Ugur Esme

Mathematical Modeling of Diameter and Circularity Deviation in Wire Electrical Discharge Machining of a Hot Work Tool Steel

Abstract The suitable selection of manufacturing process and conditions are very important in manufacturing processes to obtain good surface quality and dimensional precision. Thus, it is required to know properties relating to material, surface quality and dimensional precision by means of mathematical models which allow some predictions taking into account operation conditions such as feed rate, current and pulse on time, etc. Wire electrical discharge machining (WEDM) represents a modification of electro discharge machining (EDM) and is widely used for a long time for cutting punches and dies, shaped pockets as well as other machine parts on conductive work materials. Present work is focused on the regression modeling predicting diameter and circularity deviation of a hot work tool steel. Mathematical relationships between circularity and diameter deviation as well as WEDM cutting parameters (feed rate, current and pulse on time) have been investigated. Results show that, regression analysis can be successfully applied for this mathematical model.

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.

Fracture Toughness of Friction Stir-Welded Lap Joints of Aluminum Alloys

The aim of this study is to determine the fracture toughness of friction stir-welded (FSW) lap joints of aluminum alloys. FSW lap joints of AA 2014 and AA 6063 aluminum alloy plates were performed on a conventional semiautomatic milling machine. FSW lap joints were produced on alloy plates. Fracture toughness of FSW lap joints were calculated from the results of tensile shearing tests. New empirical equations were developed for fracture toughness and energy release rate based on the relation between the hardness and fracture toughness values. Fracture toughness of FSW lap joints increases exponentially as the hardness reduces. The results of the experiments showed that the amount of Si content in Al alloys affects the fracture toughness of the FSW lap joints.

Improvement of a low-cost water jet machining intensifier using reverse engineering and redesign methodology

Water jet machining (WJM) systems are quickly gaining wide industrial acceptance for cutting metallic and non-metallic materials in complex shapes. However, WJM systems are not used extensively by small-scale and medium-scale industries due to their high cost. There is no commercially available WJM system to meet the requirements of small-scale industries. In order to satisfy their demand, a low-cost first alpha-prototype WJM system has been previously developed using conventional design techniques. The intensifier, which is the key component of a WJM, is mainly responsible for the high cost. Therefore, this study concentrates on the redesign of the intensifier used in the prototype. Technical and economical requirements, as well as the main principle used on the double-acting intensifiers, constitute strong design constraints that do not permit drastic modifications using conventional design techniques. A novel redesign methodology, developed by Otto and Wood, provides systematic approach for the product development that matches customer needs. Therefore this methodology has been modified and used to improve the existing prototype. The methodology consists of a 10-step process with four primary phases. Most of the design enhancements on the components of the prototype WJM system have been achieved through the use of the redesign methodology compared with conventional design methodology.

Surface roughness analysis and optimization for the CNC milling process by the desirability function combined with the response surface methodology

Abstract The present study is aimed for an optimization strategy for the CNC pocket millingprocess based on the desirability function approach (DFA) combined with the response surface methodology (RSM). Firstly, the milling parameters such as cutting speed, feed rate and depth of cut are designed using the rotatable central composite design (CCD). The AISI 1050 medium carbon steel is machined by a flat end 8 mm high speed steel (HSS) tool on a zigzag cutting path under air flow condition. The influence of milling parameters is examined. Secondly, the model for the surface roughness, as a function of milling parameters, is obtained using the RSM. Finally, the power and adequacy of the quadratic mathematical model has been proven by the analysis of variance (ANOVA) method. The results indicate that the feed rate is the dominant factor affecting the surface roughness, which is minimized when the feed rate and depth of cut are set to the experimental range. A high correlation coefficient of R2 = 0.99 has been obtained between the predicted and the experimental surface roughness. This reveals that the prediction system established in this study produces satisfactory results with an improved performance compared to other models in the literature. The enhanced method proposed in this study can be readily applied to different metal cutting processes with greater confidence.

Effects of welding parameters on the quality of resistance spot welded SAE 1010 steel sheet

Resistance spot welding has been commonly used in the automotive industry for joining body sheet components and it is particularly well suited for uncoated low carbon steels. The present paper reports experimental investigations on the spot welding of uncoated 1010 steel sheets. Experiments were carried out using different welding parameters, electrode tip radius and sheet thicknesses. Then, the results are used to discuss the effect of welding conditions on surface appearance, weld size, tensile shear strength, depth of fusion and heat affected zone.

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.

Taguchi-Based Grey Relation Optimization of Machining Parameters and Cutting Path Strategies in CNC Pocket Milling Operations

Abstract This study has focused on the Taguchi-based multi-response optimization of the pocket milling process for an optimal parametric combination to yield minimum surface roughness within a minimum machining time using a combination of Grey relational analysis (GRA) and the Taguchi method on the CNC process of DIN 1.0038 medium carbon steel. Sixteen experimental runs based on an orthogonal array of the Taguchi method were performed to derive multi-objective functions to be optimized within the experimental range. The objective functions have been selected in relation to parameters of the pocket milling process, i. e., surface roughness and machining time. The Taguchi approach was followed by Grey relational analysis to solve the multi-response optimization problem. The significance of these factors on overall quality characteristics of the pocket milling process has also been evaluated quantitatively by a variance analysis method (ANOVA). Optimal results have been verified by validation experiments to calculate the effectiveness of the method. The application of this method showed that proper selection of the milling parameters produces better surface roughness within the minimum machining time.

Application of Genetic Algorithms (GA) for the Optimization of Riveted Joints

Abstract Genetic algorithms have an effective search technique in a predefined research space based on natural selection theory. They use the same combination of selection, recombination, and mutation to evolve a solution to a problem. In this study, it has been demonstrated how to determine the optimal diameter, sheet thickness, and sheet width in riveted joints by means of genetic algorithms (GA). In this study the optimization of objective function for the variables in predetermined limit ranges was applied. Since the algorithms developed by this way are based on a principle to find out the best within a range like genetic process, it is becoming possible to predict the most suitable values for riveted junction dimensions in the defined limit range. The algorithms were restrained considering rivet diameter, thickness and width of the sheet, shear strength, tensile strength, and tear hazard of the sheet.