Funda Kahraman

Process Capability Analysis in Machining for Quality Improvement in Turning Operations

Abstract Process capability indices are effective tools for both, process capability analysis and quality assurance. In quality assurance programs, process capability indices reflect the performance of key quality characteristics for a control process. Quality assurance in mass production is enabled by using statistical process control techniques. In this study, various statistical process control techniques were carried out using the measured values taken from the workpieces that represent the whole process in the medium sized company. The chances for using statistical techniques for quality estimation processes have been discussed. For this purpose, normal probability plots and histograms were prepared and the process capability indices were calculated. As a result of this study, it turned out that the process capability for the whole process was inadequate and the mass production was unstable. Some actions must be taken by engineers to improve the quality level by shifting the process mean to target value and reducing the process variation.

Optimization of cutting parameters for surface roughness in turning of studs manufactured from AISI 5140 steel using the Taguchi method

Abstract This study focuses on optimizing cutting parameters based on the Taguchi method to minimize surface roughness in turning of studs manufactured from AISI 5140 steel. The Taguchi method, which is a powerful tool for designing optimized quality, is used to find the optimum surface roughness in turning operations. Rotational speed, feed rate and depth of cut were considered as control factors for the surface roughness, and L9 orthogonal array was determined for experiment trials. An orthogonal array, a signal-to-noise ratio, and an analysis of variance were employed to investigate the surface roughness characteristics of AISI 5140 steel. Minimum surface roughness was obtained at 2000 rpm rotational speed, 0.2 mm × rev−1 feed rate and 0.5 mm depth of cut. Optimal surface roughness was calculated as 1.70 μm by using optimal level of design parameters. Confirmation test showed that Taguchi method can be used precisely for optimizing the cutting parameters in turning of AISI 5140 steel. Through this study, it is possible to not only obtained the optimum surface roughness for turning operations, but also the main cutting parameters affecting the performance of turning operations. The developed model can be used in the metal machining industries in order to determine the optimum cutting parameters for minimum surface roughness.

Application of the response surface methodology in the ball burnishing process for the prediction and analysis of surface hardness of the aluminum alloy AA 7075

Abstract In this study, AA 7075 aluminum alloy has been burnished using different burnishing parameters such as burnishing force, number of passes, feed rate and burnishing speed with a ball burnishing apparatus. Burnishing parameters, which affect the surface hardness, were examined using response surface methodology with rotatable central composite design and analysis of variance. Using the experimental results, a regression model has been developed to predict surface hardness. The statistical analysis showed that, burnishing force and number of passes have the most significant effect on surface hardness. These results, which were obtained from the regression model, are highly consistent with the experiments. The absolute average error between the experimental and predicted values for surface hardness was calculated as 2.79 %. The results of our study show that response surface methodology is a suitable technique that can be efficiently used to predict surface hardness in ball burnishing process.

Advanced hybrid welding and manufacturing technologies

Abstract In this study, a detailed analysis of hybrid weld manufacturing technologies that can significantly contribute to the joining of materials has been carried out. Past, present and future projection, advantages, dis advantages, technological barriers and drawbacks of the processes are given. Detailed explanations of the recent developments of hybrid weld manufacturing technologies and main components are given. Potential industrial applications are assessed and evaluated using economic and technological results. The developments in hybrid welding manufacturing technologies generally improved metallurgical and mechanical properties of weld joints. Hybrid processes usually combine the benefits of each individual process. Due to low heat input, hybrid welds create fine grain structures, minimize base material dilution and achieve high toughness and mechanical properties. These processes are especially appropriate for high performance alloys and dissimilar metal joining. The results of this study conclude that reasonable costs and improved properties of the processed materials will lead to massive use of hybrid welding manufacturing technologies.

