Strojniški vestnik - Journal of Mechanical Engineering

Corrosion Studies on Post-Weld Heat Treated Dissimilar AISI2205 and AISI310 Joints Using Electrochemical Noise Analysis

Mahadevan Govindasamy — 2025-02-21

The corrosion behavior of dissimilar weldments between AISI310 and AISI2205 stainless steels in a 5 % calcium chloride solution at 50 °C was investigated under three conditions: as-welded, lower post-weld heat treatment at 800 °C, and higher post-weld heat treatment at 1000 °C. Microstructural examination revealed severe pitting in the as-welded sample, with pit widths ranging from 270 μm to 360 μm. The lower heat-treated sample had larger pits (310 μm to 370 μm), while the higher heat-treated sample showed homogeneous corrosion with a protective oxide coating. The as-welded sample had the highest corrosion rate, followed by the lower heat-treated sample, which had a moderate rate, and the higher heat-treated sample had the lowest rate. The corrosion current densities were 5.26×10—³ mA/cm², 4.6×10—4 mA/cm², and 1.4×10—4 mA/cm², respectively. Electrochemical noise measurements confirmed these findings, with the higher heat-treated sample showing negligible localized corrosion and homogenous corrosion behavior.

Thermal Design and Constrained Optimization of a Fin and Tube Heat Exchanger Using Differential Evolution Algorithm

Nader Afsharzadeh — 2025-02-21

Fin and tube heat exchangers (FTHEs) are utilized for gas-liquid applications frequently. In the current study, a differential evolution (DE) algorithm and JDE as its variant, with α-level constraint-handling technique, are effectively applied to optimize an FTHE. Total weight and total annual cost are selected as objective functions. Seven design variables are taken into consideration: outside tube diameter, transverse pitch, longitudinal pitch, fin pitch, number of tube rows, height, and width of shape. Meanwhile, the logarithmic mean temperature difference (LMTD) method is used for heat transfer analysis under identical conditions such as mass flow rate, inlet and outlet temperatures, heat duty, and other thermal properties. The research findings indicate that the implementation of the DE algorithm coupled with α-level comparison method on optimization problems leads to better solutions for both objective functions compared with those achieved by other approaches such as the genetic algorithm (GA) and heat transfer search (HTS) algorithm. In addition, a parametric analysis is performed for design parameters at the optimum points to show the effects on the objective functions and to identify the feasible design space. The proposed method is straightforward and can generally be employed for thermal design and optimization of FTHEs as well as any other type of compact heat exchangers (CHEs) under different specified duties.

Microstructural and Mechanical Characterization of WAAM-fabricated Inconel 625: Heat Treatment Effects

Saravanakumar Krishnasamy — 2025-02-21

Wire arc additive manufacturing (WAAM) is a promising technique for producing complex geometries of nickel-based superalloys, such as Inconel 625. In this work, the microstructure and mechanical properties of Inconel 625 alloy produced by gas tungsten arc welding (GTAW) process of WAAM technology were analyzed to investigate the effects of heat treatment on the top and bottom zones of the multi-layered wall structure. The deposited specimens were heat treated at 980 °C for 2 hours, then water quenched (solution annealing). After heat treatment, microstructure reveals that the most common phases like laves, gamma, and mono carbides (MC) are dissolved, which is clear by optical microscopy (OM), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Even after the heat treatment process, mechanical properties, such as micro-hardness results, demonstrate that the bottom zone of the multilayer wall structure has a higher hardness value than the top zone. After the secondary phases were eliminated by the solution annealing procedure, the ultimate tensile strength and yield strength were increased by nearly 17 % to 38 % and 15 % to 22 % in the top and bottom one of the multilayer wall structures, respectively.

