Izvestiya MGTU MAMI

BACKGROUND: When manufacturing monoblock hydraulic assemblies using additive technologies, their complex internal channels often cannot be post-processed. The roughness of such surfaces in the as-built state can reach significant values (up to 300 μm or more), which has a critical effect on the hydrodynamic properties. This requires accurate prediction of the effect of process roughness on the flow.

AIM: assessment of the applicability of classical calculation methods to elements with roughness characteristic of additive manufacturing, and identification of directions for their subsequent modification.

METHODS: Numerical simulation was performed in the Simcenter STAR-CCM+ software package. The study was carried out for various values of equivalent sand roughness (0–300 µm). To ensure high resolution of the physical boundary layer and the correct use of wall functions, the parameters of the prismatic layers of the computational grid were varied (total thickness in the range of 0.75–20 mm). The results were verified by comparing numerical simulation data with analytical calculations based on the Darcy–Weisbach equation and classical methods for estimating local resistance coefficients.

RESULTS: It was found that an increase in surface roughness leads to an increase in hydraulic losses in all studied elements. It is shown that the influence of the prismatic layer thickness on the loss value is nonlinear and has a limiting character for the elbow and straight pipe, while no such trend was found for the diffuser. Visualization of the velocity fields confirmed a significant change in the flow structure near the rough walls.

CONCLUSION: Computational fluid dynamics revealed a significant impact of additive manufacturing-specific roughness on pressure loss and flow structure in the studied elements. Comparison with classical calculation methods allowed assessing their applicability limits and identifying directions for subsequent modification of empirical correlations. Thus, the aim of the study has been achieved.

BACKGROUND: Development of micro jet engine is associated with scaling problems, leading to a sharp decrease in the Reynolds number and an increase in the influence of the roughness of the internal surfaces of the engine elements on hydraulic losses and overall efficiency. The selection of technological modes of additive manufacturing by powder bed fusion of a complex-integrated structure of a micro jet engine makes it possible to analyze the nature of surface roughness changes and to determine the optimal manufacturing modes.

AIM: Study of the effect of technological modes of powder bed fusion on the roughness of the resulting surfaces and development of a method for selecting printing parameters to minimize the hydraulic resistance in the flow part of a complex-integrated structure of a micro jet engine.

METHODS: Experiments on the production of samples made of the heat-resistant nickel alloy 08KhN53BMTYu have been carried out. The ranges of volumetric energy density and layer thickness were studied. The roughness was measured, a theoretical analysis of hydraulic losses in a combustion chamber was conducted.

RESULTS: The dependences of the surface roughness on the volumetric energy density and the layer thickness are found, and the lowest roughness values are determined. Based on the data obtained, diagrams linking the printing mode with critical Reynolds numbers, at which roughness begins to affect the flow, and the calculated coefficient of friction resistance for channels of various equivalent diameters, are built.

CONCLUSION: A methodological approach to the selection of technological modes of powder bed fusion for additive manufacturing of a complex-integrated structure of a micro jet engine has been developed. The obtained dependences make it possible to evaluate the effect of printing parameters on the roughness, which is necessary to optimize the process of additive manufacturing of complex-profile micro jet engine elements.

BACKGROUND: The continuous development of anti-tank weapons requires the search for new ways to improve the protective properties of tracked vehicles. Researchers identify an increase in the mobility of equipment as one of these methods. It is assumed that an increase in mobility should have a positive effect on the protective properties of the object. The approaches proposed by the researchers are based on the use of protective acceleration and increased maneuverability of machines. As a result of these arguments, recommendations are given for accelerating the vehicle in order to move it away from the line of sight and the firing plane, and the value of the velocity that the vehicles should develop is indicated. However, these recommendations are given without considering performance abilities of a tracked vehicle. In this regard, there is a need to develop the method that makes it possible to link the traction capabilities of a tracked vehicle with its security.

AIM: Assessment of the impact of traction capabilities of a tracked vehicle on its protection, taking into account road and dirt conditions and design features.

METHODS: The paper analyzes well-known approaches and recommendations for improving the protective properties of tracked vehicles. Based on the modern theory of motion, the possibilities of applying these approaches are considered, taking into account the limitations on grip properties and traction capabilities of tracked vehicles. The calculations were performed using the example of foreign samples of high-speed tracked vehicles, according to the technical specifications presented in open sources.

