Journal of Materials Processing Technology

Published by Elsevier
Print ISSN: 0924-0136
In the medical application of stent therapy, especially in coronary heart disease, a metallic stent of high quality demands the ability for precision micromaterial processing. It possesses an inherent advantage of adequate radio-opacity. This paper describes the fabrication of such a metallic stent of length 20 mm and dia. 2.1 mm with an annular tube thickness of 0.2 mm, by using a pulsed Nd:YAG laser. Fine structures with a slit width of 0.1 mm and a pitch better than 0.4 mm are created with sharpness and low roughness in the cut surface. Some features of the reduced heat affected zone and dross removal process of the cut surface are also discussed
The Simulation Based Design (SBD) is described. It can be realized through implementation and integration of new computer technologies and tools. The decisive components for successful development of SBD are: modelling methods and computational tools, virtual reality environment, an infrastructure for collaborative engineering and integration technologies and tools.
In this work, the retention of austenite in post-welded microstructures of a 0.16C–1.6Mn–1.5Si (wt.%) TRIP steel is investigated. Fully penetrated welds are produced by means of gas tungsten arc (GTA) welding and laser beam (LB) welding. The microstructure, particularly retained austenite, is analyzed using optical microscopy, Vickers hardness measurements, X-ray diffraction and saturation magnetization. It is found that the GTA welded TRIP steel contains a relatively large fraction of retained austenite, which may benefit the weldability of this steel. A minimum hardness is found in the heat-affected zone (HAZ) next to a high hardness plateau after both LB and GTA welding as a result of a large fraction of ferrite. It is suggested that for TRIP steels, proper control of the formation and decomposition of retained austenite in the HAZ is important to prevent weld failure. The hardness is therefore not a sufficient indicator for the weldability.
This paper investigates the comparative microstructural and mechanical characteristics of fusion welds (TIG) and solid-state welds (FSW) of Al–4.5 Mg–0.26 Sc heat-treatable aluminium alloy. Microstructures of base metal and welded zones are analyzed by optical (OM) and transmission electron (TEM) microscopy. Particular emphasis is laid on the evolution of hardening precipitates in welded areas. The corresponding mechanical properties are evaluated through microhardness measurements and uniaxial tensile tests. The effect of a post-weld heat treatment on both microstructure and mechanical properties is further examined. The results suggest that hardening precipitates are comparatively more affected by the TIG than by the FSW process. This results in a substantial reduction of mechanical properties of TIG welds that can be partially recovered through a post-weld heat treatment.
Microstructure of twin-roll casted (TRC) Mg–3Al–0.5Mn–0.2Mm (or AM30 + 0.2Mm) alloy strips consisted of columnar dendrites in the surface and equiaxed dendrites in the center regions, as well as widely dispersed fine primary intermetallic compounds located in the interdendritic region. Warm rolling of the TRC strips developed both deformation or shear bands and homogeneously dispersed fine particles. No evident dynamic recrystallization (DRX) was found in the TRC sheets during warm rolling. The dispersed fine particles seemed to retard DRX. The warm-rolled TRC sheets showed equiaxed fine grains with an average size of around 8 μm after annealing at 350 °C for 60 min. The TRC sheets had superior yield and tensile strengths to ingot cast (IC) samples. Elongation was similar to both TRC and IC samples.
The presence of hydrogen will cause damaging effects in steels and its alloys used in petroleum refineries, natural gas pipelines and oil fields. The present investigation was carried out to assess the effect of hydrogenation time, independent of other processing and other constitutional variables, on the mechanical properties of 0.31% carbon steel. The results revealed that as the exposure time for cathodically charged hydrogenated steel was increased, an increase in tensile strength, yield strength and breaking strength was observed with a loss in ductility. A decrease in the mechanical properties was also noticed when the specimens of medium carbon steel were charged with hydrogen for a longer period with exception of ductility. SEM studies on the fractured surfaces of the hydrogen charged specimens exhibited surfaces ranging from intergranular tear to high-pressure fractured locations.
In present paper, the influence of copper on wear-friction behaviour of hypereutectic Al–Si alloy (Al–18% Si–0.5% Mg) has been investigated. Sliding tests were conducted under dry sliding conditions against hardened steel En-31 counter surface over a range of sliding speed from 2.0 to 7.0 m/s and contact load from 10 to 80 N. It was observed that the wear rate is a function of contact load, sliding speed, composition and thermal softening characteristics of sliding metal. Wear of hypereutectic aluminium–silicon alloy is not appreciably affected with the addition of copper. However, addition of copper increases the transition load at 2.0 m/s sliding speed. Copper addition more than 2%, did not show any effect on the transition load.
In this study, artificial neural networks were used to model the hot deformation behavior of Zr–2.5Nb–0.5Cu alloy, in the strain rate range of 10−3 to 10 s−1, temperature range of 650–1050 °C and to a strain of 0.5. Strain, log strain rate and inverse of temperature were used as inputs and stress was taken as the output of the network. The feed-forward network used consisted of two hidden layers containing four and three neurons each with a log-sigmoid activation function and Levenberg–Marquardt training algorithm. The network was successfully trained across phase regimes (α + β) to β and across different deformation domains. This trained network could predict the flow stress better than a constitutive equation of the type .
