Faculty Publications
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Item Assessment of Structural Damage Due to Blasting in Hydro Power Tunnel(Springer Science and Business Media Deutschland GmbH, 2022) Naveen, G.C.; Sastry, V.R.; Ram Chandar, K.R.Excavation is a major activity in construction of mega underground hydropower project. Successful excavation of access and water conducting tunnels and caverns of different size and shapes by adopting highly economical and efficient method of excavation like drilling and blasting in extreme geological conditions makes the hydropower project a manmade marvel. The national codes which regulates the safety of structures while using explosives are successfully adopted where the tolerable limits for blast induced seismic waves are provided for different type of structures. This paper deals with impact of 9 m(W) and 8 m(H) tunnel blast induced seismic vibrations on the underground and surface concrete structures. The outcome of tunnel blasting with reference to peak particle velocity and related displacements gave a unique results where the seismic wave produced displacements up to 0.04 mm at large underground openings (250 m(L) × 18 m(W) × 59 m(H)) when compared to displacements of 0.016 mm in small openings of 9 m(W) × 8 m(H) with similar peak particle velocity levels of 20 mm/sec. These results subjected the structures which are located in the larger underground openings to lose their strength easily when compared to the structures located in small openings. Further, the structures located in the surface are more vulnerable to get damaged due to higher displacement recordings up to 0.123 mm. Experimental outcome was recorded for various blast design and results were further analyzed to optimize the blast parameters for successful control of blast induced vibration zone within 60 m. The relation between the structure locations where blast induced seismic wave propagates seems to play a key role in influencing on the structural damage, where less influence of peak particle velocity is observed. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Performance appraisal of RC beams using welded wire fabrics as lateral reinforcement in seismic zones(CAFET INNOVA Technical Society 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2011) Gowda, H.C.C.; Babu Narayan, K.S.; Venkataramana, K.Ductility is the key to design earthquake resistant structures. More rigid the structure or the element, more it attracts inertia forces. Structures and elements of infinite rigidity are out of question. Codes of practice also advocate design philosophies wherein effects of small earthquakes are to be absorbed with little or no damage, medium with damage to such extents that rehabilitation is possible and large earthquake effects to be catered without collapse. To absorb the tremendous energies that are input to structures and elements unless ductility is ensured, performance levels proposed by codes and standard practices cannot be attained. Lateral ties hold longitudinal reinforcement of R.C.elements in place and also confine the concrete. The basis of the present work is the usage of welded wire fabrics as lateral reinforcement in RC beams. A series of beams were tested with lateral ties and welded wire fabric at discrete locations and welded wire fabric alone throughout the beam with different mesh opening sizes. This paper presents the encouraging results with marginal increase in strength and considerable improvement in ductility in addition to reduced crack widths as observed for specimens having welded wire fabric with smaller mesh openings as lateral reinforcement by confining concrete. © 2011 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.Item Numerical simulation of progressive fracture propagation in petroleum reservoir rock strata using finite element modeling(CAFET INNOVA Technical Society cafetinnova@gmail.com 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2014) Goyal, R.; Singh, K.; Reddyy, D.V.Reservoir perforation allows for interfacing of the pay-zone and the production casing in the petroleum wellbore. Perforations are key interface for fluid movement in completion and they are extremely important for effective design and itis to beensured that well has appropriate number and size of perforation. For directing formation petroleu mfluid from subsurface zone, cased well must be perforated. Perforationis created by implementing controlled detonation of steel casing, cement casing and surrounding rock using specially design edand manufactured shaped charges. Perforating shockwaves and high impact pressureshattertherockto breakdown and propagate crack through it. Numerical model of acuboidal rock sample is createdto decide the preferred fracture plane. Under balance forces have also been taken in account to calculate Von-misesstress. Simulations are performed in order tostudy the behavior of compound stress during chargede to nation of rock and casing fracture. Crack propagation in different directions and principal planes has been found