Volume 20, Issue 3, 2025/Journal Proceedings in Manufacturing Systems

Abstract: The sustainability of the manufacturing processes requires new concepts regarding the choice of manufacturing technologies based on performance criteria, economic and environmental criteria, as well as legislative limitations. The research presented in this paper is concluded with a comprehensive theoretical formulation with practical applicability, which justifies the decisions made as for the sustainability of manufacturing systems. Thus, the paper contributes to the implementation of more energy-efficient technologies and the adoption of circular solutions (waste reduction, recycling, reuse, saving material and energy resources, energy conversions etc.). Using mathematical modeling, a multi-criteria equation is formulated with a conveniently chosen system of criteria, to assess the sustainability of manufacturing processes. This is meant to create a general mathematical model, capable of incorporating the accepted criteria, in the context of imposed technical conditions, allowing access to advantageous financing within the green transition.

Key words: sustainability, mathematical model, circular solutions, multi-criteria equation.

pp. 91-96 View full text

Lattice structures for material efficiency: a comparative finite element analysis

Patricia Isabela BRĂILEANU^1,*, Tiberiu Gabriel DOBRESCU², Nicoleta Elisabeta PASCU³, Ionuț Cristian PEREDERIC⁴, Gabriel George GEAMBAȘU⁵

¹⁾ Associate Prof., PhD, Department of Robots and Production Systems, National University of Science and Technology Politehnica Bucharest, Romania

²⁾ Prof., PhD, Robots and Production Systems Dep., National University of Science and Technology POLITEHNICA Bucharest, Romania

³⁾ Prof., PhD, Robots and Production Systems Dep., National University of Science and Technology POLITEHNICA Bucharest, Romania

⁴⁾ Assistant Prof., PhD Student, Robots and Production Systems Dep., National University of Science and Technology POLITEHNICA Bucharest, Romania

⁵⁾ Assistant Prof., PhD Student, Engineering Graphics and Industrial Design Dep., National University of Science and Technology POLITEHNICA Bucharest, Romania

Abstract: This study explores the use of lattice structures for optimizing material efficiency using a cubic part as an example. The main goal of the research is to evaluate the impact of these structures on material consumption, comparing them with the solid structure of the part, using static FEA (Finite Element Analysis) simulations. By performing comparative simulations, the mechanical performance and behavior of lattice structures under certain loading conditions are analyzed. Therefore, this study shows the significant potential of lattice structures in reducing the weight and material required, while maintaining structural integrity in some cases, and provides detailed understanding of the advantages and limitations of using these structures, ensuring a starting point for specialists who want to optimize mechanical parts in various application areas.

Keywords: lattice structures, Finite Element Analysis (FEA), material efficiency, additive manufacturing.

pp. 97-102 View full text

The effect of microalloying elements on the properties of martensitic stainless steels

Adrian Emanuel ONICI^1,*, Victor GEANTĂ¹, Radu ȘTEFĂNOIU¹, Ionelia VOICULESCU²

¹⁾ Eng., PhD Student, Engineering and Management of Metallic Materials Processing Dep., National University of Science and Technology POLITEHNICA Bucharest, Romania

¹⁾ Prof., PhD, Engineering and Management of Metallic Materials Processing Dep., National University of Science and Technology POLITEHNICA Bucharest, Romania

²⁾ Prof., PhD, Quality Engineering and Industrial Technologies Dep., National University of Science and Technology POLITEHNICA Bucharest, Romania

Abstract: The present work investigates the influence of microalloying with yttrium, titanium, hafnium, and zirconium on the properties of precipitation-hardened martensitic stainless steel 17-4PH. Twenty laboratory heats were designed, each weighing 25 g, with microalloying additions ranging from 1 to 5 wt.% calculated and prepared using analytical balance accuracy. The charges were melted and refined in a vacuum arc remelting (VAR) installation, ensuring controlled solidification and minimized contamination. The chemical composition of the obtained alloys was verified using X-ray fluorescence (XRF) analysis to confirm the targeted additions and homogeneity of the melts. Microstructural characterization was carried out by optical and scanning electron microscopy, while mechanical behavior was evaluated through Vickers microhardness measurements. The results revealed that the addition of yttrium and titanium led to grain refinement and the formation of stable oxides and carbides, which contributed to increased hardness and improved microstructural homogeneity. Hafnium promoted the precipitation of secondary phases, enhancing hardness but with a tendency to increase brittleness when added in higher amounts. Zirconium improved the cleanliness of the steel by acting as a strong deoxidizer, leading to more uniform microstructures. Overall, the microalloyed steels exhibited significant variations in microhardness values depending on the type and concentration of the added element, indicating that precise control of microalloying content is critical for optimizing the performance of 17-4PH stainless steels. These findings contribute to the development of advanced high-performance martensitic stainless steels tailored for demanding structural applications.

Keywords: 17-4PH stainless steel, microalloying, vacuum arc remelting ‒ VAR, XRF analysis, microhardness, microstructure.

pp. 103-109 View full text

AS-interface: modern communication protocol in industrial safety systems

Ştefan-Claudiu MUREŞAN^1,*, Adrian-Florin NICOLESCU²

¹⁾ Eng., Dep. of Robots and Manufacturing Systems, National University of Science and Technology POLITEHNICA Bucharest

²⁾ Prof., PhD, Dep. of Robots and Manufacturing Systems, National University of Science and Technology POLITEHNICA Bucharest

Abstract: With the development of industrial automation solutions and the level of automation required in the manufacturing facilities there has been a challenge in offering a well-rounded safety system, capable of dealing with all the possible safety-related scenarios that can occur in a day-to-day industrial environment. More than that, a complex safety system implies high costs with raw materials such as cables, wire ducting, connection points and manual labor, which lead to deficiencies in the project-budget with little to no direct revenue in exchange. This study focuses on developing a test-stand for a modern approach to the problem of cost and time saving in the process of integrating the safety system, maintaining the safety standards required by international associations. The results of this study can represent the beginning point for further large-scale integration in industrial fields of such solutions, leading to a decrease in budge funds reserves.

