The subject matter of the article is the processes of virtual localization of near shape parts during adaptive machining. The aim is to develop an effective method for finding the starting location of a CAD model of a part with virtual localization inside a point cloud obtained by laser scanning of a workpiece. The task is to formalize the procedure for starting positioning of the part model as the first stage of the virtual localization process. The second stage for final localization proposed to use iterative algorithms with the objective function which is sensitive to the intersection of the surface parts and the workpiece. In solving the problem the starting position used tools available in today's CAD packages and 3D scanning tools. The methods used are the methods of matrix algebra, in particular, the methods for finding the main central moments of inertia of three-dimensional objects based on the tensor of inertia. The following results were obtained. When calculating the inertia tensor components is proposed to use three-dimensional scanning data of workpiece and geometrical data of part obtained from the CAD system. The result is an algorithm starting location of CAD model in the virtual localization, which in the case of blanks with oversize close to uniform can provide enough current location parts for adaptive machining tasks. It is shown that to minimize computational errors and to ensure satisfactory accuracy of localization proposed algorithm can require several iterations of the shift vector search model. Conclusions. The scientific novelty of the results obtained is as follows: in contrast to the previously used approaches, when solving the problem of virtual localization for the starting position, using the condition of coincidence of the centers of the weight of thin shells coinciding with the surfaces of the workpiece and the part, it was proposed to additionally ensure the alignment of the main central axes of inertia of these shells, which, in the case of near shape blanks, provides a positioning accuracy that may not require additional iterative procedures.
The subject of the study is methods for determining vessel volume with complex shapes. The aim of the study is a development and scientifically substantiate of a method for fast measurement of an internal cavity volume of a vessel having a complex geometric shape in a gaseous medium based on supercritical outflow. The task of the study is the development of a method for calculating the volumes of the gas path components for the previously proposed generator of gas mixtures, which based on the supercritical outflow from intermediate tanks with constant volume, and confirmation of the proposed method capabilities using a simulation of the volume measurement process by the same method. The following results were obtained. It is proposed the method for fast measurement of vessel volume with complex shape based on supercritical flow through nozzles with the predetermined flow rate and dynamic measured pressure. The range of measurement time is substantiated for which, on the one hand, the conditions for suppressing transient processes in the measured vessels after the beginning of the supercritical outflow of the process gas are satisfied, and on the other hand, the conditions for adiabatic outflow are provided. According to the simulation of measuring the volume of a complex-shaped vessel using the proposed method, the accuracy of determining the volume of the vessel was 0.0625% in relation to the CAD system data. To use the proposed method in practice, the measuring equipment should include a reference vessel, and the measurements themselves should be carried out in two stages, using the same gas for filling in both cases. In this case, at the first stage, according to the results of the control measurement when it expires from the reference vessel, the value of the flow coefficient is specified, and at the second stage, when it expires from the measured vessel, the required target volume is determined. The process of direct volume measurement, in this case, lasts up to 1 second, the accuracy of volume determination is expected to be 0.1%.
The subject of research is a gas-dynamic process of mixture formation with a given component mass fraction during overflow through the mixer nozzles in the mixture generation system. The aim of the study is the scientific and experimental evaluation of the mixer technical solutions to ensure the accuracy and homogeneity of the gas mixture. The current work conducts numerical study on the flow of a gas flow through the mixer nozzles of the mixture generation system, ensuring its stoichiometric component composition and homogeneity. The problem is solved by developing adequate mathematical models of gas-dynamic flow and analyzing the results of numerical simulations. The following results were obtained. A mixer with the nozzles in the mixture generation system has been created and a technical solution for its design has been scientifically substantiated. The areas of flow sections of mixer nozzles are experimentally established. A mathematical model of generating a mixture with a given component mass fraction was developed and a series of numerical experiments was conducted to study its overflow through the mixer. A 3D simulation was conducted using ANSYS CFX software. The stationary formulation of the problem is applied. In the nozzles of closed overflow of the mixer, the heat exchange of the gas flow with the walls is taken into account by solving a separate problem and determining the corresponding heat transfer coefficients. At the inputs to the mixer, the ratio of the initial pressure of the components of the mixture is determined, which ensures its stoichiometric composition. The fields of the gas flow velocities, the mass flow rate of the components of the gas mixture through the mixer, and pressure and temperature fields are obtained. Based on the simulation results, it was found that the design of the developed mixer ensures the creation of a gas mixture with a homogeneity of at least 3%. With a constant pressure ratio of the mixture components to the mixer inlet, the gas mixturedosing accuracy can be achieved at least 1%.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.