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Sintered eutectoid P/M steel behaviour during cold upsetting
(ABM, ABC, ABPol, 2008-01-03) Kannan, A. Rajesh; Pandey, K.S.; Shanmugam, S; Narayanasamy, R
Cold upsetting experiments were carried out on sintered Fe-0.8%C steel preforms in order to evaluate the technical relationship that exist between the applied stresses against continuous deformation and densification. Powder preforms of 86% theoretical density and 0.40 of initial aspect ratio were subjected to incremental compressive loading of 0.04 MN under three different friction conditions such as dry, graphite and zinc stearate employed during deformation until fracture appears at free surfaces. Experimental results revealed that the response of applied stresses with induced strain and attained densification exhibits a continuous enhancement but with three different stages. Irrespective of friction conditions the first and third stage shows steep rise. which offers high resistance to deformation, whereas the second stage shows virtually steady state; deformation needed gradual increase in applied stresses but with high rate of densification. Further. preform deformed under without lubricant exhibited maximum strain hardening as well as an enhanced rate of strain hardening through out the deformation in comparison with lubricants employed conditions.
Simulation of weld bead geometry in gta welded duplex stainless steel(DSS)
(John Wiley & Sons Ltd, 2009-07-22) Sathiya, P; Jinu, G.R.; Singh, Navjot
Temperature analysis of GTA welding of Duplex Stainless Steel material (2205) is simulated using ANSYS software by finite element technique taking in account the characteristics and advantage of GTAW than other sources. A travel heat source combined with body loads was designed by analyzing thermal physical parameters, latent heat of fusion of material. Modeling was carried out by using solid modeling and direct generation technique. A residual control method was taken for precise node selection, Simulation was done by varying the parameter of GTA, welding speed. The quasisteady state temperature field of GTA welding was simulated with the FEA softwareANSYS as well as tests. The objective of this work is to compare the experimentally obtained weld bead geometry of DSS material with simulated results from ANSYS software for various weld parameters. The higher the value of joining efficiency is, the less heat energy is spent on unnecessary heating-that is generating a heat affecting zone (HAZ) or distortion. Joining of two metals or alloys is important in every aspect of engineering which leads to welding in an effective manner and carrying out the analysis. The experimental analysis shows that the model is showing good agreement with the experimental results. Comparison of the experimental and simulated results shows the maximum deviation of 1.27 and 10 for calculating bead width and depth of penetration, respectively. Copyright © 2009 P. Sathiya et al.
An experimental study of thermal fatigue on ASTM A 213 grade T-23 steel tube
(Hindawi Limited, 2009-08-31) Jinu, G.R.; Sathiya, P; Ravichandran, G; Rathinam, A
Super heater tubes are subjected to alternate heating and cooling in power plants causes crack and eventually fail. This phenomenon is termed as thermal fatigue. In this paper, a laboratory simulation for reproducing thermal fatigue phenomenon is developed to determine the number of cycles of failure occurs in super heater tubes. Thermal fatigue tests are conducted in Non-Destructive Tested T23 base and SMAW welded tubes separately. The tubes are subjected to thermal cycles from 800∘C (accelerated temperature) to room temperature (28∘C). In this work 800∘C is selected in order to achieve the crack much earlier. The selected temperature is just below the Ac1 temperature. The tubes are subjected to heat by Oxy-acetylene flame and subsequently quenched with water. The tests are carried out until open cracks are identified. Surface cracks are identified in the base and weld tubes after 120 and 80 cycles respectively. The tubes are then sectioned and subjected to optical microscopy. The causes of failures are thoroughly investigated using Scanning Electron Microscope (SEM). This study reveals that localised heating and cooling causes thermal fatigue which initiates cracks in the tubes.
Characterization of microstructure, toughness, and chemical composition of friction-welded joints of UNS S32205 duplex stainless steel
(Tsinghua University Press, 2014-03-11) Ajith, Puthuparambil Madhavan; Sathiya, Paulraj; Aravindan, Sivanandam
Friction welding is a solid-state joining process which is applied extensively because of its advantages such as low heat input, efficient application, ease in manufacturing, and environmental friendliness. The present study investigates the mechanical and metallurgical properties of UNS S32205 duplex stainless steel friction-welded joints. The process parameters, namely friction pressure, upsetting pressure, and rotational speed are individually varied from low level to high level (within the range of the machine setup) and their effects on the joint properties are analyzed. The partial-deformation zone had higher hardness than the weld and base metal. The toughness of the joints was evaluated at room temperature and at subzero temperature conditions. The impact toughness of the friction-welded joints was found to be superior to fusion-joined duplex stainless steel in room and cryogenic conditions.
