Mohammad Rafighi

AISI-301 çelik, yüksek mukavemet ve korozyon direnci özelliğiyle havacılık ve otomotiv endüstrilerinde sıklıkla tercih edilir. Bu malzemenin şekillendirilme yöntemlerinden biri de form kalıbı üzerinde hidroforming işlemidir. Bu yöntemle diyafram ile parçaya iletilen yüksek basınçla, parçanın kalıp geometrisini alması sağlanır. Ancak bu şekillendirme operasyonu esnasında öngörülemeyen geri yaylanma miktarları parçanın istenmeyen şekilde üretilmesine neden olabilir. Bu çalışmada AISI-301 çelik sac malzemenin hidroforming işlemi sonrasındaki geri yaylanması incelenmiştir. Geri yaylanmayı etkileyen faktörler olan kalınlık, büküm açısı ve büküm radyusunu incelemek üzere 0,635 mm, 1,016 mm ve 1,27 mm kalınlıkta numuneler, 2,5 mm, 5 mm, 7,5 mm ve 10 mm büküm yarıçapları ve 90° ve 120° büküm açısı olan kalıp üzerinde hidroformla şekillendirmeye tabi tutulmuşlardır. Aynı zamanda bu değişkenlerle şekillendirme prosesinin sonlu eleman analizleri PAM-STAMP programında gerçekleştirilmiştir. Analiz sonuçları ile deney sonuçları karşılaştırılarak yorumlanmıştır. Hem deneyler hem de sonlu eleman analizleri AISI-301 paslanmaz çelik sac malzemenin sac kalınlığı ve büküm radyusu oranın 0,1’e yaklaştığı durumlarda geri yaylanma miktarının 20 derecelere kadar çıktığı hesaplanmıştır.

In this experimental study, optimum cutting parameters were obtained in turning hardened AISI 4340 with three cutting inserts (ceramic, coated carbide, and CBN) using a gray relational analysis approach based on the Taguchi method. According to this approach, machining parameters such as workpiece hardness, insert type, cutting speed, feed rate, and depth of cut were optimized to minimize the cutting force components and surface roughness. Based on the 3D plots, the most effective insert type on cutting forces was ceramic, and the most effective insert type on surface roughness was cubic boron nitride. The developed regression equations can accurately predict the results, having a coefficient of determination greater than 98% for all responses. It was found that 51.93% depth of cut and 33.73% feed rate contributed to the responses based on the ANOVA results for a gray relational grade (GRG). With the confirmation experiments, improvement in GRG was found to be 0.387. Thus, this method can be applied in industries to improve the efficiency of the turning process.

This paper explores the challenges of machining difficult-to-cut metals using tools like coated carbide, ceramics, and CBN under dry conditions, addressing issues such as heat generation, tool wear and friction, chip evacuation, surface integrity, vibration, and chatter. Though cutting fluids have historically improved machinability, environmental concerns, such as toxicity and non-biodegradability, are significant. Researchers aim to enhance the economic and ecological aspects of machining by reducing cutting fluid usage. This paper provides an overview of the performance assessment and sustainability evaluation of various cooling and lubrication methods during the machining of hard-to-machine as well as difficult-to-cut metals. Additionally, the literature review highlights various environmentally friendly cooling strategies, such as minimum quantity lubrication (MQL) and cryogenic arrangements. According to the results of this review, the utilization of various cooling and lubrication technologies has the potential to enhance both sustainability and machinability properties while prolonging the lifespan of cutting tools. The findings also show that there is a lot of room for improvement in terms of optimizing and making these cooling-lubrication solutions more practical and effective.

