Browsing by Author "Shivananda Nayaka, H.S."

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A review on wrought magnesium alloys processed by equal channel angular pressing
(Inderscience Publishers, 2015) Muralidhar, M.; Narendranath, S.; Shivananda Nayaka, H.S.
Magnesium and its alloys with severe plastic deformation (SPD) techniques are more attractive as structural parts in many industrial applications because of their advantages. In this paper, the importance of wrought magnesium alloys with their applications to accomplish the essential development of components is reviewed. In addition, the different approaches of equal channel angular pressing (ECAP) process for refining the grain size to achieve the ultrafine grained material on the bulk metals are discussed. Recent developments in the ECAP process are outlined clearly with their importance to overcome many complexities. Various factors like processing temperature of a specimen, die geometry, ram speed, back pressure and processing routes influencing during ECAP process of wrought magnesium alloys at different conditions such as channel angle and corner or outer arc angle are discussed. Finally, the properties of ECAP processed wrought alloys are outlined for improving the microstructure in structural parts. © © 2015 Inderscience Enterprises Ltd.
Comparative study of turning process on EN47 spring steel with different nose radii using statistical technique
(Elsevier Ltd, 2018) Mallesha, V.; Shivananda Nayaka, H.S.
Spring steel (EN47) samples are machined (turning) using Sandvik make coated tungsten carbide tool insert with different nose radii (0.4 and 0.8mm) in dry condition and the results are compared with each other. Spring steel is widely used in the manufacturing of vehicle components such as crankshaft, knuckle and leaf spring. EN47 spring steel material is relatively low cost compare to other alloy steels. Experiments are conducted based on taguchi L9 technique. Input parameters are cutting speed, feed rate and depth of cut. The corresponding output parameters are cutting force, surface roughness and tool tip temperature have been analyzed. Experimental result reveals that better surface roughness obtained with higher nose radius. ANOVA results confirm that cutting force is influenced by depth of cut (ap), surface roughness is influenced by feed rate (f) and tooltip temperature is influenced by cutting speed (Vc). Chip morphology and machined surface samples are analyzed using scanning electron microscope (SEM). Â© 2018 Elsevier Ltd.
Effect of Multi-directional Forging on the Evolution of Microstructural and Mechanical Properties of Lightweight Al-Cu-Li Alloy AA2050
(Springer, 2023) Jagadeesh, C.; Shivananda Nayaka, H.S.; Ramesh, S.; Praveen, T.R.
Microstructural evolution and the mechanical properties of recently developed lightweight AA2050 Al-Cu-Li alloy have been presented. A processing route of multi-directional forging (MDF) at 170 °C followed by artificial aging at 150 °C was employed. Systematic EBSD analysis revealed significant grain refinement with grain size reducing from 74.3 ± 12 to 22.1 ± 2.8 µm after 12 passes of MDF. Transformation of deformation bands into subgrains with dynamic recrystallization has led to grain refinement. TEM results show the presence of large dislocation clusters and deformation bands in MDF processed samples with a large number of fine precipitates in peak aged MDF processed samples. XRD analysis shows variation in peak intensities and occurrence of peak shifts due to induced lattice strain upon MDF. A substantial increase in microhardness and strength was observed with a minor trade-off with ductility after 12th MDF pass. Further, enhancement in strengths and microhardness were observed in post-MDF aged samples. Experimental results show the combined effect of strain hardening, grain size reduction, and precipitate hardening which influence the material strength. A combination of MDF and artificial aging has shown great potential to enhance the strength and ductility of AA2050. © 2023, ASM International.
Effect of multiaxial cryoforging on microstructure and mechanical properties of a Cu-Ti Alloy
(Institute of Physics Publishing helen.craven@iop.org, 2019) Ramesh, S.; Shivananda Nayaka, H.S.; Gopi, K.R.; Sahu, S.
