Browsing by Author "Krishna, P."

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An intelligent system for squeeze casting process—soft computing based approach
(Springer London, 2016) Gowdru Chandrashekarappa, G.C.; Krishna, P.; Parappagoudar, M.B.
The present work deals with the forward and reverse modelling of squeeze casting process by utilizing the neural network-based approaches. The important quality characteristics in squeeze casting, namely surface roughness and tensile strength, are significantly influenced by its process variables like pressure duration, squeeze pressure, and pouring and die temperatures. The process variables are considered as input and output to neural network in forward and reverse mapping, respectively. Forward and reverse mappings are carried out utilizing back propagation neural network and genetic algorithm neural network. For both supervised learning networks, batch training is employed using huge training data (input-output data). The input-output data required for training is generated artificially at random by varying process variables between their respective levels. Further, the developed model prediction performances are compared for 15 random test cases. Results have shown that both models are capable to make better predictions, and the models can be used by any novice user without knowing much about the mechanics of materials and the process. However, the genetic algorithm tuned neural network (GA-NN) model prediction performance is found marginally better in forward mapping, whereas BPNN produced better results in reverse mapping. © 2016, Springer-Verlag London.
Analysis of Materials Expansion Properties for Computation of Thermal Error Compensation Values for Machine Tool Applications
(Springer Nature, 2024) Shanmugaraj, V.; Shruthi, G.; Shettigar, A.K.; Krishna, P.
One of the major causes of the total geometric inaccuracy of the machine is the thermo-mechanical error due to the deformation of machine tools, which is caused by both internal and external heat sources. Understanding the factors driving this is crucial to bring down errors to negligible values on machine tools. There are many different thermal factors, and it is a combination of all of these influences and their histories that determines the actual temperature on the distribution on the elements of machine tools. The expansion properties of the machine tool elements are analyzed in the computation of thermal expansion of these elements. Neural network as a part of artificial intelligence is widely used for this type of application as the data captured from the process is highly nonlinear. Giving the right data for the neural network training is at most important as this decides about the quality of neural network training. As the data is huge enough considering various conditions existing in the machining environment, the proper data pre-processing only will make the training much more effective. This paper’s main aim is to study the thermal expansion properties by properly analyzing the data. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.
Back propagation genetic and recurrent neural network applications in modelling and analysis of squeeze casting process
(Elsevier Ltd, 2017) Gowdru Chandrashekarappa, M.; Shettigar, A.K.; Krishna, P.; Parappagoudar, M.B.
Today, in competitive manufacturing environment reducing casting defects with improved mechanical properties is of industrial relevance. This led the present work to deal with developing the input-output relationship in squeeze casting process utilizing the neural network based forward and reverse mapping. Forward mapping is aimed to predict the casting quality (such as density, hardness and secondary dendrite arm spacing) for the known combination of casting variables (that is, squeeze pressure, pressure duration, die and pouring temperature). Conversely, attempt is also made to determine the appropriate set of casting variables for the required casting quality (that is, reverse mapping). Forward and reverse mapping tasks are carried out utilizing back propagation, recurrent and genetic algorithm tuned neural networks. Parameter study has been conducted to adjust and optimize the neural network parameters utilizing the batch mode of training. Since, batch mode of training requires huge data, the training data is generated artificially using response equations. Furthermore, neural network prediction performances are compared among themselves (reverse mapping) and with those of statistical regression models (forward mapping) with the help of test cases. The results shown all developed neural network models in both forward and reverse mappings are capable of making effective predictions. The results obtained will help the foundry personnel to automate and précised control of squeeze casting process. © 2017
A brief review on fly ash and its use in surface engineering
(2018) Bhajantri, V.; Krishna, P.; Jambagi, S.