RESULTS: In this study, the method to determine the possibilities of using protective acceleration against the main unguided anti-tank weapons has been developed. The characteristics that a tracked vehicle must possess to achieve a protective acceleration have been determined and the limits within which they can be effective have been established. The factors preventing the possibility of increasing acceleration values are identified, and recommendations for their elimination are given.

CONCLUSION: The application of the developed method makes it possible to determine the required characteristics of tracked vehicles at the design stage, to assess the feasibility of using protective acceleration depending on the type of ammunition and firing range. Recommendations are given to improve the traction capabilities of promising models of machinery. The findings can be partially extended to wheeled vehicles.

BACKGROUND: The relevance of the study is driven by the rapid development of the market for electric special-purpose vehicles, designed for utility services tasks in particular. In the context of tightening requirements for energy efficiency and performance, a key challenge is optimizing the performance of the most energy-intensive systems. The scientific problem lies in the lack of representative data on the performance of the traction battery thermal management system under real-world operating conditions characterized by high-amplitude loads caused by hydraulic equipment. The first step in solving this problem is to obtain the aforementioned data using telematics monitoring methods for subsequent analysis and identification of objective patterns.

AIM: Identification of quantitative relationships between the load profiles of an electric compact loader and the operating parameters of its traction battery thermal management system under real-world operating conditions.

METHODS: The study employed the method of telematics operational data logging. Field experiments involved operation of the loader in typical scenarios with hydraulic equipment, such as a road brush. Data on the power consumption of the traction electric motors and the hydraulic system electric motor, temperature sensors of the battery thermal management system, heater power, and battery current were collected using telematics.

RESULTS: Data on the real-world operation of the compact loader in winter conditions, obtained through telematics data logging, are presented. Relationships and patterns were established (e.g., the correlation between load current and heating power, the influence of ambient temperature). The obtained results reveal the actual behavior of the thermal management system during real-world winter operation.

CONCLUSION: The acquired data will make upcoming optimization of the thermal management system’s control algorithms possible, leading to reduced energy consumption. The results form the basis for developing a predictive system that reduces downtime and maintenance costs compared to diagnostics performed after a fault occurs.

BACKGROUND: Laser marking technology, based on the interaction of laser radiation with a substance for applying detailed images and inscriptions to various surfaces, is specified by excellent image reproduction accuracy, low power consumption and high processing rate compared to conventional methods.

Effective control of laser marking requires accurate calibration and tuning of the laser system to match surface material characteristics of treated objects. The most promising solution is introducing computer vision systems, enabling high accuracy, speed and scalability for implementation in modern production. Computer vision systems application in laser marking for quality and object orientation monitoring remains underdeveloped. This paper presents computer vision systems integration into a laser marking device through the SharpMark marker tuning algorithm.

AIM: Development of the software algorithm integrated with the computer vision system to automate the process of setting up the SharpMark laser facility for chasing and marking. The tasks solved in this study are aimed at improving image quality by optimizing the algorithm for tuning the laser system.

METHODS: The OpenCV computer vision library was used as the basis for the development of the computer vision system. The ArUco marks were used for accurate identification of the position of the marking object and calibration of the laser marker. The proposed algorithm is implemented in several sequential stages, including: detection of objects in the image, correction of image distortion (Undistort), perspective transformation (WarpPerspective) to compensate for distortions, contour extraction (FindContours) and widening of areas of interest (InflatePaths). The laser system is controlled by means of exchange of data and control commands.

RESULTS: The algorithm that determines object positions automatically and corrects contours for lens distortion by improving camera calibration accuracy has been developed. The calibration method, which defines the camera’s pixel-to-millimeter ratio, enables image linking to marker coordinates for precise marking with an accuracy of up to 0.1mm over a 10 cm distance. The algorithm automatically marks multiple objects within the working area.

CONCLUSION: The practical value of this study lies in enhancing SharpMark’s efficiency by means of optimization of the calibration algorithm. The proposed algorithm is applicable to similar computer vision-equipped laser marking systems and to any automated pattern recognition systems based on computer vision systems.