Key words: AS-Interface, Safety, Industrial Automation, Communication, Control Systems.

pp. 111-116 View full text

Corrosion effects on pipes made of Cr-Mo steel from central heating systems

Vasile IORDACHESCU^1,*, Ion Mihai VASILE², Ionelia VOICULESCU³

¹⁾ Eng., PhD Student, Quality Engineering and Industrial Technology Dep., National University of Science and Technology POLITEHNICA Bucharest, Romania

²⁾ Lecturer, PhD, Quality Engineering and Industrial Technologies Dep., National University of Science and Technology POLITEHNICA Bucharest, Romania

³⁾ Prof., PhD, Quality Engineering and Industrial Technologies Dep., National University of Science and Technology POLITEHNICA Bucharest, Romania

Abstract: The paper refers to the analysis of the factors contributing to the occurrence of corrosion, one of the main degradation mechanisms affecting the reliability and service life of Cr-Mo steel pipes used in thermal energy production facilities. These steels, appreciated for their resistance to high temperatures and good creep behavior, are often exposed to aggressive environments characterized by high temperature (160-450^oC) and pressure (140-200 bar), as well as by the presence of oxygen, water vapor and corrosive compounds, such as sulfates and chlorides. In most cases the combined action of these factors leads to the formation of oxide layers, the occurrence of pitting corrosion and the thinning of the pipe walls, which can compromise structural integrity and operational safety. The paper investigates the aspect and amplitude of corrosive attacks observed in Cr-Mo steel pipes in service, under various working conditions. Pipe samples taken from decommissioned district heating installations, which had operated for long periods of time ranging from 27 to 41 years, were examined in cross-section, measuring the thicknesses of the oxidized layers and the microhardness. It was found that the thickness of the oxide crusts depends on the alloy class of the steels, the nature of the working environment and the operating temperature.

Key words: corrosion, heat-resistant steels, microstructure, microhardness._Hlk116987430

pp. 117-128 View full text

Matlab simulation of ESP32 integration with a Raspberry PI soft-PLC via MQTT

Adrian MAROȘAN^1,*, Claudia Emilia GÎRJOB², Anca Lucia CHICEA³, Cristina Maria BIRIȘ⁴, Alexandru BÂRSAN⁵, Paula DRAȘOVEAN⁶, Timotei MORARIU⁷

¹⁾ PhD, Lecturer., Machines and Industrial Equipment, University "Lucian Blaga" of Sibiu, Faculty of Engineering, Romania

²⁾ PhD, Conf., Machines and Industrial Equipment, University "Lucian Blaga" of Sibiu, Faculty of Engineering, Romania

³⁾ PhD, Conf., Machines and Industrial Equipment, University "Lucian Blaga" of Sibiu, Faculty of Engineering, Romania

⁴⁾ PhD, Conf., Machines and Industrial Equipment, University "Lucian Blaga" of Sibiu, Faculty of Engineering, Romania

⁵⁾ PhD, Lecturer., Machines and Industrial Equipment, University "Lucian Blaga" of Sibiu, Faculty of Engineering, Romania

⁶⁾ Assist. Prof., PhD Student, Machines and Industrial Equipment, University "Lucian Blaga" of Sibiu, Faculty of Engineering, Romania

⁷⁾ Assist. Prof., PhD Student, Machines and Industrial Equipment, University "Lucian Blaga" of Sibiu, Faculty of Engineering, Romania

Abstract: This paper presents a MATLAB-based simulation framework for evaluating the temporal behaviour of an ESP32–MQTT–Soft-PLC integration intended for future deployment on a Raspberry Pi Soft-PLC platform. The proposed setup emulates a typical industrial IoT chain in which a virtual ESP32 node acquires synthetic ADC-like sensor data with Gaussian noise, performs preprocessing and normalisation, injects software jitter at task level, and publishes timestamped JSON messages via a Python MQTT client over a TLS-secured connection to a cloud-based MQTT broker. On the control side, a MATLAB Soft-PLC subscribes to the same MQTT topic, updates a process image at the beginning of each scan cycle and executes an ON-delay (TON) timing logic, while logging all relevant timestamps for performance analysis. End-to-end latency is defined as the time difference between publication at the ESP32 node and processing in the Soft-PLC, whereas jitter is evaluated as the deviation of the actual scan time from a nominal scan period. For a 30-second experiment with a 50 ms nominal scan time, the measured end-to-end latency exhibits a mean of 568.06 ms, with values ranging from 64.11 ms to 1144.76 ms, while the Soft-PLC scan time shows an average of 62.64 ms and a maximum of 172.03 ms. These results characterise the architecture as a soft real-time solution suitable for monitoring, data acquisition and supervisory control, but not for hard real-time applications with strict millisecond-level deadlines. The framework thus provides a practical basis for analysing latency and scan jitter before migrating the ESP32–Soft-PLC integration to real Raspberry Pi-based controllers.

Key words: ESP32, Raspberry Pi, Soft-PLC, MQTT, MATLAB, latency, real-time simulation, digital twin.

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