Fly ash is a by-product obtained from coal power plants. Over the past two decades, handling this industrial waste has been a great challenge for many developing countries. However, this menace can be used in many industrial applications viz., civil, automobile and aerospace applications. In civil industry, the fly ash has been used in concreate to enhance the porosity that increases the curing time of the concrete. The fly ash has been gaining importance these days as a feedstock material for many thermal spray processes. In automobile sector, the fly ash has been used as a thermal barrier coating in IC engines, whereas in aerospace industry, which demands lighter and stronger materials, the fly ash has been used as a reinforcement material. Hence, so far, fly ash has been used as an either single or a composite feed stock material in thermal spray processes. The fly ash with other materials like alumina, titania and red mud have been deposited using thermal spray processes. These coatings have exhibited higher wear, corrosion and erosion resistance as compared to the uncoated specimens. In this paper, a brief review on fly ash and its use, especially its use as a feed stock in thermal spray coating, is presented. Therefore, the use of fly ash has opened a new frontier of research in thermal spray coating area where economically viable coatings can be produced using industrial waste like fly ash. � 2018 Author(s).
Characterization and thermal analysis of laser metal deposited ?-TiAl thin walls
(Elsevier Editora Ltda, 2021) Mallikarjuna, B.; Bontha, S.; Krishna, P.; Balla, V.K.
The present work focuses on investigating the effect of process variables (power, travel speed, powder flow rate) on microstructure and mechanical properties of Laser Metal Deposited (LMD) ?-TiAl thin walls. To this end, LMD technique was used to deposit ?-TiAl thin walls at different processing conditions. Microstructures of as-deposited samples were investigated using both optical and scanning electron microscopy. X-ray diffraction (XRD) technique was used to determine the phases present. Microhardness measurements were carried out along both longitudinal and build directions. Microstructural analysis of as-deposited samples revealed a fine lamellar structure comprising of ? and ?2 phases. Colony size of 30–60 ?m and lamellar spacing between 0.1 and 0.7 ?m were observed. XRD analysis confirmed the presence of ? and ?2 phases. Comparison of elemental analysis results on both powder and as-deposited samples revealed a negligible loss of Al and no oxygen pick up in the deposited thin walls. Hardness values were found to decrease with an increase in wall height, and hardness values increased marginally (5%) with an increase in travel speed. Further, 3D transient thermal analysis was also carried out to complement the LMD of thin walls in terms of melt pools and cooling rates. It was found that the melt pool depth (MPDc = 0.266 mm) is smaller at the centre than the edge (MPDe = 0.513 mm) of the wall. A higher cooling rate of 1.05 × 105 °C/s near the wall substrate was found for 200–12. © 2021
Control and dynamic optimization of middle vessel batch distillation column for the separation of ethanol/propanol/butanol mixture
(Institution of Chemical Engineers, 2021) Krishna, P.; Desikan, B.; Sankar Rao, C.
The middle vessel batch distillation column is an alternative to the regular batch distillation column. This configuration allows simultaneous separation of the light fraction (accumulated at top), heavy fraction (accumulated at bottom) and the intermediate fraction (accumulated in the middle vessel) in a single column. The objective of this article is to extensively analyse and discuss different control systems for the middle vessel batch distillation column (MVBDC) and dynamically optimize the column. Three control structures such as composition level cascade, composition temperature cascade, and temperature control system, have been tested and evaluated. Further, a dynamic optimization study has been performed on the control system providing the fastest separation. The optimizer is set to minimize the total energy consumed during the process. This resulted in a decrease in batch time from 26.8 to 25.2 h and a 13.5% decrease in overall energy usage. The presented dynamic optimization technique and control system design is useful for improving the performance of the MVBDC. © 2021 Institution of Chemical Engineers
Elucidating Corrosion Behavior of Hastelloy-X Built Using Laser Directed Energy Deposition-Based Additive Manufacturing in Acidic Environments
(Springer Science and Business Media Deutschland GmbH, 2021) Diljith, P.K.; Jinoop, A.N.; Paul, C.P.; Krishna, P.; Bontha, S.; Bindra, K.S.
