Sushanta Kumar Panigrahi

Bio: Sushanta Kumar Panigrahi is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Alloy & Microstructure. The author has an hindex of 28, co-authored 81 publications receiving 2594 citations. Previous affiliations of Sushanta Kumar Panigrahi include Indian Institute of Technology Roorkee & École centrale de Nantes.

Analytical approach to damage prediction in incremental sheet metal forming

Abstract: Incremental sheet metal forming (ISF) is known to exhibit higher formability compared to conventional stamping. It is established that the mechanism of failure during ISF is by fracture occurring at higher effective strain than the local necking observed in traditional forming processes. The deformation limit in ISF is therefore estimated numerically using a suitable continuum damage model. However, simulation of incremental forming process including the damage model is often computationally expensive. In the present work, a simpler alternative combining finite element simulation and numerical solution outside finite element software is utilized. The finite element simulation is performed ignoring the damage model. The stress and strain history thus obtained in critical locations is utilized to estimate the damage evolution. The proposed method is useful when utilizing uncoupled continuum damage models. The proposed method is validated for typical cases by comparing it against the predictions from finite element method. Excellent correlation is observed between the proposed method and finite element simulation results.

Modified Method of Characteristics for Analysing Cold Flow in Bell-Type Rocket Nozzle

Abstract: To achieve higher thrust force, numerical investigation of flow behaviour of bell-type rocket nozzle has been carried out in the present research work. Analysis of thermodynamic properties is performed by using ANSYS Fluent software. K-ω shear stress transport model has been used to study the turbulent components of thermodynamic properties. Overall performance gain of a bell-type nozzle and nozzle geometric modifications are discussed. The nozzle geometric modifications are highlighted by executing a C-code with concepts of the method of characteristics (MOC) and modified method of characteristics (MMOC). With modified geometry as per the modified method of characteristics (MMOC), the present numerical study has ensured the fully expanded cold flow in nozzle. The results obtained by the method of characteristics (MOC) are compared with the calculations of the thrust force for the modified geometry.

A comprehensive study on size-effect, plastic anisotropy and microformability of aluminum with varied alloy chemistry, crystallographic texture, and microstructure

Abstract: Fabrication of microparts with large aspect-ratio and complex shapes remains a huge challenge for industries and microforming is a potential solution to manufacture such microparts. However, similarity in specimen-deformation and microstructural length scales during microforming results in size effect, leading to unpredictable plastic behavior and increased process scatter. One approach to counter size effect is by engineering suitable microstructure in the material. In the present work, three grades of Al (AA1070, AA5083, AA2014) with unique alloy chemistry and microstructural profile are processed by cryorolling (CR) to 95% thickness reduction. By imparting controlled postprocess annealing on the CR materials, three distinctive microstructures – (i) ultrafine grained (UFG) with average grain size around 1 μm, (ii) fine grained (FG) with average grain size near to 5 μm, and (iii) coarse grained (CG) with approximate average grain size of 20 μm are engineered. The influence of alloy chemistry, grain boundary engineering and crystallographic texture on microformability are studied. For pure Al (AA1070), the UFG and FG microstructures show superior microformability than the CG counterparts. The equiaxed UFG grains present in these microstructures mitigate the size effect abnormalities by increasing the number of grains in the deformation volume and uniformly distributing the complex microforming strain via grain boundary mediated plasticity. Their corresponding texture containing strong Copper mixed with scattered Cube elements promotes in-plane strain condition and high resistance to localized thinning. Also, the material shows near-zero planar anisotropy that leads to a homogenous in-plane strain distribution. Unlike pure Al, the UFG and FG Al alloys suffer from increased strain localization due to presence of solute clouds and nanoprecipitates. They influence strain-aging (Portevin–Le Chatelier effect), strain gradient hardening phenomenon, and shear propensity during failure of the Al alloys. A composite texture consisting of a combination of Brass, Dillamore, S, and β-fiber elements in the Al alloys is found to be detrimental to their microformability. The Dillamore texture is contributed by formation of adiabatic shear bands during deformation of Al alloys.

Friction Stir Welding of Austenitic Stainless Steel to an Aluminum‐Copper Alloy

Abstract: Friction stir welding of austenitic stainless steel AISI 321 to an Al-Cu alloy AA 2219-T87 (3 mm thick sheets) was investigated for a specific aerospace application. Welding experiments were carried out using WC-Co tools with different pin profiles. The effects of process parameters, including tool positioning were studied. After careful process optimization, welds with a tensile strength of close to 250 MPa were successfully produced. The welds showed a very rugged stainless steel/aluminum interface as well as some fragments of stainless steel in the stir zone, confirming complete removal of the oxide film on the stainless steel faying surface due to the wearing action of the stirring aluminum. A very thin intermetallic layer (consisting of FeAl, Fe3Al and AlCrFe2 phases) was observed in the SS/Al interface.

Nanostructured aluminium alloys produced by severe plastic deformation: New horizons in development

Abstract: In recent years, much progress has been made in the studies of nanostructured Al alloys for advanced structural and functional use associated both with the development of novel routes for the fabrication of bulk nanostructured materials using severe plastic deformation (SPD) techniques and with investigation of fundamental mechanisms leading to improved properties. This review paper discusses new concepts and principles in application of SPD processing to fabricate bulk nanostructured Al alloys with advanced properties. Special emphasis is placed on the relationship between microstructural features, mechanical, chemical, and physical properties, as well as the innovation potential of the SPD-produced nanostructured Al alloys.