Grey-based fuzzy algorithm for the optimization of the ball burnishing process

Abstract In the present study, Grey based fuzzy algorithm was used for the optimization of complex multiple performance characteristics of the ball burnishing process. Experiments have been planned according to Taguchis L16 orthogonal design matrix. Burnishing force, number of passes, feed rate and burnishing speed were selected as input parameters, whereas surface roughness and microhardness were selected as output responses. Using Grey relation analysis (GRA), Grey relational coefficient (GRC) and Grey relation grade (GRG) were obtained. Then, Grey-based fuzzy algorithm was applied to obtain Grey fuzzy reasoning grade (GFRG). Analysis of variance (ANOVA) was carried out to find the significance and contribution of parameters on multiple performance characteristics. Finally, a confirmation test was applied at the optimum level of GFRG to validate the results. The results also show the feasibility of the Grey-based fuzzy algorithm for continuous improvement in product quality in complex manufacturing processes.

Regression Based Neural Network Modeling for Forecasting of the Metal Volume Removal Rate in Turning Operations

Abstract The present paper focuses on two techniques, namely regression and neural network, for predicting tool wear. Predicted values of tool wear by both techniques were compared with experimental values. Also, the effects of the main machining variables on tool wear have been determined. The metal volume removed (MVR) was taken as response (output) variable and cutting speed, feed rate, depth of cut and hardness were taken as input parameters, respectively. The relationship between tool wear and machining parameters was found out by direct measurement of the tool wear by MVR. The results showed the ability of regression and neural network models to predict the tool wear, accurately.

Modeling and optimization for fly ash reinforced bronze-based composite materials using multi objective Taguchi technique and regression analysis

Purpose This paper aims to investigate the effect of fly ash reinforcement ratio (Rr) and sintering temperature (T) on the transverse rupture strength (TRS), hardness and density of fly ash reinforced bronze-based composite materials by using multi-objective Taguchi technique, analysis of variance (ANOVA) and regression analysis. Design/methodology/approach The bronze-based composite materials containing 5, 10 and 15 Wt.% fly ashes were prepared by using spark plasma sintering carried out under a pressure of 35 MPa, at 750, 800 and 850 °C for 3 min. Sintering temperature and fly ash reinforcement ratio were considered as input parameters; the TRS, hardness and density were considered as output parameters. Experiments were designed according to Taguchi L9 orthogonal array. Multi signal-to-noise ratio (MSNR) was computed to define the optimal process parameters. ANOVA was conducted to detect the importance of the input parameters for the process performance. Moreover, the linear model was developed for predicting the performance parameters by using regression analysis. Findings Fly ash can be a good alternative as reinforcement to reduce the cost for composite materials. Optimal process parameters had obtained 850°C sintering temperature and 5 per cent reinforcement ratio by using multi-objective Taguchi technique. The per cent contributions of the control factors on the performance parameters had obtained sintering temperature (95.78 per cent) and fly ash reinforcement ratio (3.00 per cent) with ANOVA. The obtained results indicate that the sintering temperature was found to be the dominant factor among controllable factors. However, the reinforcement ratio showed an insignificant effect. Originality/value It has been indicated that multi-objective Taguchi technique and regression analysis are effective and powerful tools in modeling and simultaneous optimization of quality characteristics for composite materials.

Abrasive wear and frictional behavior of polyoxymethylen

Abstract In the present study, abrasive wear and frictional behaviors of polyoxymethylene were investigated experimentally. To realize this, a test apparatus was designed and fabricated. Wear tests were carried out under dry conditions at room temperature. A central composite design was used to describe response and to estimate the parameters in the model. An empirical model had been developed to predict wear loss as a function of applied load and sliding distance. Friction coefficient decreases with increase in applied load. On the other hand, it is also found that friction coefficient increases with the increase in sliding velocity.

Cold formability of AISI 1020 steel sheets

Abstract A forming limit diagram (FLD) illustrates the behavior of sheet metal under different levels of strain. The line describing the behavior of the metal is called forming limit curve (FLC). Forming limit diagram provides information on the maximum stress the metal can undergo before fracturing or necking. The diagrams are constructed by using forming limit test of sheet metal and measuring the deformation. In this study, formability of AISI 1020 sheet metal with different thickness were investigated using experimental data obtained from forming limit test. Forming limit diagram, strain hardening exponent (n) and height of cup values have been obtained for evaluating formability of the studied material. After each test, deformation of the grid was measured by using Mylar band and the true major and true minor strains were computed. Same formability results have been found from the FLD, strain hardening exponent and height of the cup for studied materials.