Rotary ultrasonic machining of woven CFRP composite in a cryogenic environment

Thirumalai Kumaran, S.,Ko, Tae Jo,Li, Changping,Yu, Zhen,Uthayakumar, M. ELSEVIER SCIENCE 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.698 No.-

<P><B>Abstract</B></P> <P>In the present study, rotary ultrasonic machining (RUM) was adopted to perform drilling of carbon fiber reinforced plastics (CFRP) in a cryogenic environment. An L27 orthogonal array was selected to conduct experiments by varying the spindle speed (denoted as N), feed rate (denoted as f), and ultrasonic power (denoted as P). The thrust force (denoted as Fz), exit burr area, and surface roughness (denoted as Ra) were measured to evaluate the machining performance. The influence of process parameters and the regression model were derived for each output quality response. Additionally, multi-objective optimization was performed using desirability analysis, and the predicted levels were used for confirmation. The results indicated that the feed rate (f) contributed more to the thrust force (Fz) by 45.85% and a maximum thrust force was recorded at 0.1 mm/rev. A decrease in spindle speed (N) was associated with an increase in feed rate (f) and ultrasonic power (P), and it resulted in minimum exit burr area. The influence of ultrasonic power (P) was highly significant in reducing burrs with a contribution of 52.45%. Conversely, the surface roughness (Ra) of the drill holes decreased at 3000 rpm, and this was attributed to the brittle fracture of the fibers at a lower temperature. Both N (30.88%) and f (30.83%) had an equal influence on producing a better surface finish in the drill holes. Furthermore, the predicted optimal settings were used to validate the results and were found to be within 95% confidence and prediction interval. Finally, the microscopic images of tool wear, burr formation, and drill hole surface morphology were analyzed and examined.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Prediction of regression model for RUM of CFRP in a cryogenic environment. </LI> <LI> Output responses such as thrust force, burr area and roughness are investigated. </LI> <LI> The adequacy of an ANOVA model is checked for each output response. </LI> <LI> Optimization is performed by desirability analysis and the results are validated. </LI> <LI> Tool wear, burr formation, and drill hole surface morphology are analyzed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

De-bundled single-walled carbon nanotube-modified sensors for simultaneous differential pulse voltammetric determination of ascorbic acid, dopamine, and uric acid

Thirumalai, Dinakaran,Subramani, Devaraju,Yoon, Jang-Hee,Lee, Jaewon,Paik, Hyun-jong,Chang, Seung-Cheol The Royal Society of Chemistry 2018 NEW JOURNAL OF CHEMISTRY Vol.42 No.4

<P>A new approach based on differential pulse voltammetry (DPV) was developed for the simultaneous determination of ascorbic acid (AA), dopamine (DA), and uric acid (UA) using a modified glassy carbon electrode (GCE). The sensor was constructed by a simple “one-step” technique, wherein de-bundled single-walled carbon nanotubes (SWCNTs) were drop-cast onto the GCE. Without de-bundling, the SWCNTs were poorly dispersed in aqueous solution and were ineffective for the one-step procedure. De-bundling of the SWCNTs was achieved using a small amount (0.1 wt%) of the synthesized polymer dispersant, sulfonated poly(ether sulfone) (SPES); the de-bundled SWCNTs had a high aspect ratio (length = 2.5 ± 1.0 μm; height = 2 ± 1 nm, as determined using transmission electron microscopy and atomic force microscopy). The de-bundled SWCNTs also led to enhanced electrocatalytic activity and selectivity of the modified sensor for the simultaneous determination of AA, DA, and UA in DPV measurements: the peak-to-peak separation values were 221, 119, and 340 mV (<I>vs.</I> Ag/AgCl) for DA-AA, UA-DA, and AA-UA, respectively. The dynamic linear ranges for AA, DA, and UA were 0.2-1.6 mM, 5.0-50 μM, and 5.0-60 μM, and the detection limits were 10.6 μM, 15 nM, and 113 nM (S/N = 3), respectively. The analytical performance of the developed sensor was demonstrated in the determination of AA and DA in commercial pharmaceutical samples (vitamin C tablets and DA injection). The characteristics of the modified sensor make it promising for the individual or simultaneous determination of AA, DA, and UA.</P>

Electrochemical reactive oxygen species detection by cytochrome <i>c</i> immobilized with vertically aligned and electrochemically reduced graphene oxide on a glassy carbon electrode

Thirumalai, Dinakaran,Kathiresan, Vijayaraj,Lee, Jaewon,Jin, Sung-Ho,Chang, Seung-Cheol Royal Society of Chemistry 2017 The Analyst Vol.142 No.23

