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“If we start working today towards developing LTA systems, in 10 years India will lead the sustainable air transportation” esteemed academician, Prof. Rajkumar S Pant, Professor of Aerospace Engineering stated in his lecture at SRM University-AP. The seasoned expert from the prestigious institute of IIT Bombay delivered a lecture on “The Design and Development of Lighter Than Air Systems” at SRM university-AP on October 16, 2023, as part of the Distinguished Lecture Series 2023 organised by the Department of Mechanical Engineering. The lecture extensively discussed the latest developments in the area of conceptual design, sizing, design, development and flight/field testing of LTA Systems.

In his lecture, Prof. Pant encouraged students to explore the dynamics of Lighter Than Air Systems, beginning with aerostats and then gradually proceeding to more complex airships. The session highlighted the disaster of Hindenburg, breaking the myth that airship transportation is dangerous and unreliable. Prof. Pant engaged the session with video presentations on the building, developing and working of airships and aerostats that have been conducted at the Lighter-Than-Air Systems Laboratory of IIT Bombay. His lecture also showcased some of the research and development activities that have been carried out in the LTA Systems Laboratory of IIT Bombay including Project HERCARA, and other projects carried out in collaboration with ISRO and DRDO.

The distinguished lecture was followed by a workshop on “Sizing of Reusable Indoor Hot Air Balloon (RIHAB)”. The workshop provided the students with practical knowledge and hands-on experience on LTE systems and vehicles inducing research interest in the domain of aerospace engineering and sustainable air transportation. Prof. Ranjit Thapa, Dean – Research, Prof. Prakash Jadhav, Head – Department of Mechanical Engineering, faculty and students at the university actively participated in the lecture and the workshop.

The Department of Mechanical Engineering proudly congratulates G Chandra Mouli, PhD scholar for receiving the Best Oral Paper Presentation Award at the International Conference on Advances in Materials, Ceramics & Engineering Sciences (AMCES – 2023) organised by Dayananda Sagar University, Bangalore, held during March 13-15, 2023. The paper titled “A New Approach to Enhance Microhardness and Corrosion Resistance with In-Situ Shot-Peened Al – Zn Coatings on ZK60 Magnesium Alloy by Cold Spray” was awarded the first prize among the 200+ papers presented at the conclave.

Congratulations to G Chandra Mouli and his mentor, Prof, GS Vinodkumar, Professor, Department of Mechanical Engineering for their cutting-edge research in enhancing the thickness, microhardness and corrosion resistance of metals!

Abstract

This paper aims to develop an improved microhardness and corrosion protective coating (Pure Al-Zn, Al-Zn-Al2O3 and Shot peened Al-Zn) on an Mg alloy substrate, by using the cold spray (CS) technique. A mixture of metal, ceramic/hard particles (Al2O3) and Shot-peened (Large Ni particles) has been used to improve the feedstock powder flowability and coating deposition efficiency. The long-term corrosion properties are evaluated by immersing these coupons in NaCl solution as a function of immersion time durations. The coatings are well-characterised for their structural, morphological, mechanical and electrochemical properties. Thus, it has been observed that in-situ-shot peening helps to enhance the thickness, microhardness and corrosion resistance.

Closed-cell metal foams are crucial to heavy industry machinery as they primarily function as impact-absorbing materials. Stabilizing closed-cell metal foams is a pivotal element in the process of manufacturing closed-cell metal foams. On this note, Prof GS Vinod Kumar from The Department of Mechanical Engineering has published a paper entitled Production, stability, and properties of in-situ Al–5ZrB2 composite foams in the journal Materials Science and Engineering: A with an impact factor of 6.044.

Abstract

Stabilization is an essential requirement to produce closed-cell metal foams. In the melt route of foaming, usually ceramic particles are used as foam stabilizers. For the first time, the present study introduces ZrB2 particles as foam stabilizers. We demonstrate the foaming of in-situ based Al composite containing submicron ZrB2 particles. The effect of foaming temperature and holding time on the structural and mechanical properties of the foams was studied. The composites and foams were characterized using XRD, SEM/EDS, and optical scanning techniques. The mechanical properties of the foams were determined by subjecting the foams to a quasi-static compression test. Submicron ZrB2 particles present in the cell wall and at the gas-solid interface promoted foam stability. All the foams exhibited a good cellular structure with high expansion. Among the foams, the foams prepared at 680 ºC with a holding time of 120 s exhibited the smallest cell size and the best mechanical properties. The structural and mechanical properties of the Al–5ZrB2 foams were found to be comparable to conventional foams.

Novel in-situ ZrB2 particles were produced to form Al-5ZrB2 composites. ZrB2 particles present in the melt tend to stabilize the H2 gas bubbles produced from the decomposition of TiH2. The macrostructure was best observed when foamed at 680 ºC and held for 120 sec. Because of its finer pores ( ̴ 3mm ), excellent compressive strength and energy absorption capacity was exhibited comparable to conventional Al foams.

The paper observes a wide-range of possibilities for the application of in-situ Al–5ZrB2 composite foams to modify bullet proof vests, car body parts, sound and heat proof walls in theatres, naval ship bodies, etc.

Prof Vinod Kumar also discusses the future application of this technique in use of metallic powders as blending agent for effective dispersion of blowing agent in the melt and in the field of compressive and energy absorption studies for Al composite foams.

