Journal Articles

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    Surface hardening of high-strength low alloy steels (HSLA) dual-phase steels by ball burnishing using factorial design
    (2007) Rao, D.S.; Hebbar, H.S.; Komaraiah, M.
    Burnishing is used increasingly as a finishing operation which gives additional advantages such as increased hardness, fatigue strength, and wear resistance. Experimental work based on 34 factorial design was carried out to establish the effects of ball burnishing parameters on the surface hardness of high-strength low alloy steels (HSLA) dual-phase (DP) steel specimens. Statistical analysis of the results shows that the speed, feed, lubricant and ball diameter have significant effect on surface hardness.
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    Investigations on the effect of ball burnishing parameters on surface hardness and wear resistance of HSLA dual-phase steels
    (2008) Rao, D.S.; Hebbar, H.S.; Komaraiah, M.; Kempaiah, U.N.
    Surface finish has a vital influence on most functional properties of a component like fatigue life, wear resistance, corrosion resistance, etc. This has given birth to processes such as lapping, honing, burnishing, etc. Burnishing is a fine finishing operation involving the cold working plastic deformation of surface layers to enhance the surface integrity and the functional utility of a component. The present study has been carried out to establish the effect of burnishing parameters viz. feed rate, speed, force, ball diameter and lubricant on surface hardness, and wear resistance of HSLA dual-phase steel specimens. The result indicates that burnishing parameters have significant effect on the surface hardness and wear resistance.
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    Mechanical properties of fly ash reinforced aluminium alloy (Al6061) composites
    (2011) Anilkumar, H.C.; Hebbar, H.S.; Ravishankar, K.S.
    The results of an experimental investigation of the mechanical properties of fly ash reinforced aluminium alloy (Al 6061) composites samples, processed by stir casting route are reported in this paper. Three sets of composites with fly ash particle sizes of 4-25, 45-50 and 75-100 ?m were used. The particle size ranges chosen as the said particle sizes were available more by weight fraction when sieve analysis was conducted on the sample collected for experiments and also the ones for which results are not reported. Each set had three types of composite samples with the reinforcement weight fractions of 10, 15 and 20%. The mechanical properties studied were the tensile strength, compressive strength, ductility and hardness. Unreinforced Al6061 samples were also tested for the same properties. It was found that the tensile strength, compressive strength and hardness of the aluminium alloy (Al 6061) composites decreased with the increase in particle size of reinforced fly ash. Increase in the weight fractions of the fly ash particles increases the ultimate tensile strength, compressive strength, hardness and decreases the ductility of the composite. The scanning electron micrographs of the samples indicated uniform distribution of the fly ash particles in the matrix without any voids.
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    Influence of weave pattern and composite thickness on mechanical properties of bamboo/epoxy composites
    (Institute of Physics Publishing helen.craven@iop.org, 2019) Kanaginahal, G.M.; Hebbar, H.S.; Kulkarni, S.M.
    The results of an attempt made for studying the influence of weave pattern and composite thickness of plain and twill weave bamboo fabric reinforced epoxy/phenalkamine composites on static mechanical properties are reported in this paper. Plain weave and Twill weave bamboo fabric of 125 gsm were used as reinforcements with medium viscous epoxy B-11 resin and highly viscous AI 1041 phenalkamine bio-based hardener. Thickness of composite achieved were 3.1, 4.3 and 5.4 mm with fiber weight fraction at 18% by hand layup method. The aim was to study the influence of weave pattern and thickness of composite on the tensile, flexural and impact properties. Fourier Transform Infra-Red results showed the presence of cellulose, polysaccharides, cardanol groups and hydrogen bonding of reinforcement and matrix. X-Ray Diffraction peaks displayed higher intensities for twill weave fabric. Tensile studies of fabrics showed 7% higher strength for twill weave compared to that of plain weave fabric in warp direction. Twill weave composites with 5.4 mm thickness showed an increase of 12% in tensile strength and 8% increase in stiffness compared to plain weave composite of same thickness. Twill weave composite with 5.4 mm thickness showed an increase of 22% in flexural strength and 28% in stiffness compared to plain weave composite of same thickness. Izod impact results displayed an increase of 16% in absorbed energy for 5.4 mm thickness twill weave composite when compared with plain weave composite of same thickness. Fractography of fractured specimens of tensile test displayed fiber pullouts for plain weave composites and fiber breakage for twill weave composites. Twill weave composites have shown better wettability than that of plain weave composites. © 2019 IOP Publishing Ltd.
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    Effect of Zinc and Bio-Glass Addition on Mechanical Properties and Corrosion Behavior of Magnesium-Based Composites for Orthopedic Application: A Preliminary Study
    (Springer, 2022) Moudgalya, K.V.S.; Sekar, P.; Hebbar, H.S.; Rahman, M.R.
    Magnesium is extensively researched as a biodegradable implant material. However, achieving a combination of biomechanical properties viz., controlled degradation, bio-transformability and osteoconductivity is highly challenging. Indeed, bio-composites developed by reinforcing bio-ceramics with metals are gaining research interest. In this current work, the suitability of a bio-composite developed by reinforcing 5, 10 and 15% of bioglass (BG) in Mg and Mg-3 wt.% Zn metal matrix is investigated. The bio-composites containing Mg, Mg-BG and Mg-Zn-BG are processed by vacuum sintering and tested for important mechanical and corrosion properties. Particle size analysis revealed that magnesium exhibited a larger mean particle size while zinc evinced the lowest average particle size. The density-porosity analysis showed that porosity was found to increase linearly with the addition of BG. In contrast, the compressive strength of Mg-BG and Mg-Zn-BG composites increased up to 10 wt.% BG and decreased drastically for 15 wt.% BG reinforcement. The addition of Zn and BG significantly enhanced the Vickers hardness, showing an increasing trend with the increase in BG reinforcement content. Immersion corrosion study in phosphate buffered saline revealed that 10 wt.% BG reinforced composite exhibited the least corrosion rate. Thus, composites developed by reinforcing BG in Mg-3Zn metal matrix showed enhanced mechanical and corrosion properties in the physiological environment. The possible corrosion mechanism of Mg, Mg-Zn and Mg-Zn-BG composites is also proposed and compared. © 2022, ASM International.
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    Unveiling the role of heat treatment approaches in tailoring corrosion performance of laser powder-directed energy deposited SS304
    (Elsevier B.V., 2025) Sasindran, J.; Narayanan, J.A.; Babu, I.A.; Balan, A.S.S.; Hebbar, H.S.; Bontha, S.
    This study investigates the effect of different post-processing heat treatment approaches on the corrosion behavior of Laser Powder-Directed Energy Deposited (LP-DED) SS304. Samples were fabricated using optimized LP-DED parameters: laser power of 400 W, scan speed of 800 mm/min, feed rate of 4 g/min, 0.6 mm beam diameter, and 33 % track overlap.Electrochemical analysis revealed significant differences in corrosion performance depending on the applied heat treatment approach. This treatment resulted in changes to residual stress, microstructure, and oxide layer characteristics which together influence the corrosion rate (CR). The stress-relief annealed (SRA) samples significantly improved corrosion resistance by up to 90 % compared to the as-built condition, while preserving the fine microstructure formed during the LP-DED process and maintaining a stable protective oxide layer. Solution treated and different quenched samples exhibited varying CR depending on the cooling rate and resulting coarse grain structure. These findings highlight the significant influence of post-processing heat treatments on corrosion behavior and microstructural characteristics. © 2025 Elsevier B.V.