<P>A new amperometric biosensor for hydrogen peroxide (H2O2) and superoxide anion (SO) has been developed. The biosensor developed uses cytochrome <I>c</I> (Cyt <I>c</I>) modified glassy carbon electrodes coupled with electrochemically reduced graphene oxide (ErGO). To immobilize Cyt <I>c</I>, the “one step” electrochemical deposition of vertically aligned and ErGO (VAErGO) has been performed by using a pulse reverse technique, thus resulting in a very simple and efficient system. The well-established vertical alignment of ErGO was confirmed by atomic force microscopy and the electrochemical characteristics of the biosensor were investigated by cyclic voltammetric, electrochemical impedance spectroscopy and amperometric techniques. The surface coverage (<I>Γ</I>) of immobilized Cyt <I>c</I> was effectively increased by the vertical alignment of ErGO and found to be 1.03 × 10<SUP>−10</SUP> mol cm<SUP>−2</SUP>. The direct electron transfer property of Cyt <I>c</I> was also improved by VAErGO and the heterogeneous electron transfer rate constant (<I>k</I>et) was estimated to be 6.40 s<SUP>−1</SUP>. To detect H2O2 and SO, amperometric measurements were carried out at different operating potentials (0.0 V <I>vs.</I> Ag/AgCl for H2O2 and +0.2 V for SO). The sensitivity and detection limit for H2O2 were found to be 46.3 μA mM<SUP>−1</SUP> cm<SUP>−2</SUP> and 2.3 μM, and for SO were found to be 32.1 μM nA<SUP>−1</SUP> cm<SUP>−2</SUP> and 6.84 nM s<SUP>−1</SUP>, respectively. Additionally, the designed biosensor exhibited strong anti-interference ability and satisfactory reproducibility.</P>

An analysis of ceramic tool condition monitoring for enhanced and secured manufacturing

Thirumalai Ramanathan,Vivekraj M 한양대학교 세라믹연구소 2022 Journal of Ceramic Processing Research Vol.23 No.2

In metal cutting tool wear is complex phenomenon which occurs in several ways and it could not be avoided. Due to the hightool wear rate the close dimensional accuracy of the parts are not achieved and as a result the manufacturing execution systemfails in sending secured data to the systems properly. High security data transmission is essential in manufacturing executionsystem. Various algorithms are used for cryptography in the today’s market for securing the data. This paper employs aceramic tool for machining Inconel 718 to obtain close dimensional tolerance and thereby enhancing the secured data transfereffectively. The novelty of the work is incorporating the ceramic tool in the turning process and there by improving the secureddata transmission in the industrial automaiton. The outcome of the work is to measure the accuracy and precision of themachined parts from the ceramic cutting tool and to find the comparative improvement in the usage of several algorithms usedin enhanced secured data transmission.

Signalling networks and dynamics of allosteric transitions in bacterial chaperonin GroEL: implications for iterative annealing of misfolded proteins

Thirumalai, D.,Hyeon, Changbong Royal Society 2018 Philosophical transactions. Biological sciences Vol.373 No.1749

<P>This article is part of a discussion meeting issue 'Allostery and molecular machines'.</P>

Debundling of Carbon Nanotube by Sulfonated Poly(ether sulfone) and Silver Nanowire for Hydrogen Peroxide Sensor

Thirumalai Dinakaran,Subramani Devaraju,Bosung Shin(신보성),Hyun-jong Paik(백현종),Seung-Cheol Chang(장승철) 한국고분자학회 2017 폴리머 Vol.41 No.6

탄소섬유전극을 기반으로 효소가 불필요한 과산화수소(H₂O₂) 센서를 분산된 은 나노와이어와 단일벽 탄소나노튜브를 탄소섬유전극 표면에 드롭캐스팅법으로 고정화하여 제작하였다. 센서 제작에 사용된 탄소나노튜브는 고분자 분산제인 술폰화 폴리(에테르 술폰)에 의하여 효과적인 길이/직경의 종횡비를 나타낼 수 있도록 개별 분산되었으며 센서의 성능 향상을 위하여 은 나노와이어와 더불어 컴포지트 형태로 제작되어 새로운 센서 제작법에 활용되었다. 제작된 센서는 H₂O₂에 대하여 높은 전기촉매활성과 재현성, 빠른 분석 시간 및 우수한 감도를 나타냄을 확인하였다(센서 감도: 1.3 μA·mM<SUP>-1</SUP>, 검출 한계: 0.69 μM (S/N=3) 및 검출 시간: 3초 미만). 따라서 본 연구에서 개발된 고분자 분산제를 사용한 단일벽 탄소나노튜브의 수용액 내에서의 분산도 향상은 효소가 불필요한 H₂O₂ 센서의 설계 및 제작에 활용될 것으로 기대된다. A new non-enzymatic hydrogen peroxide (H₂O₂) sensor based on carbon fiber microelectrodes (CFMEs) has been developed. The CFMEs were modified using a simple drop casting procedure with effectively dispersed silver nanowires (AgNWs) and debundled single-walled carbon nanotubes (SWCNTs). In aqueous solution, the SWCNTs were debundled with a high length/diameter aspect ratio using a synthesized polymer dispersant, sulfonated poly(ether sulfone) (SPES). Enhanced electrocatalytic activity of the sensor for the reduction of H₂O₂ was obtained with the sensor sensitivity of 1.3 μA·mM<SUP>-1</SUP> and the detection limit of 0.69 μM (S/N=3) with a quick turnaround time (less than 3 s). The results clearly reveal that the AgNW-SWCNTs/CFMEs possess high electro-catalytic activity and efficient sensitivity with high reproducibility and fast amperometric response production. Therefore, the proposed debundling approach can be expanded to design and develop nonenzymatic hydrogen peroxide sensors.