A robust body of published works helps advance research capabilities and contribute to the larger research domain. Two latest paper publications from the Department of Mechanical Engineering are co-authored by Prof G S Vinod Kumar and his PhD student, Mr Akshay Devikar.

The first paper, Stabilization and Mechanical Properties of Mg-3Ca and Mg-3Ca/SiC/5p foams alloyed with Beryllium, got published in the Journal of Materials Engineering and Performance and had an impact factor of 2.036.

Liquid processing of Magnesium is complicated due to its uncontrolled flammability in the presence of oxygen. However, owing to the lightweight property of Mg, it can be used as a structural material in various sectors such as naval, aerospace, automobile, biomedical, heat exchangers, and military applications. Therefore, using Ca and Be as alloying elements and oxidation preventers, the researchers produced lightweight Mg foams (of density 0.17 g/cm 3), which float on water. SiC particles provide excellent Mg foam stabilisation as well. The compression tests revealed the highest strength for Mg-3Ca foam containing both Be and SiC. Thus, the burning problem of Mg was overcome by adding Ca and a trace quantity of Be to make lightweight foams, which were strengthened by SiC particles.

Abstract

The present paper investigates the stabilisation of Mg-3Ca alloy and Mg-3Ca/SiC/5p composite foams with and without the addition of 0.12 wt.% beryllium. In Mg-3Ca alloy foam, Be addition has significantly improved the expansion and pore structure. Whereas, in the case of Mg-3Ca/SiC/5p composite foams, the SiC particles stabilised the foam effectively, while Be addition did not show any distinguishable improvement in the foam structure. The formation of BeO and the dense coverage of SiC particles in the gas-solid interface of Mg-3Ca and Mg-3Ca/SiC/5p composite foams, respectively, are the reasons for the foam stabilization. Mg-3Ca/SiC/5p composite foam exhibited the lowest foam density of 0.10 g/cm3. The quasi-static compression test shows that Mg-3Ca-0.12Be/SiC/5p composite foam containing Be exhibited lower foam density and higher normalized compressive strength. The energy absorption capacity per unit foam density in Be containing foams was also higher.

The second paper, the Effect of Beryllium on the stabilization of Mg-3Ca alloy foams, is published in the journal Materials Science and Engineering B with an impact factor of 3.407.

Mg-3Ca alloy foams of density as low as 0.25 g/cm3 were successfully produced via the liquid metal route in an open-air atmosphere with trace Be addition. The stable BeO layer formed at the gas-solid interfaces of pores restricted the Mg + CO2/CO reaction, thereby reducing the gas loss responsible for foaming. Be addition (0.13 wt.%) resulted in a high-volume expansion of Mg-3Ca foam (694 %). Metallic single films also exhibited smooth and crack-free interfaces with Be addition.

Abstract

The present work is the first-ever study where the influence of beryllium (Be) addition on the stability of Mg alloy foam was investigated. Mg-3Ca alloy foams were produced by the liquid processing route with and without Be micro-addition. CaCO3 was used as a blowing agent. Mg-3Ca alloy foam without Be resulted in stable foam but exhibited low expansion with poor foam structure. Be addition significantly increased foam expansion and improved their structure. The expansion and the structure of the Mg foams obtained are comparable with that of commercially available aluminum foams. The XPS analysis confirmed the presence of BeO at the gas-solid interface of Mg foam. Be stabilizes the gas-solid interface of the foam by forming a smooth and crack-free surface of the BeO layer, which prevents the continuous oxidation of liquid foam and minimises the loss of blowing gas, thereby enhancing the stability of Mg-3Ca alloy foams.

Bulletproof vests, Car body parts, Hip and Knee implants, Sound and heat-proof walls in theatres, Naval ship bodies, etc., are some of the applications of the research findings. The researchers have collaborated with Dr Manas Mukherjee (Associate Professor) and his PhD student, Mr Biswaranjan Muduli of the Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai, for this work. Stabilisation using other alloying elements and ceramic particles for improving mechanical properties of Mg foams specific to application requirements and establishing structure-property relationship from the point of view of melt viscosity by altering the foaming parameters are the future plans of the research team.

The research project titled Development of Novel Gold and Silver Alloys was sanctioned to Prof G S Vinod Kumar from the Department of Mechanical Engineering. The project was sanctioned by Waman Hari Pethe Sons, a leading Gold/Diamond jewellery manufacturing company based in Maharashtra, with a total outlay of Rupees 17 Lakhs. The tenure of the project is two years, from May 2022 to May 2024.

Prof Vinod Kumar’s research interests mainly revolve around the hardening of 22 carats and 24 carats gold for light-weight and high-strength jewellery and the novel processing of light alloy (Al and Mg) foam and studying the structure and properties. He has been intensely involved in the development of technologies for improving the hardness of 22k gold for weight saving and high strength in the cast and hand-made jewellery. This was jointly patented by SRM and Titan. He also has several industrial research partnerships and funded projects to his credit.

The present project aims to develop novel high carat gold (24,22 and 18 carats) for high-strength and light-weight jewellery applications and novel silver alloys (high pure (99%) or sterling silver (92.5%)) having better anti-tarnishing capability. It further aims to develop colour gold alloys (Black, violet and pink gold). The project also involves both the lab-scale and industrial development of the process for scaling up jewellery production of the gold and silver alloys.

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