Influence of plastic viscosity of mix on Self-Compacting Concrete with river and crushed sand

J.S. Kalyana Rama,M.V.N. Sivakumar,K. Sai Kubair,A. Vasan 사단법인 한국계산역학회 2019 Computers and Concrete, An International Journal Vol.23 No.1

In view of the increasing utility of concrete as a construction material, the major challenge is to improve the quality of construction. Nowadays the common problem faced by many of the concrete plants is the shortage of river sand as fine aggregate material. This led to the utilization of locally available materials from quarries as fine aggregate. With the percentage of fines present in Crushed Rock Fines (CRF)or crushed sand is more compared to river sand, it shows a better performance in terms of fresh properties. The present study deals with the formulation of SCC mix design based on the chosen plastic viscosity of the mix and the measured plastic viscosity of cement pastes incorporating supplementary cementitious materials with CRF and river sand as a fine aggregate. Four different combinations including two binary and one ternary mix are adopted for the current study. Influence of plastic viscosity of the mix on the fresh and hardened properties are investigated for SCC mixes with varying water to cement ratios. It is observed that for an increasing plastic viscosity of the mix, slump flow, T500 and J-ring spread increased but V-funnel and L-box decreased. Compressive, split tensile and flexural strengths decreased with the increase in plastic viscosity.

Optimization of low temperature hydrogen sensor using nano ceramic-particles for use in hybrid electric vehicles

J. Niresh,N. Archana,S. Neelakrishnan,V. M. Sivakumar,D. S. Dharun 한양대학교 세라믹연구소 2020 Journal of Ceramic Processing Research Vol.21 No.3

Hydrogen sensing in automobile application is the need of the hour as fuel cell based hybrid electric vehicle is developingat a faster pace. Nickel ferrite (NiFe2O4) nanoparticles embedded reduced graphene oxide (rGO) prepared by a facilehydrothermal thermal process was employed as a chemiresistive sensor for the detection of H2 gas. To study themorphological and structural features the synthesized samples were characterized by transmission electron microscopy(TEM), X-Ray diffraction and Raman Spectroscopy. 50 nm cube shaped NiFe2O4 nanoparticles were found to bedistributed on few layered rGO nanosheets. The electrical conductivity of pristine n type NiFe2O4 and NiFe2O4/rGO weretested at various operating temperatures. Hydrogen sensing characteristics were measured by forming a thick film of thesynthesized nanocomposite paste on an alumina substrate. Sensing results showed that NiFe2O4/ 1% rGO showed themaximum response at an optimum temperature of 80 ºC towards 200 ppm of hydrogen gas among four variants. Integration of NiFe2O4 nanoparticles on rGO nanosheets has markedly enhanced the conductivity of the nanocomposite. The sensor showed a lower detection limit of 8 ppm with two linear ranges from 30-90 ppm and 100 to 700 ppm. Furtherthe sensor was tested for its selectivity and stability.

Effect of heating location and size on mixed convection in lid-driven cavities

Sivakumar, V.,Sivasankaran, S.,Prakash, P.,Lee, J. Pergamon Press ; Elsevier Science Ltd 2010 COMPUTERS & MATHEMATICS WITH APPLICATIONS - Vol.59 No.9

A numerical study is performed to analyze the mixed convection heat transfer and fluid flow in lid-driven cavities with different lengths of the heating portion and different locations of it. The left wall has been heated fully or partially to a higher temperature, whereas the right wall is maintained at a lower temperature. Three different lengths of the heating portion and three different locations of it are used along the hot wall. The remaining portions of the left wall, and the top and the bottom walls of the cavity are insulated. The finite volume method is used to discretize the governing equations which are then solved iteratively. The velocities and pressure are coupled by the SIMPLE algorithm. Results are presented graphically in the form of streamlines, isotherms and velocity profiles. It is concluded that the heat transfer rate is enhanced on reducing the heating portion and when the portion is at middle or top of the hot wall of the cavity.

Extraction, Multi-response Analysis, and Optimization of Biologically Active Phenolic Compounds from the Pulp of Indian Jamun Fruit

J. Prakash Maran,V. Sivakumar,K. Thirugnanasambandham,R. Sridhar 한국식품과학회 2014 Food Science and Biotechnology Vol.23 No.1

An aqueous extraction technique was appliedto optimize the extraction process variables of temperature(40oC-60oC), time (20-100 min), and the solid-to-liquidratio (1:10-1:15) using a Box-Behnken experimentaldesign and response surface methodology. Maximumextraction yields of total phenolics and flavonoids, andanti-oxidant activities were obtained from Indian jamunfruit. Effects of the extraction temperature and the solid-toliquidratio were found to be significant (p<0.05) for allresponses. Second order polynomial models were developedfrom experimental data to predict the effects of theindependent variables on the responses. Optimum extractionconditions (temperature of 54oC, time of 50 min, and asolid-to-liquid ratio of 1:8.5) for the maximum extractionyield of total phenolics (1,332.36 mg GAE/100 g) andflavonoids (110.94 mg QE/100 g), and the anti-oxidantactivity (233.55mg AAE/100 g) were achieved. Experimentalvalues matched well with predicted values obtained underoptimum conditions.

