Browsing by Author "Sharma, P."

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Analysis and Optimization of WEDM Performance Characteristics of Inconel 706 for Aerospace Application
(Springer Netherlands rbk@louisiana.edu, 2018) Sharma, P.; Dupadu, D.; Narendranath, S.
Wire Electrical Discharge Machining (WEDM) has established itself for manufacturing of precise and complex shape components for aerospace application due to the high quality requirement of aerospace components such as normal residual stress, no cracks, no recast layer, no porosity; still there is a need to optimize the control parameter settings and evaluate the performance characteristics of the WEDM process. The experiments have been conducted on Inconel 706 which is a newly-developed superalloy specially for aircraft application. A hybrid approach has been used to optimize the material removal rate (MRR) as well as surface roughness (SR) and significant control parameters have been identified using analysis of variance (ANOVA). Microstructure analysis revealed the formation of microglobules, melted debris and microholes on the machined surface, but no microcrack was detected due to the high toughness of the alloy. Energy dispersive X-ray spectroscopy (EDAX) has been carried out to study the metallurgical changes in the WED machined surface. The topography analysis of the curved surface revealed the best surface quality of the machined component at low pulse on time and high pulse off time. A thick recast layer of 39.6 µm was observed at high pulse on time and low servo voltage. Microhardness of the machined surface was changed up to a depth of 70 µm due to cyclic thermal loading during the WEDM process. © 2017, Springer Science+Business Media Dordrecht.
Climatic effects on sugarcane productivity in India: A stochastic production function application
(2015) Kumar, A.; Sharma, P.; Ambrammal, S.K.
The present study estimates the influence of climatic and non-climatic factors on mean yield and yield variability of sugarcane crop in different weather seasons (e.g., rainy, winter and summer) in India. Sugarcane mean-yield for fourteen major sugarcane growing states from different agro-ecological zones are delimitated in panel data during 1971-2009. Regression coefficient for mean yield and yield variability production function (i.e. risk increasing or decreasing inputs) has been estimated through log-linear regression model with the help of Just and Pope (stochastic) production function specification. Empirical results based on feasible generalise least square (FGLS) estimations shows a significant effect of rainfall, maximum and minimum temperatures on sugarcane mean yield and yield variability. Whereas, average maximum temperature in summer and average minimum temperature in rainy season have a negative and statistically significant impact on sugarcane mean yield. Sugarcane mean yield positively gets affected with average maximum temperature during rainy and winter season. Copyright � 2015 Inderscience Enterprises Ltd.
Climatic effects on sugarcane productivity in India: A stochastic production function application
(Inderscience Publishers, 2015) Singh, A.; Sharma, P.; Ambrammal, S.K.
The present study estimates the influence of climatic and non-climatic factors on mean yield and yield variability of sugarcane crop in different weather seasons (e.g., rainy, winter and summer) in India. Sugarcane mean-yield for fourteen major sugarcane growing states from different agro-ecological zones are delimitated in panel data during 1971-2009. Regression coefficient for mean yield and yield variability production function (i.e. risk increasing or decreasing inputs) has been estimated through log-linear regression model with the help of Just and Pope (stochastic) production function specification. Empirical results based on feasible generalise least square (FGLS) estimations shows a significant effect of rainfall, maximum and minimum temperatures on sugarcane mean yield and yield variability. Whereas, average maximum temperature in summer and average minimum temperature in rainy season have a negative and statistically significant impact on sugarcane mean yield. Sugarcane mean yield positively gets affected with average maximum temperature during rainy and winter season. Â© Â© 2015 Inderscience Enterprises Ltd.
Combined effect of multidirectional forging and heat treatment on erosion and corrosion behaviour of the Mg-Zn-Mn alloys
(Korean Society of Mechanical Engineers, 2024) Anne, G.; Hegde, A.; Kudva, S.A.; Sharma, P.; Kumar, P.; Matapati, M.; Ramesh, S.; Sharma, S.S.
