic heating conditions. This problem has two aspects, which differ in specificity of the approaches to designing the elements of space shuttle systems (SSS). The first aspect is associated with ensuring the reliable functioning of the most thermally stressed elements of the re-entry glider, which are structures with large angles of attack, such as fuselage nose and leading edge, wing loading edge, elevators and air intake edges. The second aspect mainly concerns ensuring the allowable temperature level of the spacecraft pressure shell on all flight path segments, especially during re-entry in the Earth’s atmosphere. In view of this, one of the main goals in creating SSSs is to develop a reliable heat shield having acceptable size and weight parameters, and cost. The successful solution of these problems is determined in many respects by the optimal choice of appropriate classes of materials: special high-temperature alloys, structural ceramics, highmelting-point metallic and polymeric composite materials. For the modern structures of SSSs, the use of structural metallic materials is worth-while in many respects. Rig test procedures are proposed. A complex of gas-dynamic test rigs was used as the basic equipment, whose fundamental design features and methodological solutions ensure the complete rig test cycle for the solution of problems in both directions. The methodological basis of rig tests is a set of specialized procedures for the simulation of thermally stressed states of the material and the intesity of the external action of the environment, which provide the equivalence of material damage processes and the limit state of the structural element under investigation under model and full-scale conditions. The fundamental basis of these approaches is the classical similarity and dimensional theories, the main postulates of which have been transformed and adapted to the problems of the study of the strength of materials and damageability of structural elements under thermal cyclic loading in corrosive environments. The developed procedures and experimental means allowed the modeling of aerodynamic heating processes of the structural elements of space shuttles. It has been shown that the implemented methods enable the evaluation of functional characteristics, determination of a set of properties and refinement of the technology for the formation of structural elements of aerospace vehicles operating under the conditions of aerodynamic heating to extremely high temperatures.

Studies of surface layer material degradation of the most loaded elements of gas turbine engine structural components revealed the essential changes in the structure and elemental composition of this layer in the thermal fatigue crack initiation zones, as well as along the propagating crack lips. The intensity of the observed changes implies the necessity of their account in the stress-strain state calculations and residual life estimations of high-temperature structural components of gas turbine engines.

Thermal and stress-strain states of the wedge-shaped specimen, which simulate GTE blade edge material state, have been analyzed under thermal cyclic loading in a gas flow. A significant influence of the mechanisms and kinetics of degradation in the surface layer material properties on the stress state of various zones of the wedge-shaped specimens and the character of thermal fatigue crack initiation and growth depending on the damage level is shown. The results of investigation of the influence of dimensions, localization and kinetics of thermal fatigue cracks on the change of the structure (specimen) stress-strain state as a whole are presented.

The paper describes a method and main results of a refined stress-strain state evaluation for a welded joint of the hot collector to steam generator nozzle of a nuclear power plant with a WWÉR-1000 reactor, which takes into account a fuller range of the actual loading conditions in operation. In calculations, we considered the stresses induced by uncompensated thermal expansion of the reactor elements. The results of 3D finite element calculations suggest that the level of local stresses in the area of the joint exceeds the metal yield stress. The calculated stresses for the outer nozzle surface agree satisfactorily with the in-situ strain measurement data.

The procedure for calculating the life of header – steam generator connector weld joints is proposed. It allows for running out the material plasticity reserve upon static cyclic elastoplastic loading as well as operating conditions, local stress concentrations, and residual stresses after welding.

he paper describes a 32-channel system for studying full-scale structures developed with the use of the state-of-the-art components. It provides continuous long-term measurement of strains and temperatures up to + 350°C and accumulation and storage of measurement data. The system was used to record the elastic strains and temperatures of a welded joint of the hot collector to the PGV-1000 steam generator nozzle in the period between the preventive maintenances. The measurement results reveal a complex pattern of strain and temperature distribution different from the axisymmetric one.

Safe operation of nuclear power plants is impossible without providing strength of their equipment and pipelines in view of real loading conditions. In this context, it becomes clear why each case of initiation of crack-type damages in pieces of equipment presents significant interest for experts in the field of strength of materials. During operation within the design service life, cracks were detected in the welding unit of the hot collector and the branch pipe of the PGV-l000 steam generator of a nuclear power plant with a VVER-l000 reactor. The investigations performed in this connection failed to reveal the cause of damage initiation. All the discovered damages (cracks) were located practically in the same place of the welding units of the hot collector and the branch pipe, which, in this case, indicates the presence of a common factor of loading that acts in the unit and was not considered in strength calculations earlier.