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Stress Relaxation for Formability Improvement
Hariharan, Krishnaswamy,Majidi, Omid,Kim, Chong Min,Lee, Myoung Gyu,Barlat, Fré,dé,ric Trans Tech Publications, Ltd. 2013 Key Engineering Materials Vol.554 No.-
<P>Improved formability has been reported due to stress relaxation when the continuous forming cycle is interrupted with steps by adjusting the punch motion. The contribution of stress relaxation and its parameters on the ductility of materials has not been established so far. In the present work, the stress relaxation behavior of three materials, low carbon steel, DP and TRIP steels are studied. The influence of strain rate and strain on the ductility enhancement due to stress relaxation is analyzed. It is observed that stress relaxation improved the ductility of materials in all the cases and therefore can be used as a potential method to improve formability in sheet metal forming.</P>
Shape optimization of NACA0012 using Computational Fluid Dynamics and Response Surface Methodology
Hariharan Kallath,Jun Seok Lee(이준석),June Kee Min(민준기) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11
Airfoil shape optimization has been studied for a long time. The present study is related to the shape optimization of NACA 0012 airfoil profile using computational fluid dynamics and response surface methodology tools at Reynolds number 2 million, Mach number 0.15 and 10 deg angle of attack. The shape of the airfoil is parameterized differently, and a set of numerical simulations were carried out for all combinations of the parameters. The need for remeshing during CFD analysis is successfully bypassed using mesh morphing methods. Response surfaces are fitted to the drag and lift coefficient outcomes from the simulations based on several statistical criteria. Three optimization problems were formulated, and the shape of airfoil was optimized for each optimization problem. The optimized shape is compared and reported concerning the baseline shape.
Mandibular implant overdenture - treatment modalities and maintenance - an integrative overview
Hariharan Ramakrishnan,Maniamuthu Ragupathi 대한치과이식임플란트학회 2022 The Korean Academy of Implant Dentistry Vol.41 No.1
Implant overdenture treatment planning should be carried out meticulously to ensure positive treatment outcomes over several years. Various factors, namely the number of implants to be placed, their length and diameter, type of abutment, nature of the residual edentulous ridge, available bone density, interarch distance, jaw relation, mouth opening, soft tissue architecture, design of the prosthesis, including the type of teeth and their size, and type of attachment to be used should all be taken into consideration while planning the treatment. The maintenance phase of the implant therapy includes the implant, prosthesis, and attachments. The treatment connects the dentist, patient, and hygienist triad. The dentist with the support of the hygienist should provide detailed explanations regarding the treatment and motivate the patient, and the patient, in turn, should sincerely follow the protocol for maintenance as explained by the dentist. The patient should also come back for periodic recall visits as scheduled by the prosthodontist/implantologist. This overview covers the evolving and changing aspects of mandibular implant overdenture treatment and maintenance.
Hariharan, Chinnasamy,Govardhan, Mukka Korean Society for Fluid machinery 2013 International journal of fluid machinery and syste Vol.6 No.3
While performing numerical simulations, it is general industrial practice to neglect the clearance gap between the impeller and the inlet duct. In the present work, the effect of clearance gap on the performance of an industrial sized centrifugal blower is simulated for two volutes of width ratios and various flow coefficients. The results show that the clearance has a positive effect at low mass flow rates. This is observed in the pressure rise (1.3%) as well as in efficiency (0.7%). At higher mass flow rates, it has a negative effect with a drop in efficiency of 1% and pressure drop of about 1.4%. The effect of clearance gap on volute with higher width ratio is smaller when compared with the volute with smaller width ratio.