In this paper, the effect of semi-solid isothermal heat treatment on the microstructure of Mg–6A1–1Zn–0.7Si alloy, especially on the semi-solid microstructural evolution and the modification of Chinese script shaped Mg2Si phase, are first investigated. The research results indicate that it is possible to produce the Mg–6A1–1Zn–0.7Si alloy with non-dendritic microstructure by the semi-solid isothermal heat treatment. After treated at 575–585 °C for 120 min, the experimental alloy can obtain a non-dendritic microstructure with a 12–21% liquid content and an average size range of 48–67 μm of the unmelted primary solid particles. In addition, the semi-solid isothermal heat treatment can modify the Chinese script shaped Mg2Si phases in experimental alloy. After treated at 580 °C or 585 °C for 120 min, the morphology of Mg2Si phases in the experimental alloy changes from the initial Chinese script shape to granule and/or polygon shapes.
Drilling composite materials is a very common and an important process used in industry to perform the assembly of aerospace and automotive composite structures. However, drilling composite materials present a number of problems such as delamination associated with the characteristics of the material and with the used cutting parameters. In order to reduce these problems a study is present with the objective of evaluating the cutting parameters (cutting velocity and feed) and the influence of the matrix under specific cutting force (kc), delamination factor (Fd) and surface roughness (Ra) in two types of matrix (Viapal VUP 9731 and ATLAC 382-05). A plan of experiments, based on the orthogonal array, was established considering drilling with prefixed cutting parameters in two hand lay-up FRPs materials. Finally the analysis of variance (ANOVA) was preformed to investigate the cutting characteristics of FRPs composite material using a cemented carbide (K10) drill with appropriate geometry.
Schema of asymmetrical rolling of bimetallic plate (a) a v = V G /V D = 1 and (b) a vopt = V G /V D < 1.
Distribution of bimetallic plate curvature for asymmetrical process rolling for thickness layer ratio value of H T /H M = 2/10.
The optimal conditions for production of bimetallic plate St36K + 0H13J in asymmetrical hot rolling
As an elaboration of the new technologies for rolling of bimetallic plates there are many problems, both with ensuring a uniform strain distribution and producing a straight band as well. This research was carried out for three varied bimetallic layer thickness HT/HM = 6/22, 10/18 and 9/9. The analysis of bimetallic plate production is a complex and difficult problem to solve in a theoretical way. In the paper was presented a problem of hot rolling St36K + 0H13J plates (according to Polish Standards). Computer analyses for asymmetrical rolling process have been performed in this work to optimize the conditions for production of bimetallic plates. A Finite Element Method—Forge2 program has been applied in the computer simulation.
In this study, Al–8.5Fe–1.1V–1.9Si alloy was synthesized by the spray-atomization and -deposition technique. The microstructure and mechanical properties of the alloy were studied using transmission electron microscopy (TEM), X-ray diffraction (XRD), and tensile tests. The secondary phases in the microstructure of the spray-deposited alloy were examined. The tensile test results indicate that the spray-deposited Al–8.5Fe–1.1V–1.9Si alloy both at room and elevated temperature displays superior tensile strength due to the presence of the thermally stable Al12(Fe,V)3Si particles.
Stainless steel is an important engineering material that is difficult to be cut by oxy-fuel methods because of the high melting point and low viscosity of the formed oxides. However, it is suitable to be cut by laser. This work aims to evaluate the optimum laser cutting parameters for 1.2 mm austenitic stainless steel sheets by using pulsed and CW Nd:YAG laser beam and nitrogen or oxygen as assistant gases, each one separately. It was shown that the laser cutting quality depends mainly on the laser power, pulse frequency, cutting speed and focus position. The optimum cutting was achieved during pulsed mode at applied power 210 W, frequency 200–250 Hz, speed 1–1.5 m/min, focus position −0.5 to −1 mm, nitrogen pressure 9–11 bar and oxygen pressure 2–4 bar. Increasing the frequency and cutting speed decreased the kerf width and the roughness of cut surface, while increasing the power and gas pressure increased the kerf width and roughness. Comparing with oxygen, nitrogen produced brighter and smoother cut surface with smaller kerf, although it did not prove to be economical. In CW mode, the speed can be increased to more than 8 m/min with equivalent power and gas pressure (limited by the laser system). Pulsed mode was also not economical, especially in limited frequency laser systems, where the pulse overlap should be controlled by both frequency and speed. In CW, the speed can be increased to the maximum system limit. The results should be included in computerized database for the automatic implementation of laser process.
The effect of fractional density and height-to-diameter ratio (aspect ratio) on radial crushing strength for sintered hot-upsetted Fe–0.8%C as well as Fe–0.8%C–0.5%Mo powder metallurgy rings were investigated. Rings of predetermined geometry were machined from the hot deformed preforms of different initial densities. It was found that increasing density of the rings had increased the radial crushing strength irrespective of compositions. Further, it was observed that the hardness values were continuously increasing with increasing fractional density. Increasing the aspect ratio of preforms substantially increased the hardness values for any theoretical density attained. It was also observed from fractographs that majority of the rings crushed in a brittle manner.
