AbstractThe study results of the possibilities of fulfilling the optimization task of placing (packing) 3D-models of products in build space using a genetic algorithm are presented. The proposed algorithm for the location of 3D models of products in build space allows to reduce the time of technological preparation and increase the productivity of the process and the efficiency of using the additive machine. The efficiency of use can be ensured by reducing the relative share of the unused volume of the layered build space, which is relevant for SLA, SLM, SLS, and other methods of additive technologies. A step-by-step determination of the free space for placing the next product is proposed, starting from the lower level of the machine platform. An increase in the efficiency of the proposed algorithm was provided by preliminary sorting of 3D models of products according to specified criteria. The rational values of the genetic algorithm parameters have been determined using the example of the placement of a group of industrial products with a rather complex design. Evaluation of the effectiveness of the proposed algorithm for placing 3D models was carried out based on a comparative analysis of the number of layers and the efficiency of filling the build space (relative volume of its use) for the manufacture of a group of 3D models of industrial products. The study was carried out using the developed system “Technological preparation of materialization of complex products by additive technologies”.KeywordsAdditive manufacturingTechnology planningTriangulated modelPackingGenetic algorithm

AbstractThe paper presents the results of a study into the processing and physical and mechanical properties of mixtures based on liquid glass (LG) with furfuryl oxypropyl cyclocarbonate (FOPCC) for chromite compounds. The patterns of the interaction between triethanolamine-modified liquid glass with furfuryl oxypropyl cyclocarbonate and chromite sand were established. Parameters such as compressive strength, flexural strength, and tensile strength were studied, which were determined using standard methods. Mathematical models of the properties of mixtures on chromite sand with liquid glass and FOPCC were developed based on the planned experiment. Mathematical models represent a system of equations linking the compressive strength, tensile strength, and flexural strength of the mixture with controlled variables of a technological nature for which the contents of liquid glass, FOPCC, and triethanolamine were chosen. Based on the data obtained, it was found that the flexural strength, tensile strength, and compressive strength increase with an increase in the content of LG and FOPCC. The compositions of cold-hardening mixtures on chromite sand were optimized, allowing obtaining high-quality cores with high strength properties. It has been established that FOPCC is a material that has a double effect; it hardens the mixture during preparation and softens it after pouring metal during decoring. The optimum binder content is 4,5 to 5,5%, and the optimum hardener content is 0.4 to 0,6%. A technological procedure has been developed to prepare chromite sand-based CHM. As a result, the surface quality was improved, and the burn-on on the castings was reduced.KeywordsChromite sandLiquid glassTriethanolamineOptimizationMechanical propertiesStrength properties

The work investigates the physical, mechanical, and technological properties of mixtures to manufacture cores in a foundry. The filler is technical salt, the binder is an aqueous solution of sodium silicate, and the hardener is a solution based on propylene carbonate on a silicate basis. These rods are used to make internal surfaces in thin-walled castings. The work proposes a new method of manufacturing cores based on cold-hardening mixtures (CHM), which harden at room temperature. The planned experiment was chosen as the basis for modeling the properties of the mixture. The following parameters were chosen as optimization parameters: compressive strength, friability, and durability. According to the developed mathematical models, the mixture composition was optimized. The optimum binder content is 4.0 to 6.0%, and the hardener content is 0.3 to 0.4%. A technological process of preparing CHM for readily removable salt cores has been developed. As a result, the surface quality of the internal surfaces of castings improved. The cycle of core production was reduced, and the casting cleaning costs were reduced due to the elimination of the decoring process; environmental safety of the technological process was provided to the use of non-toxic materials.

The aim of the research is to develop a technology for the preparation and drying of moulds and cores based on sand-plaster mixtures, which allows obtaining exact details of a complex form of required quality. The levels of the basic properties of sand-plaster moulds and cores – strength, durability, gas permeability, friability – making up the quality of a casting have been determined in the research paper. Mathematical patterns of the properties of the moulding mixture on the basis of plaster have been developed. The composition of the mixture satisfying the requirements of the quality of castings has been determined experimentally with the use of multifactorial optimization methods. The research studies of the process of plaster mould drying have been done, and the technological process of mould drying has been developed using a microwave machine. Manufactured cores and moulds have not only possessed high strength properties but also have allowed escaping from such defects as gas holes in die castings (castings). The proposed mode of drying can reduce the drying time by 40–50% and reduce costs by 30–70% depending on the size of the core.

The paper presents the mechanism of solidifying mixtures on a soluble glass base with complex ethereos solidifiers, such as ethylene glycol acetates, triacetate with furfuryl alcohol and furfuryl oxypropyl cyclocarbonates. The castings comparative manufacturing technology based on cold-solidifying mixtures on soluble glass with these solidifiers is given. To experimentally determine and establish the regularities of increasing of the compressive strength of the mixture using ether hardeners and technological additives: ethylene glycol monoacetate (EGMA), ethylene glycol diacetate (EGDA), ethyl silicate (ES-40), ethylene glycol (EG), tetraethoxysilane (TEOS), triacetate with furfuryl alcohol (TAC with FA) and furfuryl oxypropyl cyclocarbonates are established. The basic physical and mechanical properties of mixtures with these additives, such as compressive strength, survivability, friability, gas permeability, and knocking-out ability were determined by standard methods according to the state standards (GOST). The most effective ethereos solidifiers, which allow obtaining high-quality mixtures on soluble glass with the highest strength properties, were determined.

Future power systems are expected being operated under increasingly stressed conditions and increased uncertainties. The future single European electricity market will entail higher energy trading volumes, for which augmented use of HVDCs is expected to facilitate cross-border bulk power transfers. In traditional power systems a change in demand at one point of network is reflected throughout the system by a change in frequency. However, significant interconnections using HVDC will affect the classical ability of traditional AC system to overcome “together” frequency deviations which may result in a cascading failure and system collapse. Future HVDC systems shall fulfil requirements referring to frequency stability and also intervening in the frequency quality. As consequence HVDC systems will operate providing ancillary service depends on the framework of service. This paper proposes a flexible Automatic Generation Control (AGC) system for embedded HVDC links in order to provide frequency sensitive response and control power interchange.

Within the framework of the shell theory, we develop a mathematical model that describes the axisymmetric stress-strain states of multilayer annular welded joints of the pipes under the action of residual incompatible strains localized near the weld. The residual stresses are evaluated on the basis of the solutions of inverse problems of the shell theory with intrinsic stresses by using the experimental data obtained by the method of speckle interferometry. We created an experimental installation and special software that enable one to evaluate and reproduce residual stresses in the zone of multilayer welded joint. The plots of circumferential residual stresses as functions of the distance from the axis of the weld are presented.

Transscleral laser (YAG:Nd, (lambda) equals 1.06 micrometers ) for ophthalmology has been developed and assembled for pulse laser transscleral treatment of eyes structures by means of adaptive optical fibers tip. `Adaptivity' means that we have used some exactly defined levels of optical fiber tip contact pressure to eyes surface to replace intertissues liquid. Such kind of fiber tip permit us apply more laser irradiation power due to decreasing of laser beam absorption in the liquid of eyes tissue. The different laser power levels, pulse duration, exposure time have been considered in correspondence with many types of adaptive fiber optical tips to optimize both transscleral coagulation and cutting process. To exactly determine the dependencies of laser irradiation spatial distributions behind sclera via contact tips pressure levels we have used as a adequate enough model He-Ne laser and eyes tissue samples. Laser system consist of power supply, control unit, laser head with cooling system, adapter for different kind of optical fibers tips. All of the above has been mounted as one case.