This paper reports an investigation on the electrochemical corrosion behavior of laser directed energy deposition (LDED)-based additive manufacturing built Hastelloy-X (Hast-X) bulk samples for the first time in various acidic environments (2M HNO3, 2M HCl, and 2M H2SO4). Open-circuit potential results reveal that corrosion activity is more in HCl than the other two media. The corrosion rate (CR) estimated using the Tafel extrapolation method shows that the corrosion rate (CR) is the most in HCl and least in HNO3. Potentiodynamic studies reveal activeâ€“passive behavior of Hast-X in all the media and it is seen that the material stays in passivation for a longer potential range in HCl. Further, pitting potential is observed to be comparable in all three media. The cyclic polarization curve shows no loops, which points out the absence of pitting in the samples immersed in any of the media. The estimated CR for Hast-X in all the acidic environments under investigation comes within the acceptable CR for nickel-based alloys (4Â mpy). The morphology of the corroded surface is analyzed using stereo microscope and it confirms the absence of pitting in all the three samples. These observations confirm the suitability of LDED built Hast-X components for applications in investigated acidic environments. Â© 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
Experimental investigation of mode I interlaminar fracture toughness in T300/914 composite
(Elsevier Ltd, 2020) Sachin, S.; Nayaka, S.H.; Santhosh, B.; Krishna, P.
An aerospace structural material T300/914 has been studied to understand the Mode I interlaminar fracture toughness. For experimental analysis a Double Cantilever Beam (DCB) test is conducted on the laminate to estimate the Mode I interlaminar fracture toughness of the sample. A 48-layer laminate was prepared by hand layup process and an insert included at the mid plane to produce the artificial initial crack required for the test. All the tests are conducted in accordance to the ASTM standards. Pulse-Echo test results and C-Scan images of the laminate were analyzed to find the defects in the laminate. The data from DCB test were analyzed by Modified Beam theory, Compliance calibration method and modified compliance calibration methods to find the interlaminar fracture toughness. A crack length correction method is implemented for data reduction. Numerical analysis of the data derives results in accordance with the experimental analysis. Â© 2019 Elsevier Ltd. All rights reserved.
Experimental study of Mode i and Mode II interlaminar fracture toughness on aerospace structural composite T300/914
(2019) Sachin, S.; Nayaka, H.S.; Santhosh, B.; Krishna, P.
Carbon epoxy composite T300/914 which has wide applications in aerospace industries, as a structural material, has been analyzed, to determine the interlaminar fracture toughness. Laminates with a thickness of 4.6 mm, consisting of 48 layers of T300/914, are considered for estimating the inter-laminar fracture toughness. These specimens have been fabricated by hand layup method followed by controlled curing in an autoclave. Tests have been conducted in accordance with ASTM standards, for Mode I by Double Cantilever Beam (DCB) test and End Notch Flexure (ENF) test for Mode II. Pulse-Echo test results and C-Scan images of the specimens were also analyzed to locate the exact position of delamination. During the preliminary tests, it was found that the interlaminar fracture toughness varied, because of bonding of release film with the sides of the laminate. By Modified Beam Theory, Mode I and Mode II fracture toughness values of the prepared specimens were found to be 0.090 kJ/m2and 0.542 kJ/m2, respectively. It was also noted that the fracture toughness of the specimens from the same laminate varied with the degree of compaction. � 2018 Author(s).
Experimental study of Mode i and Mode II interlaminar fracture toughness on aerospace structural composite T300/914
(American Institute of Physics Inc. subs@aip.org, 2019) Sachin, S.; Shivananda Nayaka, H.S.; Santhosh, B.; Krishna, P.
Carbon epoxy composite T300/914 which has wide applications in aerospace industries, as a structural material, has been analyzed, to determine the interlaminar fracture toughness. Laminates with a thickness of 4.6 mm, consisting of 48 layers of T300/914, are considered for estimating the inter-laminar fracture toughness. These specimens have been fabricated by hand layup method followed by controlled curing in an autoclave. Tests have been conducted in accordance with ASTM standards, for Mode I by Double Cantilever Beam (DCB) test and End Notch Flexure (ENF) test for Mode II. Pulse-Echo test results and C-Scan images of the specimens were also analyzed to locate the exact position of delamination. During the preliminary tests, it was found that the interlaminar fracture toughness varied, because of bonding of release film with the sides of the laminate. By Modified Beam Theory, Mode I and Mode II fracture toughness values of the prepared specimens were found to be 0.090 kJ/m2and 0.542 kJ/m2, respectively. It was also noted that the fracture toughness of the specimens from the same laminate varied with the degree of compaction. Â© 2018 Author(s).
Friction and wear study of graphite and bronze filled epoxy matrix composites
(Elsevier Ltd, 2022) Patil, N.; Krishna, P.
