Vibration modeling and analysis of wire during the WEDM process

During the wire electrical discharge machining (WEDM) process, the vibrations of the wire generated by the gap force is the main cause of imprecision. To achieve more precise results with better accuracy, understanding of the vibration management of the wire is essential. In this article, the wire’s vibration behavior is introduced briefly, followed by an exploration of an equation, derived from Hamilton’s principle, which expresses the vibration of a wire moving axially. This equation is presented under some simplified assumptions. In addition, the relationship between the maximum amplitude of the vibration and the main relative variables is presented. The solution demonstrates that a thicker workpiece results in a larger amplitude of vibration, yet the axial speed of the wire has no impact on the maximum amplitude.     

Optimization of sand-casting process variables—a process window approach

The present competitive market focuses on producing high-quality products with the lowest possible cost. To help accomplish this objective, various quality-enhanced tools have been put forward in recent years and, of these, process window approach (PWA) has emerged as perhaps the most viable and efficient technique for process quality improvement. The PWA is a powerful tool for quickly optimizing and confirming the quality and robustness of a process setup for any parameters. The work in this paper focuses on implementing a proposed PWA in order to optimize the sand-casting operation variables. In this research, the authors have kept their prime focus on minimizing the defects developed in the sand-casting process by PWA. Analysis of various critical process parameters and the interaction among them is carried out with the help of Taguchi method of experimental design. To optimize the results obtained and to make the analysis more precise and cost-effective, response surface methodology (RSM) is also incorporated. The optimized parameters obtained using the Taguchi method and RSM are then tested in an industrial case study. It is validated by proposed process window approach.     

Optimization of roll forming process parameters—a semi-empirical approach

The roll forming process parameters play a major role in the quality of the final roll-formed product. Optimum configuration without any cost increase in the roll forming line could present accurate and flawless products. In this paper, a roll forming process experimental modelling of a symmetrical U-section profile from advanced high strength steel (AHSS) material (type DP600) is presented. The factors selected for this study are the roll forming line velocity, the inter-distance between roll stations, the roll gap, and the diameter of the rolls. An optimization procedure for the roll forming line, via statistical design of the experimental simulation runs, is also presented. The optimum values of process parameters are calculated for minimum elastic longitudinal strains and shear strains, at strip edge, for each roll station. A reduction of 20–35% in elastic longitudinal strains could occur for all roll stations, and 30–50% reduction in shear strains occurs for roll stations with a greater folding angle, as this leads to roll-formed products of a better quality. Finally, the contribution of each factor on the longitudinal and shear strains has been calculated, showing that the inter-distance between the roll stations plays a dominant role in the roll forming process.     

Electrothermal theory approach for numerical approximation of the μ-EDM process

A fundamental study of microelectric discharge machining (μ-EDM) based on the physics of single spark and electrothermal theory has been carried out. The machining phenomena in the μ-EDM process are investigated through simulations using finite element method. By creating the single-discharge crater, the topography is measured using an atomic force microscope and the simulation results compared with the experimental result. A temperature distribution along the radius and depth of the workpiece is thus reported. For verification purpose, single-discharge experiments with RC pulse circuit are performed with tungsten carbide as the electrode and stainless steel as the workpiece. The diameter-to-depth ratios of the crater obtained by the simulation and the experiments are 2.92 and 2.67, respectively. The simulation results are found to be in close agreement with experimental results.     

