Publications

Machine learning approach towards laser powder bed fusion manufactured AlSi10Mg thin tubes in laser shock peening

Ondřej Stránský, Ivan Tarant, Libor Beránek, František Holešovský, Sunil Pathak, Jan Brajer, Tomáš Mocek, Ondřej Denk

2024 — Surface Engineering — DOI: https://doi.org/10.1177/02670844231221974 — https://journals.sagepub.com/doi/epub/10.1177/02670844231221974

The industry's demand for intricate geometries has spurred research into additive manufacturing (AM). Customising material properties, including surface roughness, integrity and porosity reduction, are the key industrial goals. This necessitates a holistic approach integrating AM, laser shock peening (LSP) and non-planar geometry considerations. In this study, machine learning and neural networks offer a novel way to create intricate, abstract models capable of discerning complex process relationships. Our focus is on leveraging the certain range of laser parameters (energy, spot area, overlap) to identify optimal residual stress, average surface roughness, and porosity values. Confirmatory experiments demonstrate close agreement, with an 8% discrepancy between modelled and actual residual stress values. This approach's viability is evident even with limited datasets, provided proper precautions are taken.

Investigations on tip relieving of spur gears by non-contact process

Vivek Rana, Neelesh Kumar Jain, Sunil Pathak

2023 — Materials and Manufacturing Processes — DOI: https://doi.org/10.1080/10426914.2023.2176877 — https://www.tandfonline.com/doi/full/10.1080/10426914.2023.2176877?scroll=top&needAccess=true&role=tab

Microstructure and surface quality of SLM printed miniature helical gear in LSPwC

Sunil Pathak, Marek Böhm, Jan Kaufman, Jaromír Kopeček, Sanin Zulić, Ondřej Stránský, Jan Brajer, Libor Beránek, Tomáš Mocek

2023 — Surface Engineering — DOI: https://doi.org/10.1080/02670844.2023.2207934 — https://doi.org/10.1080/02670844.2023.2207934

The work describes the influence of underwater laser shock peening without coating (LSPwC) on selective laser melting manufactured meso-size (outside diameter ≤ 10 mm) helical gears. Five experiments were conducted using energies in the 200 mJ up to 1 J, while the spot size and overlap were kept constant as 1 mm and 90 %, respectively. Responses were measured and compared in terms of surface residual stresses, surface roughness, and microstructure of LSPwC-treated samples. Results show the development of significant compressive residual stresses in the root of the LSPwC processed helical gear, where it changes the state from tensile +45 MPa to compressive −421 MPa. Surface roughness has shown improvement, while volumetric material peak confirms the reduction by over 50%. Microstructure study was performed at the surface and by cross-section using scanning electron microscopy and electron backscatter diffraction analysis. The grain refinement and change in misorientation were observed, confirming plastic deformation.

Porosity and Microstructure of L-PBF printed AlSi10Mg thin tubes in Laser Shock Peening

Ondřej Stránský, Sunil Pathak, Jan Kaufman, Marek Böhm, Jaromír Kopeček, Libor Beránek, František Holeškovský, Šimon Petrášek, Lucie Hlavůňková, Zbyněk Soukup

2023 — Journal of Materials Research and Technology — DOI: https://doi.org/10.1016/j.jmrt.2023.10.013 — https://www.sciencedirect.com/science/article/pii/S2238785423024626?via%3Dihub

Laser powder bed fusion (L-PBF) has emerged as one of the most promising technologies for producing complex geometries that are difficult to achieve with other methods. However, its widespread adoption is hindered by issues such as deleterious microstructure, tensile residual stresses, and porous structure, mainly while working with aluminum alloys. To address these challenges, laser shock peening (LSP) offers a potential solution by mitigating the negative effects associated with aluminum L-PBF. This study investigates the impact of the important LSP parameters, namely energy, spot size, and overlap on L-PBF printed thin AlSi10Mg tubes. A total of 17 specimens were examined by varying the mentioned parameters at three levels each. The outcome of the study was evaluated in terms of residual stresses, porosity, microstructure and surface roughness. The results have shown significant improvements in residual stresses, where a maximum improvement of over 200 % was observed and a decrease in porosity by 70 %. Furthermore, the microstructure analysis revealed grain refinement and dislocation redistribution as material reactions, aligning with the observed microhardness increase. These findings demonstrate the viability of LSP as a post-processing method for demanding applications, effectively addressing the limitations of the L-PBF process.

Laser shock peening in the tooling industry

Jan Kaufman, Sanin Zulic, Sunil Pathak, Marek Böhm, Ondřej Stránský, Tomáš Mocek

2022 — The Laser User — https://www.hilase.cz/en/laser-shock-peening-in-the-tooling-industry/

Upgrading additively manufactured parts using laser shock peening

Sanin Zulic, Sunil Pathak

2022 — Laser Systems/Europe — https://www.lasersystemseurope.com/analysis-opinion/upgrading-additively-manufactured-parts-using-laser-shock-peening

Additive manufacturing (AM) has brought enormous benefits to mankind and has already shown its usefulness in a variety of cutting edge fields. Metallic additive manufacturing, which fosters the development of smart technologies and production systems, is one of the essential pillars of Industry 4.0. Additionally, AM is a vital facilitator of the circular economy, aiming to reduce use of resources while increasing commercial prospects. As a result, less material will be used, and physical inventory will be minimised.