Multidirectional forging (MDF) was successfully applied to the Mg-4Zn-1Mn alloy for five passes at 300 °C. The grain size of 5 pass MDF processed samples reached 18 ± 3 µm from 256 ± 6 µm, and ?-Mg, MgZn2 and MnZn13 peaks were observed. Further MDF processed samples were solution treated (ST) at 300 °C for 2 h and quenched in SAE 20W40 oil and followed by artificial ageing (A) at 170 °C for four different timings including 1.5 h, 2 h, 2.5 h and 3.5 h respectively. The peak hardness of 219 Hv (5 pass MDF + H sample) was found in 2h artificial ageing which is 3.1 times higher compared to counterpart homogenised samples. Improvement of mechanical properties was attributed to smaller grain size and precipitation strengthening as well as distribution of the secondary phases. The combined effect of MDF and heat treatment was analysed using solid particle erosion tests at 30° and 90° impact angles using alumina. It was observed that higher impact angle (90°) had more erosion rate in all conditions and 5 pass MDF + H samples exhibited better erosion (0.0001 mg/g) due to higher hardness. On the other hand, polarisation and electrochemical impedance spectroscopy measurements were used to assess the alloys’ corrosion behaviour. The 3 pass MDF + H sample was found to have a corrosion rate of 0.0235 mm/y, which is two times lower than the counterpart 3 pass MDF processed samples and sixteen times lower than the homogenised sample (0.3838 mm/y). This was primarily due to the secondary phases’ better distribution and smaller grain size. © The Korean Society of Mechanical Engineers and Springer-Verlag GmbH Germany, part of Springer Nature 2024.
Design, fabrication and testing of a 2 DOF compliant flexural microgripper
(Springer Verlag service@springer.de, 2018) Dsouza, R.D.; Karanth P, K.P.; Theodoridis, T.; Sharma, P.
This paper presents the development of a monolithic two degrees of freedom (2 DOF), piezoelectric actuated microgripper for the manipulation of micro-objects. Micromanipulation and microassembly are the major subjects of interest in recent times and are becoming increasingly important in many domains. An effort is being made to develop a novel 2 DOF microgripper, each jaw being able to move independently to grasp and rotate objects of micro sizes. Microgripper is developed based on the compliant mechanism. The designed 2 DOF compliant microgripper is modeled using FEM and PRBM approach further validated experimentally. The microgripper is actuated using APA 120-S piezoelectric stack actuators. The displacement of the microgripper and the gripping force is measured by image processing technique using LabVIEW tools. The microgripper is subjected to various tests to measure the displacement amplification ratio and micromanipulation experiments. Wire of various sizes are used to test the grasping and rotating sequence of the microgripper. The theoretical, simulation and experimental results reveal the good performance of the microgripper. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.
Effect of addition of Ce and accumulative roll bonding on structure-property of the Mg-Ce-Al hybrid composite and its prediction and comparison using artificial neural network (ANN) approach
(Institute of Physics, 2024) Anne, G.; Bhat, N.; Vishwanatha, H.M.; Ramesh, S.; Maruthi Prashanth, B.H.; Sharma, P.; Aditya Kudva, S.; Jagadeesh, C.; Nanjappa, Y.
Light alloys play a crucial role in realizing the national strategy for energy conservation and emission reduction, as well as promoting the upgrading of manufacturing industries. Mg/Al composite laminates combine the corrosion resistance and ductility of aluminium alloy with the lightweight characteristics of magnesium alloy. The addition of Ce (rare earth elements) can improve the mechanical properties of magnesium via grain refinement and improve the ductility of the hybrid composites. In the present work, an investigation on addition of Ce into the Mg/Al matrix through Accumulative Roll Bonding (ARB) has been presented. The Mg/Ce/Al hybrid composite consists of Mg-4%Zn alloy and Al 1100 alloy with 0.2% Ce particles added between the dissimilar layers. The changes occurred in the evaluation of microstructure, corrosion and mechanical properties of the Mg/Ce/Al hybrid composite as a result of deformation process and also the addition of Ce have been explicated. The ARB parameters: temperature, rolling speed, percentage reduction, and aging time, have been studied. An increase of about 2.36 times in strength and hardness of the hybrid composite, has been reported. Further, the structure-property relations in the Mg/Ce/Al hybrid composites were aslo predict and compare using machine learning models: Decision Tree and Multi-Layer Perceptron (MLP) models. © 2024 The Author(s). Published by IOP Publishing Ltd.