Workability studies on Al+2.5%TiO2+Gr powder metallurgy composites during cold upsetting
(Universidade Federal de Sao Carlos, 2014-11-17) Ravichandran, Manickam; Sait, Abdullah Naveen; Anandakrishnan, Veeramani
Al+2.5%TiO2+Gr composites were synthesized through powder metallurgy technique and their workability behavior has been studied under tri-axial stress state condition. The powders were compacted using suitable punch and die in 400 kN hydraulic press and sintered at a temperature of about 590 °C for a period of 3 hours in an electric muffle furnace. The sintered preforms were characterized by XRD and SEM analysis. Then the preforms were subjected to incremental compressive loading of 10 kN until the cracks found at the free surface. The true axial stress (σz), true hoop stress (σe), true hydrostatic stress (σm) true effective stress (σeff), formability stress index (β) and stress ratio parameters [(σz/σeff), (σm/σeff), (σe/σeff)] were calculated for all the preforms and these are correlated with the true axial strain (ez). It is inferred that, the addition of TiO2 and Gr to the Al matrix material increases the stress ratio parameters and formability stress index (β). A hardness test was also conducted for sintered and cold forged preforms and results are reported.
Artificial neural network modeling studies to predict the friction welding process parameters of Incoloy 800H joints
(Elsevier B.V., 2015-02-26) Anand, K; Barik, Birendra Kumar; Tamilmannan, K; Sathiya, P
The present study focuses on friction welding process parameter optimization using a hybrid technique of ANN and different optimization algorithms. This optimization techniques are not only for the effective process modelling, but also to illustrate the correlation between the input and output responses of the friction welding of Incoloy 800H. In addition the focus is also to obtain optimal strength and hardness of joints with minimum burn off length. ANN based approaches could model this welding process of INCOLOY 800H in both forward and reverse directions efficiently, which are required for the automation of the same. Five different training algorithms were used to train ANN for both forward and reverse mapping and ANN tuned force approach was used for optimization. The paper makes a robust comparison of the performances of the five algorithms employing standard statistical indices. The results showed that GANN with 4-9-3 for forward and 4-7-3 for reverse mapping arrangement could outperform the other four approaches in most of the cases but not in all. Experiments on tensile strength (TS), microhardness (H) and burn off length (BOL) of the joints were performed with optimised parameter. It is concluded that this ANN model with genetic algorithm may provide good ability to predict the friction welding process parameters to weld Incoloy 800H. © 2015 Karabuk University
Finite element modelling and characterization of friction welding on UNS S31803 duplex stainless steel joints
(Elsevier B.V., 2015-05-06) Asif. M, Mohammed; Shrikrishana, Kulkarni Anup; Sathiya, P.
Solid state joining techniques are increasingly employed in joining duplex stainless steel materials due to their high integrity. Continuous drive friction welding is a solid state welding technique which is used to join similar and dissimilar materials. This joining technique is characterized by short cycle time, low heat input and narrow heat affected zones. The simulation becomes an important tool in friction welding because of short welding cycle. In the present work, a three dimensional non-linear finite element model was developed. The thermal history and axial shortening profiles were predicted using ANSYS, a software tool. This numerical model was validated using experimental results. The results show that the frictional heating stage of the process has more influence on temperature and upsetting stage has more impact on axial shortening. The knowledge of these parameters would lead to optimization of input parameters and improvement of design and machine tools.
Effect of temperature and strain rate on compressive response of extruded magnesium nano-composite
(National Engg. Reaserch Center for Magnesium Alloys, 2015-10-01) Selvam, B; Marimuthu, P; Narayanasamy, R; Senthilkumar, V; Tun, K.S.; Gupta, M
The hot deformation behaviour of extruded magnesium-zinc oxide nano composite has been studied using hot compression test. The test was conducted in the temperature range of 250-400 °C and in the strain rate range of 0.01 to 1.5 s-1.The processing map was obtained using the power dissipation efficiency with the functions of temperature and strain rate. The workability and instability domains were observed in the processing map for a nano composite. The optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images were used to confirm the formation of dynamic recrystallization (DRX), dynamic recovery (DRY) and instability regions. The workability region of the composite was identified at a working temperature of 400 °C and the strain rate of 0.01 s-1 from the processing map. The instability regions were observed at higher strain rates (>0.1 s-1) and temperatures (250-400 °C).