Titanium Alloy Particles Formation in Electrical Discharge Machining and Fractal Analysis

Irshad Ahamad Khilji, Siti Nadiah Binte Mohd Saffe, Sunil Pathak, Ştefan Ţălu, Slawomir Kulesza, Miroslaw Bramowicz, Venugopal Jayarama Reddy

2022 — Journal of The Minerals — DOI: https://doi.org/10.1007/s11837-021-05090-2 — https://link.springer.com/article/10.1007/s11837-021-05090-2

A large amount of material is machined by electrical discharge machining (EDM) and the machined debris is flushed away as waste. The present study aims to establish EDM as a top-down method which can effectively machine hard-to-cut materials while the by-product, i.e., metal debris, can be utilized as micro/nano particles. In the present work, titanium-alloy grade 5 was machined using a die-sink EDM and the debris was collected from the dielectric fluid with a multistage filtration system. The collected debris was cleaned and the particles were characterized. Particles were examined by scanning electron microscopy, x-ray diffraction, and energy-dispersive x-rays to determine size, shape, and chemical crystal structure. The average size of the formed particles was 5.14 µm and they were spherical. A fractal analysis was performed on the SEM images to deepen the study of the formed particles.

Surface Morphology of Nimonic Alloy 263™ in Nanosecond Pulsed Laser Ablation

Sunil Pathak, Zhehao Jiang, S. Subramani, J. Radhakrishnan, Sundar Marimuthu

2022 — Springer Cham — ISBN: 978-3-031-03830-3 — DOI: https://doi.org/10.1007/978-3-031-03830-3 — https://link.springer.com/book/10.1007/978-3-031-03830-3

This book covers the fundamentals of different laser-based manufacturing and processing, namely laser shock peening, laser micromachining, laser cleaning, cladding, remelting, laser honing, and other several aspects of lasers. The book discusses the general laser interaction with different materials. The application of laser-based post-processing of additive manufacturing and repair engineering is reported. It also provides the reader with mechanism of lasers in manufacturing and recent developments in tools, technologies, controls, and operations.

Improving functional performance characteristics of spur gears through flank modifications by non-contact advanced finishing process

Vivek Rana, Neelesh Kumar Jain, Sunil Pathak

2022 — The International Journal of Advanced Manufacturing Technology — DOI: https://doi.org/10.1007/s00170-022-10566-9 — https://doi.org/10.1007/s00170-022-10566-9

This paper describes reduction in noise, vibrations, total and tooth-to-tooth, and longwave transmission errors, total and tooth-to-tooth composite errors, and radial runout of spur gears by imparting them flank modifications and their combinations by a non-contact advanced finishing process referred to as pulsed electrolytic dissolution. Eight spur gears were modified using innovatively developed 5 cathode gears and apparatus by imparting them 5 flank modifications (i.e. tip relief, root relief, end relief, profile crowning, lead crowning) individually and their 4 selected combinations. Vibrations at all rotational speeds and noise at 900 and 1200 rpm are reduced for all modified spur gears at all the values of applied loads. End relieved spur gear showed maximum reductions in noise and vibrations by 5 dBA and 3.77 m/s2 respectively for 1200 rpm speed. Reduction amount in noise and vibrations of modified gears increase with rotary speed. Lead crowned gear showed maximum reductions of 146 µm in total transmission error, 109 µm in total composite error, and 102 µm in radial runout. End relieved gear showed maximum reductions of 37 µm in tooth-to-tooth and 139 µm longwave transmission errors. Tip relieved, and tip and root relieved gear showed maximum reduction of 121 µm in tooth-to-tooth composite error. This work proves that the developed non-contact process can very effectively impart different flank modifications individually and their combinations to spur gears without any twist error. Lead crowning, end relieving, tip relieving, and tip and root relieving are main flank modifications that significantly improve functional performance characteristics of spur gears. It will result in their enhanced operating performance and service life, which will help their manufacturers and end-users.

Fatigue life enhancement of additive manufactured 316l stainless steel by LSP using a DPSS laser system

Sanin Zulić, Danijela Rostohar, Jan Kaufman, Sunil Pathak, Jaromír Kopeček, Marek Böhm, Jan Brajer, Tomáš Mocek

2022 — Surface Engineering — DOI: https://doi.org/10.1080/02670844.2022.2060463 — https://doi.org/10.1080/02670844.2022.2060463

Present work aims to study the fatigue life behaviour of additively manufactured (AM) stainless steel 316L in a laser shock peening (LSP) process. The fatigue behaviour of as-built samples and LSPeened sample were studied on the AM samples. A new diode-pumped laser system was utilized as an instrument to perform LSP operations. LSP operation was performed under two different sacrificial layers of different materials i.e. vinyl tape and aluminium tape. The other essential LSP parameters, namely energy, pulse width, spot size, overlap, and number of layers were kept constant based on the previous experimental findings. The characterization was done for analyzing the residual stresses using a hole drilling process, and a 4-point bending machine. A considerable improvement in compressive residual stress and fatigue life was observed in the LSPeened samples. Such improvements in residual stresses and fatigue life may pave a road to establishing diode-pumped lasers for LSP applications.