Microstructural analysis and optimization of welding parameters for AA1100 welded plates

Thirumalai R,Karthick S,Giriraj M 한양대학교 세라믹연구소 2022 Journal of Ceramic Processing Research Vol.23 No.2

Friction stir welding (FSW) process is used in this research work to optimize the welding process parameters of welding ofAA1100 aluminium alloy. Taguchi grey relational analysis is used for optimization of the process parameters. The weldingprocess parameters considered in this research work are tool rotational speed, feed and axial load against the responseshardness, tensile strength at room and elevated temperature and % elongation at room and elevated temperature. L27orthogonal array is used to conduct the experiments and the impact of the process parameters on the responses are analyzedand presented. The characterization of the weld is analyzed and it is seen that the fine dimples projects ductile fracture andthe cracks present on flat surface exhibits brittle fracture.

Waterjet Erosion Studies of Aluminum Based Composite

S. Thirumalai Kumaran(띠루말라이 쿠마란),T. J. Ko(고태조),Zhen Yu(위전),M. Uthayakumar(우다야쿠마),P. Balamurugan(발라무루간) 한국기계가공학회 2016 한국기계가공학회 춘추계학술대회 논문집 Vol.2016 No.10

Tribological properties of modified jojoba oil as probable base stoke of engine lubricant

K. Thirumalai Kannan,S. Rameshbabu 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.4

This paper investigates the tribological characteristics of modified jojoba oil (MJO) as a base stoke for SAE20W40 mineral oil (LO). In addition, a graphene nanoparticle was also added as an additive in MJO and studied for its performance. MJO was obtained from a two-stage transesterification process: acid esterification and base esterification. Six samples were formulated with the partial replacement of modified jojoba oil as 0, 10, 20, 30, 40 and 50 % by volume to the SAE20W40 mineral oil. Tribological tests were conducted on a four ball tribometer test rig under extreme pressure and anti-wear conditions with the formulated blends. Subsequently, 0.075 wt% of graphene nano additive was added in the above mentioned oil ratios and investigated once again in a four ball tester. Surface analysis was carried out, using scanning electron microscope (SEM). The experimental results showed that the blend of 20 % jojoba oil exhibited a lower wear scar diameter than other blends at extreme load conditions. An addition of 0.075 wt% of graphene nano-additive to the formulated blends also enhanced its lubrication properties. The surface characteristic study revealed that the addition of nano additives witnessed lesser wear scars with 10 and 20 % of jojoba blends. Among the blends, 20 % of jojoba oil was considered as an acceptable blend to enhance the mineral properties in comparison with SAE20W40 mineral oil.

Multi-criteria decision making in the selection of machining parameters for Inconel 718

R. Thirumalai,J. S. Senthilkumaar 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.4

Taguchi’s methods and design of experiments are invariably used and adopted as quality improvement techniques in several manufacturing industries as tools for offline quality control. These methods optimize single-response processes. However, Taguchi’s method is not appropriate for optimizing a multi-response problem. In other situations, multi-responses need to be optimized simultaneously. This paper presents multi-response optimization techniques. A set of non-dominated solutions are obtained using non-sorted genetic algorithm for multi-objective functions. Multi-criteria decision making (MCDM) is proposed in this work for selecting a single solution from nondominated solutions. This paper addresses a new method of MCDM concept based on technique for order preference by similarity to ideal solution (TOPSIS). TOPSIS determines the shortest distance to the positive-ideal solution and the greatest distance from the negative-ideal solution. This work involves the high-speed machining of Inconel 718 using carbide cutting tool with six objective functions that are considered as attributes against the process variables of cutting speed, feed, and depth of cut. The higher-ranked solution is selected as the best solution for the machining of Inconel 718 in its respective environment.