Effect of wire diameter on surface integrity of wire electrical discharge machined Inconel 706 for gas turbine application
(Elsevier Ltd, 2016) Sharma, P.; Dupadu, D.; Narendranath, S.
Inconel 706 superalloy has established itself in the field of gas turbine industry because of its easy fabricability combined with high mechanical strength. Due to its high stress rupture and tensile yield strength, conventional machining of this superalloy exhibits poor surface and low dimensional accuracy of the machined components. It is well known that most of the gas turbine components include complex shaped profile with high precision and hence, wire electrical discharge machining (WEDM) of Inconel 706 has been performed to achieve the feasibility in manufacturing of complex shaped components for gas turbine application. In the current investigation, the effect of wire diameter on WEDM performance characteristics such as cutting speed, surface roughness, surface topography, recast layer formation, microhardness, microstructural and metallurgical changes have been evaluated. It was investigated that smaller diameter wire is advantageous over the larger diameter wire since it improves productivity as well as surface quality of the machined components under the same settings of control parameters. In addition, smaller diameter wire has shown comparatively lower recast layer thickness, minimum hardness alteration and shorter manufacturing time. The XRD result has confirmed the presence of residual stress within WED machined component. © 2016 The Society of Manufacturing Engineers
Effect of Wire Material on Productivity and Surface Integrity of WEDM-Processed Inconel 706 for Aircraft Application
(Springer New York LLC barbara.b.bertram@gsk.com, 2016) Sharma, P.; Dupadu, D.; Narendranath, S.
Inconel 706 is a recently developed superalloy for aircraft application, particularly in turbine disk which is among the most critical components in the gas turbine engines. Recently, wire electrical discharge machining (WEDM) attained success in machining of gas turbine components which require complex shape profiles with high precision. To achieve the feasibility in machining of these components, the research work has been conducted on Inconel 706 superalloy using WEDM process. And, the effect of different wire materials (i.e., hard brass wire, diffused wire, and zinc-coated wire) on WEDM performance characteristics such as cutting speed, surface topography, surface roughness, recast layer formation, residual stresses, and microstructural and metallurgical alterations have been investigated. Even though, zinc-coated wire exhibits improved productivity, hard brass wire was found to be beneficial in terms of improved surface quality of the machined parts. Additionally, lower tensile residual stresses were obtained with hard brass wire. However, diffused wire has a moderate effect on productivity and surface quality. Under high discharge energy, higher elemental changes were observed and also the white layer was detected. © 2016, ASM International.
Energy efficient quality of service aware virtual machine migration in cloud computing
(2018) Sharma, N.K.; Sharma, P.; Ram Mohana Reddy, Guddeti
This paper deals with mulit-objective (network aware, energy efficient, and Service Level Agreement (SLA) aware) Virtual Machines (VMs) migration at the cloud data center. The proposed VMs migration technique migrate the VMs from the underutilized PMs to the energy efficient Physical Machines (PMs) at the cloud data center. Further, the multi-objective VMs migration technique not only reduces the power consumption of PMs and switches but also guarantees the quality of service by maintaining the SLA at the cloud data center. Our proposed VMs migration approach can find the good balance between three conflict objectives as compared to other algorithms. Further, the cloudsim based experimental results demonstrate the superiority of our proposed multi-objective VMs migration technique in terms of energy efficiency and also reduces the SLA violation over state-of-the-art VMs migration techniques such as Interquartile Range (IQR), and Random VMs migration techniques at the cloud data center. � 2018 IEEE.