A Novel Multi-objective Genetic Algorithms-Based Calculation of Hill’s Coefficients
Hariharan, K.,Chakraborti, N.,Barlat, F. d.,Lee, M. G. Springer Science + Business Media 2014 Metallurgical and Materials Transactions A - Physi Vol.45 No.6
<P>The anisotropic coefficients of Hill's yield criterion are determined through a novel genetic algorithms-based multi-objective optimization approach. The classical method of determining anisotropic coefficients is sensitive to the effective plastic strain. In the present procedure, that limitation is overcome using a genetically evolved meta-model of the entire stress strain curve, obtained from uniaxial tension tests conducted in the rolling direction and transverse directions, and biaxial tension. Then, an effective strain that causes the least error in terms of two theoretically derived objective functions is chosen. The anisotropic constants evolved through genetic algorithms correlate very well with the classical results. This approach is expected to be successful for more complex constitutive equations as well.</P>
Recent Advances in Infant Cry Signal Analysis and Emotion & Stress Recognition using Speech Research
( Hariharan Muthusamy ) 한국감성과학회 2017 한국감성과학회 국제학술대회(ICES) Vol.2017 No.-
Crying is a common symptom in the first 3 months of life and carries the information about the neurological and medical status of infants. According to statistics in 2015, Highest rate of infant deaths within the first year of life was recorded in the Africa region (55 per 1000 live births) than the European region (10 per 1000 live births). Every year, 15 million babies are born too early and this number is rising. The rate of preterm birth ranges from 5% to 18% of babies born across 184 countries. These statistics are completely independent of the information present in the infant cries. Early detection of risks for vulnerable children would allow implementing prevention strategies and policies in childhood. The aim of this research is to examine the ability of information embedded in infant cries to distinguish between several pathologies thereby cry analysis could be applied successfully in diagnostics and in the early detection of the infant at risk for developmental difficulties. Human beings use different forms of gestures, facial expressions, body languages and speeches for communication. These communications convey both messages and emotional states of the speakers. A speech signal carries the speaker’s linguistic information and also his/her gender, age, ori- gin and emotional states. ERS usually comprises four stages: pre-processing, feature extraction, feature selection and classification/recognition of emotion from speech signals. The aim of this research is to use both speech and its glottal waveforms to distinguish six different types of emotions and different style of speech under stress.
Hariharan, P. S.,Venkataramanan, N. S.,Moon, Dohyun,Anthony, Savarimuthu Philip American Chemical Society 2015 The Journal of Physical Chemistry Part C Vol.119 No.17
<P>A triphenylamine-based fluorophore, 4-((4-methoxyphenyl)(phenyl)amino)benzaldehyde (<B>1</B>), exhibits external-stimuli-responsive self-reversible solid-state fluorescence switching, tunable fluorescence, and a rare phenomenon of temperature-dependent fluorescence. Mechanically grinding a crystalline powder of <B>1</B> converts the blue fluorescence (λ<SUB>max</SUB> = 457 nm) to green (λ<SUB>max</SUB> = 502 nm), but blue fluorescence robustly self-recovers within 8 min. X-ray analysis and theoretical studies suggest that the change from a highly twisted molecular conformation and crystalline form into an amorphous phase with more planar conformation is responsible for the fluorescence switching. Self-reversible fluorescence switching did not show a significant change in fluorescence for several cycles of measurement. Interestingly, <B>1</B> in toluene showed a rare phenomenon of fluorescence enhancement with increasing temperature via activating more vibrational bands that lead to stronger twisted intramolecular charge-transfer (TICT) emissions. Morphological-change-mediated fluorescence tuning has also been demonstrated by fabricating nanoparticles of <B>1</B>. The conversion of highly polydispersed, featureless, different-shaped nanoparticles into nearly uniformly sized spherical nanoparticles (20–25 nm) converts green (λ<SUB>max</SUB> = 502 nm) to blue fluorescence (λ<SUB>max</SUB> = 478 nm). The self-reversible multi-stimuli-responsive fluorescence switching and polymorphism and nanofabrication-mediated fluorescence tuning suggest its potential application in sensors, particularly for fluorescent thermometers.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2015/jpccck.2015.119.issue-17/acs.jpcc.5b00310/production/images/medium/jp-2015-00310a_0012.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp5b00310'>ACS Electronic Supporting Info</A></P>
Stress relaxation and its effect on tensile deformation of steels
Hariharan, K.,Majidi, O.,Kim, C.,Lee, M.G.,Barlat, F. Scientific and Technical Press ; Elsevier Science 2013 Materials & design Vol.52 No.-
The tensile deformation of metallic materials, when interrupted without unloading, exhibit relaxation of stress. The stress relaxation phenomenon can alter the mechanical behavior of the materials. Stress relaxation phenomenon during tensile test is studied in three steel grades with different microstructures. The influence of stress relaxation on uniform elongation has not been reported before. The uniform elongation varies with strain at which material relaxes and is found to increase upto 3.5%. Contradicting with the published results, the stress drop during stress relaxation varies with strain and the possible reasons are explained. The stress drop during relaxation is governed by strain hardening mechanism in low carbon steel and strain aging mechanism due to martensite in dual phase (DP) and transformation induced plasticity (TRIP) steels.