Cu-Ti alloy, processed by multiaxial forging (MAF) at cryogenic temperature with a cumulative strain up to 1.64, was investigated for microstructure and mechanical properties. The deformed microstructures were analyzed using optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The average grain size of 2 ?m was achieved in the deformed sample after 3 cycles of MAF. TEM studies indicated that the shear bands width of the deformed sample after 3 cycles reduced to 1 ?m. Tests for mechanical properties indicated an increase in tensile strength and hardness and it was found to be correlated with an increase in dislocation density and grain boundary strengthening mechanism. Ultimate tensile strength (UTS) of 390 MPa, 480 MPa, and 590 MPa was observed in MAF processed samples after 1, 2, and 3 cycles, respectively. Hardness increased from 65 Hv (as-received) to 240 Hv after 3 cycles of MAF. Fractography analysis showed that, with an increase in number of MAF cycles, dimple size reduced up to 1 cycle and percentage elongation increased after 2 cycles of MAF. © 2018 IOP Publishing Ltd.
Enhancing mechanical properties of Ti-64 alloy through ECAE: lubricant optimization, microstructural evolution and optimal process parameters
(Springer-Verlag Italia s.r.l., 2025) Castelino, M.R.; Mallikappa, N.; Karinka, S.; Vijayan, V.; Shivananda Nayaka, H.S.; Valder, J.
This study explores the application of Equal Channel Angular Extrusion (ECAE) in enhancing the microstructural and mechanical properties of Ti-64 alloy. Finite Element (FE) analysis validates experimental outcomes, revealing a significant reduction in grain size, improved strength, and hardness. Microstructural analysis indicates dynamic recrystallization, transforming larger alpha (?) grains into smaller ones. Tensile testing demonstrates increased yield and ultimate strength in ECAE-treated specimens due to decreased grain size and heightened dislocation density. Lubricant optimization achieves low friction coefficients (0.02 and 0.04), reinforcing ECAE effectiveness. FE simulations and ANOVA analysis identify influential factors, leading to optimal parameter combinations. Isothermal ECAE successfully reduces grain size, resulting in substantial improvements in yield strength, ultimate strength, and hardness. These findings highlight ECAE's efficacy in enhancing the mechanical properties of Ti-64 alloy, with specific applications in biomaterials, particularly dental implants and bone support, as well as aerospace fasteners, where Ti-64 contributes to increased fuel efficiency, reduced emissions, and enhanced structural integrity. © The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature 2024.
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).
Influence of cold rolling process on microstructure and mechanical properties of Cu-1.5%Ti alloy
(American Institute of Physics Inc. subs@aip.org, 2018) Ramesh, S.; Shivananda Nayaka, H.S.; Anne, G.; Gopi, K.R.
The effects of cold rolling on the microstructure evolution and mechanical properties of Cu-1.5%Ti alloy were investigated. The results showed that the tensile strength of the Cu-1.5%Ti alloy increased with an increase of rolling deformation at room temperature. Significant grain refinement took place during rolling process revealed in optical microstructure and transmission electron microscope analysis. XRD patterns revealed peaks indexed to Cu, Cu3-Ti2 and Cu4-Ti3 after 8-pass rolling process. Microhardness of the rolled Cu-1.5%Ti alloy layers increased incessantly with increase in the number of rolling passes. Tensile strength increased up to 294 MPa which was about 1.54 times higher than that of the cast Cu-1.5%Ti alloy. Fracture surfaces of the rolled Cu-1.5%Ti alloy revealed the dimples in the structure, which is an indication of ductile fracture. Â© 2018 Author(s).
Influence of equal channel angular pressing and laser shock peening on fatigue behaviour of AM80 alloy
(Elsevier B.V., 2019) Praveen, T.R.; Shivananda Nayaka, H.S.; Swaroop, S.