Transient out-of-plane distortion of multi-pass fillet welded tube to pipe T-joints
(China Ordnance Society, 2016-07-19) Vetriselvan, R.; Devakumaran, K.; Sathiya, P; Ravichandran, G.
The out-of-plane distortion induced in a multi-pass circumferential fillet welding of tube to pipe under different weld sequences and directions was studied using Finite Element Method (FEM) based Sysweld software and verified experimentally. The FEM analyses consisted of thermal and mechanical analyses. Thermal analysis was validated with experimental transient temperature measurements. In the mechanical analysis, three different weld sequences and directions were considered to understand the mechanism of out-of-plane distortion in the tube to pipe T-joints. It was learnt that the welding direction plays a major role in minimizing the out-of-plane distortion. Further, during circumferential fillet welding of the tube to pipe component, the out-of-plane distortion generated in the x direction was primarily influenced by heat input due to the start and stop points, whereas the distortion in the z direction was influenced by time lag and welding direction. The FEM predicted distortion was compared with experimental measurements and the mechanism of out-of-plane distortion was confirmed.
Experimental and numerical analyses of magnesium alloy hot workability
(National Engg. Reaserch Center for Magnesium Alloys, 2016-10-25) Abbassi, F; Srinivasan, M; Loganathan, C; Gupta, M
Due to their hexagonal crystal structure, magnesium alloys have relatively low workability at room temperature. In this study, the hot workability behavior of cast-extruded AZ31B magnesium alloy is studied through hot compression testing, numerical modeling and microstructural analyses. Hot deformation tests are performed at temperatures of 250 °C to 400 °C under strain rates of 0.01 to 1.0 s−1. Transmission electron microscopy is used to reveal the presence of dynamic recrystallization (DRX), dynamic recovery (DRY), cracks and shear bands. To predict plastic instabilities during hot compression tests of AZ31B magnesium alloy, the authors use Johnson–Cook damage model in a 3D finite element simulation. The optimal hot workability of magnesium alloy is found at a temperature (T) of 400 °C and strain rate (ε˙) of 0.01 s−1. Stability is found at a lower strain rate, and instability is found at a higher strain rate.
Modelling of Cr3C2-25% NiCr laser alloyed cast iron in high temperature sliding wear condition using response surface methodology
(Polish Academy of Sciences, 2018) Jeyaprakash, N; Duraiselvam, M; Raju, R
The wear behaviour of Cr3C2-25% NiCr laser alloyed nodular cast iron sample were analyzed using a pin-on-disc tribometer. The influence of sliding velocity, temperature and load on laser alloyed sample was focused and the microscopic images were used for metallurgical examination of the worn-out sites. Box-Behnken method was utilised to generate the mathematical model for the condition parameters. The Response Surface Methodology (RSM) based models are varied to analyse the process parameters interaction effects. Analysis of variance was used to analyse the developed model and the results showed that the laser alloyed sample leads to a minimum wear rate (0.6079×10-3 to 1.8570×10-3 mm3/m) and coefficient of friction (CoF) (0.43 to 0.53). From the test results, it was observed that the experimental results correlated well with the predicted results of the developed mathematical model.
Machine learning for high risk pregnancies pre-term birth prediction: A retrospective
(Science Publishing Corporation Inc, 2018-04-20) Ramla, M; Sangeetha, S; Nickolas, S
Any birth before 28 weeks of gestation is termed as Pre-Term. This has substantial impact in the emotional reactions of mothers. The post-traumatic stress notably in the mother could be of chronic psychological risk. Moreover, it is to be addressed in the global scenario for sustainable development. Predicting stillbirths is still a distant reality. A plethora of works have been carried out and this paper present the summaries and analysis of current research. The primary focus of the paper is to throw light on the challenging issue of Preterm Birth Prediction. Myriad of machine learning techniques are used by various researchers each with its own estimation accuracy and type of ML model.