This study aims to characterize the twisting behavior of bi-directional functionally graded (FG) micro-tubes under torsional loads within the modified couple stress theory framework. The two material properties involved in the torsional static model of FG small-scale tubes, i.e., shear modulus and material length scale parameter, are assumed to possess smooth spatial variations in both radial and axial directions. Through the utilization of Hamilton’s principle, the governing equations and boundary conditions are derived, and then, the system of partial differential equations is numerically solved by using the differential quadrature method. A verification study is conducted by comparing limiting cases with the analytical results available in the literature to check the validity of the developed procedures. A detailed study is carried out on the influences of the phase distribution profile and geometric parameters upon twist angles and shear stresses developed in FG micro-tubes undergoing external distributed torques.

This study investigates the performance comparison of machining of UNS S32750 super-duplex stainless steel under single- and double-nozzle pulse mode minimum quantity lubrication (MQL) conditions. The pulse mode MQL system delivers lubricant pulses at specific intervals. The Taguchi L₉ design, with three factors and their three levels, was taken to perform the CNC turning experiments under both single-nozzle and double-nozzle MQL cooling environments. The surface roughness (Ra), tool-flank wear (VB), tool-flank temperature (Tf), power consumption (Pc), and material removal rate (MRR) are evaluated and compared as performance indicators. In comparison to single-nozzle MQL, the responses of Ra, VB, Tf, and Pc were found to be decreased by 11.16%, 21.24%, 7.07%, and 3.16% under double-nozzle conditions, respectively, whereas MRR was found to be 18.37% higher under double-nozzle conditions. The MQL pulse time was found to be an important variable that affects Ra, VB, Tf, and MRR significantly. Under both cooling scenarios, common wears such as abrasion, built-up edges, adhesion, and notch wear are detected. Furthermore, the Pugh matrix-based sustainability evaluation results revealed that the double-nozzle MQL technique was superior to single-nozzle MQL, achieving improved sustainability for machining super-duplex stainless steel.

Dry hard-turning is a vital manufacturing method for machining hardened steel due to its low cost, high machining efficiency, and green environmental protection. This study aims to analyze the effect of various machining parameters on cutting forces and surface roughness by employing RSM and ANOVA. In addition, multi-objective optimization (Grey Relation Analysis: GRA) is performed to determine the optimum machining parameters. Dry hard-turning tests were carried out on AISI 4140 steel (50 HRC) using coated carbide and CBN inserts with different nose radii. The results show that the cutting force components are greatly affected by the cutting depth and cutting speed for both cutting inserts. As the level of cutting depth and cutting speed rise, the cutting forces also increase. However, the feed rate was the main factor in surface roughness. A low feed rate and high cutting speed lead to good surface quality. According to the results, CBN inserts exhibited better performance compared to carbide inserts in terms of minimum cutting forces and surface roughness. The lowest radial force (Fx = 55.59 N), tangential force (Fy = 15.09 N), cutting force (Fz = 30.49 N), and best surface quality (Ra = 0.28 µm, Rz = 1.8 µm) were obtained using a CBN tool. Finally, based on the GRA, the (V = 120 m/min, f = 0.04 mm/rev, a = 0.06 mm, r = 0.8 mm) have been chosen as optimum machining parameters to minimize all responses simultaneously in the machining of AISI 4140 steel using both carbide and CBN inserts.

This experimental study presents the machinability comparison of TiCN-Al₂O₃-TiN, TiAlN-TiN, and TiAlSiN coated carbide inserts in hard turning AISI 4340 steel. The primary purpose of this research is to determine the most appropriate cutting inserts in turning hardened AISI 4340 (30–40 HRC) steel considering surface roughness (Ra), cutting sound (Cs), power consumption (P), radial force (Fx), tangential force (Fy), and feed force (Fz). To fulfill this objective, the turning experiments for each tool were executed based on the Taguchi L₉ design. The comparative assessment of cutting tools revealed that the TiAlSiN coated tool exhibited superior performance compared to other tools. Machining with the TiCN-Al₂O₃-TiN coated tool showed 32.05% greater roughness than with the TiAlN-TiN coated tool, and 68.80% higher surface roughness than the TiAlSiN coated tool. The main novelty of this research is considering the cutting sound and power consumption as responses to select the most suitable cutting tools. Moreover, a novel grey-crow search hybrid was executed to perceive the optimal value of the input parameters. The optimal local value of cutting speed for the TiAlSiN coated tool was found to be 220 m/min, while for the TiCN-Al₂O₃-TiN and TiAlN-TiN tools, it was the same as 182 m/min. Considering the optimum cutting parameters, the material removal rate for TiCN-Al₂O₃-TiN, TiAlN-TiN, and TiAlSiN was found to be 639.9 mm³/min, 606.4 mm³/min, and 761.2 mm³/min, respectively. Thus, the TiAlSiN coated tool has greater MRR capability in comparison to other tools. Therefore, this leads to the conclusion that the TiAlSiN tool may be the better choice in comparison to other selected tools for turning hardened steels.