Effect of hybrid electrochemical smoothing–roller burnishing process parameters on roundness error and micro-hardness

In this paper, a novel finishing process, which integrates the merits of electrochemical smoothing (ECS) and roller burnishing (RB) for minimizing the roundness error and increasing surface micro-hardness of cylindrical parts, is proposed. Through simple equipment attachments, electrochemical smoothing–roller burnishing (ECS–RB) can follow the turning process on the same machine. To explore the optimum combinations of the ECS–RB process parameters in an efficient and quantitative manner, the experiments were designed on the basis of the response surface methodology technique. The effect of ECS–RB parameters, namely, burnishing force, applied voltage, inter-electrode gap, and workpiece rotational speed on the roundness error and surface micro-hardness was studied. From the multi-objective optimization, the optimal combination of parameter settings are burnishing force of 350 N, applied voltage of 8.2 V, inter-electrode gap of 2.75 mm, and rotational speed of 970 rpm for achieving the required lower roundness error and higher surface micro-hardness. Surface micro-hardness considerably increases about 31.5% compared to the initial surface micro-hardness, and about 2.32 μm roundness error can be achieved using the optimum combination of process parameters. Therefore, the combination of ECS and RB is a feasible process by which it potentially reduces roundness error and surface micro-hardness of axis-symmetric parts improving their reliability and wear resistance.     

Optimization of green sand casting process parameters of a foundry by using Taguchi��s method

An optimization technique for process parameters of green sand casting of a cast iron differential housing cover based on the Taguchi parameter design approach is proposed in this paper. The process parameters considered are green strength, moisture content, pouring temperature, and mould hardness vertical and horizontal. An attempt has been made to obtain optimal level of the process parameters in order to yield the optimum quality characteristics of the cast iron differential housing cover castings. An orthogonal array, the signal-to-noise (S/N) ratio, and analysis of variance are used to analyze the effect of selected process parameters and their levels on the casting defects. The results indicate that the selected process parameters significantly affect the casting defects of grey cast iron differential housing cover castings. A confirmation run is used to verify the results, which indicated that this method is more efficient in determining the best casting parameters for differential housing cover.     

An experimental study of process variables in turning operations of Ti–6Al–4V and Cr–Co spherical prostheses

Ti–6Al–4V and Cr–Co alloys are extensively used in manufacturing prostheses due to their biocompatibility, high strength-to-weight ratio and high resistance to corrosion and wear. However, machining operations involving Ti–6Al–4V and Cr–Co alloys face a series of difficulties related to their low machinability which complicate the process of controlling the quality levels required in these parts. The main objective of this paper is to study the influence of cutting parameters, machine tool control accuracy and metrology procedures on surface roughness parameters and form errors in contouring operations of Ti–6Al–4V and Cr–Co workpieces. The machining performance of the two biocompatible materials is compared, focusing the study on part quality at low feed per revolution and the stochastic nature of plastic deformations at this regime. The results showed a better surface roughness control for Ti–6Al–4V, whereas for Cr–Co alloys, the performance presents high variability. In the case of form errors (sphericity), contouring errors and metrology procedures are important factors to be considered for quality assurance. In addition, the study analyses the correlation of the machining performance with different sensor signals acquired from a low cost non-intrusive multi-sensor, showing a high correlation of signals from acoustic emission sensors and accelerometers in the machining of spherical features on Ti–6Al–4V parts. The findings of this research work can be taken into account when designing prostheses components and planning their manufacturing processes.     

Development of a system for monitoring tool condition using acousto-optic emission signal in face turning—an experimental approach

In automated manufacturing systems, one of the most important issues is accurate detection of the tool conditions under given cutting conditions so that worn tools can be identified and replaced in time. In metal cutting as a result of the cutting motion, the surface of workpiece will be influenced by cutting parameters, cutting force, and vibrations, etc. But the effects of vibrations have been paid less attention. In the present paper, an investigation is presented of a tool condition monitoring system, which consists of a fast Fourier transform preprocessor for generating features from an online acousto-optic emission (AOE) signals to develop a database for appropriate decisions. A fast Fourier transform (FFT) can decompose AOE signals into different frequency bands in the time domain. Present work uses a laser Doppler vibrometer for online data acquisition and a high-speed FFT analyser used to process the AOE signals. The generation of the AOE signals directly in the cutting zone makes them very sensitive to changes in the cutting process due to vibrations. AOE techniques is a relatively recent entry into the field of tool condition monitoring. This method has also been widely used in the field of metal cutting to detect process changes like displacement due to vibration and tool wear, etc. In this research work the results obtained from the analysis of acousto-optic emission sensor employs to predict flank wear in turning of AISI 1040 steel of 150 BHN hardness using Carbide insert and HSS tools. The correlation between the tool wear and AOE parameters is analyzed using the experimental study conducted in 16 H.P. all geared lathe. The encouraging results of the work pave the way for the development of a real-time, low-cost, and reliable tool condition monitoring system. A high degree of correlation is established between the results of the AOE signal and experimental results in identification of tool wear state.     