AM80 magnesium alloy was processed with Equal Channel Angular Press (ECAP)for grain refinement. Laser shock peening without coating (LSPwC)were executed on ECAP processed sample at 8 GW cm?2 and further grain refinement were observed at surface. SEM image expose the grain refinement at different stage of processing, and fine grains of sub-micron size were observed at surface level after ECAP + LSPwC. Residual stress were measured using X-ray diffraction, sin2(?)method and compressive residual stress was found after ECAP. LSPwC intensify the compressive residual stress at surface. Increases in magnitude of residual stresses were noticed with 200 and 300% of LSPwC. Increase in surface roughness were noticed from 0.6 to 6.8 ?m by increasing the percentage of LSPwC coverage. Fatigue tests were acknowledged the effect of ECAP and ECAP + LSPwC on reliability of grain refinement technique. ECAP sample showed fatigue life of 7539 cycles against as received. Highest fatigue life of 85,268 life cycles was observed with ECAP + LSPwC by 100% of coverage. Further process of LSPwC for 200 and 300%, fatigue life was significantly decreases to 22,987 and 384 cycles respectively. SEM images of fractured surface exhibits effect of ECAP and LSPwC on crack initiation and propagation for failure. © 2019 Elsevier B.V.
Influence of Multi Axial Forging (MAF) on Microstructure and Mechanical Properties of Cu-Ti Alloy
(Elsevier Ltd, 2018) Ramesh, S.; Shivananda Nayaka, H.S.; Gopi, K.R.
Multi axial forging (MAF) is one among the severe plastic deformation (SPD) processes, where large strains are imposed into the component. In the present work, as-received Cu-1.5%Ti alloy was subjected to MAF for 2 and 4 cycles at room temperature. Microstructure showed grain refinement after 2 and 4 cycles. Average grain size obtained for MAF processed samples after 2 and 4 cycles are 120 Î¼m and 40 Î¼m, respectively compared to initial grain size of 800 Î¼m. The Mechanical properties were analyzed for as-received and MAF processed samples. Tensile test showed increased ultimate tensile strength (493 MPa) for MAF 4-cycle sample compared to as-received (191 MPa) condition with accumulated strain of 2.18 for 4 cycles. Increase in hardness was observed for MAF processed sample of 143 Hv for 4-cycle compared to as-received sample of 67 Hv. Â© 2018 Elsevier Ltd.
Influence of Multiaxial Cryoforging on Microstructural, Mechanical, and Corrosion Properties of Copper-Titanium Alloy
(Springer, 2019) Ramesh, S.; Shivananda Nayaka, H.S.; Sahu, S.; Gopi, K.R.; Shivaram, M.J.; Arya, S.
Multiaxial forging (MAF) was used to process Cu-4.5%Ti (wt.%) alloy at cryogenic temperature up to three cycles with a cumulative strain of 1.64. Microstructures, mechanical, and corrosion properties of as-received and deformed samples were analyzed. Microstructural analysis showed that average grain size decreased from 70 µm to 200 nm, and electron backscattered diffraction (EBSD) analysis revealed the transformation of high-angle grain boundaries (HAGBs) to low-angle grain boundaries (LAGBs). Variations in intensity of peaks were observed by x-ray diffraction (XRD) technique. Microstructural investigation showed elongated grains with shear bands having width ~ 200 nm for 3-cycle sample. Tensile testing and micro-hardness tests showed improvements in ultimate tensile strength (UTS), yield strength (YS), and micro-hardness, with the increase in MAF cycles. Ultimate tensile strength and hardness increased from 605 MPa and 252 HV (for as-received) to 1284 MPa and 428 HV for three cycles of MAF-processed sample, respectively. Improvement in strength and hardness was attributed to refined grain structure. Corrosion study was carried out for different cycles of MAF-processed samples using potentiodynamic polarization, and corroded surfaces were analyzed using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) analysis. © 2019, ASM International.
Influence of Multidirectional Forging on Microstructural, Mechanical, and Corrosion Behavior of Mg-Zn Alloy
(Springer New York LLC barbara.b.bertram@gsk.com, 2019) Ramesh, S.; Anne, G.; Shivananda Nayaka, H.S.; Sahu, S.; Ramesh, M.R.
