Different Combinations Of Process Parameters Research Articles

Energy density analysis on single tracks formed by selective laser melting with CoCrMo powder material

Selective laser melting (SLM) is an advanced manufacturing technology based on layer by layer building to produce solid parts from metallic powder (Kruth et al., CIRP Ann Manuf Technol 56:730–760, 2007). Commercial SLM machines are configured to use specific parameters to process different metallic powder grades. This paper proposes a methodology that makes it possible to analyze the effect of energy density on the formation of single tracks from CoCrMo powder, using a noncommercial machine to select process parameters with open source technology. Full factorial experimental work was carried out to produce single tracks under different combinations of process parameters. A major application of this research work is to develop more flexible machine configurations applicable to different materials.

Study of Crack Formation and Resolidified Layer in EDM Process on T90Mn2W50Cr45 Tool Steel

This article is concerned with analysis of crack formation and spherical form of resolidified layer on T90Mn2W50Cr45 tool steel surface, which is processed in electrical discharge machine (EDM). Crack and resolidified layer are examined by scanning electron microscope (SEM) with different magnification. Experiments were conducted on the T90Mn2W50Cr45 tool steel surface for different combination of process parameters like pulse: on time, off time, and current. The crack formation is influenced by the base material (T90Mn2W50Cr45 tool steel) properties, electrode wear, and resolidified layer. SEM with lower magnification will show the crack formation on the surface, while higher magnification will show the structure of the resolidified layer. It was found that the pulse current is directly proportional with resolidified layer thickness and crack density.

On the role of cooling and tool rotational direction on microstructure and mechanical properties of friction stir processed AZ91

This paper deals with an experimental investiga- tion focused on the effects of water cooling treatment, friction stir processing pass number, and tool rotational direction on the microstructure and mechanical properties of friction stir processed AZ91 magnesium alloy. Specimens were produced using different combinations of process parameters. Parallel to increasing the amount of oxide par- ticles in the processed area, water cooling was found to reduce the final grain size and enhance their hardness and strength. Changing the rotational direction in each pass reduces the grain size severely (from 150 to ~4 μm) and increases the hardness (from 63 to 98 HV) and strength (from ~130 to ~250 MPa). However, no significant differ- ence was found in wear resistance of the specimens pro- duced with different process parameters.

Structural Aspects of the Behavior of Lead-Free Solder in the Corrosive Solution

In oxidizing environments, most tin-based lead (Pb)-free alloys form a tin oxide that is easily eroded or mechanically damaged, affecting corrosion resistance and thus reliability of the soldered joints. In this study, the effect of microstructure heterogeneity on corrosion behavior of Pb-free solder candidate systems has been investigated on the example of as-cast and heat-treated alloys. The research was focused on a comparison between the corrosion resistance of binary Sn-Zn and ternary Sn-Zn-Cu alloys. Accelerated corrosion tests were performed by means of electrochemical methods in the sodium sulfate solution (VI), Na2SO4, of about 0.5 M concentration, pH adjusted to 2 by means of concentrated H2SO4 acid. In these tests, the corrosion potentials as well as polarization curves were determined for the selected alloys in as-cast state and after their heat treatment using different combinations of processing parameters. The measurements of basic electrochemical characteristics were made, i.e., the corrosion current (i corr μA/cm2) and Tafel coefficients, both cathodic (b c V/dec) and anodic (b a V/dec) ones. Detailed structural characterization of as-cast and heat-treated alloys before and after accelerated corrosion tests has been made under a wide range of magnifications using light microscopy and scanning electron microscopy observations. The results showed that structural heterogeneity of the examined alloys, attributed to the presence of secondary phases, and affected by their size and distribution, significantly influences the behavior of the examined Pb-free Sn-Zn-based alloys in the corrosive environment.

Relationship Between Mechanical Properties of Lead-Free Solders and Their Heat Treatment Parameters

The research was undertaken to establish mechanical properties of as-cast and heat-treated Sn-Zn-based alloys of binary and ternary systems as candidates for lead (Pb)-free solder materials for high-temperature applications. The heat treatment of as-cast alloys was made under different combinations of processing parameters (168 h/50 °C, 42 h/80 °C, and 24 h/110 °C). The systematic study of structure-property relationships in Sn-Zn, Sn-Zn-Ag, and Sn-Zn-Cu alloys containing the same amount of Zn (4.5, 9, 13.5 wt.%) and 1 wt.% of either Ag or Cu was conducted to identify the effects of chemical composition and heat treatment processing parameters on the alloy microstructure and mechanical behavior. Structural characterization was made using optical microscopy and scanning electron microscopy techniques coupled with EDS analysis. Mechanical properties (initial Young’s modulus E, ultimate tensile strength UTS, elastic limit R 0.05, yield point R 0.2, elongation A 5, and necking Z) were determined by means of static tensile tests. All the examined Sn-Zn-based alloys have attractive combination of mechanical characteristics, especially tensile strength, having values higher than that of common leaded solders and their substitutes of Pb-free SAC family. The results obtained demonstrate that the Sn-Zn-based alloys present competitive Pb-free solder candidates for high-temperature applications.