The composite material is made of different materials. It retains the advantages of the original material and reflects combined characteristics of all the constituents. Polymer matrix composites are popular in the recent industrial applications. Friction and wear governs the tribological aspects of polymer composites. This paper revel the experimental study of friction and wears behavior of epoxy composites filled with bronze and graphite fillers as per ASTM standards. Three compositions were studied and it was found that composition ‘A’ has lowest coefficient of friction (0.281) whereas composition ‘C’ has highest coefficient of friction (0.325). The composition ‘A’ has lowest wear rate of 0.5 μm/s and composition ‘C’ showed highest wear rate of 3.25 μm/s. Use of graphite and bronze along with epoxy exhibited formation of lubricating layer and enhanced friction and wear behavior of the composites. © 2021
Investigation of high-temperature oxidation behavior of Ti-48Al-2Cr-2Nb fabricated using electron beam powder bed fusion and feature added with laser directed energy deposition
(Elsevier B.V., 2025) Gurugubelli, R.C.; Balla, V.K.; Krishna, P.; Bontha, S.
This study investigates the microstructure and high-temperature oxidation behavior of Ti-48Al-2Cr-2Nb (Ti-4822) alloy at 950°C processed using Electron Beam Powder Bed Fusion (EB-PBF) with feature addition using Laser Directed Energy Deposition (LDED). The EB-PBF substrates in As-Built (AB) and EB-PBF + Hot Isostatic Pressing (HIP) conditions were used for feature addition using LDED. Oxidation studies revealed oxide scales mainly comprising alternating bands of TiO2 and Al2O3. The oxidation rate constant of AB + LDED samples was 1.223 mg2 cm?4 h?1 and AB+ HIP + LDED samples was 0.874 mg2 cm?4 h?1. The oxide scale thickness on the LDED-feature side was higher than that observed on the AB, /AB + HIP side (of the AB+LDED, AB+HIP+LDED) samples suggesting their poor oxidation resistance. This can be attributed to the ultra-fine massive-like ?-TiAl microstructure in LDED compared to the nano-sized ?2/? lamellae seen in EB-PBF (AB/ AB+HIP). Delamination and spallation of the oxide scale were observed at the interface between the substrate and LDED feature owing to the difference in oxide-scale growth rates and the presence of ?2-Ti3Al. © 2025 Elsevier B.V.
Isothermal oxidation behavior of As-deposited and HIPed Ti-48Al-2Cr-2Nb alloy processed using Electron Beam Powder Bed Fusion
(Elsevier Ltd, 2025) Gurugubelli, R.C.; Balla, V.K.; Rajasekaran, B.; Krishna, P.; Bontha, S.
This work focuses on oxidation behavior of Electron Beam Powder Bed Fusion (EB-PBF) processed Ti-48Al-2Cr-2Nb at elevated temperatures. Two different sample conditions were considered: As-deposited (AD) and post-processed by hot isostatic pressing (HIPed). The oxidation studies were carried out at 750 °C, 850 °C, and 950 °C for 30, 60, and 100 h. The oxidized samples were analyzed for oxide layer growth and kinetics using Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray Spectroscopy (EDS), Raman Spectroscopy, and X-ray Diffraction (XRD) techniques. Results indicate that oxide layers are composed of alternative bands of TiO2 and Al2O3. These oxide layers spalled at 850 °C and 950 °C after an exposure of 100 h. The HIPed samples exhibited superior oxidation resistance when compared to AD samples, with an oxidation rate constant of 0.134 mg2 cm4 h?1 at 950 °C (100 h). The presence of homogenized microstructure with large nano-scale lamellar colonies aided in uniform oxide layer growth. EB-PBF samples exhibit fine fully lamellar microstructure due to the rapid heating and cooling cycles. Hence EB-PBF (AD and HIPed) samples exhibited better oxidation resistance when compared to conventionally processed Ti-48Al-2Cr-2Nb. © 2025 Elsevier B.V.
Laser directed energy deposited Ti-48Al-2Cr-2Nb alloy: An investigation of high temperature oxidation behavior
(Elsevier B.V., 2024) Gurugubelli, R.C.; Balla, V.K.; Rajasekaran, B.; Krishna, P.; Bontha, S.
