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1

An Influence of Parameters of Micro-electrical Discharge Machining on Wear of Tool Electrode

Puthumana G.

Archive of Mechanical Engineering

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2017

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Vol. LXIV, nr 2

149--163

EN

To achieve better precision of features generated using the micro-electrical discharge machining (micro-EDM), there is a necessity to minimize the wear of the tool electrode, because a change in the dimensions of the electrode is reflected directly or indirectly on the feature. This paper presents a novel modeling and analysis approach of the tool wear in micro-EDM using a systematic statistical method exemplifying the influences of capacitance, feed rate and voltage on the tool wear ratio. The association between tool wear ratio and the input factors is comprehended by using main effect plots, interaction effects and regression analysis. A maximum variation of four-fold in the tool wear ratio have been observed which indicated that the tool wear ratio varies significantly over the trials. As the capacitance increases from 1 to 10 nF, the increase in tool wear ratio is by 33%. An increase in voltage as well as capacitance would lead to an increase in the number of charged particles, the number of collisions among them, which further enhances the transfer of the proportion of heat energy to the tool surface. Furthermore, to model the tool wear phenomenon, a regression relationship between tool wear ratio and the process inputs has been developed.

2

Modelling, analysis and optimisation of weld bead parameters of nickel based overlay deposited by plasma transferred arc surfacing

Siva K., Murugan N., Raghupathy V.P.

Archives of Computational Materials Science and Surface Engineering

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2009

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Vol. 1, nr 3

174-182

EN

Purpose: Plasma Transferred Arc surfacing is increasingly used in applications where enhancement of wear, corrosion and heat resistance of materials surface is required. The shape of weld bead geometry affected by the PTA Welding process parameters is an indication of the quality of the weld. In the paper the modelling, analysis and optimization of weld bead parameters of nickel based overlay deposited by plasma transferred arc surfacing are made. Design/methodology/approach: The experiments were conducted based on a five factor, five level central composite rotatable design and a mathematical model was developed using multiple regression technique. The direct and interaction effects of input process parameters of PTA Hardfacing on weld bead geometry are discussed. Finally, Microsoft Excel Solver has been used to optimize the process parameter with a view to economize the powder and achieve the desirable bead dimensions. Findings: Penetration, dilution and total area are increased when the welding current is increased but reinforcement marginally increases and then decreases. Penetration, weld width, dilution and total area decrease when travel speed is increased. Reinforcement increases slightly and then decreases. Practical implications: The developed mathematical models can be used to predict the dimensions of the weld bead and dilution. Originality/value: This paper highlights the development of a mathematical model correlating various process parameters to weld bead geometry in PTA hardfacing of Colmonoy 5, a Nickel based alloy over Stainless steel 316 L plates.

3

Interaction model for predicting bead geometry for Lab Joint in GMA welding process

Thao D.T., Kim I.S.

Archives of Computational Materials Science and Surface Engineering

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2009

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Vol. 1, nr 4

237-244

EN

Purpose: The prediction of the optimal bead geometry is an important aspect in robotic welding process. Therefore, the mathematical models that predict and control the bead geometry require to be developed. This paper focuses on investigation of the development of the simple and accuracy interaction model for prediction of bead geometry for lab joint in robotic Gas Metal Arc (GMA) welding process. Design/methodology/approach: The sequent experiment based on full factorial design has been conducted with two levels of five process parameters to obtain bead geometry using a GMA welding process. The analysis of variance (ANOVA) has efficiently been used for identifying the significance of main and interaction effects of process parameters. General linear model and regression analysis has been employed as a guide to achieve the linear, curvilinear and interaction models. The fitting and the prediction of bead geometry given by these models were also carried out. Graphic results display the effects of process parameter and interaction effects on bead geometry. Findings: The fitting and the prediction capabilities of interaction models are reliable than the linear and curlinear models and it was found that welding voltage, arc current, welding speed and 2-way interaction CTWD welding angle have the large significant effects on bead geometry. Research limitations/implications: The these models developed are extended to shielding gas composition, weld joint position, polarity and many other parameters which are not included in this research in order to establish a closed loop feedback control system to minimize possible errors from uncontrolled variations. Practical implications: The developed models apply real-time control for bead geometry in GMA welding process and perform the Design of Experiments (DOE) analysis steps in order to solve optimisation problems in GMA welding process. Originality/value: The interaction factors, welding voltage arc current, CTWD welding angle, also imposes a significant effect on bead geometry. With the experimental data of this study, the interaction models have a more reliable fitting and better predicting than that of linear and curvilinear models.

4

Evolutionary bands for the expected response in nonlinear regression

Prętki P., Obuchowicz A.

Prace Naukowe Politechniki Warszawskiej. Elektronika

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2006

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z. 156

359-364

EN

In this paper evolutionary algorithms are applied to computation of confidence intervals for the expected response of nonlinear models. A simple phenotypic evolutionary algorithm was adapted to deal with nonlinear constraints and utilized to find the maximum and minimum value of a nonlinear model responses inside a confidence region. Moreover, the adequacy of the proposed approach is tested in a series of numerical simulations, and compared with the commonly applied linearization technique.