T.Louie Frango et al., International Journal of Advanced Engineering Technology, E-ISSN 0976-3945 Research Paper ARTIFICIAL NEURAL NETWORK (ANN) MODELING FOR PREDICTING HARDNESS OF NI-CBN COMPOSITE COATINGS T.LouieFrango1, K.Ramanathan2, G.N.K.RameshBapu3, P.Marimuthu4 Address for Correspondence 1 Assistant Professor, Department of Mechanical Engineering, Mahath Amma Institute of Engineering and Technology, Pudukkottai-622101. 2 Assistant Professor, Department of Mechanical Engineering, A. C. College of Engineering &Technology, Karaikudi-4. 3 Senior Principal Scientist, Central Electrochemical Research Institute, Karaikudi, 630 006. 4 Principal & Professor, Department of Mechanical Engineering, Syed Ammal Engineering College, Ramanathapuram623502, ABSTRACT Nickel-CBN composite coatings are produced by electro deposition using conventional techniques at various cathode current densities, pH and temperature. Electro deposition was carried out from a conventional Watts bath. Natural CBN powder of 68 m size was used in this study. The volume fraction of CBN deposition in composite coated specimens was measured gravimetrically. An Artificial Neural Network (ANN) model was developed using 27 practical data obtained by designing an experiment with three level of experiment namely Low, Medium and High to predict the harness of CBN deposition in NiCBN metal matrix. Within the range of input variables for the present case (pH) = 3 to 5; current density (i) = 3 to 5 A/dm2; temperature (T)= 40 to 600C, the prediction capability of Artificial Neural Network(ANN) is very close to the experimental measurement of hardness of Ni-CBN composite coatings. KEYWORDS: Hardness value (HV), ANN model, Ni-CBN composite coatings, MATLAB 1. INTRODUCTION Particle-reinforced metal matrix composites generally exhibit wide engineering applications due to their enhanced hardness, wear and corrosion resistance compared to pure metal or alloy [1]. Composite electroplating has been identified to be a technologically feasible and economically superior technique for the preparation of such kind of composites. Cubic boron nitride (CBN), a man-made material, is known to be the second hardest material to diamond. Because of their outstanding properties, diamond and CBN compacts have been used in the tool industry for machining applications. Because of its excellent mechanical and electrical properties, CBN is of great interest for a number of applications (e.g. grinding powders, wear parts, electronic parts, etc.). Searching the literature, the impression arises that the applications of CBN are kept a bit secret. Most of the relevant references are patents (up to 90% depending on the topic) giving less exact data about the process. Papers published in journals giving detailed information are rare. The volume percent incorporation of CBN powder in the Ni-CBN composite coating measured gravimetrically was earlier demonstrated [2]. The amount of CBN deposited in the composite metal matrix is mainly affected by the process parameters such as current density, pH value, temperature of the bath solution and concentration of CBN dispersed in the electrolyte. Volume fraction of CBN influences the hardness of Ni-CBN composite coatings, hence it is essential to develop a prediction model for estimating the hardness of Nickel-CBN composite using the above parameters. 2. ARTIFICIAL NEURAL NETWORK (ANN) ANN is a neural system of imitative biology, and the principle of human brain operation. Using a large amount of data out of which they build knowledge bases, ANN establishes analytical model to solve the problem in the estimation, prediction, decision making and diagnosis. Neural network consist of simple processors, which are called neurons, linked by weighted connections. Each neuron has inputs and generates an output that can be seen as the reflection of local information that is stored in connections. The output signal of a neuron is fed to other neurons as input signals via interconnections. Since the capability of a single neuron is limited, complex functions can be realized by connecting many neurons. It is widely reported that structure of neural network, representation of data, normalization of inputs, outputs and appropriate selection of activation functions have strong influence on the effectiveness and performance of the trained neural network [3]. A Neural network consists of at least three layers i.e., input layer, hidden layer, and output layer, where inputs are applied at the input layer and outputs are obtained at the output layer and learning is achieved when the associations between a specified set