Understanding chip formation mechanisms in hard turning is an important area of research. In this study, experiments with varying cutting conditions and tool edge geometry were performed concurrently with finite element simulations. The aim was to investigate how the two mechanisms reported in literature namely—surface shear-cracking (SCH) and catastrophic thermoplastic instability (CTI) contribute to overall chip geometry and machining forces. By varying tool edge geometry and cutting conditions predominance of one over another is discussed. The calculation prescribed by Recht [Recht, R., 1964. Catastrophic thermoplastic shear. J. Appl. Mech. 31, 189–193] for representative cutting conditions resulted in a small critical cutting speed of 0.034 m/min indicating CTI was operative in the range of cutting conditions tested. FEM simulations were conducted on a subset of experimental conditions. Chip geometry and forces were compared between experiments and simulations. The experimental results indicated that SCH predominated in a majority of conditions. However, formation of saw-tooth chips in the FEM simulations established the occurrence of CTI also. Specifically, the edge radius did not alter chip geometry parameters. However, machining forces decreased with cutting speed and chip formation frequency increased linearly with cutting speed. A more negative rake angle also increased the chip pitch. The findings also indicate that only an intrinsic length scale governs saw-tooth chip formation in hard turning.
For the manufacture of bearing steels of low distortion potential, 100Cr6 steel billets were spray formed with respect to metallurgical homogeneity. Microstructure and properties of the billets produced under different thermal conditions were studied and evaluated. A heat transfer model of a growing billet was established to investigate the thermal profiles of the billet during spray forming. An apparent correlation between the cooling and solidification condition of the deposit and its metallurgical properties has been disclosed by means of numerical simulation and experiment.
Recent improvements in the machine tools technology (specially the stiffness and positioning accuracy) as well as the advent of the cubic boron nitride (CBN) ceramic cutting tools made the finishing operations for machining hardened steel parts possible, using tools with defined cutting geometry in substitution to the traditional grinding operations. The advantages presented by the hard turning are sufficiently attractive for many plants, however these are still reluctant to adopt and substitute a well known and dominated process (grinding) for other one not totally understood. Aiming to expand the knowledge of the processing effects of hard turning on the finishing of the machined workpiece, as well as the effects on the tool wear life. Series of experiments with seven different types of CBN inserts had been carried out using inserts with wiper geometry, coated with TiAlN and TiN as well as with no coated ones. The cutting parameters had been specified in such a form to cover the entire field recommended by tool suppliers. The machined part was an axle of DIN 100Cr6 steel tempered to 62 HRc. All the machining operations were carried out at a Mazak-Quick-Turn using an tool holder DCLNR-164D with insert geometry ISO CNGA120408SO1020 with edge with T preparation with 0.102 mm × 20°. The tool wear control was carried out using an optic microscope Zollern Saturn and a roughness profiler Hommelwerk T8000. Following parameters were parameters were determined: VBMAX, Ra, material removal rate and the tool life determined by the Taylor's equation obtained for theoretically ideal cutting conditions. Preliminary analyses of the results compares with the literature indicating that they are significant.
This paper investigates the influence on parting-off mechanisms of a significantly higher impact velocity compared to commercial methods. A specially developed method, allowing for parting-off velocities ranging from 38 to 285 m/s has been applied to 100Cr6 steel bars. Two different heat treatments; spheroidise annealing (SA) and quench and tempering (QT) were employed to produce two different microstructures of a hardness of 255 and 310 HV, respectively. It appears that the failure mechanisms active in the current process are virtually identical to failure occurring during high-velocity parting-off using commercially available machines, which displays shear fracture and adiabatic shear banding. It was also concluded that the estimated energy consumed during parting-off is not dependent on microstructure. Prior to parting-off, impact results in shear localisation, which is somewhat increased with increased impact speed. Furthermore, shear strains at fracture also increases with impact speed, from a value of about 2.2 at the lowest impact velocity to almost 3.5 at an impact velocity of 285 m/s. The heavy deformation causes a grain refinement. Right below the fracture surface three subzones can be found in the microstructure; a white etching band (WEB) (only present on some locations), equiaxed grains and then elongated subgrains. The grain size within these zones varies between 50 and 150 nm. The findings of elongated subgrains of a mutual orientation, adjacent subgrains having {1 1 0} type of planes in parallel, support the theory of formation of white etching bands being a mechanically rate controlled process.
In this paper, the performance of three cemented carbide cutting tools, two coated tungsten based cemented carbide — one with Al2O3 (black) outer layer and the other with TiN (golden), and an uncoated titanium based (silver grey) cemented carbide tool, with 80° — diamond insert shape were investigated during finish turning of AISI 1010 steel. The PCBNR tool holder, giving a side cutting edge angle of +15°, was used. Cutting tests were performed with constant depth of cut and at various cutting speeds and feed rates to investigate the performance of the tools under dry cutting conditions. Cutting forces and surface roughness were measured. The chips produced by the three type of tools during experimental trials were examined to determine the secondary shear zone, chip thickness and the angle of maximum crystal elongation. The tool which had the CVD with TiCN/TiC and PVD with TiN coating layer sequence performs best under the conditions tested, as lower forces with little variation were encountered, very good surface finish could be obtained and chips with minimum SSZ thickness could be produced, that contributed to low chip strain and therefore to low residual stresses on the workpiece surface.
