Research Themes

Research in our lab may be classified under three thematically interlinked areas – additive manufacturing, extreme mechanics, and natural materials manufacturing as shown below. Details of work being done in each of these thematic areas are available under the individual tabs.

For a complete list of articles/reviews/preprints, please visit the [Publications] page. Details of individual projects are given below under each vertical

For information about individual group members and their interests, please see the [People page].

If you wish to get in touch or visit one of our labs, please visit the [Contact Section]

Research Projects

mech.

Mechanics of moving interface defects

Interface defects are important because they govern diverse phenomena ranging from plasticity to friction. Using a combination of high-speed imaging and theoretical methods, we are presently investigating the mechanics of moving interface defects. Applications include Schallamach-type waves at elastic interfaces [1], spontaneous shear localization in plasticity [2] and crack bifurcation in residual stress fields [3]. Experimental techniques involve both in situ imaging and ex situ evaluation and a variety of theoretical ideas, drawing from elastodynamics, viscoplasticity and perturbation theory, are employed [4, 5]. We are also interested in interface stability problems related to moving defects, including Saffman-Taylor fingering, dendrite formation and diffusion-limited patterns.

References

1. Ansari MA, Viswanathan K (2022). “Propagating Schallamach-type waves, resemble interface cracks.” Physical Review E. Accepted.
2. Viswanathan K, Yadav S, Sagapuram D (2020). “Shear Bands in Materials, Processing: Understanding the Mechanics of Flow Localization From, Zener’s Time to the Present.” Applied Mechanics Reviews, 72(6).
3. Aben H, Anton J, Õis M, Viswanathan K, Chandrasekar S, Chaudhri MM, (2016). “On the extraordinary strength of Prince Rupert’s drops.”, Applied Physics Letters, 109(23), 231903.
4. Viswanathan K, Sundaram NK, Chandrasekar S (2016). “Slow wave, propagation in soft adhesive interfaces.” Soft Matter, 12(45),, 9185-9201. .
5. Viswanathan K, Chandrasekar S (2014). “Geometric treatment of, conduction electron scattering by crystal lattice strains and, dislocations.” Journal of Applied Physics, 116(24), 245103.

Failure of disordered materials

Disordered materials abound in engineering practice, ranging from silicate glasses to fine-grained and additively manufactured metallic structures. Yet much is unknown about their failure mechanisms and general high-strain rate behaviour. For instance, a central question of interest is how plastic flow and crack growth are mediated in the absence of a well defined crystal lattice. We are investigating catastrophic failure and fracture in systems such as consolidated sands [1], toughened glass [2] and highly work hardened structural metals [3].

We are presently developing experimental capabilities for evaluating dynamic fracture and theoretical/numerical tools for predicting crack propagation in disordered solids. The broader aim of this work is to use natural (e.g., residual stress) and engineered (e.g., internal features) disorder to control deformation and deflect cracks in critical structures.

References

1. Dikshit R, Dey A, Gupta N, Varma SC, Venugopal I, Viswanathan K, Kumar, A (2021). “Space bricks: From LSS to machinable structures via MICP.”, Ceramics International, 47(10), 14892-14898.
2. Aben H, Anton J, Õis M, Viswanathan K, Chandrasekar S, Chaudhri MM, (2016). “On the extraordinary strength of Prince Rupert’s drops.”, Applied Physics Letters, 109(23), 231903.
3. Sagapuram D, Viswanathan K (2018). “Viscous shear banding in cutting of, metals.” Journal of Manufacturing Science and Engineering, 140(11),, 111004.

Large-strain deformation and mechanochemistry

Large strain plastic deformation phenomena in cutting and forming are rendered complex by the presence of free surfaces and interfaces. As part of an effort to understand such plastic flow fields, we’ve developed a digital imaging tool-chain based on novel image correlation techniques. Capturing flow fields in the vicinity of such dynamically changing interfaces requires the use of carefully designed correlation techniques, defined on multi-sampled random grids [1]. This enables the capture of unsteady, non-homogeneous deformation as well as obtain accurate quantitative predictions of frictional interactions [2]. The framework hence allows us to explore a range of phenomena occurring in large strain plasticity.

One such phenomenon we’ve been investigating is the mechanics of mechanochemical effects in plastic deformation. Mechanochemistry refers to the alteration of mechanical deformation behaviour via a suitable chemical environment. We’ve shown how suitable adsorbed films can significantly change near-surface plastic flow fields, often resulting in ductile-to-brittle transitions [3]. We’re presently exploring the use of such mechanochemical effects to produce monodisperse powders for additive manufacturing and powder metallurgy applications.

References

1. Gupta D, Udupa A, Viswanathan K (2021). “Evaluating performance metrics, in non-homogeneous cutting processes using a random-grid based digital, image correlation (DIC) method.” Manufacturing Letters, 30, 44-48.
2. Sagapuram D, Viswanathan K (2018). “Evidence for Bingham plastic, boundary layers in shear banding of metals.” Extreme Mechanics, Letters, 25, 27-36.
3. Sugihara T, Udupa A, Viswanathan K, Davis JM, Chandrasekar S (2020)., “Organic monolayers disrupt plastic flow in metals.” Science, Advances, 6(51), eabc8900.

mat.