Multidirectional forging (MDF) was applied to Mg-6%Zn alloy up to 5 passes successfully at 280 °C. MDF-processed materials were characterized using optical microscope, scanning electron microscope, electron backscatter diffraction, transmission electron microscope, and x-ray diffraction. Obtained results showed a significant reduction in grain size (up to 3.8 ?m) having a large fraction of high-angle grain boundaries after 5 passes of MDF process. Maximum tensile strength of 230 MPa was achieved for 5-pass MDF-processed Mg-6%Zn alloy which is about ~ 2.0 times higher in comparison with that of homogenized alloy (117 MPa) and was attributed to higher dislocations density and grain refinement. Corrosion behavior of the alloy was investigated in 0.1 M NaCl solution using potentiodynamic polarization test, electrochemical impedance spectra analysis, and immersion tests. It was found that the corrosion rate of 5-pass MDF sample improved (0.34 mm/year) ~2.5 times in comparison with that of homogenized Mg-6%Zn alloy (0.86 mm/year) due to fine grain structure, which creates more grain boundaries that act as a corrosion barrier. © 2019, ASM International.
Investigation of Cutting Force Tool Tip Temperature and Surface Roughness during Dry Machining of Spring Steel
(Elsevier Ltd, 2018) Mallesha, V.; Shivananda Nayaka, H.S.
Today's growing demand for steels and spring steels are widely used in industries as they possess high yield strength and their property resistance to deform easily. Spring steels have huge demand in many large scale industries, because of their applications in nuclear power plant, jet engine parts, forming tools and extrusion dies. EN47 is one of such spring steels with relatively low cost. Machinability study of EN47 material was analysed using a L27 orthogonal array (OA) for dry turning condition using TiCN/Al2O3/TiN CVD coated tungsten carbide insert with nose radius of 0.4mm. Depth of cut (d), Speed (v), feed (f) and are varied to the level-3. During machining, cutting forces and cutting temperatures was measured using Kistler based dynamometer and heat gun respectively. Surface roughness was measured by using Mitutoyo SJ201 after machining. Machined surface and chip were analysed using scanning electron microscope (SEM). Tool tip temperature, surface finish and cutting forces are optimized using Design of Experiments technique and proof trails are conducted with satisfactory results. Â© 2017 Elsevier Ltd.
Investigation of dry sliding wear properties of multi-directional forged Mg–Zn alloys
(National Engg. Reaserch Center for Magnesium Alloys zhangdingfei@cqu.edu.cn, 2019) Ramesh, S.; Anne, G.; Shivananda Nayaka, H.S.; Sahu, S.; Ramesh, M.R.
Effect of multi-directional forging (MDF) on wear properties of Mg–Zn alloys (with 2, 4, and 6 wt% Zn) is investigated. Dry sliding wear test was performed using pin on disk machine on MDF processed and homogenized samples. Wear behavior of samples was analyzed at loads of 10 N and 20 N, with sliding distances of 2000 m and 4000 m, at a sliding velocity of 3 m/s. Microstructures of worn samples were observed under scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD) and the results were analyzed. Mechanical properties were evaluated using microhardness test. After 5 passes of MDF, the average grain size was found to be 30 ± 4 µm, 22 ± 3 µm, and 18 ± 3 µm, in Mg–2%Zn, Mg–4%Zn, and Mg–6%Zn alloys, respectively, with significant improvement in hardness in all cases. Wear resistance was improved after MDF processing, as well as, with increment in Zn content in Mg alloy. However, it decreased when the load and the sliding distance increased. Worn surface exhibited ploughing, delamination, plastic deformation, and wear debris along sliding direction, and abrasive wear was found to be the main mechanism. © 2019
Investigation of Microstructure and Mechanical Properties of ECAP-Processed AM Series Magnesium Alloy
(Springer New York LLC barbara.b.bertram@gsk.com, 2016) Gopi, K.R.; Shivananda Nayaka, H.S.; Sahu, S.
