DEVELOPMENT OF A NATIONAL STANDARD FOR TESTING METHODS FOR SELF-COMPACTING CONCRETE MIXTURE

In world practice, self-compacting concrete is increasingly used due to its unique properties and advantages. Self-compacting concrete mixtures have high ductility, better fluidity, high density with low water content due to the use of special effective mineral and chemical additives that provide high performance for concrete. The rheological properties of SCC differ significantly from those of conventional concrete. In this regard, when designing the composition of concrete and controlling its quality in laboratory and production conditions, several methods for controlling the quality of a self-compacting concrete mixture were created. The purpose of this standard was to create a single regulatory document regulating the assessment of the quality of a self-compacting concrete mixture. Concrete from a self-compacting mixture can be used for underground and hydrotechnical construction for the erection of structures of large length, complex geometric shape and densely reinforced structures.

Technological assurance of the quality of processing of products from aluminum alloys with a complex geometric shape using magnetic abrasive processing

In the presented article, the issue of the implementation of magnetic abrasive processing is considered in order to ensure the quality of surfaces of complex shapes of parts made of corrosion-resistant aluminum alloys. The implementation was carried out through theoretical and experimental research. In a theoretical study, the features of processing corrosion-resistant aluminum alloys, existing and possible schemes for magnetic-abrasive processing of surfaces of complex geometric shapes, including a combination of various working movements of the workpiece and pole pieces, are considered. In an experimental study, the dependence of the quality of the processed surface (roughness) on the size of the working gap between the workpiece and the working pole was determined. The result of the research is the determination of the optimal treatment schemes for surfaces with a complex geometric shape, as well as the derived exponential dependence of the change in surface roughness on the size of the working gap.

Development of the Skin of the Surface of the Tunnel Part of the Ship's Hull

In modern shipbuilding, extremely high requirements are imposed on the speed of the vessel. The material costs for ensuring the seaworthiness of modern transport vessels account for about half of the constant operating costs. Experimental materials confirm that the geometry of the surface of the tunnel part of the vessel's hull has a significant effect on its propulsive coefficient. Improving the shape of the tunnel part allows you to change the hydrodynamic pressure and reduce the negative effect of the flow formed when the vessel moves forward. At the same time, the complex geometric shape of this part of the hull significantly complicates the preparation of maps of its cutting and, as a result, its production, since it is a set of complex surfaces of double curvature. This article describes a practical approach to solving the problem of constructing a sheet cutting map. For modeling a three-dimensional model and controlling the shape of the surface, the capabilities of the Rhinoceros 6 system are presented. The results are presented as the deviation in the area of the deployable and non-deployable surfaces.

AUTOCLAVE MOLDING OF LOWER WING PANEL SKINS FROM 1441 ALLOY PLATES

The paper considers the main features of the process of autoclave molding of complex geometric shape parts from plates of medium-strength alloy 1441, combined with aging to the state of T11 heat treatment. The article provides the results of modeling of the autoclave molding process of skin fragments of the lower wing panel made of 1441 alloy, and the temperature-time parameters of this process determined during the research. The paper generalizes the results of examination of mechanical and corrosion characteristics of the fragments of the lower wing panel. The possibility of obtaining high accuracy of geometry of complex shaped elements while ensuring uniformity of characteristics in the entire area of parts is shown.

Application of Algorithms for Placement of Orthogonal Polyhedrons for Solving the Problems of Packing Objects of Complex Geometric Shape

The article is devoted to the development and research of algorithms for placing objects of complex geometric shapes. To solve the placement problem is proposed an approach which consists in transforming the shape of all objects and further application of the developed algorithm for placing orthogonal polyhedrons of arbitrary dimension to the resulting transformed objects. In the process of transforming the shape of the objects being placed, they are initially voxelized, after which the developed decomposition algorithm is applied to the resulting voxelized objects, which provides the formation of orthogonal polyhedrons consisting of the largest possible orthogonal objects. The proposed model of potential containers is used to describe the free space of containers as a set of orthogonal areas. The developed algorithm for the placement of orthogonal polyhedrons provides a fast solution to NP-hard problems of placing objects of complex geometric shapes without resorting to the use of time-consuming nonlinear programming methods. Examples of the practical application of the developed algorithms for modeling the dense layout of parts of complex geometric shapes on the platform of a 3D printer are given.

Solving the Problem of Packing Objects of Complex Geometric Shape into a Container of Arbitrary Dimension

The article is devoted to algorithms developed for solving the problem of placement orthogonal polyhedrons of arbitrary dimension into a container. To describe all free areas of a container of complex geometric shape is applied the developed model of potential containers. Algorithms for constructing orthogonal polyhedrons and their subsequent placement are presented. The decomposition algorithm intended to reduce the number of orthogonal objects forming an orthogonal polyhedron is described in detail. The proposed placement algorithm is based on the application of intersection operations to obtain the areas of permissible placement of each considered object of complex geometric shape. Examples of packing sets of orthogonal polyhedrons and voxelized objects into containers of various geometric shapes are given. The effectiveness of application of all proposed algorithms is presented on an example of solving practical problems of rational placement of objects produced by 3D printing technology. The achieved layouts exceed the results obtained by the Sinter module of the software Materialise Magics both in speed and density.