Fracture and Size Effect on Strength of Plain Concrete Disks under Biaxial Flexure Analyzed by Microplane Model M7

Kirane, Kedar,Baž,ant, Zdeně,k P.,Zi, Goangseup American Society of Civil Engineers 2014 Journal of engineering mechanics Vol.140 No.3

The biaxial tensile strength of concrete (and ceramics) can be easily tested by flexure of unreinforced circular disks. A recent experimental study demonstrated that, similar to plain concrete beams, the flexural strength of disks suffers from a significant size effect. However, the experiments did not suffice to determine the size effect type conclusively. The purpose of this study is to use three-dimensional stochastic finite-element analysis to determine the size effect type and shed more light on the fracture behavior. A finite-element code using the microplane constitutive Model M7 is verified and calibrated by fitting the previously measured load-deflections curves and fracture patterns of disks of thicknesses 30, 48, and 75 mm, similar in three dimensions, and on flexure tests on four-point loaded beams. It is found that the deformability of the supports and their lifting and sliding has a large effect on the simulations, especially on the fracture pattern, and the strength and Young's modulus of concrete must be treated as autocorrelated random fields. The calibrated model is then used to analyze the size effect over a much broader range of disk thicknesses ranging from 20 to 192 mm. The disks are shown to exhibit the typical energetic size effect of Type I, that is, the disks fail (under load control) as soon as the macrofracture initiates from the smooth bottom surface. The curve of nominal strength versus size has a positive curvature and its deterministic part terminates with a horizontal asymptote. The fact that material randomness had to be introduced to fit the fracture patterns confirms that the Type 1 size effect must terminate at very large sizes with a Weibull statistical asymptote, although the disks analyzed are not large enough to discern it.

Analysis and numerical simulation of the three-dimensional Cauchy problem for quasi-linear elliptic equations

Tran, Q.V.,Kirane, M.,Nguyen, H.T.,Nguyen, V.T. Academic Press 2017 Journal of mathematical analysis and applications Vol.446 No.1

<P>This work is concerned with solving the Cauchy problem for quasilinear elliptic equations whose exponential instability is manifestly seen by the catastrophic growth in the representation of the exact solution. Our proposed regularization procedure consists in damping the unbounded terms in the representation. Moreover, we show that its solution converges to the exact solution uniformly and strongly in L-2 under a priori assumptions on the exact solution. In order to verify our analysis and the accuracy of the numerical procedures, we exhibit two numerical examples. Our main tools for simulation are the trigonometric polynomial approximation, and the fast Fourier transform in combination with the cubic Hermite interpolation. (C) 2016 Elsevier Inc. All rights reserved.</P>

On a Riesz-Feller space fractional backward diffusion problem with a nonlinear source

Tuan, N.H.,Hai, D.N.D.,Long, L.D.,Nguyen, V.T.,Kirane, M. Koninklijke Vlaamse Ingenieursvereniging ; Elsevie 2017 Journal of computational and applied mathematics Vol.312 No.-

<P>In this paper, a backward diffusion problem for a space-fractional diffusion equation with a nonlinear source in a strip is investigated. This problem is obtained from the classical diffusion equation by replacing the second-order space derivative with a Riesz-Feller derivative of order alpha is an element of (0, 2]. A nonlinear problem is severely ill -posed, therefore we propose two new modified regularization solutions to solve it. We further show that the approximated problems are well-posed and their solutions converge if the original problem has a classical solution. In addition, the convergence estimates are presented under a priori bounded assumption of the exact solution. For estimating the error of the proposed method, a numerical example has been implemented. (C) 2016 Elsevier B.V. All rights reserved.</P>

Three-dimensional finite element modeling of pulsed AC gas metal arc welding process

Kiran, D. V.,Cheon, J.,Arif, N.,Chung, H.,Na, S. J. Springer Science + Business Media 2016 INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TE Vol.86 No.5

