Impulse Pressure-Assisted Diffusion Bonding (IPADB): Review and Outlook

Diffusion bonding is a solid-state welding technique used to join similar and dissimilar materials. Relatively long processing times, usually in the order of several hours as well as fine polished surfaces make it challenging to integrate diffusion bonding in other production processes and mitigate widespread use of the technology. Several studies indicate that varying pressure during diffusion bonding in contrast to the traditionally applied constant load may reduce overall processing- and bonding times. Such processes are referred to as impulse pressure-assisted diffusion bonding (IPADB) and they are, for the first time, reviewed in this work using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) methodology. Results of the review indicate that varying pressure can indeed reduce bonding times in diffusion bonding and reduce the requirements for pre-bond surface preparation. Additional research is required and should go beyond small and simple sample geometries to concentrate on making IPADB accessible to industrial applications.

ДИНАМИЧЕСКИЙ АНАЛИЗ КОМПОЗИТНОГО ОБТЕКАТЕЛЯ РАКЕТЫ ПРИ ОТДЕЛЕНИИ С УЧЕТОМ РАССЛОЕНИЯ СТРУКТУРЫ

The dynamic processes in the rocket fairing when the pyrotechnic separation system is triggered are considered. The fairing construction is mixed and includes composite and metal elements. The main composite construction element is a fiberglass shell with regular and irregular winding zones. The speed acceleration required to separate the fairing occurs under the action of impulse pressure from the powder gases in the pyrotechnic system. The displacement of the fairing is made up of displacements of the movement as a rigid whole along its axis and vibrations caused by deformations. The calculation of the fairing movement is carried out according to a three-dimensional FEM model using software that uses a topologically regular discretization system. The problem solution in time is performed according to the implicit Wilson finite-difference scheme. When studying the fairing dynamics, it is allowed to break the structure of the shell in the form of lamination, which in the FEM scheme is modeled by a special method. A cut with double nodes is created on the surface of the proposed lamination along topological planes by transforming the finite element mesh. Modification of the stiffness matrix and mass matrix for the transformed mesh is performed based on the created information base of degenerate finite elements and formalized matrix operations. In numerical studies, two types of lamination from irregular zones of fiberglass winding are considered – the internal location from the flange and edge location with access to the fairing free edge. The results of calculating vibrations along the sides of lamination and data on the redistribution of dynamic stresses due to lamination are presented. Radial and axial displacements when passing through the lamination surface discontinue, the magnitude of which for internal lamination is much less, which is explained by the compression of deformation for this case, in contrast to the lamination that goes to the boundary. When estimating the relative axial displacements, the component of the displacement of a rigid whole, determined by a separate calculation, was excluded. The maximum radial displacements during lamination from the edge reach 3 mm, which is one and a half times higher than for an undamaged shell. Axial stresses are maximal from the action of inertial forces during acceleration. Its redistribution over the layers is significantly greater for the edge lamination, for which the maximum values increase almost two times concerning the undamaged shell, which determines this type of lamination as more dangerous.

Technology of Managing Reactions of Biological Objects at Anthropogenically Transformed Territories

Solving the problem of increasing plant resistance, the development of environmentally-friendly technologies is particularly important, which also contribute to the reduction of resource costs for production and load on the environment. The research results indicate a positive effect from the treatment of plants and seeds with electrochemically activated (ECA) water, electric fields, and impulse pressure (IP). Pre-sowing treatment of seeds with ECA water increases the germination rate and seed germination energy, improves the development of plants, improves morphological parameters, etc. The reactions of economically dangerous pests and causative agents of infectious plant diseases to the use of ECA water are identified. The combination of pre-sowing seed treatment with the treatment of vegetative plants provides the highest possible result.