The friction and wear characteristics of AISI 1020 and 5115 steel surfaces improved by various thermochemical heat treatments such as carburizing, carbonitriding and boronizing were determined. Samples prepared from the test materials were treated at liquid and gases carburizing, gases carbonitriding and solid boronizing mediums. The hardness distributions, microstructures and X-ray diffraction studies were performed.The wear tests were carried out with pin-on-disc sample configurations and weight losses were determined as a function of sliding distance and applied load. The friction behaviours of tested samples were also examined. Thus, the heat treating capacity of a simple steel such as AISI 1020 was determined and compared with other treated steel samples.
This paper is a part of series of investigation which aims to study the effect of post weld heat treatments (PWHTs) on the residual stress of low carbon steel AISI 1020 welded components.In this study different PWHT parameters have been investigated by applying different schemes of soaking temperatures of 450, 550 and 650°C, heating rates of 50, 100 and 400°C/h, time durations of 0.5, 2 and 10 hours, and cooling rates of 10, 40 and 125°C/h.Hole drilling method has been used to determine the magnitude and distribution of residual stresses before and after the application of PWHTs. A comparison between the residual stresses for all these different heat treatments have been made to assess the most effective scheme and factor for reducing the residual stress.
In this study, the effects of boronizing treatment on material's dimensional changes and surface roughness were investigated. The parameters chosen were substrate material composition, surface roughness before boronizing treatment, and boronizing time. The AISI 1020, AISI 1040 and AISI 2714 were chosen as substrate materials whereas Ekabor I was selected as boronizing powder. Materials were boronized at 900 °C by using a solid boronizing method for 2 or 4 h. The gradual growth of boride layer on the surface, dimensional changes and their effects on surface roughness were investigated. Variations in topographical surface roughness were determined by SEM. With the boronizing treatment, dimensional increases of the material's were observed. The dimensional increase was one fifth of boride layer thickness for AISI 1020 or AISI 1040, whereas it was one third of boride layer thickness for AISI 2714. Boronizing treatment had also a significant effect on surface roughness of materials. A “threshold roughness” term was defined in our study. This term is a surface roughness value for smooth surfaces, which received boronizing treatment. For the same material and with the same boronizing conditions, the threshold roughness value was achieved after boronizing, when surface roughness of material was below the threshold roughness value, before boronizing was applied. However, when surface roughness of a material was above that threshold roughness value, surface roughness value decreased with boronizing treatment. The thereshold roughness value depended on substrate material composition and boronizing parameters.
This study is part of the ongoing research at the Department of Mechanical Engineering of the University of Brescia on FEM simulations of cutting operations. In recent years, the application of finite element method (FEM) to cutting operations has proved to be effective to study the cutting process and chip formation. In particular, the simulation results can be used as a practical tool both by researchers and machine and tool makers to design new tools and to optimize the cutting process.Several papers are available on two-dimensional simulation of cutting process because the three-dimensional versions of FEM software required a big effort in computational time. The present work aims to simulate three-dimensional cutting operations. In particular orthogonal cutting and oblique cutting operations are modeled. The FEM software used for this study is DEFORM 3D. The simulation results are compared with simulations and experimental data found in literature. A good agreement has been found, confirming the ability of simulations in predicting chip flow in cutting processes.
This paper addresses a fundamental issue of component manufacture. In particular, it deals with the question of how to get designers to design parts where they may not be familiar with the processes used to manufacture them. The paper describes the development of a CAD linked stand alone computer-based metalforming process module which can be used by design engineers to identify cost effective manufacturing options in conjunction with work reported in [Forming feature representation and process selection in cold extrusion, in: Proccedings of to the Ninth International Conference on Metal-Forming, Birmingham, UK, 125–126 (2002) 456–463].
In the present work an attempt has been made to determine the heat flux transients during quenching of Ø28 mm × 56 mm height and Ø44 mm × 88 mm height AISI 1040 steel specimens during lateral quenching in brine, water, palm oil and mineral oil. The heat flux transients were estimated by inverse modeling of heat conduction. The variation of heat flux transients with surface temperature for different quenching media is investigated. Higher peak heat flux transients are obtained for 28 mm diameter specimen than 44 mm diameter specimen during quenching in aqueous media. However quenching with oil media shows opposite results. Agitation of quenching medium increases the peak heat flux during the quenching of steel specimen in all the quenching media. Peak hardness is obtained at the surface and with smaller diameter specimens during agitation.