<P>The behavior of the welding arc in the pulsed DC and AC gas metal arc welding processes was studied using real-time recorded current, voltage waveforms, and synchronized high-speed video at different electrode negative (EN) ratios for a constant wire feed rate. The regression equations were developed to predict the arc root dimensions as a function of welding current, voltage, time, and the EN ratio. A methodology was proposed to estimate the available energy rate distribution to the electrode and the base plate during the positive and negative cycles in pulsed AC gas metal arc welding (pulsed AC-GMAW) process. For an approximately equal peak positive current, the increase in the pulse time enhanced the molten electrode droplet diameter, arc plasma distribution, and the arc root dimensions. The fraction of the available arc energy rate supplied to the base plate was higher in positive pulse when compared to the negative pulse. A three-dimensional finite element modeling of pulsed DC-GMAW and pulsed AC-GMAW processes was performed to estimate the weld pool profile and temperature distribution in the weldment. The computed weld width, penetration, and the thermal cycles were in reasonable agreement with the corresponding experimental results. The peak temperature of the region in the weld pool near to the Gaussian distributed heat source experience fluctuations which were in synchronization with the current waveform. Increase in the EN ratio decreased the peak temperature while increased the cooling rate in the weldment. This reduced the bainite phase and enhanced the martensite phase in the weldment.</P>

Pyknodysostosis: report of a rare case with review of literature

Kiran Kumar Kotagudda Ramaiah,Giju Baby George,Sheeba Padiyath,Rupak Sethuraman,Babu Cherian 대한영상치의학회 2011 Imaging Science in Dentistry Vol.41 No.4

Pyknodysostosis is a rare autosomal recessive disorder characterized by the post natal onset of short limbs, short stature, and generalized hyperostosis along with acro-osteolysis with sclerosis of the terminal phalanges, a feature that is considered essentially pathognomonic. Other features include persistence of fontanelles, delayed closure of sutures, wormian bones, absence of frontal sinuses, and obtuse mandibular gonial angle with relative mandibular prognathism. We report a case of 17-year-old girl who presented with a chief complaint of retention of deciduous teeth. General physical examination demonstrated short stature, frontal and parietal bossing, depressed nasal bridge,beaked nose, hypoplastic midface, wrinkled skin over the finger tips, and nail abnormalities. Radiographs showed multiple impacted permanent and supernumerary teeth, hypoplastic paranasal sinuses with acro-osteolysis of terminal phalanges, and open fontanelles, and sutures along with wormian bones in the lambdoidal region.

The ultrafast nonlinear optical response and multi-photon absorption of a new metal complex in the near-infrared spectral range

Kiran, A J,Lee, H W,Sampath Kumar, H C,Rudresha, B J,Bhat, B R,Yeom, D-I,Kim, K,Rotermund, F IOP Publishing 2010 Journal of optics Vol.12 No.3

<P>A new coordination compound, chloro(1,10-phenanthroline-<I>N</I>, <I>N</I><SUP>′</SUP>)(triphenylphosphine)copper(I) dichloromethane, incorporated in poly(methyl methacrylate) exhibits superior nonlinear optical properties in the near-infrared spectral region. Its nonlinear response time and third-order nonlinear optical susceptibility at 800 nm are ≤ 90 fs and 1.8 × 10<SUP> − 10</SUP> esu, respectively. Considerable nonlinear absorption is observed with this sample, near 800 and 1250 nm. The contribution of the excited states to the total nonlinear absorption process is discussed. The results reveal the potential of this newly designed compound for multi-photon absorption-based photonic applications.</P>

Variation of embryonic diapause induction in bivoltine silkworm Bombyx mori L (Lepidoptera: Bombycidae) under controlled conditions

( Kiran Rudramuni ),( Bharath Kumar Neelaboina ),( Shivkumar ),( Mir Nisar Ahmad ),( Sukhen Roy Chowdhury ) 한국잠사학회 2021 International Journal of Industrial Entomology Vol.43 No.2

Mulberry silkworm is classified into uni, bi and multivoltine based on the frequency of diapause incidence. The variation in the incidence of diapause in bivoltine silkworm provides a unique opportunity to study the process of evolution of adaptive plasticity towards seasonal variations. The diapause expression in bivoltine silkworm is highly variable and is determined by environmental factors experienced by the maternal generation. Diapause in natural populations is functionally associated with the overwintering mechanism that facilitates survival in harsh winter conditions. In contrast, under standard commercial rearing conditions, the domesticated bivoltine silkworm is known to enter diapause in every generation. This paper presents a short review of the literature dealing with the role of temperature, photoperiod, diapause hormone and its receptor in diapause induction. Also, we briefly review the incidence of non-diapause eggs in bivoltine silkworm under controlled conditions.