out. Usingthese results, location ofchargesoncasingcanbe defined to propagate fracture indesired locations. This report presents numerical analysis of fracture propagation during charged detonation using finite element methods (FEM).. © 2014 CAFET-INNOVA TECHNICAL SOCIETY.Item Determination of fracture toughness and fatigue crack growth rate using circumferentially cracked round bar specimens of Al2014T651(Elsevier Masson SAS infos@masson.fr 62 rue Camille Desmoulins Issy les Moulineaux Cedex 92442, 2015) Neelakantha, V.L.; Jayaraju, T.; Naik, P.; Kumar K, D.; Rajashekhar, C.R.; Kumar, M.Fracture toughness (KIC) and fatigue crack growth rate (FCGR) are the important material properties in fracture mechanics. ASTM-E399 and ASTM-E647 are the standards for determination of KIC and FCGR of metallic materials. These standards recommend the use of compact tension (CT) or single edge notched bend (SENB) test specimens. Literature review indicates that CT or SENB specimens are complex in nature, difficult to manufacture, require typical fixtures for loading during experimentation and the test procedures using CT or SENB are time consuming and cumbersome. An alternate specimen geometry which can overcome the above said drawbacks is needed by the industry which can be used as standard test specimen geometry. This research work explains use of circumferentially cracked round bar (CCRB) specimens of high strength Al2014T651 alloy for determination of KIC and FCGR.The pre-cracked round bar specimen was loaded in tensile in a universal testing machine and pulled till failure. Using suitable stress intensity factor equations the fracture toughness can be calculated. In case of crack growth test, the pre-cracked round bar specimen is allowed to rotate under fatigue load. The ratio of length of crack propagated to the number of cycles to failure was the crack growth rate. The SEM analysis of fractured surfaces was also done.The results are comparable with the values reported in the literature obtained by using standard test specimens. There are numerous advantages of using round bar specimen in KIC and FCGR tests. It is concluded that, the methodology of determination of fracture toughness and fatigue crack growth rate using CCRB specimens is relatively simple, reliable, fast and economical. CCRB specimen may be recommended as a standard test specimen for fracture toughness as well as crack growth tests. © 2015 Elsevier Masson SAS. All rights reserved.Item Hydrogen-Induced Cold Cracking in High-Frequency Induction Welded Steel Tubes(Springer Boston, 2016) Banerjee, K.Detailed investigation was carried out on 0.4C steel tubes used for the telescopic front fork of two-wheelers to establish the root cause for the occurrence of transverse cracks at the weld heat-affected zone of the tubes. Fractographic and microstructural observations provide evidences of delayed hydrogen-induced cracking. The beneficial microstructure for avoiding the transverse cracks was found to be the bainitic-martensitic, while martensitic structure was noted to be deleterious. © 2016, The Minerals, Metals & Materials Society and ASM International.Item Experimental investigation of effect of specimen thickness on fracture toughness of Al-TiC composites(Gruppo Italiano Frattura, 2016) Raviraj, M.S.; Sharanaprabhu, C.M.; Mohan Kumar, G.C.In this paper, the macro and micro-mechanical fracture behavior was studied for aluminum (Al6061) alloy matrix, reinforced with various proportions of TiC particles such as 3wt%, 5wt% and 7wt%. The Al6061-TiC metal matrix composites were produced by stir casting method to ensure uniform distribution of the TiC particulates in the Al matrix. The compact tension (CT) specimens were machined according to ASTM E399 specifications to evaluate the fracture toughness for Al6061-TiC metal matrix composites. The CT specimens were machined for crack to width (a/W) ratio of 0.5 and thickness to width (B/W) ratios of 0.2 to 0.7 with an increment of 0.1. Load versus crack mouth opening displacement (CMOD) data was plotted to estimate stress intensity factor KQ for various thicknesses of the specimen. The fracture toughness KIC was obtained by plotting stress intensity factor versus thickness to width ratios of specimen data. The fracture toughness of these composites varied between 16.4-19.2 MPa?m. Scanning Electron Microscope (SEM) studies was made on the fractured surface of the specimens to understand the micro-mechanisms of failure involve in these composites. Void initiation is more significant in the matrix near the interface. The micro-cracks grow from these micro-voids and crack propagates by linking these micro cracks locating the crack path preferentially in the matrix adjacent to the interface indicating ductile fracture. © 2016, Gruppo Italiano Frattura. All rights reserved.Item Wire Electro Discharge Machining Performance of TiNiCu Shape Memory Alloy(Springer Netherlands, 2016) Manjaiah, M.; Narendranath, S.; Basavarajappa, S.The study presents the effect of Wire Electro Discharge Machining (WEDM) system parameters on