Surface textural analysis using acousto optic emission- and vision-based 3D surface topography��a base for online tool condition monitoring in face turning

In metal cutting as a result of the cutting motion, the surface of workpiece will be influenced by cutting parameters, cutting force, and vibrations, etc. Thus, by monitoring the machined surface topography of the workpiece and extracting the relevant information the cutting process and tool wear state should be able to be monitored and quantified. But the effects of vibrations have been paid less attention. The work in the present paper is divided into two parts. First part consists of a data acquisition and signal processing using acousto optic emission sensor (i.e., laser Doppler vibrometer) for online tool condition monitoring and the second part of the work presents the surface topography analysis of machined surfaces during the progression of the tool wear. Most of the work presented is also a study where surface metrology is being used to measure all aspects of the machining in combination with an online metrology tool. The encouraging results of the work pave the way for the development of a real-time, low cost, and reliable tool?Ccondition?Cmonitoring system. A high degree of correlation is established between the results of the acousto optic emission signal- and vision-based surface textural analysis in identification of tool wear state.     

Process characterization of vibrostrengthening and application to fatigue enhancement of aluminum aerospace components��part I. Experimental study of process parameters

Vibrostrengthening is a fatigue-enhancement process, originally developed by the Russian aviation industry (Rumyantsev et al. 2004). A potential alternative to shot peening, currently a standard industrial surface treatment for fatigue enhancement, vibrostrengthening offers the potential for shorter processing times and uniform treatment of the surface, especially when dealing with fragile parts and complex part geometries. Vibrostrengthening is a modification of a vibratory finishing process in which the parts or workpieces and a medium of hard granular particles are vibrated together in a processing tub causing the particles to mechanically work the surface of the workpiece. In vibrostrengthening, the workpiece is fixed inside a vibratory tub, increasing the relative velocities between the particles in the medium and the workpiece. This gives rise to more aggressive mechanical working of the workpiece surface. The resulting plastic deformation at the surface produces a sub-surface compressive residual stress, which together with a better surface finish, is conjectured to improve the fatigue strength of workpiece. This paper is an experimental study of vibrostrengthening of aluminum components for fatigue life enhancement. The effects of various process parameters on the fatigue strength of a specimen are studied to experimentally characterize the process. These experiments also demonstrate that the vibrostrengthening process produces significant fatigue enhancement on experimental samples produced by machining. Further, these experiments verify that, in fact, fatigue enhancement in the vibrostrengthening process is a result of the combined effect of inducing a compressive residual stress field within the material and improving the material??s surface finish. Fatigue tests indicate that the fatigue enhancement of this process is comparable to, if not better than, shot peening. One important reason for such a favorable comparison, given the lower levels of residual stress that result from this process, is the superior surface finish it produces. A companion paper (Sangid et al. 2010) presents a study involving process visualization to understand and explain the process mechanics; further, a computational model is produced to characterize the fatigue enhancement of the process through the compressive residual stress field and surface topography.     