Lubrication and cooling (LC) are critical for mechanical devices’ effective and dependable functioning, because they decrease friction and wear of moving components, ensuring superior efficiency. However, the cutting fluids in machining operations are a key cause of fear, due to their high cost, environmental impact, and health risks, particularly in computer numerical control (CNC) machine tools (MTs). During the industrial revolutions, MTs superseded manual labour and increased efficiency and output. Therefore, much research was conducted on lubrication and cooling in CNC machine tools (LC in CNC MTs). Therefore, it has become necessary to review and highlight research hotspots and gaps using specific means that can benefit budding researchers. The present review aims to identify research hotspots and gaps of LC in CNC MTs utilizing content and visualization analysis, employing VOSviewer and Biblioshiny software. The analysis comprises 136 documents retrieved by Scopus between 1988 and 2022. The analysis revealed a consistent growth in publications, primarily consisting of articles, with a minor proportion of review documents and conference papers. The keywords were categorized into seven clusters, with a notable prevalence of ‘surface roughness’ and ‘CNC machine tools’. A word cloud was generated to visualize the author’s frequently used keywords, where larger font sizes represented higher frequency. The treemaps demonstrated that ‘CNC’ appeared 34 times and contributed 8%, followed by ‘machine’, ‘tool’, ‘machining’, and ‘thermal’. In the abstract-terms tree plot, ‘machine’ appeared 235 times and contributed 7%, followed by ‘CNC’, ‘machining’, ‘tool’, and ‘cutting’. The content and visualization analysis identified six research hotspots: computer control systems, machine tools, computer numerical control, machining, numerical control systems, and surface roughness (Ra). The research gaps are temperature, cooling systems, cutting forces, energy utilization, tool life, nanoparticles, electric power utilization, and energy conservation. Based on hotspots and gaps, literature evaluations extensively addressed the strong roadmap of technical improvements and problems of LC in CNC MTs. A complete visualization and content analysis also produced a conceptual framework for best practices, and the study offers insight into the issues and prospects.

Advances in developed and developing countries are more attributable to growth in industrial activities that directly impact increasing energy demand. Energy availability has been inconsistent globally, necessitating energy storage (ES) for use as per requirement. Various energy storage technologies (ESTs) are available in mechanical, electrochemical, electrical, chemical, and thermal forms to fulfil the energy demand of a user as and when required. The factors responsible for making a commercially viable energy storage product are further being researched for an eco-friendly and optimal solution to store energy for a longer duration. Researchers are employing different strategies to evaluate the energy efficiency of storage technologies. This paper uses the VIKOR technique to analyze ESTs while assigning objective weights with the entropy weights method based on identified energy performance indicators and ranking them according to their commercialization viability. The method helps a consumer choose better ESTs as per their requirement while manufacturers compete with each other to enhance the commercial value of their energy storage products. Sensitivity analysis has been performed to understand the uncertainties, pros, and cons with the limitations and scope of using the decision model and thus taking an informed decision. The analysis of different energy storage technologies has indicated Hydrogen Fuel Cells (HFC) to be impressive and promising for the future.