the Material Removal Rate (MRR), surface roughness and surface morphology of Ti 50Ni 45Cu 5 SMA developed using vacuum arc melting. The WEDM parameters such as pulse on time, peak current, pulse off time and table feed were selected as control factors over MRR and surface roughness. The results reveal that the surface roughness and MRR increases with increased peak current, pulse on time and table feed but decreases slightly with pulse off time. Higher MRR was attained at 5Amps peak current and 70 ?m/s table feed. Better surface roughness was obtained for a combination of lower pulse on time, peak current and table feed with high pulse off time. Surface defects such as recast layer, craters, micro–cracks, pockmarks and voids were found on the machined surface. The globule of appendages formed around the craters and the intensity of the crater was evident for the higher surface roughness with an increase in peak current and pulse-on time during WEDM. © 2015, Springer Science+Business Media Dordrecht.Item Strategy for refinement of nodal densities and integration cells in EFG technique(Techno-Press, 2016) Bhavana Patel, V.S.S.; Narayan, B.K.S.; Venkataramana, K.MeshFree methods have become popular owing to the ease with which high stress gradients can be identified and node density distribution can be reformulated to accomplish faster convergence. This paper presents a strategy for nodal density refinement with strain energy as basis in Element-Free Galerkin MeshFree technique. Two popular flat plate problems are considered for the demonstration of the proposed strategies. Issue of integration errors introduced during nodal density refinement have been addressed by suggesting integration cell refinement. High stress effects around two symmetrical semi-circular notches under in-plane axial load have been addressed in the first problem. The second considers crack propagation under mode I and mode II fracture loading by the way of introducing high stress intensity through line crack. The computational efficacy of the adaptive refinement strategies proposed has been highlighted. © 2016 Techno-Press, Ltd.Item Effect of BaO addition on the structural and mechanical properties of soda lime phosphate glasses(Elsevier Ltd, 2016) Edathazhe, A.; Shashikala, H.D.The phosphate glasses of composition (26-x)Na2O-xBaO-29CaO-45P2O5 (x = 0,5,10,15 mol%) are prepared by melt-quenching technique. The variations in structural and mechanical properties are studied on glasses prepared at 1000, 1100 and 1200? C. The density of glasses increases with barium content for glasses prepared at different temperatures. The molar volume is nearly constant with compositional parameter. The amorphous nature of samples is confirmed by XRD. The calculated values of mass percentage of elements in the batch composition and EDS data are in a reasonable agreement. The FTIR spectra show that the main structural units in these glasses are Q1 and Q2 phosphate units. The frequency of the P[sbnd]O[sbnd]P band remains constant with barium substitution. The microhardness is measured using Vickers indentation method by applying 0.98 N for 10 s. The hardness and fracture toughness are independent of composition. The nature of crack formations is examined by SEM. The brittleness and crack length are correlated with plastic flow in the material. © 2016 Elsevier B.V.Item Effect of specimen crack lengths on stress intensity factor for Al6061-TiC composites using experimental and 3D numerical methods(Emerald Group Publishing Ltd. Howard House Wagon Lane, Bingley BD16 1WA, 2017) Raviraj, M.S.; Sharanaprabhu, C.M.; Mohan Kumar, G.C.Purpose-The purpose of this paper is to present the determination of critical stress intensity factor (KC) both by experimental method and three-dimensional (3D) finite element simulations. Design/methodology/approach-CT specimens of different compositions of Al6061-TiC composites (3wt%, 5wt% and 7wt% TiC) with variable crack length to width (a/W0.3-0.6) ratios are machined from as-cast composite block. After fatigue pre-cracking the specimens to a required crack length, experimental load vs crack mouth opening displacement data are plotted to calculate the KC value. Elastic 3D finite element simulations have been conducted for CT specimens of various compositions and a/W ratios to compute KC. The experimental results indicate that the magnitude of KC depends on a/W ratios, and significantly decreases with increase in a/W ratios of the specimen. Findings-From 3D finite element simulation, the KC results at the centre of CT specimens for various Al6061-TiC composites and a/W ratios show satisfactory agreement with experimental results compared to the surface. Originality/value-The research work contained in this manuscript was conducted during 2015-2016. It is original work except where due reference is made. The authors confirm that the research in their work is original, and that all the data given in the article are real and authentic. If necessary, the paper can be recalled, and errors corrected. © Emerald Publishing Limited.