Optimization of WEDM process of pure titanium with multiple performance characteristics using Taguchi’s DOE approach and utility concept

This paper describes the development of multi response optimization technique using utility method to predict and select the optimal setting of machining parameters in wire electro-discharge machining (WEDM) process. The experimental studies in WEDM process were conducted under varying experimental conditions of process parameters, such as pulse on time(T_on), pulse off time(T_off), peak current (IP), wire feed (WF), wire tension (WT) and servo voltage (SV) using pure titanium as work material. Experiments were planned using Taguchi’s L27 orthogonal array. Multi response optimization was performed for both cutting speed (CS) and surface roughness (SR) using utility concept to find out the optimal process parameter setting. The level of significance of the machining parameters for their effect on the CS and SR was determined by using analysis of variance (ANOVA). Finally, confirmation experiment was performed to validate the effectiveness of the proposed optimal condition.     

Experimental analysis of coating layer behavior of Al–Si-coated boron steel in a hot bending process for IT applications

The utilization of high-strength steel for automotive structural parts has increased since the oil crisis in the 1970s owing to its high strength and potential for weight reduction. Because of the limited formability of high-strength steels, automotive components are increasingly produced through hot press forming. In some instances, high-strength steel sheets are coated with an Al–Si layer in order to prevent scaling of components during hot press forming, and this can increase their reliability with a view to the dimensional accuracy and stress distribution when they are in service. In this contribution, the coating degradation mechanisms of Al–Si-coated boron steel after the hot bending process are reported. The issues related to coating degradation during hot press forming are critically reviewed at different positions on a part that was subject to hot bending. In addition, the hardness and friction coefficient were tested by a nano-indenter at various positions. The relationship between the experimental parameters and coating layer properties is also reported. It is concluded that the bending deformation affected the coating layer behavior the most.     

Multi response optimization of process parameters based on Taguchi��Fuzzy model for coal cutting by water jet technology

The process of material cutting and fracture by high velocity water jets is a complex series of phenomena which may involve compression, tension, shear, erosion, wears, cracking, wave propagation, and cavitations damage. This makes the exact analysis of the jet cutting process to be very complicated. The problem of water jet coal cutting is a multiresponse problem. There are two output variables, depth of cut and cutting width whose optimization will result in the increase in the productivity of coal cutting. In this paper, a Taguchi?CFuzzy decision method has been used to determine the effective process parameters for improving the productivity of coal mines. The Taguchi method of experimental design is a widely accepted technique used for producing high quality products at low cost. The optimization of multiple responses in complex processes is common; therefore, to reduce the degree of uncertainty during the decision making, fuzzy rule-based reasoning was integrated with the Taguchi loss function.     

Optimization of an aluminum profile extrusion process based on Taguchi’s method with S/N analysis

Taguchi’s design of experiment and numerical simulation were applied in the optimization of an aluminum profile extrusion process. By means of HyperXtrude, the extrusion process was simulated and the effects of process parameters on the uniformity of metal flow and on the extrusion force were investigated with the signal to noise ratio and the analysis of variance. Through analysis, the optimum combination of process parameters for uniform flow velocity distribution was obtained, with the billet diameter of 170?mm, ram speed of 2.2?mm/s, die temperature of 465°C, billet preheated temperature of 480°C, and container temperature of 425°C. Compared with the initial process parameters, the velocity relative difference in the cross-section of extrudate was decreased from 2.81% to 1.39%. In the same way, the optimum process parameters for minimum required extrusion force were gained, with the billet diameter of 165?mm, ram speed of 0.4?mm/s, die temperature of 475°C, billet preheated temperature of 495°C, and container temperature of 445°C. A 24.7% decrease of required extrusion force with optimum process parameters was realized. Through the optimization analysis in this study, the extrusion performance has been greatly improved. Finally, the numerical results were validated by practical experiments, and the comparison showed that the optimization strategy developed in this work could provide the effective guidance for practical production.     