Exploring alternate powders for additive manufacturing

Metal powders form the starting stock material for a variety of emerging manufacturing processes, ranging from additive manufacturing (AM) to high performance powder metallurgy (PM). Spherical metal powders are typically produced via atomization techniques that are extremely expensive and highly inflexible, requiring heavy capital investment. We have developed scalable techniques for producing spherical metal powders using an abrasion-based process that result in higher yield and competitive powder quality [1]. A detailed thermal analysis of the process has also outlined practical conditions for optimal yield [2]. We are presently exploring related mechanical and mechano-chemical techniques for producing non-spherical metal and refractory powders, specifically for AM applications. The performance of these powders in the specific context of DED-based metal AM is also under investigation.

References

1. Dhami HS, Panda PR, Viswanathan K (2022). “Production of powders for, metal additive manufacturing applications using surface grinding.”, Manufacturing Letters, 32, 54-58.
2. Dhami HS, Panda PR, Mohanty DP, Viswanathan K (2022). “An Analytical, Method for Predicting Temperature Rise Due to Multi-body Thermal, Interaction in Deformation Processing.” JOM, 74, 513-525.

Pattern formation in rapid solidification

The formation of dendrites and cellular structures in solidification have been studied for decades by the physics and materials science communities. However, under rapid solidification conditions, assumptions of thermal equilibrium and steady state interface motion break-down, hence necessitating the use of non-equilibrium or kinetic phase diagrams. We are investigating the formation of solidification patterns in confined geometries [1, 2] to help tailor the properties of metallic powders for powder metallurgy applications.

As part of this effort, we are presently studying interface instabilities in the context of rapidly moving solidification fronts, as occur for instance in laser-based additive manufacturing applications. For these, we use a combination of model experiments, linear stability analysis and asymptotic methods as well as numerical computations.

References

1. Dhami HS, Viswanathan K (2020). “On the Formation of Spherical, Particles in Surface Grinding.” In ASME 2020 15th International, Manufacturing Science and Engineering Conference. American Society of, Mechanical Engineers.
2. Dhami HS, Panda PR, Viswanathan K (2022). “Production of powders for, metal additive manufacturing applications using surface grinding.”, Manufacturing Letters, 32, 54-58.

Manufacturing & processing of natural materials

Natural materials provide alternative and sustainable solutions for several mass market applications. As part of a broad programme on the processing of natural materials, we are presently interested in two material systems—areca sheath for the production of foodware, and natural soils for the sustainable production of bricks. In the former, and in collaboration with Purdue University and BMS College (Bangalore), we’re evaluating the formability of sheath materials under various physical conditions [1] as well understanding their water diffusion properties [2] for packaging applications. In the latter system, a collaborative effort with the Kumar lab (IISc), we are attempting to understand the mechanical properties of naturally consolidated sands [3] using a combination of mechanical experiments and numerical simulations.

References

1. Mohanty DP, Udupa A, Chandra A, Viswanathan K, Mann JB, Trumble KP,, Chandrasekar S (2021). “Mechanical Behavior and High Formability of, Palm Leaf Materials.” Advanced Energy and Sustainability Research,, 2000080.
2. Mohanty DP, Udupa A, Viswanathan K, Gilpin CJ, Chandrasekar S,, Dayananda M (2021). “Diffusion of water in palm leaf materials.”, Journal of the Royal Society Interface, 18(185), 20210483.
3. Dikshit R, Dey A, Gupta N, Varma SC, Venugopal I, Viswanathan K, Kumar, A (2021). “Space bricks: From LSS to machinable structures via MICP.”, Ceramics International, 47(10), 14892-14898.

mach.

Modular Additive Manufacturing (MAM)

Under the Modular Additive Manufacturing (MAM) programme, we’re developing several solutions (patents pending) for metal AM including a reconfigurable test-bed platform, modular deposition heads and plug-n-play delivery systems for handling both conventional spherical and unconventional non-spherical metal powders. For more information about these technoloqies, please feel free to contact us.

Accelerated projectile impact test-bench

This is test-bench built in collaboration with the Vikram Sarabhai Space Centre (VSSC), ISRO to evaluate material damage due to projectile impact. The primary features of the system include capability for performing high-speed imaging analyses, controlled pressure-velocity characteristics and flexible target plate specifications. The test bench can be used to perform two types of impact tests. The first is a modified Taylor impact where a deformable projectile (material of interest) is impacted against a comparatively rigid plate. The second is conventional projectile impact involving a rigid projectile (commonly maraging steel) and a deformable target plate. The platform is presently being used for several mechanics experiments in our laboratory.

Space-technology development

In collaboration with the UR Rao Satellite Centre (URSC), ISRO and the Kumar lab (IISc), we are developing a suite of in-house capabilities for space-related technology development. On-going work includes a lab-on-chip inspired biological payload (called MANAS), a random-positioning device for simulating microgravity, as well as a vaccuum chamber for simulating outer space atmospheres.

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