Sudhy S Panicker
@adishankara.ac.in
Department of Mechanical Engineering
ASIET Kalady
Scopus Publications
Scholar Citations
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Scopus Publications
Bhupesh Singh Katiyar, Sudhy S. Panicker, and Sushanta Kumar Panda
Springer Science and Business Media LLC
M. Arunkumar, P. Aneesh Kumar, S. Sampreeth, and Sudhy S. Panicker
Elsevier BV
Sudhy S Panicker and Sushanta Kumar Panda
SAGE Publications
The present work demonstrates a comparative investigation of the nonisothermal warm forward redrawing behavior of AA5754-H22 and AA6082-O sheets. The design and development of a new warm forward redrawing process was demonstrated. The complete redrawing was obtained by keeping the redrawing die and binder at 200 °C and cooling punch near to room temperature using water circulation. This process improved the thickness and surface strain distribution in redrawn cups without the onset of strain localization at the bottom corner. A thermomechanical finite element (FE) model of the nonisothermal warm redrawing process was developed applying the temperature-dependent Barlat-89 yield criterion and the Cowper–Symonds strain rate sensitive hardening model. The FE model reasonably predicted the part depth, earing development, thickness distribution, and surface strain evolution of the redrawn cups. The evolution of temperature distribution within the redrawing cup during the process was captured from FE simulations, and its role in the improvement in redrawing depth was demonstrated. Furthermore, the post-forming characterization of redrawn cup wall was also evaluated by microhardness and ring hoop tensile tests. It was found that the hardness, hoop tensile strength, and energy absorption capacity of AA5754-H22 cups were better than AA6082-O cups.
Yumi Choi, Jinwoo Lee, Sudhy S. Panicker, Hong-Kyo Jin, Sushanta Kumar Panda, and Myoung-Gyu Lee
Elsevier BV
Abstract High strength aluminum alloys have drawn much attention as the requirement for lightweight vehicle design increases in the automotive industry. However, inferior formability due to higher strength poses a technical hurdle against successful application of high strength aluminum sheets in automotive components. In this study, the mechanical properties of 7075 aluminum alloy sheet after W-temper heat treatment, which consists of solution heat treatment and subsequent quenching, are investigated. Detailed experimental and numerical studies are conducted on the anisotropy, non-proportional deformation behavior, and corresponding constitutive modeling in comparison with the corresponding characteristics of peak aged T6 heat-treated as-received alloy sheets. Based on the experimentally characterized mechanical properties and associated constitutive laws, the formability and springback of the W-tempered sheet are analyzed using the Marciniak–Kuczyinski forming limit diagram and U-draw bending springback simulations, respectively, by employing the Yld2000-2d anisotropic yield function and distortional hardening-based homogeneous anisotropic hardening model. Additionally, the improved constitutive modeling of the W-tempered 7075 aluminum sheets due to the effect of serrated flow characteristics on the hardening and frictional behaviors is discussed.
S.S. Panicker, K.S. Prasad, G. Sawale, S. Hazra, B. Shollock, and S.K. Panda
Elsevier BV
Abstract In this work, novel warm deep drawing and redrawing test setups were designed and developed, and a process sequence was proposed to enhance the forming depth of AA6082 sheet. The complete redrawing of the cup was ensured by maintaining the temperature of redrawing die and binder at 200 °C and water-circulated cooling punch near to room temperature. The warm redrawing negated the sudden thinning and strain localization at cup corner, producing an overall draw ratio of 3.38. Further, the fully redrawn cups were subjected to solution heat treatment (SHT) and subsequent different artificial aging cycle to evaluate the impact on post-forming strength. The post-forming cup wall strength was characterized using Vickers microhardness test and ring hoop tensile test (RHTT). Approximately 30% improvement in microhardness of redrawn cup wall was obtained as compared to that of the undeformed sheet, and it was due to the significant grain refinement occurred during the warm deep drawing and subsequent redrawing process as characterized by SEM and EBSD techniques. Moreover, it was observed that the heat treatment had a pronounced effect on both the hardness and ultimate hoop tensile strength of the cup wall, and the peak aged cup wall hardness and tensile strength were 119 VHN and 316.8 MPa, respectively. As verified by TEM micrographs, the precipitation of coherent large needle-shaped β′′ precipitate was responsible for the significant improvement in the strength during the aging treatment. However, the presence of plate-shaped incoherent β-Mg2Si precipitate marginally decreased the total elongation at peak aged condition. Finally, the fractographs of redrawn and different artificially aged RHTT samples were analyzed to comprehend the nature of failure.