In metal industries, the use of cutting fluid has become more problematic in terms of both employee health and environmental pollution. But the use of cutting fluid generally causes economy of tools and it becomes easier to keep tight tolerances and to maintain workpiece surface properties without damages. Because of them some alternatives has been sought to minimize or even avoid the use of cutting fluid in machining operations. Some of these alternatives are dry machining and machining with minimum quantity of lubrication (MQL). This paper deals with experimental investigations in the role of MQL on cutting temperature, chip formation and product quality in turning AISI-1040 steel at different industrial speed-feed combinations by uncoated carbide insert. The results have been compared with dry machining and machining with soluble oil as coolant. The experimental results indicate that such MQL enables substantial reduction in the cutting temperature, dimensional inaccuracy depending upon the levels of the cutting velocity and feed rate. It was also noted that the chip formation and chip–tool interaction become more favorable under MQL condition. Therefore, it appears that MQL, if properly employed, not only provides environment friendliness but can also improve the machinability characteristics.
The performance of a multilayer tungsten carbide tool was described using response surface methodology (RSM) when turning AISI 1045 steel. Cutting tests were performed with constant depth of cut and under dry cutting conditions. The factors investigated were cutting speed, feed and the side cutting edge angle (SCEA) of the cutting edge. The main cutting force, i.e. the tangential force and surface roughness were the response variables investigated. The experimental plan was based on the face centred, central composite design (CCD). The experimental results indicate that the proposed mathematical models suggested could adequately describe the performance indicators within the limits of the factors that are being investigated. The feed is the most significant factor that influences the surface roughness and the tangential force. However, there are other factors that provide secondary contributions to the performance indicators. In the case of surface roughness, the SCEA2 and the interaction of feed and SCEA provides these contributions whilst for tangential force, the SCEA2, the interaction of feed and SCEA; and the cutting speed provides them.
This paper presents tool condition monitoring (TCM) of dry turning processes on automatic lathes, and describes the information generated by different measuring systems applied to the single point turning situation. The outputs measured were correlated with the state and wear rate of the cutting tools.Semi-finishing and rough-shaping tests have been carried out at different cutting speeds. Uncoated sintered carbide inserts have been used in both processes, while TiC–TiN coated inserts have only been used in the semi-finishing processes. The behaviours of the utilised power, the tool-holder shank vibrations and the surface roughness vs. pass number were studied. The main criteria used for the wear assessment, were the roughness checks on work pieces in the semi-finishing processes, the electrical input by the lathe motor together with the vibrations level in the rough-shaping processes.The life of the tool inserts was assessed for each test, and Taylor's equation was determined for the three types of inserts used.The parameters investigated show that the results are directly influenced by degree of the tool wear and also give indications when the tool insert has reached the end of its life.Coated inserts permit approximately 50% longer machining time, a higher wear mark width and a reduced applied power consumption, compared with uncoated inserts. The end of tool life in the semi-finishing processes, when compared to the rough-shaping processes, refers to the higher power range used in the latter.The established relationships can be used in the evaluation of a tool insert's life and subsequently give rise to clear indications of the opportunity for higher productivity.
Investigation was carried out to study the microstructural changes (if any) in medium carbon steel (En-8) deformed at low strain rate (quasistatic) and very high strain rates employing different temperatures. A dynamic compression test rig was used for firing a flat ended cylindrical tool steel projectile against disc shaped specimen placed upon a comparatively rigid anvil. Metallographic specimens were prepared from as-received material as well as from the specimens deformed at low and very high strain rates. The mode of deformation was revealed by metallographic examination of all the deformed specimens. When the specimens were compressed, deformed grains were obtained. No deformation twins were observed in the steel used in the present study which deformed at various strain rates and at sub-zero, room and warm temperatures. It is envisaged that the initiation of twinning during impact was affected by the presence of alloying elements and inclusions in the medium carbon steel, despite its high strain rate sensitivity.
High production machining of steel inherently generate high cutting temperature, which not only reduces tool life but also impairs the product quality. Conventional cutting fluids are ineffective in controlling the high cutting temperature and rapid tool wear. Further, they also deteriorate the working environment and lead to general environmental pollution. Attempts have already been initiated to control the pollution problem by cryogenic cooling which helps also in getting rid of recycling and disposal of conventional fluids.The present work deals with experimental investigation in the role of cryogenic cooling by liquid nitrogen jet on tool wear and surface finish in plain turning of AISI 1060 steel at industrial speed-feed combination by two types of carbide inserts of different geometric configurations.The results have been compared with dry machining and machining with soluble oil as coolant. The results of the present work indicate substantial benefit of cryogenic cooling on tool life and surface finish. This may be attributed to mainly reduction in cutting zone temperature and favorable change in the chip–tool interaction. Further, it was evident that machining with soluble oil cooling failed to provide any significant improvement in tool life, rather surface finish deteriorated.
Titanium alloys are widely used in applications that demand a good combination of high strength, good corrosion resistance and low mass. Beta-Titanium alloys offer the highest specific strength among titaniumbased materials. The mechanical properties lead to challenges in machining operations such as high process temperatures, high specific mechanical loads and rapidly increasing tool wear. The high chemical reactivity of titanium leads to rapidly developing flank and notch wear limiting cutting speeds and tool life. Applying industrial gases instead of conventional cooling and lubrication fluids promises increased productivity. In this work, the effectiveness of carbon dioxide snow (CO2) as a coolant for turning Ti–10V–2Fe–3Al is analyzed. The carbon dioxide is provided in a pressurized gas bottle and is fed to the tool tip through holes in the tool holders clamping jaw. Compared to flood emulsion cooling the flank wear was uniform spreaded and tool life was increased by a factor of two even at higher cutting speeds. Tool-life-limiting notch wear and the burr formation at the workpiece have been suppressed.