Energy efficient quality of service aware virtual machine migration in cloud computing
(Institute of Electrical and Electronics Engineers Inc., 2018) Sharma, N.; Sharma, P.; Guddeti, R.M.
This paper deals with mulit-objective (network aware, energy efficient, and Service Level Agreement (SLA) aware) Virtual Machines (VMs) migration at the cloud data center. The proposed VMs migration technique migrate the VMs from the underutilized PMs to the energy efficient Physical Machines (PMs) at the cloud data center. Further, the multi-objective VMs migration technique not only reduces the power consumption of PMs and switches but also guarantees the quality of service by maintaining the SLA at the cloud data center. Our proposed VMs migration approach can find the good balance between three conflict objectives as compared to other algorithms. Further, the cloudsim based experimental results demonstrate the superiority of our proposed multi-objective VMs migration technique in terms of energy efficiency and also reduces the SLA violation over state-of-the-art VMs migration techniques such as Interquartile Range (IQR), and Random VMs migration techniques at the cloud data center. Â© 2018 IEEE.
Enhancing surface characteristics of Mg-Zn-Sr alloy through cryo-ball burnishing; modeling and experimentation
(Korean Society of Mechanical Engineers, 2024) Kudva, S.A.; Anne, G.; Ramesh, S.; Sharma, P.; Jagadeesh, C.; Ritti, L.; Naik, G.M.; Divya Deepak, G.D.
In this investigation, the impact of the cryo-ball burnishing process on both the mechanical and corrosion properties of the Mg-4Zn-1Sr alloy was systematically explored. To better understand the plastic deformation occurring in Mg-4Zn-1Sr during cryo-burnishing, a finite element analysis (FEA) model was developed. The microstructure of cryo-ball burnished samples underwent characterization through scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), and surface properties were assessed using atomic force microscopy (AFM). Additionally, electrochemical impedance spectroscopy and potentiodynamic polarization tests were conducted in a simulated body fluid using an electrochemical workstation. Experimental findings revealed significant grain refinement and the presence of residual dislocations during the cryo-burnishing process, as evident in TEM analysis. XRD analysis indicated the presence of Mg, Mg17Sr2 and SrZn2 phases, with observable peak broadening in the cryo-burnished samples, attributed to structural refinement and lattice strain incorporation. Microhardness values increased with greater depth of press, with the DFN 1071 sample displaying a hardness of 80 ± 4 Hv (Ra = 1.853 µm), marking a 54 % improvement compared to the homogenized sample. The enhanced corrosion resistance of the Mg-4Zn-1Sr alloy due to cryo-burnishing is attributed to the combined effects of grain refinement, residual dislocations, and intermetallic phases. © The Korean Society of Mechanical Engineers and Springer-Verlag GmbH Germany, part of Springer Nature 2024.
Enhancing wear resistance of AZ61 alloy through friction stir processing: experimental study and prediction model
(Institute of Physics, 2024) Anne, G.; Ramesh, S.; Sharma, P.; Maruthi Prashanth, B.H.; Aditya Kudva, S.; Kumar, P.; Sahu, S.; Bhat, N.
In this study, friction stir processing (FSP) is proposed for the treatment of AZ61 alloy, and an artificial neural network is built to predict and compare the experimental wear results. The effects of different processing parameters, including spindle speed (800-1200 rpm), traveling speed (5-15 mm min−1), and depth of press (0.8-1.2 mm) on the microstructural evolution, mechanical properties, and wear behavior are investigated. Microstructural analysis reveals a grain size of 14 ± 2 μm for the FSP1 sample, with observed shifting of x-ray diffraction (XRD) peaks, indicative of texture development. Increasing spindle and traveling speeds increase the surface roughness, as observed by average roughness (Ra) values of 68.4 nm for a rotational speed of 800 rpm, traveling speed of 5 mm min−1, and shoulder depth of 0.8 mm (FSP1) and 116.3 nm for rotational speed of 1200 rpm, traveling speed of 15 mm min−1, and shoulder depth of 1 mm (FSP9). Microhardness values increase to 113.36 Hv for FSP1 and 79. 51 Hv for FSP9 compared to 65.92 Hv for the base material (BM) sample. The decrement in hardness from FSP1 to FSP9 can be attributed to increased heat input, resulting in coarse microstructure. Wear results show that FSP1 exhibits the lowest weight loss (0.003 g) and coefficient of friction (COF) (0.28) compared to other FSP conditions and BM samples (weight loss of 0.022 g and COF of 0.68). This work demonstrates the efficacy of friction stir processing in enhancing the wear resistance of magnesium alloys. © 2024 The Author(s). Published by IOP Publishing Ltd.