Free vibration and static analysis of functionally graded skew magneto-electro-elastic plate

Kiran, M.C.,Kattimani, S.C. Techno-Press 2018 Smart Structures and Systems, An International Jou Vol.21 No.4

This article presents a finite element (FE) model to assess the free vibration and static response of a functionally graded skew magneto-electro-elastic (FGSMEE) plate. Through the thickness material grading of FGSMEE plate is achieved using power law distribution. The coupled constitutive equations along with the total potential energy approach are used to develop the FE model of FGSMEE plate. The transformation matrix is utilized in bringing out the element matrix corresponding to the global axis to a local axis along the skew edges to specify proper boundary conditions. The effect of skew angle on the natural frequency of an FGSMEE plate is analysed. Further, the study includes the evaluation of the static behavior of FGSMEE plate for various skew angles. The influence of skew angle on the primary quantities such as displacements, electric potential, and magnetic potential, and secondary quantities such as stresses, electric displacement and magnetic induction is studied in detail. In addition, the effect of power-law gradient, thickness ratio, boundary conditions and aspect ratio on the free vibration and static response characteristics of FGSMEE plate has been investigated.

Designing novel chalcone single crystals with ultrafast nonlinear optical responses and large multi-photon absorption coefficients

Kiran, A.J.,Lee, H.W.,Ravindra, H.J.,Dharmaprakash, S.M.,Kim, K.,Lim, H.,Rotermund, F. Elsevier 2010 Current Applied Physics Vol.10 No.5

A chalcone single crystal, 1-(4-chlorophenyl)-3-(4-methoxyphenyl)prop-2-en-1-one that is transparent over the visible to infrared region is introduced as a new potential material to third-order nonlinear optical applications. The crystal exhibits ultrafast optical response (@?90 fs) and large optical nonlinearity in the wavelength range 800-1200 nm. A very large effective two-photon absorption coefficient β<SUB>eff</SUB>exceeding 120 cm/GW can be obtained with this chalcone crystal, at a low intensity threshold of 41 MW/cm<SUP>2</SUP> The mechanism of nonlinear absorption at different levels of intensity has been discussed. The crystal shows no damage against the laser pulse intensity as high as 8 GW/cm<SUP>2</SUP> We discuss the molecular and crystal designing of chalcones with large and ultrafast optical nonlinearity combined with low optical cut-off (<450 nm).

Computational investigation on secondary flows in a linear turbine cascade with tapered dual fence

Kiran K. N.,Sushanlal Babu,Anish S. 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.2

The focus of the present work is to minimize the secondary flow losses inside a linear turbine cascade by means of a novel design of streamwise dual fence. The leading edge and trailing edge of the fences have been modified so as to reduce the total pressure loss coefficient in the passage. The study has been carried out computationally based on RANS simulations with SST turbulence model. Numerous simulations have been undertaken with single fence and dual fence models and compared with the base case model. The dual fence model with tapered trailing edge exhibits significant loss reduction compared to the base case. A suitable fence height ratio (FHR) has been identified for the dual fence model. The FHR = 2 configuration reduces the secondary flow kinetic energy by 78 % within the blade passage and it reduces the exit angle deviation significantly throughout the span. Detailed flow field analysis has been carried out to understand the physical mechanism behind the loss reduction with dual fence models. It is observed that fence-1 breaks the pressure side leg of the horse shoe vortex at the beginning of their formation itself. The radial penetration of the suction side leg of the horse shoe vortex is restrained by fence-2. These combined effects prevent the formation and mixing of two prominent loss core regions thereby avoiding the accumulation of low energy fluid near the suction side of blade.