Quantitative Sequential Modelling Approach to Estimate the Reliability of Computer Controlled Pneumatically Operated Pick-and-Place Robot

Satheesh Pandian Durairaj — 2025-02-21

Pneumatically controlled pick-and-place robots are an integral part of contemporary manufacturing processes and have the potential to enhance the precision and velocity of numerous production-related tasks. As automation continues to disrupt various sectors, the role of these robots is becoming increasingly crucial. Achieving peak performance in robot operations requires a relentless focus on safety and reliability. As a result, subsequence reliability should be considered carefully from the initial part of the design phase. Roboticists need to identify the dependable subsequences and parts of the robot’s operational framework in prior to access the system’s overall reliability. This analytical technique aids in component identification and demonstrates how to measure redundancy to ensure dependability and robustness. Based on recent theories and frameworks, the researchers can understand the factors that have more impact towards the reliability of pneumatically driven pick-and-place robots. Thus, this research work improves an exhaustive dependability analysis of a computer-controlled pneumatically operated pick-and-place robot. As part of our methodology, we use modern LabVIEW software to conduct a comprehensive failure analysis and estimate the reliability of the sequence.

Connection Between the Dynamic Character of the Cutting Force and Machined Surface in Abrasive Waterjet Machining

Jelena Baralić — 2025-02-21

This paper presents the results of research on the effect of traverse speed on cutting forces and machined surface in abrasive water jet machining. The results indicated that there is a significant connection between the dynamic character of the cutting force in abrasive waterjet machining, namely, peaks in the cutting force signal, with the appearance of irregularities and uncut parts in the machined surface. Also, the research showed that the increase of the traverse speed produces an increase in the mean value of the static component of the cutting force. In experiments, the vertical component of the cutting force has been measured for an Aluminium AlMg3 12 mm thick rod cut at traverse speeds from 900 mm/min to 1100 mm/min. Cutting with higher traverse speeds yields more irregularities, which are connected with the appearance of peaks in the measured cutting force.

A Mathematical Model of the Dimensional Chain for a Generation 2 Wheel Hub Unit

Stanisław Adamczak — 2025-02-21

This article overviews wheel hub design solutions and proposes a mathematical model of the dimensional chain and a tolerance formula for calculating axial clearance for a generation 2 wheel hub assembly with ball bearings. The dimensional chain analysis and its synthesis are carried out using three partial interchangeability methods. The possibility of manufacturing the hub bearing using selection compensation was proposed. The considerations made provide an alternative to the current method of process design based on numerous trials and considerable cost.

Numerical and Experimental Investigation of Aspect Ratio Effect on Aerodynamic Performance of NACA 4415 Airfoil Section at Low Reynolds Number

Hatice Cansu Ayaz Ümütlü — 2025-02-21

In this study, the effect of aspect ratio on the aerodynamic coefficients is investigated for a NACA 4415 airfoil profile. Four different aspect ratios which are 3, 5, 7, and 9 are evaluated with the computational fluid dynamics (CFD) simulations and the experiments. The CFD studies are performed using a three-dimensional (3D) computational domain and by using the k–ω shear stress transport (SST) turbulence model for turbulence calculations. The measurements of the aerodynamic forces are carried out in open jet type wind tunnel using a three-component balance. CFD and experimental studies are performed at angles of attack from 0° to 25° and Reynolds number 85e3. The results show that as the aspect ratio increases, separation points move towards the leading edge of the airfoil and the stall angle reduces. Furthermore, it is observed that the lift coefficients increase with the increasing aspect ratio. The results obtained indicate that there is a harmony between the experimental data and the CFD solutions.

Integration of Phase Change Material and Heat Exchanger for Enhanced Solar Desalination – A Comparative Performance Investigation

Jothilingam Manickam — 2025-02-21

The performance and comparative analysis of several solar desalination systems using various configurations and materials are examined in this study. The study looks at how these systems perform by measuring their overall productivity, temperature differentials, energy storage capacity, and thermal efficiency. A thorough assessment across a variety of characteristics was made possible by the consistent environmental conditions of the experiments. When phase change materials (PCM) were used as an energy storage medium, the overall amount of heat loss was significantly reduced. Studies comparing different solar stills revealed clear benefits, especially when heat exchangers were used. Improved evaporative heat transfer coefficients, higher temperature differentials (ΔT), more usable heat absorption by the distilled water, and increased daily output were all seen in solar stills equipped with heat exchangers. The modified solar still with PCM and a heat exchanger had the best thermal efficiency, reaching 56 %, according to the results. The key objective of the research was to minimize heat loss and maximize freshwater yield. This design proved to be the most successful method for producing freshwater. This thorough assessment and comparative study of several solar desalination systems offers insightful information for improving the productivity and efficiency of solar-powered water distillation technologies under a range of environmental circumstances.