Evaluation of WEDM performance characteristics of Inconel 706 for turbine disk application
(Elsevier Ltd, 2015) Sharma, P.; Dupadu, D.; Narendranath, S.
Inconel 706 is a newly developed superalloy, which offers high mechanical strength alongwith easy fabricability thus making it suitable for turbine disk applications. Although Inconel 706 exhibits a substantial increase in stress rupture and tensile yield strength compared to other superalloys, its conventional machining yields poor surface finish and low dimensional accuracy of the machined components. Hence, wire electrical discharge machining (WEDM) of Inconel 706 has been performed and various performance attributes such as material removal rate (MRR), surface roughness (SR), recast surface, topography, microhardness, microstructural and metallurgical changes of the machined components have been evaluated. The experimental results revealed that servo voltage, pulse on time, and pulse off time greatly influence the MRR and SR. Due to high toughness of Inconel 706, no micro cracks were observed on the machined surface. Micro voids and micro globules are significantly reduced at low pulse on time and high servo voltage. But, there is a propensity of thick recast layer formation at high pulse on time and low servo voltage. EDAX analysis of recast surface exposed the existence of Cu and Zn which have migrated from the brass wire. The subsurface microhardness was changed to 80. ?m due to significant thermal degradation. © 2015 Elsevier Ltd.
Examining the Influence of StackinSequence on the Mechanical Properties of Hybrid Abaca-Jute Vinyl Ester Composites
(Springer Nature, 2024) Ramesh, S.; Maruthi Prashanth, B.H.; Anne, G.; Naik, G.M.; Reddy, R.; Jagadeesh, C.; Sharma, P.; Prashanth Pai, M.
This research looked on the impacts of layer arrange-ment on inter-laminar shear strength (ILSS), tensile, flexural, and impact capabilities of hybrid composite developed from 25% abaca and 25% jute fabrics reinforced 50% vinyl ester. Furthermore, the samples frac-tured under the tensile load were examined using SEM images. Utilizing a hot press process, these hybrid laminates were fabricated and sample preparation and testing were done as per ASTM criteria. The findings demonstrate that among Abaca-Jute-Abaca-Jute (AJAJ), Abaca-Jute-Abaca (AJJA), and Jute-Abaca-Abaca-Jute (JAAJ) vinyl ester composites, the Abaca-Jute-Jute-Abaca (AJJA) composites showed higher tensile modulus and strength by 23–33%, the flexural modulus and strength by 3–22%, the impact behavior, and ILSS strength by 11–33%. These benefits could be attributed to the presence of abaca fiber on the exterior of lami-nates. Fractography studies revealed that the fiber-resin bonding was superior. AJJA composites were found to be stronger than commonly used plastics in automobile interiors, making them a promising alternative. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.
Experimental Investigation on Surface Integrity in Cryogenic Machining of Maraging Steel
(Springer, 2025) Varghese, V.; Sharma, P.; Ramesh, M.R.; Dupadu, D.; Sunilkumar, S.