The hot workability of the nickel-base alloy NIMONIC 115 has been investigated by means of torsion testing in extended ranges of strain rate (0.01–1 s−1) and temperature (1140–1180 °C). The flow curves have shown, in general, an increase in equivalent stress up to a peak value followed by a softening until rupture. At 1140 °C, for strain rates varying between 0.01 and 1 s−1, the peak in flow stress is followed by a marked softening up to a steady state condition which can be attributed to the occurrence of dynamic recrystallisation. The hot ductility vs. true temperature, occurring during torsion tests, has been analysed. Flow behaviour of NIMONIC 115 alloy vs. process parameters has been modelled by means of an equation relating the hyperbolic sine of flow stress to the temperature-modified strain rate. The results have been analysed and discussed.
This paper studies the surface finish and integrity of glass, silicon, some advanced ceramics and aluminum-based metal matrix composites (MMCs) reinforced with ceramic particles, precision machined by various machining processes. The studies revealed that grinding/lapping operations using inexpensive machine tools can produce ductile streaks on glass and silicon surfaces under good grinding/lapping conditions. This resulted in significantly shortened polishing time to secure an acceptable surface finish. If there are several processes to manufacture a lens, each preceding process is very important for the successive processes. In order to reduce the total manufacturing time, it is preferable to obtain better ground/lapped surfaces with as many ductile streaks as possible in order to reduce the polishing time. Toroidal SiC surfaces ground with flat-face cup wheels indicated 100% ductile machining, and did not require polishing. Ground ZrO2 showed a numerous ductile streaks. Plastic deformation was the major mechanism of material removal at high wheel speeds. Grinding of aluminum-based MMCs reinforced with Al2O3 or SiC particles using a 3000 grit diamond wheel at depths of grinding of 1 and 0.5 μm produced many ductile streaks on the Al2O3 and SiC particles, respectively. There was almost no sub-surface damage. The machines used for the experiments reported in this paper are not expensive ultra-precision machines.
A generalised three-parameter gamma distribution was fitted to three creep failure data sets obtained from BSCC. The log normal, Weibull, gamma and exponential distributions are nested within this generalised distribution and emerge when the parameters of the generalised distribution take on particular values. Standard statistical tests for parameter restrictions were then used to identify which of the above-named distributions are most supported by the data.Confidence limits for 50%, 10% and 1% quantiles of log failure time were computed using distributions most and least supported by the data. The extent to which such uncertainty about distributional form effects the size of confidence limits was also analysed.At the three stress and temperature ranges studied, the log normal distribution was best supported by the data, the Weibull distribution was least supported, whilst the two-parameter gamma and exponential distributions were rejected by the data. In each case a wide variety of three-parameter gamma distributions were supported by the data and this significantly increased the confidence limits at the lower quantile ranges.
The role of processing parameters on the densification mechanism and microstructural evolution in laser sintered Al–12Si powder has been explored. It was established that both the densification mechanism and microstructural evolution in laser sintered Al–12Si powder were controlled by the specific laser energy input. Analysis of the cross-section of laser sintered microstructures of Al–12Si powders indicated that the tops of the grains in the previous layer are partially re-melted and then undergo epitaxial growth in the next layer where the heat affected zones (HAZ) grain boundaries and solidification grain boundaries (SGBs) are continuous along the fusion boundary.
The objectives of the present study were to characterize the distribution of residual stress and the microstructure changes induced by welding in the heat-affected zone (HAZ) of 13%Cr–4%Ni used in hydraulic turbine fabrication to deduce best practices. To characterize residual stress after welding, hole-drilling, X-ray diffraction (XRD) and the contour method were used on a FCAW 6 passes UNS W41036 (410NiMo) weld deposited on UNS S41500 (13%Cr–4%Ni) stainless steel; the results were put side to side with the weld microstructure and hardness to assess their criticality. Transverse compression was found in and around the last bead of the weld by XRD and hole-drilling. Longitudinal compression stress was found in and around the last bead while longitudinal tension was found near the low-temperature HAZ. The contour method showed that despite high compression in the last bead, high longitudinal tension exists in the rest of the weld and just below the weld. The superposition of both residual stress distribution and results from microstructural characterization shows that in multipass welding of 13%Cr–4%Ni martensitic stainless steel, cracking susceptibility is higher in the weld than in the HAZ, let it be fatigue cracking, environment-assisted cracking or cold cracking during welding. Post-weld heat treatment proved to be very efficient in lowering residual tension found in the first bead and in lowering the hardness of the weld. These results underline the importance of following proper procedures when welding these steels; this being even more true when the assembly is loaded in fatigue.