Magnesium alloy Mg-Al-Mn (AM70) was processed by equal channel angular pressing (ECAP) at 275 °C for up to 4 passes in order to produce ultrafine-grained microstructure and improve its mechanical properties. ECAP-processed samples were characterized for microstructural analysis using optical microscopy, scanning electron microscopy, and transmission electron microscopy. Microstructural analysis showed that, with an increase in the number of ECAP passes, grains refined and grain size reduced from an average of 45 to 1 µm. Electron backscatter diffraction analysis showed the transition from low angle grain boundaries to high angle grain boundaries in ECAP 4 pass sample as compared to as-cast sample. The strength and hardness values an showed increasing trend for the initial 2 passes of ECAP processing and then started decreasing with further increase in the number of ECAP passes, even though the grain size continued to decrease in all the successive ECAP passes. However, the strength and hardness values still remained quite high when compared to the initial condition. This behavior was found to be correlated with texture modification in the material as a result of ECAP processing. © 2016, ASM International.
Investigation of Tribological Characteristics of Cu-Ti Alloys Processed by Multi-Axial Cryo-Forging
(Springer, 2022) Ramesh, S.; Shivananda Nayaka, H.S.; Anne, G.; Arun, M.N.; Naik, G.M.
Cu-XTi alloys (X = 1.5 and 4.5%) were subjected to multi-axial forging (MAF) under cryogenic condition up to three passes successfully. Characteristics of the MAF-processed alloys were analyzed using microstructural analysis, hardness and wear tests. Worn surface morphology and elemental analysis was performed by scanning electron microscopy. The hardness of samples increases with higher MAF passes due to strain hardening and grain refinement. Wear test was done for six various sliding distances (500, 1000, 1500, 2000, 2500 and 3000 m), two different loads (10 and 20 N), and two different velocities (1 and 2 m/s) using the pin-on-disk wear test rig. Wear loss of as-received samples is higher than MAF-pressed samples due to an increase in hardness, but wear loss increases as the load increases. Coefficient of friction is reduced with the increase in MAF pass, which is due to strain hardening effect. The worn surface exhibits the plastic deformation regions, delamination, plowing and formation of oxide layers, which was revealed by energy-dispersive X-ray spectroscopy analysis. Also, MAF-processed samples exhibited abrasive wear mechanism as a result of formation of oxygen layer as revealed in SEM micrographs. © 2022, ASM International.
Microstructural and mechanical characterisation of Al-Zn-Mg-Cu alloy processed by multi-directional cryo-forging
(Elsevier Ltd, 2021) Ramesh, S.; Anne, G.; Naik, G.M.; Jagadeesh, C.; Shivananda Nayaka, H.S.
Aim of the present investigation is to study the microstructural and mechanical properties of Al-Zn-Mg-Cu alloy before and after multi-direction forging (MDF) at cryogenic condition up to 3 cycles. Microstructure evolution of specimen was examined using optical microscope and orientation imaging microscopy as well as X-ray diffraction. Mechanical properties were measured by tensile test and Vickers micro hardness. Microstructural investigation shows that after 3 cycle of MDF average grain size was reduced to 8 Î¼m with low angle grain boundaries (LAGBs) and high dislocation density. Mechanical examination displays an improvement in hardness, yield strength and ultimate tensile strength is due to increases in grain boundaries and strain hardening effect. After 3 cycles of MDF process with cumulative strain Ï‚Î”Ïµ = 3.64 led to the formation of fine grain structure, and microhardness were observed to be 168 HV. Â© 2021 Elsevier Ltd. All rights reserved.
Microstructural Evolution and Strengthening of AM90 Magnesium Alloy Processed by ECAP
(Springer Verlag, 2017) Gopi, K.R.; Shivananda Nayaka, H.S.; Sahu, S.