Investigation on dry sliding wear behavior of Mg/BN nanocomposites
(National Engg. Reaserch Center for Magnesium Alloys, 2018-05-30) Kaviti, R. Vara Prasad.; Jeyasimman, D; Parande, Gururaj; Gupta, Manoj; Narayanasamy, R
The present research objective is to investigate the effect of boron nitride nanoparticles reinforcement on dry sliding wear behavior of pure Magnesium and magnesium nanocomposites. The fabricated nanocomposites contains varied percentages of boron nitride such as 0% (pure Mg), 0.5%, 1.5% and 2.5% were synthesized by using powder metallurgy technique and followed by a hot working process called hot extrusion. The pin on disk equipment was used for conducting the wear tests for traditional loads of 5 N, 7 N and 10 N at different sliding speeds of 0.6, 0.9 and 1.2 m/s against the steel disk at room temperature. For all traditional loads and sliding speeds, the changes in wear rate and friction co-efficient (µ) with respect to sliding distances were observed and analyzed. The wear characteristics are observed with the help of scanning electron microscopy under given test conditions. To investigate dominant wear mechanisms for various test conditions, the morphologies of all worn composites surfaces were analyzed. Final results show that, for all nanocomposites the wear level raises with respect to the sliding speeds and loads. Magnesium reinforced with 0.5% boron nitride shows lower wear rates and low friction coefficient values compare with magnesium reinforced with 1.5% boron nitride and 2.5% boron nitride nanocomposites
Gain enhancement of cross shaped patch antenna for IEEE 802.11ax Wi-Fi applications
(Electromagnetics Academy, 2018-12-07) Rajalakshmi, Pitchai; Gunavathi,. N
In this paper, a dual band high gain miniaturized cross shaped patch antenna is proposed for IEEE 802.11ax applications. The radiating patch size is 0.330λ0x0.417λ0 on a low cost Flame Retardant 4 substrate. A cross shaped radiating element is designed to cover the upper band of IEEE 802.11ax, and a four ring circular Complementary Split Ring Resonator (CSRR) is etched on the cross shaped radiating element to cover the lower band of IEEE802.11ax. Thus the dual bands of 802.11ax are achieved. In order to enhance the gain, 2x2 array hexagonal metamaterial unit cell is positioned behind the substrate. To extract the constitutive parameters of the circular CSRR, NRW (Nicolson-Ross-Wier) retrieval method is used. The measured maximum gain is approximately 6 dBi, 10 dBi for 2.4 GHz, 5 GHz, respectively. Parametric study on the geometrical dimensions is investigated using HFSS 15.0.
Microstructure and tribological evolution during laser alloying WC-12%Co and Cr3C2−25%NiCr powders on nodular iron surface
(Elsevier B.V., 2019-01-30) Jeyaprakash,N; Yang, Che-Hua; Duraiselvam, Muthukannan; Prabu, G
The laser surface alloying has emerged as an important tool to form wear resistant layer. In this work, the characteristics of laser alloyed WC-12%Co and Cr3C2-25%NiCr powders over nodular cast iron and their effects on microstructure, microhardness and wear resistance properties has been investigated. Results shows that the laser alloyed layers are crack free with a very fine structure, improved homogeneity and good metallurgical bonding with the substrate. Microhardness of the alloyed layer has been remarkably increased from 220 HV0.3 to 1199 HV0.3 and 905 HV0.3. The results shown that the wear resistance of the laser alloyed layer was improved by 97.77% and 89.77% for WC-12%Co and Cr3C2−25%NiCr, respectively, compared to that of the substrate nodular cast iron. The enhancement in wear resistance was due to the combined results of the solution strengthening effect, grain refining and good bonding between the hard phases and the matrix.
Development and characterization of stainless steel fiber-based copper-free brake liner formulation: A positive solution for steel fiber replacement
(Tsinghua University Press, 2019-05-10) Vijay, R; Singaravelu, D. Lenin.; Jayaganthan, R
This study deals with the development of drum brake liner for a multi-utility vehicle possessing a hydraulic brake system by varying 7 weight % of steel fiber and stainless steel fiber each, in friction composite formulations. The developed friction composites were tested for physical, chemical, corrosion, mechanical, thermal properties, and tribological characteristics, under near-actual conditions using an inertia dynamometer as per industrial standards. Finite element analysis software (ANSYS) analysis was performed to show the thermal stress distribution of the developed friction composites at the maximum temperature rise due to heat generated during brake stops, and an extensive evaluation method was used to rank the composites. The study concludes that the brake factor of the stainless steel fiber-based friction composite produces stable performance in all conditions with a lower liner temperature rise of 340 °C and lower thermal stress at 4.255294 MPa. However, the steel fiber-based composites produced high performance at the beginning but deteriorated after a certain period due to higher levels of corrosion and a high temperature rise of 361 °C resulting in a negative fade (−0.84%) and more thermal stress (5.619102 MPa). The primary plateau, secondary plateau, back transfer of drum wear debris, and the distribution of constituents on the worn surface of the developed composites in a resin matrix were identified and studied using a scanning electron microscope (SEM) equipped with energy-dispersive spectroscopy. © 2019, The Author(s).