The cost of design, for most products, has shown itself to be a small part of the manufacturing cost and experience has shown that at least 70% of the cost of a manufactured part is decided at the design stage. This is therefore, the logical stage at which to invest more time and effort into getting the design right first time. With the development of computer aided design (CAD) and computer aided manufacture (CAM), the time and cost analysis of a design has been improved immensely.During the design, the material and manufacturing process combinations will be chosen from those with which the product design team is most comfortable. As a result, the opportunity for major manufacturing improvements may be lost through the limited selection of manufacturing processes and associated materials in the early stage of product design.The aim of this research is to develop an expert system that is linked into a 3D design package, which will give an analysis of alternate methods of manufacture for producing the design. The methods used to develop the system will be database design, and expert system development, along with concurrent engineering (CE) methodology. This paper examines the steps involved in developing the system using the IDEF modelling techniques and highlights key CE methodologies.
Cold upsetting experiments were carried out on sintered aluminium–iron composite preforms in order to evaluate their work-hardening characteristics. The effect of the iron content, the iron particle-size range and the initial aspect ratio of the preforms on work hardening has been investigated thoroughly. Analysis of the experimental data has shown that the strain-hardening exponent n increased with decreasing values of the iron powder particle-size range, also being found to be greater for lower aspect ratio preforms compared to higher aspect ratio preforms. Irrespective of the initial aspect ratio and the iron content, the finer iron particle dispersoids showed an enhanced rate of work hardening, whereas a minimum level was shown by coarser iron particle-size dispersoids. The strength coefficient K was found to increase with decreasing iron particle-size range in the aluminium matrix. Both n and K values were found to decrease when the dispersed iron-particle range was greater (as in the present investigation). Further, it has been found that the rate of change of the n and K values were not the same for both of the aspect ratios of the preforms tested: indeed, a pronounced difference existed. This has established that the initial geometry of the P/M preforms plays a predominant role in influencing both n and K. In general, as the iron content in the aluminium matrix was increased, K was found to increase also, irrespective of the iron particle-size and the initial aspect ratio.
Transfer molding is used extensively in electronic packaging. To achieve a high production rate and high molding quality, it is necessary to have strict control on the epoxy resin characteristics as well as identify the optimal process conditions of the transfer molding. In this paper, process simulations of transfer molding for electronic packages were conducted according to Taguchi experiments. The simulation results were then used to derive quality indexes by using TOPSIS (techniques for order preference by similarity of ideal solution) algorithm. Through the analysis of the quality indexes, optimal process conditions can be identified. Two verification tests were carried out and results of the tests are found very close to the predictions. This project has demonstrated that numerical simulation combining with Taguchi method and TOPSIS can be a useful tool for optimization of process conditions for transfer molding of electronic packages.
Nanostructured Al2O3–13 wt.% TiO2 coating was fabricated by plasma spray with nanocrystalline powders and the microstructures of the feedstock and the coating were characterized by means of XRD, SEM and TEM. It was found that three forms of substructure existed in the coating: one evolving from the unmelted part of the feedstock and showing a round-shaped morphology; one resembling the liquid-phase-sintered structure consisting of the flattened partially melted region and fully melted region; another being of the particulate-reinforced-solid solution type with fine particles distributed in the matrix. The TEM analysis revealed that partially melted α-Al2O3 particles were in the size range of 20–70 nm and were embedded in the TiO2-rich matrix. The mechanism of the substructure formation was also explained in terms of the melting and flattening behavior of the powders during plasma spray processing.
Vacuum brazing tests were carried out on the age-hardened steel of the 14-5 PH type using the 82Au–18Ni solder. It has been found that structure of the joint consisted of two kinds of Au–Ni solid solutions: one is rich in gold and the other rich in nickel. The influence of roughness of the surfaces to be joined and the distance between them as well as duration of the brazing on the joint structure and properties have been determined. The maximum tensile strength (Rm = 1260 MN/m2) was obtained for the joints of polished surfaces without any distances elements, brazed in temperature 1273 K for 7.2 ks and aged in temperature 723 K for 7.2 ks. In the further part of this paper the interdiffusion in the 14-5 PH steel/Au–18Ni solder system is analyzed. A special attention is put on the Ni–Au system which is a base of the brazed joints. The objective of this study is to calculate the intrinsic diffusivities of Au and Ni which have been used for modelling of mass transport during vacuum brazing. The generalized darken method (GDM) of interdiffusion and the inverse method (IM) have been used for the calculations of the effective intrinsic diffusivities of Au, Ni and other elements. These diffusivities have subsequently been employed to compute the concentration profiles in the 14-5 PH steel/Au–18Ni solder system and been compared with the experimental results.
High-chromium (14–30%) cast iron alloy samples, with variations in the carbon and nickel content, were prepared in order to study their hardness, resilience, corrosion resistance, and wear behaviour by means of simulating the conditions found at the sugar industry processes. Microstructural characterisation of alloys was made by scanning electron microscopy (SEM), and electrochemical trials in order to assess corrosion susceptibility were performed with a specific sugar solution. Chemical analyses were carried out using atomic absorption to evaluate the deterioration with regard to the attack to chemical composition of alloys, wear, ionic solutions, and the microstructural changes undergone by the different alloys employed.The behaviour of alloys to wear and corrosion depends mainly on the chemical composition and effect of the alloying elements, the formation of carbides during solidification, and the presence of impurities and inclusions at a surface level.The results obtained in this study made possible the selection of better alloys, which can be employed at the sugar industry, such as 0.97C–29.5Cr–1.84Ni which has a high chromium content.