Modelling the Cutting Process and Cutting Performance in Abrasive Water jet Machining Using Genetic-Fuzzy Approach

Unconventional machining processes are used only when no other traditional machining process can meet the necessary requirements efficiently and economically. Abrasive Waterjet Machining (AWJM) is one of the most recently developed mechanical type unconventional hybrid manufacturing technologies. It is superior to many other cutting techniques in processing various materials, particularly in processing difficult to cut materials. This technology is being increase used in various industries. Therefore, optimum choice of the process parameters is essential for the economic, efficient, and effective utilization of these processes. Process parameters of AWJM are generally selected either based on the experience, and expertise of the operator or from the propriety machining handbooks. In most of the cases, selected parameters are conservative and far from the optimum. This hinders optimum utilization of the process capabilities. Selecting optimum values of process parameters without optimization requires elaborate experimentation which is costly, time consuming, and tedious. Process parameters optimization of AWJM essential for exploiting their potentials and capabilities to the fullest extent economically. This paper presents a Fuzzy Logic (FL) - based modeling of AWJM process and optimization of its rule base, data base and consequent part utilizing a Genetic Algorithm (GA). A binary coded GA has been used for the said purpose. While modeling with FL, the output parameters, namely Material Removal Rate (MRR) and Surface Finish (Ra) have been predicted for different combinations of process parameters, such as waterjet pressure at the nozzle exit diameter of abrasive-water jet nozzle traverse or feed rate of the nozzle mass flow rate of water and mass flow rate of abrasives between nozzle and the work piece.

Mathematical modeling of Fe(II), Cu(II), Ni(II) and Zn(II) removal in a horizontal rotating tubular bioreactor

Industrial wastewaters polluted with toxic heavy metals are serious ecological and environmental problem. Therefore, in this study multi-heavy metals (Fe(2+), Cu(2+), Ni(2+) and Zn(2+)) removal process with mixed microbial culture was examined in the horizontal rotating tubular bioreactor (HRTB) by different combinations of process parameters. Hydrodynamic conditions and biomass sorption capacity have main impact on the removal efficiency of heavy metals: Fe(2+) 95.5-79.0%, Ni(2+) 92.7-54.8%, Cu(2+) 87.7-54.9% and Zn(2+) 81.8-38.1%, respectively. On the basis of experimental results, integral mathematical model of removal heavy metals in the HRTB was established. It combines hydrodynamics (mixing), mass transfer and kinetics to define bioprocess conduction in the HRTB. Mixing in the HRTB was described by structured cascade model and metal ion removal by two combined diffusion-adsorption models, respectively. For Langmuir model, average variances between experimental and simulated concentrations of metal ions were in the range of 1.22-10.99×10(-3) and for the Freundlich model 0.12-3.98×10(-3), respectively. On the basis of previous facts, it is clear that developed integral bioprocess model with Freundlich model is more efficient in the prediction of concentration of metal ions in the HRTB. Furthermore, the results obtained also pointed out that the established model is at the same time accurate and robust and therefore it has great potential for use in the scale-up procedure.

Study of the scale behaviour in the finishing mill to improve the strip surface quality

The cracking behaviour of the oxide layer formed during hot rolling was studied together with different combinations of process parameters in order to find their single influence on the surface quality and formation of oxide defects. Several trials were performed on the CRM pilot line to study in detail the impact of strip reduction, strip temperature, entry scale thickness, roll degradation, lubrication, skin cooling, chemical composition and humidity on the scale behaviour. In general, the degree of deformation, entry scale thickness and rolling temperatures are the most important parameters and the importance decreases in that order.

An experimental design approach to manufacture of parts using fused deposition modelling

Investigating the mechanical properties of the parts manufactured from rapid prototyping (RP) machine is important for rapid manufacturing. It is necessary that, the identification of effect of different combination of process parameters to get the desired mechanical properties. This paper presents a method to manufacture parts with different combination of process parameters of fused deposition modelling (FDM) using design of experiments. The effect of road width (RW) and raster angle (RA) on density, hardness, and surface roughness is investigated. The experiments have been conducted based on second order central composite rotatable design which is one type of response surface methodology. The 13 samples are prepared and tested. From the results, the regression coefficients are calculated and fitted to the general form of quadratic equation for two factors. By using statistical analysis, the significance of the various factors is determined. The final relation shows the effect of input parameters over the output response.