Modeling and analysis of the effects of processing parameters on the performance characteristics in the high pressure die casting process of Al–SI alloys

The high pressure die casting (HPDC) process has achieved remarkable success in the manufacture of aluminum–silicon (Al–SI) alloy components for the modern metal industry. Mathematical models are proposed for the modeling and analysis of the effects of machining parameters on the performance characteristics in the HPDC process of Al–SI alloys which are developed using the response surface methodology (RSM) to explain the influences of three processing parameters (die temperature, injection pressure and cooling time) on the performance characteristics of the mean particle size (MPS) of primary silicon and material hardness (HBN) value. The experiment plan adopts the centered central composite design (CCD). The separable influence of individual machining parameters and the interaction between these parameters are also investigated by using analysis of variance (ANOVA). With the experimental values up to a 95% confidence interval, it is fairly well for the experimental results to present the mathematical models of both the mean particle size of primary silicon and its hardness value. Two main significant factors involved in the mean particle size of primary silicon are the die temperature and the cooling time. The injection pressure and die temperature also have statistically significant effect on microstructure and hardness.     

Angular distortion analysis of the multipass welding process on combined joint types using thermo-elastic–plastic FEM with experimental validation

In this research, the capability of the multipass welding advisor (MWA) is to be evaluated in analyzing the angular distortion that is induced by gas metal arc welding (GMAW) process used to join a combination of butt and T-joint with thickness of 9 mm. The MWA in SysWeld 2010 is applied to develop and compare 2D/3D finite element analysis (FEA) based on the thermal elastic–plastic approach with low manganese carbon steel S355J2G3 as parent and weld material. For this simulation, the heat source of GMAW follows the Goldak's double ellipsoid model that is available within the FEA code. Detailed procedures of MPA are presented throughout this study followed with a comparison between 2D and 3D results of distortion and computational time on the combined types. To validate the simulation results, a series of experiments was conducted on low carbon steel using robotic welding process, GMAW power source with shielding gas composition of Ar (80 %)/CO₂ (20 %), and both-sided clamping method. It was established that the results of 3D simulation and experiments showed acceptable accuracy, while 2D results offers a fast solution analysis time in estimating distortion trend.     

Performance evaluation of PVD TIALN coated carbide tools vis-à-vis uncoated carbide tool in turning of titanium alloy (Ti-6Al-4V) by simultaneous minimization of cutting energy,dimensional deviation and tool wear

Titanium alloys are difficult-to-machine materials because of their poor machinability characteristics. Machining and machining performance evaluation for such materials is still a challenge. Individual machining performance indices like cutting forces, cutting energy and tool wear lead to ambiguous understanding. In this work, a Cumulative Performance Index (CPI) is defined which amalgamates non-dimensional forms of specific cutting energy, back force and average principal flank wear in turning. The CPI focuses upon simultaneous minimization of specific cutting energy, dimensional deviation and average principal flank wear. The defined index is then used to evaluate performance of five commercially available physical vapor deposited (PVD) TiAlN coated tungsten carbide/cobalt inserts vis-à-vis uncoated tungsten carbide/cobalt insert in turning of Ti-6Al-4V. Cutting forces were monitored during turning and tool wear was measured after turning experiments. The results showed that the performance of coated inserts was either comparable or poor than uncoated insert; and in no case, coated inserts performed better than uncoated insert. Although commercial recommendations are in place to use PVD coated inserts for enhanced machinability of titanium alloys, the use of coated inserts is not justified keeping in view the energy spent in coating and insignificant improvement in performance.     

Experimental studies on optimization of process parameters and finite element analysis of temperature and stress distribution on joining of Al�CAl and Al�CAl2O3 using ultrasonic welding

This study is carried out to optimize the process parameters like weld time, weld pressure, and amplitude of vibration to maximize the weld strength in Al?CAl welding using Taguchi??s design of experiments methodology. Experiments are conducted using 0.3-mm thick pieces of aluminum, and the temperature generated at the weld interface and the weld strength for all the specimens are measured. Also, a finite element model is developed that is capable of predicting the interface temperature and stress distribution during welding. Further, a preliminary study on the joining of alumina to aluminum is also carried out, and the finite element models of temperature and stress distribution during welding are simulated. Results of experimental work and FEM studies are compared and found to be in good agreement.