Sudhy S. Panicker and Sushanta Kumar Panda
Springer Science and Business Media LLC
Warm forming is an attractive formability improvement technique which can be utilized to intensify the usage of aluminum alloy sheets in autobody constructions. In the present work, laboratory-scale stretch forming and deep drawing experiments were performed to demonstrate the comparative formability improvement in AA6082-O and AA5754-H22 aluminum alloy sheets at elevated temperatures. Significant enhancement of limiting dome height and forming limit diagram (FLD) was observed when stretch forming was performed at 200 °C. Warm deep drawing under both isothermal and nonisothermal conditions was carried out, and drastic improvement in drawability was found only under nonisothermal condition with an initial temperature gradient of 93 °C across the blank. Thermomechanical finite element (FE) models of the warm forming processes were developed using temperature-dependent Barlat-89 yield model coupled with Cowper–Symonds strain rate sensitivity model. The limiting dome heights, failure locations and strain distributions were well predicted by implementing experimental FLD as the failure criterion. Further, the effect of evolution of nonisothermal temperature gradient on the improvement in drawability of both the materials was analyzed in terms of cup height, earing profile, thickness distribution and surface strain evolution.
Sudhy S. Panicker, Kaushik Bandyopadhyay, and Sushanta Kumar Panda
Springer Nature Singapore
Sudhy S. Panicker, K. Sajun Prasad, Shamik Basak, and Sushanta Kumar Panda
Springer Science and Business Media LLC
In the present work, uniaxial tensile tests were carried out to evaluate the stress–strain response of AA2014, AA5052 and AA6082 aluminum alloys at four temperatures: 303, 423, 523 and 623 K, and three strain rates: 0.0022, 0.022 and 0.22 s−1. It was found that the Cowper–Symonds model was not a robust constitutive model, and it failed to predict the flow behavior, particularly the thermal softening at higher temperatures. Subsequently, a comparative study was made on the capability of Johnson–Cook (JC), modified Zerilli–Armstrong (m-ZA), modified Arrhenius (m-ARR) and artificial neural network (ANN) for modeling the constitutive behavior of all the three aluminum alloys under the mentioned strain rates and temperatures. Also, the improvement in formability of the materials was evaluated at an elevated temperature of 623 K in terms of cup height and maximum safe strains by conducting cylindrical cup deep drawing experiments under two different punch speeds of 4 and 400 mm/min. The cup heights increased during warm deep drawing due to thermal softening and increase in failure strains. Also, a small reduction in cup height was observed when the punch speed increased from 4 to 400 mm/min at 623 K. Hence, it was suggested to use high-speed deformation at elevated temperature to reduce both punch load and cycle time during the deep drawing process.
Sudhy S. Panicker and Sushanta Kumar Panda
ASME International
Automotive industries are very much interested in implementing warm forming technology for fabrication of light weight auto-body panels using aluminum alloys without localized thinning or splitting. A nonheat treatable and low formable AA5754-H22 aluminum alloy sheet was selected in the present work, and a laboratory scale warm deep drawing test set-up and process sequences were designed to improve material flow through independent heating of punch and dies. Significant enhancement in cup depth was observed when the temperature of punch and dies were set to 30 °C and 200 °C, respectively. Thermo-mechanical finite-element (FE) model of the nonisothermal deep drawing test was developed successfully to study the improvement in material flow incorporating Barlat-89 yield theory using temperature dependent anisotropy coefficients and Cowper–Symonds hardening model. It was found that a nonisothermal temperature gradient of approximately 93 °C was established within the blank from the center to flange at the start of deformation, and subsequent evolution of temperature gradient helped in improving material flow into the die cavity. The effect of temperature gradient on forming behavior in terms of cup height, ear profile, and thinning development across flange, cup wall, and blank center were predicted and validated with experimental results.
Sudhy S. Panicker, Har Govind Singh, Sushanta Kumar Panda, and Richard Dashwood
Springer Science and Business Media LLC
AbstractAutomotive industries are very much interested in characterization of formability improvement of aluminum alloys at elevated temperatures before designing tools, heating systems, and processing sequences for fabrication of auto-body panels by warm forming technology. In this study, tensile tests of AA5754-H22 aluminum alloy were carried out at five different temperatures and three different strain rates to investigate the deformation behavior correlating with Cowper-Symonds constitutive equation. Laboratory scale warm forming
facilities were designed and fabricated to perform limiting dome height and deep drawing tests to evaluate forming limit strains and drawability of sheet metal at different tool temperatures. The forming limit strain and dome height improved significantly when both the die and punch were heated to 200 °C. Remarkable improvement in deep drawn cup depth was observed when die and punch temperatures were maintained at 200 and 30 °C, respectively, producing a non-isothermal temperature gradient of approximately 93 °C across the blank from flange to center. The forming behavior at different isothermal and non-isothermal conditions were predicted successfully using a thermo-mechanical FE model incorporating temperature-dependent properties in Barlat-89 yield criterion coupled with Cowper-Symonds hardening model, and the thinning/failure location in deformed cups were validated implementing the experimental limiting strains as damage model.
Sudhy S. Panicker and Sushanta Kumar Panda
Elsevier BV
Tensile properties of AA5754 alloy were evaluated within a temperature range 30-250˚C with three different strain rates. The total elongation was found to increase with temperature despite decrease in strain hardening exponent, and this is due to exponential rise of strain rate sensitive index (m-value). Formability evaluated by limiting dome height test was compared with the results obtained from FE simulations incorporating two different material models to investigate the effect of anisotropy parameters (R-value) and m-value in warm forming. It was found that the improvement in formability in warm condition is significantly influenced by m-value.