Research

My groups's research interests fall in the broad category of experimental and computational investigation of materials, structures and manufacturing processes. These include to some extent, the experimental supervision and in great detail formulating and application of computational frameworks and material constitutive models for metals, soft materials and their interfaces at different length scales. Our interests in these models are broad, spanning a wide range of macro-, micro- and nano-scale phenomena. Main areas of my research in the recent past and present include

1. Data Driven Computational Mechanics

Data driven computational mechanics in the context of boundary value problems deal with the direct use of experimental data to eliminate the efforts, uncertanties and error induced during material constitutive model formulations and inverse modelling (material parameter identification). We have developed a data driven solver to deal with more than two state variables, i.e. stresses, strains, strain rates, and failure, for nanomaterials.

2. Deformation and Failure in Materials and their Interfaces

2.1 Metal/Ceramic Interface Fracture

Metal/ceramic interface fracture of niobium/alumina bicrystal interface had been studied at Max-Planck Institute for metal research, Stuttgart, Germany since last three decades. It was found that fracture energy of the system changes in some case by 20 times for different orientations of the bicrystal specimen. In this work a length scale bridging procedure was proposed to simulate the interface fracture of niobium/alumina bicrystal specimens. An automatic identification procedure has been proposed to identify crystal plasticity parameters involved in the material constitutive equations. Using this procedure, a large number of parameters can be identified in few minutes that used to take weeks if done manually. Effect of crystal orientation on the crack initiation energies was studied. It was found that by changing the orientation of the single crystalline material does influence the fracture energies of the bicrystal interface. The trends of these fracture energies were found to be the same as were found in the experiments. The physical phenomena involved in the variation of fracture energies for different orientations of the interface were explained quantitatively using the analyses results. A correlation was derived among macroscopic parameter (fracture energy), and micro- and nano-scale parameters, such as cohesive strength, work of adhesion and yield stress.

Related Animations:

Selected Publications

2.2 Ductile Damage at Different Length Scales

Ductile damage in metals is the main focus of the research. My research group is involved in understanding and developing multiscale computational frameworks for materials undergoing ductile deformation and failure. We have investigated single and dual phase alloys in this context and developed computational frameworks to simulate ductile damage at various length scales.

Selected Publications

2.3 Biomaterials

This research focuses on developing computational frameworks for soft biological materials to predict deformation and failure.

Selected Publications

2.4 Nanocrystalline Materials

This research focussed on developing a multiscale constitutive model for nanocrystalline material to predict the deformation and failure at various loading rates.

Selected Publications

2.5 Composites and Syntactic Foam

Selected Publications

3. Stress Corrosion Cracking

Stress corrosion cracking is a common failure mode for steels and other high strength alloys in corrosive environments. The aim of this research is to understand underlying physical mechanisms of stress corrosion cracking in steels and develop multiscale computational framework by incorporating these physical mechanisms for better predictions.

Selected Publications

4. Additive Manufacturing

4.1 Laser Assisted 3D Metal Printing

Aim of this work is to understand the effect of scan speed, laser power, environment temperature, and scan pattern on the induced residual stresses and distortion with in the component. Also to develop a computational methodology to simulate microstructure evolution during laser melting and solidification to understand its effect on macroscale residual stresses and distortion.

4.2 Ultrasonic Consolidation

Ultrasonic consolidation process is a rapid manufacturing process used to weld thin layers of metals at low temperatures and low energy consumption. Experimental results have shown that ultrasonic consolidation is a combination of both surface (friction) and volume (plasticity) softening effects. In this work, a first attempt to simulate the ultrasonic consolidation of metals by taking into account both effects (surface and volume) at various length-scales. Comparison of the simulation results with experimental results shows similar behaviour.

It was also investigated that how different kinds of fibre and sensors can be embedded in different alloys using ultrasonic consolidation process. Also, how these embedding processes can be simulated and then optimized.

Related Animations:

Selected Publications

5. Substractive Manufacturing

This research aimed at understanding and developing computational modes for subtractive manufacturing, i.e. material removal through cutting. Work has been focussed on different materials, for example surface defect machining of silicon by considering the high-pressure phase transformation (HPPT). Other works involved machining of nickel based super alloys to understand the residual stress relaxation of the forged and quenched components.

Selected Publications

6. Conventional and Unconventional Forming Processes

This research has focused on understanding multiscale deformation and failure behaviour of materials during conventional and unconventional forming processes. Some examples of the processes under investigation include sheet metal forming, incremental sheet forming, extrusion, and wire drawing. Experimental investigation are then used to develop computational frameworks for better predictions.

Selected Publications

7. Residual Stress Measurement and Predictions

The aim of this research is to explore and investigate the possibility of measuring thermally induced residual stresses in IN718 materials quenched under different quenching conditions. Measurements were performed using slitting method, contour method and hole drilling method. FEA based modelling was performed to predict the induced residual stresses. Finally, a machining strategy was devised through computational modelling to understand predict residual stress relaxation.

Selected Publications