Study of the scale behaviour in the finishing mill to improve the strip surface quality

The cracking behaviour of the oxide layer formed during hot rolling has been studied together with different combinations of process parameters in order to find their single influence on the surface quality and formation of oxide defects. Several trials have been performed on the CRM pilot line to study in detail the impact of strip reduction, strip temperature, entry scale thickness, roll degradation, lubrication, skin cooling, chemical composition and humidity on the scale behaviour. In general the degree of deformation, entry scale thickness and rolling temperatures are the more important parameters and the importance decreases in that order.

Investigation of surface treatment effects in micro-injection-moulding

Micro-injection-moulding as a replication method is one of the key technologies for micro-manufacture. An important stage in micro-injection-moulding which can affect the accuracy and mechanical properties of the produced components is part de-moulding. During this stage, part-mould forces can cause a variety of defects to micro-parts, including stress marks, deformation, fracture and stretching of the polymer structures. Therefore, in this paper, the effects of different surface treatments on the de-moulding behaviour of parts with micro-features are investigated. In particular, the de-moulding of a representative micro-part was studied as a function of two different tool coatings, diamond-like carbon and silicon carbide, in combination with four process parameters, employing the design of experiment approach. In addition, the results obtained using different combinations of process parameters were analysed to identify the best processing conditions in regards to de-moulding behaviour of polycarbonate and acrylonitrile butadiene styrene micro-parts when utilising these two coatings.

Process optimization in laser surface structuring of alumina

The efficacy of pulsed Nd:YAG laser for the laser surface structuring (dressing) of porous alumina ceramic was optimized using the Taguchi analytical procedure. The laser processing parameters like the pulse width, repetition rate and the scanning speed were evaluated and the factors essential to optimize the interdendritic porosity and grain size were predicted. The analysis of variance (ANOVA) helped to identify the processing parameters that contributed the most to minimize the porosity and maximize the grain size. The pulse repetition rate was the most significant factor in minimizing the interdendritic porosity while the scanning speed played a vital role in increasing the grain size. The Taguchi method could yield a combination of different process parameters that could be used to optimize the microstructural features.

Modelling of input–output relationships in cement bonded moulding sand system using neural networks

Cement bonded sand moulds can be used to cast ferrous metals with a good dimensional control. To determine input–output relationships in the cement bonded moulding sand system, both forward and reverse mappings were carried out using feed forward neural networks trained with the help of a back propagation algorithm and a genetic algorithm, separately. In the forward mapping, mould properties, namely compression strength and hardness, were predicted for different combinations of process parameters, such as percentages of cement, of accelerator and of water and testing time. In the reverse mapping, the process parameters were determined as the functions of mould properties. A batch mode of training had been provided to the neural networks with the help of one thousand training data generated artificially using the conventional statistical regression equations derived earlier by the authors. The performances of the developed models were compared among themselves and with those of the statistical regression model, for twenty randomly generated test cases. Neural network based approaches had proved their ability to carry out both the mappings. In forward mapping, the results of the neural network based approaches were found to be comparable with those of conventional regression analysis. Moreover, the genetic algorithm trained neural network was seen to perform better than the back propagation trained neural network for both the forward and reverse mappings.

Relationship between base metal properties and friction stir welding process parameters

Friction stir welding (FSW) is a solid state welding process for joining aluminum alloys and has been employed in aerospace, rail, automotive and marine industries for joining aluminium, magnesium, zinc and copper alloys. In FSW, the base metal properties such as yield strength, ductility and hardness control the plastic flow of the material under the action of rotating non-consumable tool. The FSW process parameters such as tool rotational speed, welding speed, axial force, etc. play a major role in deciding the weld quality. In this investigation, an attempt has been made to establish relationship between the base material properties and FSW process parameters. FSW joints have been made using five different grades of aluminium alloys (AA1050, AA6061, AA2024, AA7039 and AA7075) using different combinations of process parameters. Macrostructural analysis has been done to check the weld quality (defective or defect free). Empirical relationships have been established between base metal properties and tool rotational speed and welding speed, respectively. The developed empirical relationships can be effectively used to predict the FSW process parameters to fabricate defect free welds.

Predictive depth of jet penetration models for abrasive waterjet cutting of alumina ceramics

A study of the depth of jet penetration (or depth of cut) in abrasive waterjet (AWJ) cutting of alumina ceramics with controlled nozzle oscillation is presented and discussed. An experimental investigation is carried out first to study the effects of nozzle oscillation at small angles on the depth of cut under different combinations of process parameters. Based on the test conditions, it is found that nozzle oscillation at small angles can improve the depth of cut by as much as 82% if the cutting parameters are correctly selected. Depending on the other cutting parameters in this study, it is found that a high oscillation frequency (10–14 Hz) with a low oscillation angle (4–6°) can maximize the depth of cut. Using a dimensional analysis technique, predictive models for jet penetration when cutting alumina ceramics with and without nozzle oscillation are finally developed and verified. It is found that the model predictions are in good agreement with the experimental results with the average percentage errors of less than 2.5%.

