Gauri Rajendra Mahalle
@bits-pilani.ac.in
Research Scholar,
Mechanical Engineering Department, BITS-Pilani, Hyderabad Campus, TS, India
RESEARCH INTERESTS
• Sheet Metal Forming
• Material Modelling and Characterization
• Finite Element Analysis
• Machine Design, Product Design & Development
• Fracture Mechanics and Damage Modelling
• Warm and Hot Forming of Advanced High Strength Materials
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Aarjoo Jaimin, Gauri Mahalle, Nitin Kotkunde, and Swadesh Kumar Singh
Informa UK Limited
Gauri Mahalle, Nitin Kotkunde, Amit Kumar Gupta, and Swadesh Kumar Singh
SAGE Publications
Wrinkling is generally induced because of metal instability and considered as an undesirable defect in sheet metal forming processes. Wrinkling leads to severe influence on functional requirements and aesthetic appeal of final component. Thus, the present research is mainly dedicated on the experimental and numerical analysis for wrinkling behavior prediction of Inconel 718 alloy at elevated temperature conditions. Initially, Yoshida buckling tests (YBT) have been conducted to investigate wrinkling tendencies of Inconel 718 alloy from room temperature (RT) to 600°C by an interval of 200°C. Subsequently, Finite Element (FE) analysis of YBT has been performed to analyze post buckling behavior. Critical strain values at onset of wrinkling are determined and strain based wrinkling limit curves (ε-WLCs) are plotted at different temperatures. In-plane principal strains are transferred to effective plastic strain (EPS) versus triaxiality (η) space to differentiate the transformation between safe and wrinkling instability. Finally, complete forming behavior of alloy is represented by means of fracture, forming, and wrinkling limit curves. The gap between forming and wrinkling limit curves at elevated temperature is ∼1.5 times higher than that at room temperature.
Satyajit Dey, Zhijin Lyu, Gauri Mahalle, Anas Achouri, and Abdullah Al Mamun
Elsevier BV
Gauri Mahalle, Thomas P. Davis, William E. Lee, and Abdullah Al Mamun
Elsevier BV
Gauri Mahalle, Prathamesh Takalkar, Nitin Kotkunde, Amit Kumar Gupta, and Swadesh Kumar Singh
Springer International Publishing
V. Dharam Singh, Gauri Mahalle, Nitin Kotkunde, Swadesh Kumar Singh, and M. Manzoor Hussain
Informa UK Limited
ABSTRACT The α-Brass alloy is gaining special attention for electrical and thermal conductivity applications because of being easily formed/workability and retaining high strength after forming. This makes crucial to understand the plastic deformation behaviour and work hardening behaviour of a material for reliable finite element simulations. In present study, the hot uniaxial tensile flow stress analysis of α-Brass alloy thin sheet has been carried out under a quasi-static strain rates of 0.1–0.001/s at the temperature range of 300 K–773 K. Flow stress behaviour has significantly affected with test temperatures, strain rates and sheet orientations. Anisotropy in terms of yield stress variation and % elongation by in-plane anisotropy and Anisotropy index have been evaluated. Further, stress–strain relation has been analysed by popular empirical strain hardening equation namely, Hollomon and Swift. The work hardening behaviour of alloy has been well-defined by Swift relationship compare to Hollomon empirical relation.
V Dharam Singh, Gauri Mahalle, M Manzoor Hussain, Nitin Kotkunde, and Swadesh Kumar Singh
Informa UK Limited
K. Seshacharyulu, Gauri Mahalle, Nitin Kotkunde, Swadesh Kumar Singh, and B. Balu Naik
Informa UK Limited
K. Seshacharyulu, Gauri Mahalle, Nitin Kotkunde, Swadesh Kumar Singh, and B. Balu Naik
Springer Science and Business Media LLC
Gauri Mahalle, Nitin Kotkunde, Amit Kumar Gupta, and Swadesh Kumar Singh
Springer Science and Business Media LLC
It is vital to envisage accurately the fracture limits of high strength superalloys when noticeable localized necking or thinning tendency is not observed during sheet-metal stretch forming process. The present study mainly focuses on fracture limits evaluation of Inconel 718 alloy (IN718) in the effective plastic strain (EPS) vs. average triaxiality space. First, uniaxial tensile test, to analyze the material properties, were instigated at different test temperatures (RT-700 °C). Subsequently, stretch forming is performed to evaluate forming and fracture forming limit diagrams (FLD and FFLD) of IN718 using Nakazima test. It is observed that forming and fractured limits of IN718 are significantly influenced by variation of processing temperatures (with approximately 65–70% improvement in major safe and fracture strains) in all deformation regions (with respect to RT). In average triaxiality (η) vs effective plastic strain (EPS) space, higher fracture limits of IN718 are noticed in the entire triaxiality path of deformation region. Seven different ductile fracture models, namely McClintock (M-Mc), Brozzo, Rice-Tracey (R-T), Ko, Oh, Cockcroft and Latham (C-L), and Clift, are formulated so as to foresee the fracture loci of IN718 in EPS vs. triaxiality space. Overall, Oh model, showed best predictability at all temperatures with least Average absolute error (AAE < 13.5%).