of input output pairs as established in Figure.1. Here Feed forward back propagation (FFBP) algorithm is used for the prediction of hardness of Ni-CBN in the deposit for the given condition. Figure.3 shows the architecture of a standard supervised training FFBP ANN and Figure 2 shows the perception. Figure 1. ANN Model with two hidden layers Figure 2. A typical processing element (Perception). Int J Adv Engg Tech/Vol. VII/Issue II/April-June,2016/1234-1237 T.Louie Frango et al., International Journal of Advanced Engineering Technology, E-ISSN 0976-3945 Figure 3. Standard supervised training feed forward neural network ANN approach is applied in many fields. Egon Eckert et al [7] applied this tool in the field of chemical engineering for modeling of pyrolysis, utilizing the characterization of atmospheric gas oil based on incomplete data. N. Daneshvar et al [8] used ANN for modeling of decolorization of textile dye solution. Modeling capability of the artificial neural network (ANN) to predict the effect of the hot deformation parameters on the strength of Al-base metal matrix composites was carried by Issam S. Jalham [9] in metal forming area. Joseph H.W. Lee et al [10] carried out neural network modeling to predict the algal blooms dynamics of coastal water. For predicting the yield strength, tensile strength and elongation of cast alloys, Mehmet Sirac Ozerdem et al [11] developed ANN modeling and validated the model. ANN model to predict the oxides of nitrogen (NOx) emissions from diesel engine under various operating variables was performed by obodeh et al [12]. Reza soleymany et al [13] optimized the coating variables of physical vapour deposition and chemical vapour deposition process for achieving the maximum hardness of titanium film. Subramanian et al [13] has developed regression model and ANN model for estimating the deposition rate of copper-tin during electroplating. From the literatures it is evident that ANN is a viable and more useful modeling tool and it is used almost in all fields such as engineering, biology etc. This paper deals about using such a powerful tool for predicting the hardness of Nickel-CBN composite developed by electroplating technique. Most important coating variables such as current density, pH and bath temperature were considered as inputs for the ANN model. 3. EXPERIMENTAL PROCEDURE 3.1 The electrolyte: The conventional Watts bath of the following composition was used: Nickel sulphate- 225 g/l; Nickel chloride- 30 g/l; Boric acid- 40 g/l. The electrolyte was purified in the conventional manner for removal of organic and inorganic impurities [4]. The pH value of the electrolyte was adjusted electrometrically using dilute H2SO4 or NH3. 0.01-g/l sodium lauryl sulphate was added to the electrolyte as anti-pitting agent before plating. The temperature of the electrolyte was maintained using a thermostat. 3.2. Plating procedure: Deposition was carried out on a 500 ml capacity using conventional technique. Nickel anodes and mild steel cathodes were used. The cathodes of 7.5×2.5 cm area were mechanically polished, degreased, bent to 90°, suitably masked to expose an effective plating area of 12.5 cm2, electro cleaned, first cathodically and then anodically, washed, rinsed and then introduced into the plating electrolyte with the area to be plated in the vertical plane closer to the bottom of the cell facing the anode. A bagged nickel anode bent similarly was placed above the area to be coated. CBN powder (6 to 8 μm) was added to the electrolyte in the form of slurry. The solution was stirred using a magnetic stirrer. Stirring was given initially for 30s to bring all the CBN powder into the suspension and then stopped. The deposition was continued for 40 minutes to allow the particles to settle on the substrate while the deposition proceeded. The same process was repeated to obtain deposit thickness of 25-40 μm. 3.3. Ni-CBN deposition: Natural grade polycrystalline CBN powder of 6–8 μm sizes was used. Prior to the co-deposition, the CBN particles were ultrasonically dispersed in the bath for 10 min. Experiments were conducted at a fixed CBN concentration of 10 g/l, varying the plating parameters like temperature, pH, and current density. Ranges of coating parameters in the coating process are as follows: Current density, I = 3 – 5 A/dm2 ; pH value = 3 – 5; Temperature = 40 to 60 0C .For the prediction of hardness of CBN under a variation of coating conditions, a training database with regard to different coating parameters needs to be established. For the above combination of parameters, twenty seven numbers of Ni-CBN composite coatings were obtained and their hardness was measured gravimetrically. 