The study investigated the effect of machining environments such as cryogenic, wet, and dry conditions on the surface integrity of machined surfaces during end milling of MDN 250 maraging steel. During the machining of maraging steel, cutting temperatures and strain rates increased, resulting in a loss of mechanical properties and surface integrity of the machined surface. Surface integrity was an important factor influencing the components’ functional performance and quality, just like dimensional accuracy. In this study, the machining parameters such as spindle speed, feed rate, and depth of cut were kept constant, and the cutting environment was varied between cryogenic, dry, and wet conditions respectively. Surface integrity metrics such as surface roughness, microstructure evolution, residual stress, and microhardness were analyzed using Talysurf, electron back-scattered diffraction, x-ray diffraction, and Vickers microhardness test respectively. The correlated results conceded that cryogenic machining improved surface integrity compared to dry and wet machining. It also demonstrated that cryogenic machining was a viable manufacturing substitute to traditional machining using cutting fluids. The average grain size of the machined surface of the maraging steel under cryogenic, wet, and dry conditions was found to be 20.56, 24.92, and 11.54 µm respectively. The surface roughness was also reduced by up to 50% under the cryogenic environment compared to the dry environment. The residual stress results showed that stresses were compressive under dry, wet, and cryogenic environments, and the highest compressive stress was reported under a cryogenic environment (? 355 MPa). © ASM International 2025.
Impact of ply stacking sequence on the mechanical response of hybrid Jute-Banana fiber phenoplast composites
(Institute of Physics, 2024) Maruthi Prashanth, B.H.; Ramesh, S.; Shivakumar Gouda, P.S.S.; Naik, G.M.; Sharma, P.; Jagadeesh, C.; Mahantesh, M.M.; Anne, G.
Natural fiber composites are increasingly gaining popularity as a cost-effective and environmentally friendly alternative to synthetic fibers. Incorporating a variety of fibers enhances mechanical properties. The arrangement of fibers plays a crucial role in determining the mechanical characteristics of laminate composites. Therefore, the primary objective of this study is to investigate how the stacking order of jute (J) and banana (B) fibers affects the mechanical behaviour of composites made from phenolic resins. Four different fiber mat stacking sequences (J/B/B/J, B/J/J/B, J/B/J/B, and J/J/B/B) were used for developing the eco-fiber composites using the heat-press technique. Several mechanical parameters were assessed, including tensile strength, flexural strength, impact strength, and inter-laminar shear strength (ILSS). The experimental results indicated that the JBBJ composite exhibits superior tensile strength (46.65 MPa) and modulus (993 MPa) compared to the other composites due to the presence of high-strength jute fibers on the surface. Additionally, the flexural strength of the JBBJ composite (87.24 MPa) was found to be noteworthy. It was observed that the impact strength of jute fibers surpasses that of banana fibers. Consequently, the JBBJ composite demonstrates higher values for energy absorption (0.482 J) and impact strength (120 J m−1) compared to the other composites tested. Moreover, the JBBJ composite displays higher inter-laminar shear strength and hardness values compared to BJJB, JBJB, and JJBB by 30%, 35%, and 43%, respectively. Scanning electron microscope microphotographs reveal strong correlational fracture failure mechanisms, indicative of improved mechanical properties in the JBBJ composite. Based on the experimental results, it is evident that the JBBJ composite can be utilized in lightweight applications. © 2024 The Author(s). Published by IOP Publishing Ltd.
Machine Learning Solutions forÂ Predicting Bankruptcy inÂ Indian Firms
(Springer Science and Business Media Deutschland GmbH, 2025) Chaithra; Sharma, P.; Mohan, R.
The growing demand to identify potential bankrupt companies has prompted more research into bankruptcy prediction, assisting stakeholders in determining the worthiness of an investment. The Indian stock market offers investment opportunities, but it also involves risk. As a result, it is critical to invest in fundamentally sound companies for long-term investment. To address this need, we created a machine learning-based model for identifying a healthy and distressed firm in the Indian scenario. We created a dataset consisting of 118 bankrupt and 310 healthy firms. The dataset contains three labels: bankrupt, healthy, and financial distress. The addition of the financial distress category improves our ability to recognize and identify firms that are more likely to declare bankruptcy. Recognizing the shortcomings of limited data in the Indian scenario in previous research, our study aimed to include more data instances for training. The dataset included widely recognized financial ratios and macroeconomic data that recognize the interconnectedness of broader economic trends with the companyâ€™s financial health. Advanced machine learning algorithms, namely Support Vector Machine (SVM), Random Forest (RF), Extreme Gradient Boosting (XGBoost), Light Gradient Boosting Machine (LGBM), Categorical Boosting (CatBoost), Gradient Boost (GB), and K-Nearest Neighbors (KNN) were applied. The XGBoost and LGBM demonstrated the highest level of classification accuracy and also performed well on real-world data, demonstrating their potential use in supporting investors with decision-making processes. Â© The Author(s), under exclusive license to Springer Nature Switzerland AG 2025.