Incremental feature selection method for software defect prediction
(Blue Eyes Intelligence Engineering and Sciences Publication, 2019-07) Gayatri, N; Nickolas, S; Subbarao, A
Software defect prediction models are essential for understanding quality attributes relevant for software organization to deliver better software reliability. This paper focuses mainly based on the selection of attributes in the perspective of software quality estimation for incremental database. A new dimensionality reduction method Wilk’s Lambda Average Threshold (WLAT) is presented for selection of optimal features which are used for classifying modules as fault prone or not. This paper uses software metrics and defect data collected from benchmark data sets. The comparative results confirm that the statistical search algorithm (WLAT) outperforms the other relevant feature selection methods for most classifiers. The main advantage of the proposed WLAT method is: The selected features can be reused when there is increase or decrease in database size, without the need of extracting features afresh. In addition, performances of the defect prediction models either remains unchanged or improved even after eliminating 85% of the software metrics.
Investigation of high temperature wear performance on laser processed nodular iron using optimization technique
(Elsevier B.V., 2019-08-16) Jeyaprakash, N; Yang, Che-Hua; Duraiselvam, Muthukannan; Prabu, G; Tseng, Sheng-Po; Raj Kumar, D
Nodular cast iron (NCI) are used in nuclear energy and transportation industries. Also, NCI are used in gear boxes, camshaft, crank shaft, rolling mill rolls and machine tool beds. The reliability of the NCI under heavy loading condition is affected through several tribological aspects. In the present study, NCI surface has been melted by using an Ytterbium-doped fiber laser. The wear resistances of the substrate and melted surface have been analyzed by using a tribometer. Sliding speed, load and working temperatures have been considered as input parameters to tribometer. From the optimization trials, the applied load was identified as the most significant parameter followed by sliding speed and ambience temperature. The responses of the optimized tribological parameters attained by GRA was confirmed through experimental and agreed closely to the predicted value. Further, the surface of the substrate and laser melted samples were analyzed. The melted surfaces were free from surface deformities and exhibited a noticeable improvement in the wear resistance compared to the substrate.
Synthesis of alloying Al 7075 with molybdenum for functional characterization
(Blue Eyes Intelligence Engineering and Sciences Publication, 2019-09-30) Haja Maideen, A; Duraiselvam, Muthukannan; Varatharajulu, M
Alloying was conducted on Al 7075 alloy by reinforcement of the metallic portion of molybdenum (Mo) in po wder blended with dielectric fluid to strengthen wear resistance a nd investigate the lubing features of this woven surface. The present work features alloying of Al 7075 with Mo as a vital material. Mechanical attributes along with powder frustration and layered coating size and shape were investigated by scanning electron microscope (SEM), energy dispersive X-ray analysis (EDXA), optical microscope (OM), surface texture with roughness tester and wear vision using pin on disc device. The effect of Peak current (A), Pulse on time (Pon) and Pulse off time (Poff) on the wear execution of an alloyed discharge, Al 7075 auxiliary materials have also been considered using Response Surface Methodology (RSM). Analysis of Variance (ANOVA) was interpreted to add to the effectiveness of material variables on the performance characteristics. Confirmation tests were performed to compare the predicted values with the experimental values and it was found that the results matched well with the experimental results.
Hot deformation response of AL 6061-MWCNTs alloy composites
(Blue Eyes Intelligence Engineering and Sciences Publication, 2019-10-10) Jeyasimman, D; Senthilkumar V; Narayanasamy, R
In this investigation, the effect of multi walled carbon nanotubes (MWCNTs) on compressive response with Al 6061 alloy nanocomposites prepared by mechanical alloying has been investigated. Hot deformation tests required to develop processing map were conducted at three temperatures such as 250, 350 and 450°C and in the three strain rates of 0.01, 0.1 and 1.0 s-1. The development of geometric dynamic recrystallization (DRX), dynamic recovery (DRV), instability regions and shear bands were confirmed by characterization study of prepared nanocomposites after hot Compression tests. The average activation energies for hot compression response was calculated as 153.00 KJ/mole for 2 wt.% MWCNTs reinforced Al 6061 alloy (AA 6061) nanocomposites. The most favorable key processing parameters for hot deformation was identified as temperature between 370-450°C and the range of strain rate was 0.1-0.01s-1. The region which are prone to shear localization, cracks and other instability were identified using the processing map and the same was verified with microstructural images obtained using optical and SEM images. © BEIESP.

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