Bioprocess kinetics in a horizontal rotating tubular bioreactor.

A horizontal rotating tubular bioreactor (HRTB) is a plug flow bioreactor whose interior is provided with O-ring-shaped partition walls that serve as carriers for microbial biomass. During this investigation, microbial biomass was grown in suspension and on the bioreactor inner surface as a microbial biofilm with average mass that was considerably higher than suspended biomass. The dynamics of bioprocess in HRTB was studied by different combinations of process parameters (bioreactor rotation speed and mean residence time) and it was monitored by withdrawing the samples from five positions along the bioreactor. During this investigation it was also observed that mean residence time had a more pronounced effect on the bioprocess dynamics than bioreactor rotation speed. For the description of bioprocess kinetics in HRTB an unstructured kinetic model was established that defines biomass growth, product formations and substrate consumption rate by using a modified Monod (Levenspiel) model. This kinetic model defines changes in suspension and in microbial biofilm, and it shows relatively good agreement with experimental data.

Titanium matrix reinforced composites produced by hot pressing of plasma-sprayed preforms

The present work is focused on the fabrication of long fibre reinforced titanium composites by hot pressing of plasma-sprayed preforms. Thermal spraying of two different metallic matrices [Ti-6Al-2Sn-4Zr-2Mo-0.08Si (Ti6242S) and Ti-4.5Al-3V-2Mo-2Fe (SP700)] onto prearranged silicon carbide long fibres was performed using controlled-atmosphere plasma spraying equipment (CAPS), allowing deposition processes also in the high-pressure range. After optimization of the plasma spraying procedure, composite multilayers were fabricated by hot pressing at 1200 bar with different combinations of process parameters (temperature in the range 850-940 °C, and application time from 30 to 45 min). Consolidated samples were characterized by microstructural investigation and tensile testing at room and high temperature (up to 600 °C). Push-out and push-back tests were performed to investigate interfacial properties.

Titanium matrix reinforced composites produced by hot pressing of plasma-sprayed preforms

The present work is focused on the fabrication of long fibre reinforced titanium composites by hot pressing of plasma-sprayed preforms. Thermal spraying of two different metallic matrices [Ti-6Al-2Sn-4Zr-2Mo-0.08Si (Ti6242S) and Ti-4.5Al-3V-2Mo-2Fe (SP700)] onto prearranged silicon carbide long fibres was performed using controlled-atmosphere plasma spraying equipment (CAPS), allowing deposition processes also in the high-pressure range. After optimization of the plasma spraying procedure, composite multilayers were fabricated by hot pressing at 1200 bar with different combinations of process parameters (temperature in the range 850-940 °C, and application time from 30 to 45 min). Consolidated samples were characterized by microstructural investigation and tensile testing at room and high temperature (up to 600 °C). Push-out and push-back tests were performed to investigate interfacial properties.

Fermentative bioconversion in a horizontal rotating tubular bioreactor

The performance of a horizontal rotating tubular bioreactor (HRTB) was investigated with a biological system under non-sterile conditions. A spontaneously developed microbial culture was cultivated in a simple glucose/yeast extract medium. A fermentative bioconversion was examined by different combinations of process parameters (bioreactor rotation speed 5–30 min −1 and medium inflow rate 1–10 l h −1). Bioconversion dynamics in HRTB was monitored by withdrawing the samples from five positions along the bioreactor. Investigation in HRTB showed a rapid and an efficient glucose conversion into different products of metabolism. Glucose consumption rate along the HRTB depended on medium inflow rate, while bioreactor rotation speed did not have a significant influence. Complete glucose conversion in HRTB was observed at inflow rates of up to 6.5 l h −1. The pH gradient along the HRTB was detected at higher medium inflow rates (6.5 and 10 l h −1), but did not significantly influence substrate conversion efficiency. A discussion of its potential use and a comparison of HRTB with other bioreactors are also presented.

A parametric study of segregation effects during vertical Bridgman crystal growth with an axial magnetic field

This paper presents a model for the unsteady transport of a dopant during the vertical Bridgman crystal growth process with a planar crystal–melt interface and with an axial magnetic field, and investigates the effects of varying different process variables on the crystal composition. The convective mass transport due to the buoyant convection in the melt produces nonuniformities in the concentration in both the melt and the crystal. The convective mass transport plays an important role for all magnetic field strengths considered. Diffusive mass transport begins to dominate for a magnetic flux density of 4 T and a fast growth rate, producing crystals which have an axial variation of the radially averaged crystal composition approaching that of the diffusion-controlled limit. Dopant distributions for several different combinations of process parameters are presented.