This study investigates high-temperature oxidation behavior and kinetics of Laser Directed Energy Deposited (LDED) Ti-48Al-2Cr-2Nb (Ti-48-2-2) alloy at 750 °C, 850 °C, and 950 °C, for 30, 60 and 100 h. Results reveal that the oxide-scale consists of alternating bands of TiO2 and Al2O3 and its stability is strongly dependent on the oxidation temperature and duration. At 850 °C and 950 °C, the oxide-scale delaminated following 100-h exposure. LDED Ti-48-2-2 exhibited an oxidation rate constant of 0.984 mg2 cm−4 h−1 at 850 °C (100 h) and 2.09 mg2 cm−4 h−1 at 950 °C (100 h), and an activation energy of 83.7 kJ mol−1 (850°–950 °C). LDED Ti-48-2-2 exhibited poor oxidation resistance compared to conventionally processed Ƴ-TiAl alloys. This can be attributed to the absence of N-rich layer and the typical nano-scale α2/γ banded lamellar microstructure observed in other processing routes. Post-process heat treatments can be utilized to obtain the desired microstructural features. © 2024 Elsevier B.V.
Laser surface melting of ?-TiAl alloy: An experimental and numerical modeling study
(Institute of Physics Publishing helen.craven@iop.org, 2019) Mallikarjuna, M.; Bontha, S.; Krishna, P.; Balla, V.K.
The objective of present work is to study the evolution of thermal stresses during laser surface melting (LSM) of ?-TiAl alloy using experimental and numerical modeling approaches. LSM of ?-TiAl alloy samples were carried out at different processing conditions in a controlled atmosphere. Material characterization of the melted region was investigated using scanning electron microscope. It was found that fully lamellar microstructure was transformed into predominantly ?-TiAl with little amount of ?2-Ti3Al. A maximum improvement in hardness of over 72% was noticed in the melted region compared to that of the substrate. Three-dimensional thermomechanical finite element analysis of LSM of ?-TiAl alloy was carried out. Melt pool dimensions, temperature history, and residual stresses were predicted from the finite element models. Measured and predicted values of melt pool depth were in good agreement with a maximum error of 13.6% at P=400Wand V=10mms-1. Predicted residual stress in the melted region exceeded the yield strength of ?-TiAl alloy and resulted in cracking of the melted region at all process conditions. ©2019 IOP Publishing Ltd.
Low cost cpm machine for knee joint
(2012) Metan, S.S.; Krishna, P.; Mohan Kumar, G.C.
In today's world of industrialization, no single branch of Engineering and Technology can be considered independently. In order to increase productivity and profitability, industrial products are designed with the technology involving Mechanical and Electronics principles i.e. Mechatronics. Mechatronics has a vital importance in various fields such as agricultural, aviation, automobile, medical, etc. The scope of present work is to design, manufacture and test the low cost knee Continuous Passive Motion (CPM) machine. By using motorized device of CPM machine, we can gradually move the knee joints. This is not possible actively to the patient due to pain. The knee joint motion without patient's muscular effort is called as passive motion. The machine designed and developed in present work can achieve this. Once the patient is able to use his muscular power for his active joint motion, CPM is no longer medically necessary. In the present work, design and manufacturing of the Low Cost Knee CPM machine has been successfully done and is elaborated. The machine was manufactured and tested at one of the renowned Hospitals in Sholapur-India. The patient is exercised on CPM machine for three weeks and is observed to be improved to normal condition i.e. normal Range of Motion (ROM). Â© (2012) Trans Tech Publications, Switzerland.
Machinability of Hardened Alloy Steel using Cryogenic Machining
(2018) Arun, Kumar, S.; Yoganath, V.G.; Krishna, P.