Surface integrity of SLM manufactured meso-size gears in laser shock peening without coating

Sunil Pathak, Marek Böhm, Jan Kaufman, Jaromír Kopeček, Sanin Zulić, Ondřej Stránský, Ashish Shukla, Jan Brajer, Libor Beránek, J. Radhakrisnan, Danijela Rostohar, Tomáš Mocek

2022 — Journal of Manufacturing Processes — DOI: https://doi.org/10.1016/j.jmapro.2022.12.011 — https://www.sciencedirect.com/science/article/pii/S1526612522008726

Advanced Engineering of Materials through Lasers

Sunil Pathak, Jagdheesh Radhakrishnan

2022 — Springer — ISBN: 2662-4761 — https://link.springer.com/book/9783031038297

Complete reference on laser materials processing. Covers special application of laser-based post-processing of additive manufacturing and repair engineering. Presents recent developments in tools, technologies, controls, and operations.

Post-processing of selective laser melting manufactured SS-304L by laser shock peening

Sunil Pathak, Sanin Zulić, Jan Kaufman, Jaromír Kopeček, Ondřej Stránský, Marek Böhm, Jan Brajer, Libor Beránek, Ashish Shukla, Michal Ackermann, Filip Véle, Tomáš Mocek

2022 — Journal of Materials Research and Technology — DOI: https://doi.org/10.1016/j.jmrt.2022.07.014 — https://www.sciencedirect.com/science/article/pii/S2238785422010535?via%3Dihub

This paper investigates the post-processing of additively manufactured stainless steel (SS) 304 L samples through laser shock peening (LSP). Four samples, differently processed, (i) as-built (AB); (ii) as-built + annealed; (iii) as-built + polished; and (iv) as-built + annealed + polished, were used to study the effect of LSP at pre-identified parameters to understand the mechanism and behavior of processing different conditions. In addition, compressive residual stresses and surface morphology were considered as a response to measure the effects of LSP on processed samples. The results have shown significant improvements in compressive residual stresses where the values have changed from initial tensile to compressive (−1170 MPa) and remain compressive up to the depth of 1 mm in most cases. The results of this research help better understand the LSP mechanism in the post-processing of AM Parts.

Facile Manufacture of Oxide-Free Cu Particles Coated with Oleic Acid by Electrical Discharge Machining

Irshad Ahamad Khilji, Siti Nadiah Binti Mohd Safee, Sunil Pathak , Chaitanya Reddy Chilakamarry , Amiril Sahab Bin Abdul Sani, Venugopal Jayarama Reddy

2022 — Micromachines — DOI: https://doi.org/10.3390/mi13060969 — https://www.mdpi.com/2072-666X/13/6/969

Particle synthesis has seen significant advances in current trends. However, the synthesis of metal particles without oxidation is a challenge for researchers. The current study presents a straightforward, convenient, and convincing approach for manufacturing copper (Cu) particles free of surface oxide. The die-sink Electrical Discharge Machine (EDM) of copper alloys with oleic acid resulted in the formation of Cu particles with diameters between 10 to 20 µm. X-ray diffraction (XRD) was used for particle examination after cleaning and sonication with distilled water. Cu particles with oleic acid coating retained a Cu phase without oxidation after synthesis. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to determine the size and morphology of generated particles. Fourier transforms infrared (FT-IR) analysis revealed the oleic acid-coated Cu surface bonded with an oxygen atom. Also, the agglomeration and change of size involving Cu particles with increasing voltages in the pulse supply in EDM were reported.

Engineered Nanomaterials for Aviation Industry in COVID-19 Context: A Time-Sensitive Review

Sunil Pathak , Gobinda C. Saha, Musfirah Binti Abdul Hadi, Neelesh K. Jain

2021 — Coatings — DOI: https://doi.org/10.3390/coatings11040382 — https://www.mdpi.com/2079-6412/11/4/382

Titanium Alloy Particles Formation in Electrical Discharge Machining and Fractal Analysis

IRSHAD AHAMAD KHILJI, SITI NADIAH BINTE MOHD SAFFE, SUNIL PATHAK, S¸TEFAN TA˘ LU, SLAWOMIR KULESZA, MIROSLAW BRAMOWICZ, VENUGOPAL JAYARAMA REDDY

2021 — The Minerals, Metals & Materials Society — DOI: https://doi.org/10.1007/s11837-021-05090-2 — https://link.springer.com/article/10.1007%2Fs11837-021-05090-2