Equal-channel angular pressing (ECAP) was applied on AM90 magnesium alloy using processing route B C at 275?C up to four passes. Microstructural evolution and the corresponding modification in mechanical properties (strength, elongation and hardness) corresponding to the number of ECAP passes were evaluated using X-ray diffraction (XRD), electron backscatter diffraction, scanning electron microscopy, transmission electron microscopy, tensile test and microhardness test. Shear deformation was found to refine the microstructure by breaking it into smaller grains formed by dislocation reconstruction. Tensile strength and hardness were found to increase by ? 128 and 23%, respectively, for ECAP-processed 2-pass sample in comparison with that of the homogenized condition. After two passes, tensile strength and hardness started decreasing even though the grain size was still decreasing, which was found to be associated with texture modification during ECAP processing as observed by XRD analysis. © 2017, King Fahd University of Petroleum & Minerals.
Microstructural Study and Mechanical Characterization of ECAP Processed C70600 Alloy
(Springer, 2022) Sachin, S.; Shivananda Nayaka, H.S.
Copper–Nickel alloy C70600 was processed by equal channel angular pressing (ECAP), at room temperature, up to 8 passes, to study the mechanical properties and metallurgical behavior Microstructural studies showed grain refinement up to fourth ECAP pass. Microhardness value increased by 45% after 4 ECAP passes. With further increase in ECAP passes, samples attained a saturated state. Similar trend was observed in Ultimate tensile strength with an increase of 54% as compared to homogenized sample and reached a maximum value of 562 MPa. Increase in mechanical property was attributed to strengthening by grain refinement and dislocation strengthening. XRD analysis showed the absence of precipitate in the deformed specimens. © 2022, The Institution of Engineers (India).
Microstructure, mechanical and corrosion properties of accumulative roll bonded Mg-2%Zn/anodized Al-7075 composite
(Elsevier Ltd, 2018) Anne, G.; Ramesh, M.R.; Shivananda Nayaka, H.S.; Arya, S.B.
Multilayered composite of Mg-2%Zn/anodized Al-7075 was developed by accumulative roll bonding (ARB) of wrought Mg-2%Zn and anodized aluminium 7075 alloy. The Mg-2%Zn/anodized Al-7075 composite exhibited density of 2298 kg/m3 which is about 1.2 times lighter weight as compared to Al-7075 alloy. The electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) showed an average grain size of 1 Î¼m and 0.73 Î¼m in Mg-2%Zn and anodized Al-7075 layers respectively, and with high angle grain boundaries (HAGBs). Mechanical properties were evaluated by microhardness and tensile tests and found significant improvement in strength and hardness values as compared with Mg-2%Zn alloy after four pass ARB process. The multilayered composite shows better corrosion resistance as compared to rolled Mg-2%Zn alloy evaluated using using potentiodynamic polarization test. Â© 2017 Elsevier Ltd.
Tool health monitoring in lathe turning process by artificial intelligence techniques — a review
(SAGE Publications Ltd, 2025) Gavina, C.G.; Hemalatha, K.L.; Ranganath, K.J.; Rajanna, S.; Shivananda Nayaka, H.S.
Monitoring tool health is essential for maintaining efficiency, productivity, and quality in lathe turning operations. Traditional methods rely on manual assessments and subjective judgments, which can be time-consuming, inconsistent, and inadequate for detecting subtle tool wear. Therefore, this review discusses the literature review on predicting tool wear in the turning process, comprehensively examining the methods documenting for sensing and testing parameter design, image processing, and classification methods. The review outlines the use of vibration signals and images as datasets and advanced artificial intelligence techniques like machine learning, computer vision, deep learning, and expert systems to predict the accurate wear percentage in the tool. It also discusses the benefits and limitations of methods used in reviewed papers. To conclude, the performance of AI techniques from the reviewed papers, RNN from deep learning, gives more accuracy, with 97.04% predicting the tool wear. Within the Industry 4.0 framework, after a detailed review of the AI techniques, the combination of deep learning techniques that ensemble vibration signals and image information develops as a vital technology for evolving intelligent manufacturing. © The Author(s) 2024