Sandeep Pandre, Ayush Morchhale, Gauri Mahalle, Nitin Kotkunde, Kurra Suresh, and Swadesh Kumar Singh
Springer Science and Business Media LLC
Gauri Mahalle, Nitin Kotkunde, Amit Kumar Gupta, and Swadesh Kumar Singh
Elsevier BV
Abstract Fracture Forming Limit Diagram (FFLD) is gaining special attention for high strength materials like Inconel 718 alloy where the substantial necking tendency rarely seen. The present study mainly aims at accurate evolution of forming limits for Inconel 718 alloy with an improved Marciniak–Kuczynski (M-K) model coupled and various ductile fracture criteria. Firstly, uniaxial test has been performed for analyzing material properties and anisotropic parameters. The stretch forming tests have been conducted to evaluate the limiting forming limits of Inconel 718 alloy. Subsequently, an improved M-K model coupled with ductile fracture criteria has been developed for the theoretical prediction of the fracture strains. The different ductile fracture criteria, namely; Clift, Cockcroft and Latham, Oyane and Brozzo, have been implemented in the improved M-K model. A Newton–Raphson method has been used to solve improved M-K model. The improved M-K model coupled with Oyane’s fracture criterion has shown good predictability of the fracture loci with the least average absolute errors and root-mean-square deviation ( Δ avg = 0.075 and RMSD = 0.105).
Gauri Mahalle, Nitin Kotkunde, Amit Kumar Gupta, Swadesh Kumar Singh, and Chetan P. Nikhare
American Society of Mechanical Engineers
Abstract Inconel 718 is a high strength, precipitation-hardenable Ni-Fe-Cr-based superalloys, mostly used in nuclear and aerospace applications in extreme working conditions. In this work, hot deformation behavior of the Inconel 718 alloy sheet has been investigated at 700°C under multiaxial loading conditions. The forming behavior has been analyzed along three distinct deformation modes (biaxial stretch, plane strain, and uniaxial stress regions) and results were quantified using a Gurson-Tvergaard-Needleman (GTN) damage model. Firstly, uniaxial tensile tests have been performed at 700°C and quasi-static strain rates (0.0001–0.01 s−1) to identify the material constants of the damage model. Further, the standard Nakazima test has been conducted to describe the forming and fracture behavior along three deformation modes. Further, Marciniak-Kuczynski model using a GTN damage model with Barlat’89 anisotropic yield criteria have been used for theoretical prediction of failure strains for Inconel 718 alloy. This model shown a good prediction capability in terms of fracture strains. Subsequently, Finite element (FE) analysis of Nakazima test coupled with plastic and damage modeling has been carried out to predict failure behavior of the Inconel alloy. The FE predicted results showed good agreement with the experimental test in predicting the fracture behavior of the alloy. The presented results give a basis of optimal hot forming process of Inconel 718 alloy.
Gauri Mahalle, Omkar Salunke, Nitin Kotkunde, Amit Kumar Gupta, and Swadesh Kumar Singh
IOP Publishing
Gauri Mahalle, Ayush Morchhale, Nitin Kotkunde, Amit Kumar Gupta, Swadesh Kumar Singh, and Y.C. Lin
Elsevier BV
Abstract Forming and fracture forming limit diagrams are significant performance indexes for evaluating the formability of a material. In the present study, experimental and theoretical investigations of the forming and fracture behavior for precipitate-hardenable Inconel 718 superalloy, have been performed at different temperatures (Room temperature (RT) to 700 °C). Firstly, uniaxial tests have been conducted over a temperatures range and quasi-static strain rates (10−4-10−1s−1). Flow stress (tensile) has been found to be significantly affected by variation in test temperatures and strain rates. Further, yielding behavior of IN718 alloy has been predicted based on Hill'48 (r and σ based) and Barlat'89 criteria. Barlat'89 criterion has better predictability of yielding behavior for IN718 alloy at all test temperatures. Subsequently, experimental forming and fracture limit curves have been plotted at different temperatures using Nakazima test. Limiting true strains have been found to be increasing with test temperature for all deformation regions in forming limit diagrams. Marciniak Kuczynski (M-K) and Bao-Wierzbicki (B-W) model coupled with anisotropic yield criteria have been used for theoretical prediction of limiting and failure strains for IN718. The M-K and B-W models coupled with only Barlat'89 criteria have shown a good prediction ability of limiting strains with least root mean square error (RMSE) and average absolute error (AAE).