Measurement of WEDM performance characteristics of aero-engine alloy using RSM-based TLBO algorithm
(Elsevier B.V., 2021) Sharma, P.; Dupadu, D.; Narendranath, N.
Alloy-706 is a newly introduced exceptional class of turbine wheel alloy for high-performance aero-engine. To precisely measure the WEDM performance of complex aero-engine parts, the RSM-based TLBO algorithm is proposed in the current study. Morphology, topography, recast layer thickness, and roughness parameters of machined surface are studied to examine the surface integrity of aero-engine components. Better surface morphology, smoother topography, low roughness value, and minimum recast layer are observed at low pulse duration, high pulse-off period, and high servo voltage. RSM is used for statistical modeling of removal rate and average roughness. Then, these models are used in TLBO algorithm for individual and multiple performance optimizations. The Pareto optimal solutions are obtained for lower roughness value and highest removal rate. The microscopic investigation represents a considerable number of melted droplets, micro-holes, and craters on the WEDM-cut surface due to high energy discharge pulses followed by improper flushing of molten material. © 2021 Elsevier Ltd
Precision manufacturing of turbine wheel slots by trim-offset approach of WEDM
(Elsevier Inc., 2021) Sharma, P.; Dupadu, D.; Narendranath, S.
The present study aims to precisely manufacture the turbine wheel slot using a novel trim-offset approach of wire-electrical-discharge-machining (WEDM) in order to overcome the challenges of a conventional broaching process. Two dimensional model of turbine wheel slot is prepared in ‘ELCAM’ software to generate the computer-numerical-control (CNC) code of fir-tree-profile geometry. The experimental plan based on a trim-offset approach is executed to minimize the thermal damage and to improve the surface fatigue strength, which is most desirable for a long operating life of the jet engine. An average cutting speed of ~1.5 mm/min is observed for rough-cut and ~5 mm/min for trim-cut operation. Six categories of wires are used to manufacture the turbine wheel slots without any wire breakage and gap-short issue. The fabricated profile slots have demonstrated an average roughness (Ra) of 0.65 ?m, profile accuracy within ±5 ?m, minimum hardness alteration (34.87 Hv), and negligible recast layer (<5 ?m) using B-150 wire and fulfilled the essential requirements of the gas turbine industries. Compared to wire-electrochemical-machining (WECM), WEDM trim-offset approach is quite advantageous and should be beneficial for the researchers working in ‘Precision machining of aerospace materials’. © 2021 Elsevier Inc.
Proving the (In)Security of CRT Based Key Management Schemes Under SAOA Model
(Springer, 2024) Sharma, P.; Purushothama, B.R.
There have been several proposed methods in the literature for securely distributing group keys and managing group dynamics for secure group communications. While these methods claim to be secure against passive adversaries, our focus has been on a more powerful adversary known as a strong active outsider adversary. This adversary has the ability to corrupt legitimate users, which can result in the leakage of crucial secret information to the adversary. Such information can enable the adversary to recover both current and past group keys. One commonly utilized approach for ensuring secure group communication is group key management schemes based on the Chinese remainder theorem (CRT). In this paper, we evaluate prominent CRT-based key management schemes in the presence of an active adversary. Our findings indicate that the adversary can exploit the leaked information of the corrupted user to break backward secrecy. As a result, we demonstrate that the CRT-based schemes found in the literature are insecure against strong active adversaries and are therefore unsuitable for practical applications. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.