Principles for modelling technological processes investigation into the strength and durability of automatic coupler sa‐3 in railway carriages

The paper presents the durability analysis of the automatic coupler in railway carriages. The loading of the automatic coupler predetermined by the weight of a train, train speed and railway relief is a time‐dependent variable. The finite element method was used for stress‐strain state calculation taking into account acting forces. In order to reduce stress concentration, the geometry of the automatic coupler's body was modified. Modelling results for different rounded radii demonstrated it was possible to reduce stress concentration up to 34%. Under maximum forces, plastic strain occurs in the automatic coupler's body. The calculation of strain and stress state in the body of the automatic coupler shows it is under a static, low and high cycle loading. Therefore, to calculate the durability of the automatic coupler, the dependencies for low cycle nonstationary stress limited loading has been proposed evaluating low cycle quasistatic and fatigue damages. In order to evaluate high cycle fatigue damage, a linear law for the summation of loading cycles has been suggested. For low cycle damage evaluation, the calculation method for the summation of fatigue and quasi‐static damages created at one loading cycle taking into account loading level and neglecting the sequence of cycles has been put forward. Thus, to calculate the automatic coupler for each specific case, it is necessary to determine the number of loading cycles at each loading level and to evaluate durability considering dependencies presented in this paper. First published online: 27 Oct 201

Producing efficiency of enterprises

Straipsnyje nagrinėjama gamybos efektyvumo nustatymo ir vertinimo prielaidos gamybos įmonėsė. Sistemiškai analizuojama apribojimų teorijos (TOC – Theory of Constraints) taikymas gamyboje, siekiant efektyvesnės gamybos, pateikiama LEAN irankių diegimo gamybinėje įmonėje svarba, atkreipiamas dėmesys į gamybinės veiklos matavimą, naudojant pagrindinius valdymo rodiklius (KPI – Key Perfomance Indicators). Teorinėje straipsnio dalyje yra analizuojama Apribojimų teorijos (TOC) atsiradimo istorija, atskleidžiami rodikliai, kurie yra būtini bet kurios organizacijos ekonominiams rodikliams nustatyti. Taip pat pateikiami pagrindiniai LEAN principai. Apžvelgiama subalansuotų rodiklių sistema bei esminių veiklos rodiklių paskirtis. Straipsnio tiriamojoje dalyje pateikiamas tyrimo aprašymas apie LEAN įrankių naudingumą įmonės veikloje. Straispnyje yra keliamas probleminis klausimas – kam yra reikalingas gamybos efektyvumas ir kaip jį apskaičiuoti bei nustatyti.The article deals with assumptions for determining and evaluating production efficiency production company. The application of the theory of constraints (TOC) in production for more efficient production is systematically analyzed, the importance of LEAN tools implementation in a manufacturing company is presented, attention is paid to the measurement of production activities using key performance indicators (KPI). The theoretical part of the article analyzes the history of the emergence of the Theory of Constraints (TOC), reveals the indicators that are necessary to determine the economic performance of any organization. The basic principles of LEAN are also presented. The system of balanced indicators and the purpose of key performance indicators are reviewed. The research part of the article provides a description of the research on the usefulness of LEAN tools in the company's activities. The article raises a problematic question - who needs production efficiency and how to calculate and determine it. The aim of the article is to reveal the essence of the LEAN system and analyze its benefits in the organization. Objectives of the article: 1) To review the application of the theory of constraints in production and to reveal its benefits for more efficient production; 3) To present the benefits of KPI of production activity measurement tools in the evaluation of the company's activity; 4) Evaluate the benefits of evaluating the company's production efficiency in the organization

Improved Methodology for Power Transformer Loss Evaluation: Algorithm Refinement and Resonance Risk Analysis

The decline in power quality within electrical networks is adversely impacting the energy efficiency and safety of transmission elements. The growing prevalence of power electronics has elevated harmonic levels in the grid to an extent where their significance cannot be overlooked. Additionally, the increasing integration of renewable energy sources introduces heightened fluctuations, rendering the prediction and simulation of working modes more challenging. This paper presents an improved algorithm for calculating power transformer losses attributed to harmonics, with a comprehensive validation against simulation results obtained from the Power Factory application and real-world measurements. The advantages of the algorithm are that all evaluations are performed in real-time based on single-point measurements, and the algorithm was easy to implement in a Programmable Logic Controller (PLC). This allows us to receive the exchange of information to energy monitoring systems (EMSs) or with Power factor Correction Units (PFCUs) and control it. To facilitate a more intuitive understanding and visualization of potential hazardous scenarios related to resonance, an extra Dijkstra algorithm was implemented. This augmentation enables the identification of conditions, wherein certain branches exhibit lower resistance than the grid connection point, indicating a heightened risk of resonance and the presence of highly distorted currents. Recognizing that monitoring alone does not inherently contribute to increased energy efficiency, the algorithm was further expanded to assess transformer losses across a spectrum of Power Factory Correction Units power levels. Additionally, a command from a PLC to a PFCU can now be initiated to change the capacitance level and near-resonance working mode. These advancements collectively contribute to a more robust and versatile methodology for evaluating power transformer losses, offering enhanced accuracy and the ability to visualize potentially critical resonance scenarios