Anurag Bhattacharyya

Research Overview:

My research objective is to explore material and architected design domains to generate multi-functional structures for advanced engineering applications. Specifically I exploit geometric and material nonlinearities along with the behavior of stimuli sensitive materials to enhance local responses for controlling global structural behavior. My approach primarily consists of using computational tools like finite element analysis, adjoint sensitivity evaluations, topology optimization, high performance computing and is supported by additive manufacturing.  

Background: 

The world is looking for energy efficient, light-weight, compact and easily manufacturable multi-functional structural systems. However, designing such systems under competing constraints using conventional materials and design techniques leads to inefficiency and suboptimal performance.  This creates an opportunity for the development of computational design and optimization frameworks leveraging material properties and geometry to design structures that can exhibit mechanical properties and structural response far superior than what can be obtained via traditional methods. These methods can not only develop structures capable of mimicking the nature (e.g. developing compliant mechanisms or functionally graded structures) but can also surpass it by generating features not observed in the natural world (e.g. generation of wheeled vehicles). Structural design optimization/topology optimization (TO) methods have been successfully applied to design structures or systems with unusual deformation characteristics which cannot be designed from forward design procedures. It has been used to optimally combine several isotropic materials to design structures exhibiting extreme bulk and shear modulus values close to theoretical Hashin-Shtrikman bounds. Researchers have used TO for developing 3D architected auxetic metamaterials showing extreme Poisson ratio ranges from -0.8 to 0.8 over deformations as high as 20% which cannot be designed from conventional materials or design techniques. TO has also been successfully coupled with additive manufacturing techniques to design non-intuitive mechanisms. It has been applied to design displacement amplifier structures capable of amplifying output displacement to as high as 8 times the input displacements. Apart from the design of displacement amplifiers, TO has also been used to tailor the direction of output displacements. These kinds of structures are referred to as compliant inverters and provide displacement in the direction opposite to the input displacements. Another advantage of using TO is to design structures and mechanisms capable of changing deformation states without the use of inefficient traditional actuators. TO has been successfully applied to design shape-morphing structures by inverse design of mechanisms capable of displaying multiple stable states which cannot be designed via forward design approaches. The power of TO can also be leveraged to not only optimally design single structures or mechanisms but to co-design multiple structures under various physical and mechanical constraints thereby allowing designers the freedom to design system of structures with arbitrary levels of complexity and with tailored performance characteristics.

Currently, I am a Design Optimization Engineer at Lawrence Livermore National Laboratory working in the Center for Design Optimization (CDO) group. Previously, I worked as an  Advanced Computer Scientist at the Palo Alto Research Center, SRI International. I was associated with the Intelligent Systems Laboratory (ISL). I obtained my Ph.D. from the University of Illinois at Urbana-Champaign (UIUC) under the supervision of Prof. Kai James. At UIUC and PARC, my research was mainly focused on two broad domains:

• Exploit geometric and material nonlinearities to design multifunctional structures that can replace traditional actuators and thereby increase the efficiency of mechanical systems. 

• Design structures capable of performing complex 3D motions and morph into target shapes through external stimulus application.

The research in these domains have led to several novel designs and demonstrations. These can be summarized as below:

1. I developed a novel airfoil camber morphing mechanism that could significantly reduce the energy required for airfoil shape adaptation by leveraging bistabilty. I demonstrated that by tailoring the snap-through instabilities via TO we can actuate and maintain the shape of the morphing airfoil. The design could also reduce weight and maintenance cost by the virtue of part consolidation. 

2. Different SMP materials have different properties and unique behaviour under the application of the thermo-mechanical programming cycle. I developed an algorithmic design framework to distribute two or more SMP materials inside a design domain to obtain complex non-axial deformations just by application of simple axial stretching or compression as generally implemented for programming SMP materials.

3.  A novel hierarchical design framework for computationally designing 3D structures exhibiting large-deformation kinematics under external stimulus application was proposed, implemented, and validated experimentally.

My research interests are:

1) Topology Optimization: Multifunctional mechanism design, soft robotics, multi-physics design optimization, dynamic response.

2) Materials by design: Metamaterial design, biomimetic structures, inverse design

3) Design methods: model-order reduction, adjoint-free methods, machine learning driven structural design, structural design under uncertainty.

4) Computational fabrication: 4D printing