Gauri Mahalle, Nitin Kotkunde, Amit Kumar Gupta, and Swadesh Kumar Singh
Informa UK Limited
ABSTRACT Tensile flow behaviour attracts a continue attention in enhancing material processing and ensuring secure performance during metal forming processes. In present study, tensile deformation behaviour of Inconel 718 alloy have been investigated from room temperature (RT) to 700°C, strains (from 0.01 to 0.3 with interval of 0.01) at strain rates of 0.0001-0.01 s−1. From experimental observation, it is observed that flow stress behaviour was considerably influences by temperature and strain rate variation. Additionally, constitutive models, mainly Khan–Huang–Liang (KHL) and modified Fields–Backofen (mFB) models have developed to predict flow stress behaviour. Statistical parameters, mainly average absolute error (Δ), correlation coefficient (R) and root mean square error (s), have been evaluated the prediction capability of models. KHL model has given highest coefficient of correlation (R = 0.9182); this signifies suitability of KHL model for flow prediction of Inconel 718 alloy.
Gauri Mahalle, Nitin Kotkunde, Amit Kumar Gupta, and Swadesh Kumar Singh
Informa UK Limited
Inconel 718 alloy (IN718) is a high-strength material and is widely used in aerospace and nuclear applications for extreme working conditions. IN718 alloy is difficult to form at room temperature (...
C. Anand Badrish, Nitin Kotkunde, Gauri Mahalle, Swadesh Kumar Singh, and K. Mahesh
Springer Science and Business Media LLC
In this study, hot deformation behavior of Inconel 625 alloy has been investigated from room temperature to 700 °C at an interval of 100 °C with slow strain rates (0.0001-0.1 s−1). Flow stress behavior is significantly influenced by temperature and strain rate changes. Dynamics strain aging behavior has been reported from 300 to 700 °C. Various mechanical properties, namely tensile strength, % elongation, strain rate sensitivity and strain hardening capacity (Hc), have been studied over wide range of temperatures and strain rates. Hc values remarkably improved at higher temperatures which indicate an excellent combination of strength and ductility. Additionally, various anisotropic material parameters, namely Lankford coefficient, normal, planer and in-plane anisotropy and anisotropic index, were evaluated. Furthermore, hardening behavior of Inconel 625 alloy has been analyzed by various flow stress equations like Hollomon, Ludwik, Swift and Voce. Two-stage strain hardening behavior has been noticed at all temperatures. Ludwik and Swift equations represent poor prediction capability at lower strain region. Based on statistical parameter comparison, Voce equation prediction capability is found best in agreement with both strain regions. Finally, the fracture morphology of post-tensile specimens has been studied, indicating ductile–brittle fracture with dimples.
Gauri Mahalle, Nitin Kotkunde, Amit Kumar Gupta, R. Sujith, Swadesh Kumar Singh, and Y. C. Lin
Springer Science and Business Media LLC
An accurate constitutive model is essential for analyzing deformation behavior of material and reliable numerical simulations in metal forming processes. In this study, hot tensile tests of Inconel 718 alloy have been conducted over a wide range of temperatures (300-973 K at an interval of 100 K), strains (0.01-0.3 at an interval of 0.01) and quasi-static strain rates (0.0001, 0.001, 0.01 s−1). Flow stress behavior is significantly affected by test temperatures and strain rates. Microstructure characteristics of deformed test specimens have been examined using scanning electron microscope and electron backscatter diffraction (EBSD). The fractography study revealed that fracture is mix-mode type, i.e., ductile and brittle. Subsequently, EBSD analysis shown that dynamic recrystallization mechanism is more pronounced at a higher temperature. Furthermore, four constitutive models, namely modified Cowper–Symonds, modified Johnson Cook, modified Zerillie-Armstrong and integrated Johnson Cook–Zerillie-Armstrong (JC-ZA) models have been investigated for flow stress prediction. Capability of models has been evaluated based on the correlation coefficient (R), average absolute error (Δ) and its standard deviation (δ). Accurate prediction of flow stress behavior is found by integrated JC-ZA model with R = 0.9873, Δ = 2.44 and δ = 4.08%.