4. TRAINING THE ARTIFICIAL NEURAL NETWORK The neural network has to be first trained and then tested to use for application. The training was done with MATLAB software using a computer. MATLAB is a software package used for high performance numerical computations and visualization. It provides an interactive environment with hundreds of built in functions for technical computations, graphic and animations. MATLAB stands for matrix lab. Built in functions provides excellent tools for linear algebra computation data analysis, signal processing, optimization and others scientific computations. In this work ANN module is utilized for predicting the hardness of CBN deposition in Ni-CBN composite matrix. The features current density, pH and temperature are the inputs and the hardness of CBN is the output for training the neural networks. Weights between input layer & hidden layer and weights between hidden layer & the output layer are generated randomly for the selected topology of the network. The number of patterns used for the training of Artificial Neural Network using Feed forward back propagation algorithm is 27. Training of the ANN was performed without any allowable error. The patterns are selected for training and testing the ANN. These selected patterns were normalized so that they lie between 0 and 1. Twenty Seven patterns were selected for training the ANN. The inputs and outputs are normalized by, X i Where Xi is the value of a feature and Xmax X i X max is the maximum value of the feature. A 3-7-8-1 Feed forward back propagation network was trained and the network is shown in figure-4. Int J Adv Engg Tech/Vol. VII/Issue II/April-June,2016/1234-1237 T.Louie Frango et al., International Journal of Advanced Engineering Technology, E-ISSN 0976-3945 Figure 4. 3-7-8-1 Feed forward back propagation network. Figure 5. Performance curve of ANN model for 100 epochs 5. VALIDATING THE ARTIFICIAL NEURAL NETWORK Once the network was trained such that the maximum error for any of the training data was less than allowable error, the weights and the threshold values were automatically saved by the program. As the input values from the validation experiments were given to the ANN program, the program predicts the required output. To validate the results of the Artificial Neural Network analysis eight data as shown in Table – I were used. Once the pH, current density and temperature are fed into the trained networks, the hardness of CBN that can be obtained in the Nickel-CBN composites could be calculated quickly using ANN model 6. RESULTS AND DISCUSSION A comparison of measured hardness value and predicted hardness value using the prediction technique Artificial Neural Network (ANN) is presented in the Table -II. The Average Absolute Error of the trained ANN model is found to be only 0.06141 % and it is shown graphically in Figure.6. The closeness of ANN model in predicting the hardness of CBN deposition with actual value is shown in Figure 7. It is shown clearly that the prediction technique ANN is better in predicting the Volume fraction of CBN deposition in the Nickel-CBN composite coated specimens. TABLE –I. EXPERIMENTAL COATING PARAMETERS AND HARDNESS VALUE. Test No pH 1 2 3 4 5 6 7 8 3.5 3.5 3.5 3.5 4.5 4.5 4.5 4.5 Current density A/dm2 Temperature 0 C Hardness value (VHN) 3.5 3.5 3.5 3.5 4.5 4.5 4.5 4.5 45 55 45 55 45 55 45 55 486.67 500.98 503.71 512.78 468.49 484.98 487.75 498.34 TABLE – II COMPARISON OF MEASURED & PREDICTED HARDNESS OF NI-CBN DEPOSITION Test No Measured VHN 1 2 3 4 5 6 7 8 486.67 500.98 503.71 512.78 468.49 484.98 487.75 498.34 Predicted VHN (ANN model) 486.89 500.56 502.09 513.63 468.05 484.26 486.08 499.77 Figure 6. Percentage error of ANN model in the prediction of VHN Int J Adv Engg Tech/Vol. VII/Issue II/April-June,2016/1234-1237 Percentage Error (ANN model) -0.0452 0.0838 0.321 -0.1658 0.0939 0.1485 0.342 -0.2869 Figure 7. Closeness of ANN model in predicting Volume fraction of CBN deposition. T.Louie Frango et al., International Journal of Advanced Engineering Technology, E-ISSN 0976-3945 7. CONCLUSION A 3-7-8-1 Feed forward back propagation Artificial Neural Network (ANN) model was developed for predicting hardness of CBN in Ni-CBN composite coated metal matrix using 27 test data. The developed neural network was validated with eight data. Values obtained by the above ANN model were compared with the experimental values of the response variables to decide about the nearness of the predictions with the experimental values. 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