Fracture properties of concrete using damaged plasticity model -A parametric study

J.S. Kalyana Rama,D.R. Chauhan,M.V.N Sivakumar,A. Vasan,A. Ramachandra Murthy 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.64 No.1

The field of fracture mechanics has gained significance because of its ability to address the behaviour of cracks. Predicting the fracture properties of concrete based on experimental investigations is a challenge considering the quasi-brittle nature of concrete. So, there is a need for developing a standard numerical tool which predicts the fracture energy of concrete which is at par with experimental results. The present study is an attempt to evaluate the fracture energy and characteristic length for different grades of concrete using Concrete Damage Plasticity (CDP) model. Indian Standard and EUROCODE are used for the basic input parameters of concrete. Numerical evaluation is done using Finite Element Analysis Software ABAQUS/CAE. Hsu & Hsu and Saenz stress-strain models are adopted for the current study. Mesh sensitivity analysis is also carried to study the influence of type and size of elements on the overall accuracy of the solution. Different input parameters like dilatation angle, eccentricity are varied and their effect on fracture properties is addressed. The results indicated that the fracture properties of concrete for various grades can be accurately predicted without laboratory tests using CDP model.

Plastic viscosity based mix design of self-compacting concrete with crushed rock fines

Kalyana Rama J S,Sivakumar M V N,Vasan A,Sai Kubair,Ramachandra Murthy A 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.20 No.4

With the increasing demand in the production of concrete, there is a need for adopting a feasible, economical and sustainable technique to fulfill practical requirements. Self-Compacting Concrete (SCC) is one such technique which addresses the concrete industry in providing eco-friendly and cost effective concrete. The objective of the present study is to develop a mix design for SCC with Crushed Rock Fines (CRF) as fine aggregate based on the plastic viscosity of the mix and validate the same for its fresh and hardened properties. Effect of plastic viscosity on the fresh and hardened properties of SCC is also addressed in the present study. SCC mixes are made with binary and ternary blends of Fly Ash (FA) and Ground Granulated Blast Slag (GGBS) with varying percentages as a partial replacement to Ordinary Portland Cement (OPC). The proposed mix design is validated successfully with the experimental investigations. The results obtained, indicated that the fresh properties are best achieved for SCC mix with ternary blend followed by binary blend with GGBS, Fly Ash and mix with pure OPC. It is also observed that the replacement of sand with 100% CRF resulted in a workable and cohesive mix.

Effect of Surface Condition on the Torsional Fatigue Behaviour of 20MnCr5 Steel

S. Ramesh,S. Natarajan,V. J. Sivakumar 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.9

Torsional fatigue behaviour of steel is influenced by various significant factors on the surface of steel such as the stress state,the metallurgical conditions and the surface roughness etc. This research presents the results of the studies conducted on thetorsional fatigue life of steel for different surface stresses, conditions and microstructures. Based on the results, inferenceswere derived out of the factors and conditions which are instrumental in increasing the fatigue performance. This researchis done with the purpose of increasing the fatigue performance of power train shafts processed through vacuum carburizingfollowed by second tempering. The fatigue tests were conducted using a bi-directional torsional cyclic loading in a MTSmake torque testing machine. Various researches has been conducted in this paper to find out the impact of surface roughness,second tempering, inter granular oxidation and carbon case depth on the transmission shafts. The existence of surfaceretained austenite has not yielded a notable enhancement in fatigue performance in the power train shaft whereas existenceof martensite with minimum fraction of retained austenite enhanced the fatigue performance significantly from 12,000 to35,000 cycles on ± 3100 N m torque load.

Settlement of and load distribution in a granular piled raft

Madhav, Madhira R.,Sharma, J.K.,Sivakumar, V. Techno-Press 2009 Geomechanics & engineering Vol.1 No.1

The interactions between a granular pile and raft placed on top are investigated using the continuum approach. The compatibility of vertical and radial displacements along the pile - soil interface and of the vertical displacements along the raft - top of ground interfaces are satisfied. Results show that consideration of radial displacement compatibility does not influence the settlement response of or sharing of the applied load between the granular pile and the raft. The percentage load carried by the granular pile (GP) increases with the increase of its stiffness and decreases with the increase of the relative size of raft. The normal stresses at the raft - soil interface decrease with the increase of stiffness of GP and/or relative length of GP. The influences of GP stiffness and relative length of GP are found to be more for relatively large size of raft. The percentage of load transferred to the base of GP increases with the increase of relative size of raft.