Gauri Mahalle, Omkar Salunke, Nitin Kotkunde, Amit Kumar Gupta, and Swadesh Kumar Singh
Elsevier BV
Abstract Inconel alloys are gaining a special attention for high temperature applications in service environment of aircraft structures, rocket engines, nuclear reactors, gas turbines and pressure vessels. This makes crucial to understand anisotropic material properties and work hardening behavior of a material. In this study, various mechanical properties such as ultimate strength σ u t s , yield strength σ y s , strain hardening exponent (n) and % elongation have been evaluated by using uniaxial tensile tests. The tensile tests have been conducted from room temperature to 600°C at an interval of 100°C with different slow strain rates (0.0001, 0.001, 0.01 s−1). Additionally, anisotropy of Inconel 718 alloy has been evaluated based on various measurable parameters such as normal anisotropy, planer anisotropy, in-plane anisotropy and anisotropic index. Furthermore, stress–strain response is analyzed by empirical work hardening equation by Hollomon, Swift, Ludwick and Voce. The Artificial Neural Network (ANN) models have been developed to predict various anisotropic mechanical properties and hardening behavior of Inconel 718 alloy. The ANN model is skilled by Levenberg–Marquardt algorithm and signifies a good accuracy of model with an excellent correlation coefficient and significantly low average absolute error. Validation for the accuracy of developed ANN model is confirmed with results from f-test and mean paired t-test.
Gauri Mahalle, Nitin Kotkunde, Amit Kumar Gupta, and Swadesh Kumar Singh
Springer Singapore
Gauri Mahalle, Omkar Salunke, Nitin Kotkunde, Amit Kumar Gupta, and Swadesh Kumar Singh
American Society of Mechanical Engineers
Abstract The study of anisotropic deformation behavior of material plays a key role in optimizing the hot working process parameters. Further, trustworthiness of Finite Element (FE) analysis in hot working condition is highly dependent on accurate input of mechanical properties and anisotropic yield parameters. In present work, two different anisotropic yield criteria, namely; Hill 1948 and Barlat 1989 are developed from Room Temperature (RT) to 500 °C and different slow strain rate conditions (0.01, 0.001 and 0.0001 s−1) for Inconel 718 alloy. First, uniaxial tensile test carried out from RT to 500 °C with an interval of 100°C and at quasi-static strain rate conditions at different orientation of a sheet (0°, 45° and 90°). Based on the tensile test data, extended Von-Mises isotropic criterion i.e. Hill 1948 and Barlat 1989 yield criterion were developed at different conditions. The predictability of yield criteria has been verified using yield loci, variation of anisotropic coefficient and yield stresses. The various static parameters such as correlation coefficient, relative error and standard deviation are considered to compare the yield criteria. Based on the comparison, Barlat 1989 yield criterion shows good in agreement with experimental data.
Gauri Mahalle, Nitin Kotkunde, Amit Kumar Gupta, and Swadesh Kumar Singh
Elsevier BV
Abstract Understanding material properties and deformation behavior are key prerequisite to optimize process parameters for improving working conditions suitable for material processing and ensuring safe performance during hot working. The main objective of this study is to relate the static and dynamic flow behavior of Inconel 718 alloy with strain hardening and strain rate by a well-known constitutive model, Cowper-Symonds (CS) equation. A comparative study has been made on modified Cowper-Symonds (m-CS) strain hardening model to study the effect of strain, strain rate dependency and temperature on material behaviour. For this, m-CS is developed with various material constant for Inconel alloy and compared. By comparing the average absolute error, correlation coefficient and its standard deviation, the suitability of m-CS model was evaluated. The proposed m-CS model could predict the flow behaviour at high strain rates and elevated temperatures of Inconel alloy validated better agreement with experimental data.
Gauri Mahalle, Nitin Kotkunde, Rushabha Shah, Amit Kumar Gupta, and Swadesh Kumar Singh
IOP Publishing
Gauri Mahalle, Nitin Kotkunde, Amit Kumar Gupta, and Swadesh Kumar Singh
Elsevier BV
Abstract A reliable and accurate prediction of material properties and flow behavior of metals considering the coupled effects of strain, strain rate and temperature is a crucial parameter for optimizing the workability. In this study, hot uniaxial tensile tests have been performed on Inconel 718 alloy from Room Temperature (RT) to 600°C at an interval of 200°C and strain rates from 0.1 s-1 to 0.0001 s-1. Generally, the anisotropy of rolled sheet influences the material properties, material properties have been determined with respect to rolling direction (RD), Normal direction (ND) and transverse direction (TD). The various material properties such as yield stress (σy), ultimate tensile strength (σu), total elongation and strain hardening exponent (n) have been evaluated over the range of temperatures and strain rates. Considerable variation in the material properties have been noticed with respect to temperature than strain rate. Furthermore, microstructure analysis has been carried out using optical microscopy and Scanning Electron Microscope (SEM). SEM micrographs with EDS analysis of fracture specimens revealed carbides with the non-homogeneous distribution of large number of δ precipitates. SEM study confirms dimples and shear band which indicate predominantly ductile fracture in all the cases