Machining of hardened alloy steels demand special cutting tools such as PCBN, ceramic. However, these cutting tools are uneconomical and also demand machine tool structures, which have high stiffness and vibration dampening properties. In the current trend towards Green manufacturing it is desired to produce more with less. Green manufacturing also emphasizes on an eco-friendly process. Hence, it is postulated to improve the machinability of these materials by alternate, economical means. One such alternative is cryogenic machining. In the current research work, it is envisaged to study the machinability of hardened alloy steel using commercially available cutting tools (coated carbide) under the influence of cryogenic as the coolant. Machinability factors under influence of cryogenic machining such as tool life, surface roughness and power consumption are studied. Results show that cryogenic as an alternative to coolant during machining of hardened materials increases the process efficiency by reducing energy consumption and also showed significant improvement in tool life. The process thus demonstrates the capability of replacing the special cutting tools that are required for hard turning applications. The portability of the setup for commercial use is also considered. � 2017 Elsevier Ltd.
Machinability of Hardened Alloy Steel using Cryogenic Machining
(Elsevier Ltd, 2018) Arun Kumar, S.; Yoganath, V.G.; Krishna, P.
Machining of hardened alloy steels demand special cutting tools such as PCBN, ceramic. However, these cutting tools are uneconomical and also demand machine tool structures, which have high stiffness and vibration dampening properties. In the current trend towards Green manufacturing it is desired to produce more with less. Green manufacturing also emphasizes on an eco-friendly process. Hence, it is postulated to improve the machinability of these materials by alternate, economical means. One such alternative is cryogenic machining. In the current research work, it is envisaged to study the machinability of hardened alloy steel using commercially available cutting tools (coated carbide) under the influence of cryogenic as the coolant. Machinability factors under influence of cryogenic machining such as tool life, surface roughness and power consumption are studied. Results show that cryogenic as an alternative to coolant during machining of hardened materials increases the process efficiency by reducing energy consumption and also showed significant improvement in tool life. The process thus demonstrates the capability of replacing the special cutting tools that are required for hard turning applications. The portability of the setup for commercial use is also considered. Â© 2017 Elsevier Ltd.
Machinability studies of low alloy steels by face turning method: An experimental investigation
(2013) Lalbondre, R.; Krishna, P.; Mohankumar, G.C.
The present study is an experimental investigation on machinability of two low alloy steels, AISI 9320 and AISI 4340, by face turning method. The face turning method makes use of cylindrical steel specimen as a test piece and a triangular P-30 insert as a cutting tool for testing the machinability. The effectiveness of this method is assessed by studying: the cutting time required for the tool to reach flank wear up to 0.3mm (tool life criterion); tool wear development and wear mechanisms involved in machining; tool life studies and machinability indices of the work-material; surface roughness investigations of the machined surfaces; and chip morphology. The machinability tests undertaken in the current investigation follows some of the guidelines indicated in the international standards, ISO 3685:1993(E) and American Foundry Society (AFS) standard machinability tests. The results presented here demonstrate the ability of the face turning method: to evaluate the tool wear development and tool life studies; to rank the work material according to their machinability, to investigate surface roughness due to tool wear; to investigate chip morphology with crater wear and to characterize the machinability of steels under consideration. The face turning method used here is simple and effective for the given tool-work material pair. � 2013 The Authors. Published by Elsevier Ltd.
Machinability studies of low alloy steels by face turning method: An experimental investigation
(Elsevier Ltd, 2013) Lalbondre, R.; Krishna, P.; Mohan Kumar, G.C.
The present study is an experimental investigation on machinability of two low alloy steels, AISI 9320 and AISI 4340, by face turning method. The face turning method makes use of cylindrical steel specimen as a test piece and a triangular P-30 insert as a cutting tool for testing the machinability. The effectiveness of this method is assessed by studying: the cutting time required for the tool to reach flank wear up to 0.3mm (tool life criterion); tool wear development and wear mechanisms involved in machining; tool life studies and machinability indices of the work-material; surface roughness investigations of the machined surfaces; and chip morphology. The machinability tests undertaken in the current investigation follows some of the guidelines indicated in the international standards, ISO 3685:1993(E) and American Foundry Society (AFS) standard machinability tests. The results presented here demonstrate the ability of the face turning method: to evaluate the tool wear development and tool life studies; to rank the work material according to their machinability, to investigate surface roughness due to tool wear; to investigate chip morphology with crater wear and to characterize the machinability of steels under consideration. The face turning method used here is simple and effective for the given tool-work material pair. Â© 2013 The Authors. Published by Elsevier Ltd.