Surface quality and dimensional precision will greatly affect parts during their useful life especially in cases in which the components will be in contact with other elements or materials during their useful life. Therefore, their study and characterisation is extremely important and, above all, those cases subjected to adverse environmental conditions and in contact with other elements or materials. Thus, measuring and characterising surface properties represents one of the most important aspects in manufacturing processes. In this paper, a development of models which permit to determine surface quality of parts obtained through turning processes is carried out using the response surface methodology. To achieve this, surface quality of several parts manufactured through a material removal process such as turning will be studied by means of using profile rugosimeters. Basically, this will be done by varying cut conditions.
Grinding induces residual stresses, which can play an important role on the fatigue and wear resistance of the component. It is generally expected that conventional grinding leads to tensile residual stresses, while compressive stresses are obtained with high speed grinding (HSG). In this paper, a finite element thermomechanical model for the calculation of residual stresses induced by a surface grinding process on a steel workpiece (AISI 52100) is presented. A model giving the energy conducted as heat in the workpiece as a function of the grinding wheel speed, the workpiece speed, and the cutting depth is proposed. This model is available for conventional grinding for wheel speeds less than 120 m s−1. It is shown that, for such grinding conditions, the simulation leads to tensile residual stresses. Moreover, the computation shows that the temperature in the grinding area increases when the peripheral wheel speed increases too. So it is expected that for wheel speeds corresponding to HSG (>120 m s−1), the surface temperature can reach values leading to an austenitic transformation and therefore, during cooling, the workpiece can be subjected to a superficial quenching leading to compressive residual stresses. Finally, the present paper shows that the metallurgical phenomena in the grinding area must be surrounded and must be taken into account in future models.
SiC/Ti–15V–3Cr metal matrix composites have been developed using the hot uniaxial pressing of an assembly of Ti–15V–3Cr foils stacked between uniaxial fiber mats. The interfacial microstructures and interfacial reaction kinetics were analyzed with respect to the reactivates of the interface and the relevant elements involved. The recrystallization of the matrix materials played a great role in refining the matrix grain size, improving the diffusion bonding of the matrix/matrix interface as well as the fiber/matrix interface. A layer of chemical reaction products mainly consisting of titanium carbides was observed at the fiber/matrix interfaces. Limited reactions were observed compared with those that occurred in the SiC/Ti–6Al–4V system due to a lower processing temperature. This advantage was attributed to the temperature dependence of the reaction driving-force. Three types of reaction mechanisms were suggested based on the controlling kinetics of the reaction rate.
Extruded 6061-15 wt% SiCp composite was joined by transient liquid phase diffusion (TLPD) bonding process in argon environment using 50-μm thick copper foil interlayer. The bonding was carried out at 560 °C with two different applied pressures (0.1 and 0.2 MPa) and five different holding times (20 min, 1, 2, 3 and 6 h). Kinetics of the bonding process was significantly accelerated in the presence of reinforcement (SiC). This acceleration is attributed to the increased solute diffusivity through defect-rich SiC particle/matrix interface and porosity. Adequate bond strength (90% of the original composite strength) was achieved for bonding at 0.2 MPa pressure with 6 h of holding. This is very close to the reported highest bond strength achieved (92% of the original composite strength) for joining aluminium-based metal matrix composite by TLPD process in vacuum followed by isostatic pressing. The rejection of oxide at periphery on completion of isothermal solidification, and elimination of void at bond interface through solid state diffusion at higher pressure (0.2 MPa) were the main reasons of achieving high bond strength.
The intent of this paper is to show that a two-dimensional (2D) arbitrary Lagrangian Eulerian (ALE) finite-difference computer code can accurately predict the dynamics of the electromagnetic sheet metal forming process. The challenging aspect of simulating the deformation of thin metal parts which have been loaded by magnetic forces is solving a highly coupled system of partial differential equations. The material motion and the magnetic physics require two drastically different time steps to maintain numerical stability. The CALE computer code has the ability to solve such challenging problems. This paper highlights the CALE modeling of a number of electromagnetic sheet metal forming operations.
In order to make a machining process cost effective as well as to assure the desired objective(s), it is important to find the optimal machining parameter(s) in considering all related output variable(s). However developing many models (each one corresponding to a single output variable) leads to more time consuming as well as difficult to interact them. Moreover it has been observed that some of the output variables are inter-related with each other.In this paper, an intelligent approach based on fuzzy basis function neural network (FBF-NN) is proposed to model the cylindrical plunge grinding process. Two approaches are adopted here for automatic design of rule base (each rule is characterized by the antecedent and consequent parts) of FBF-NN using a genetic algorithm. In the first approach the rule-consequent parts are determined individually and in the second approach, those are obtained based on the inter-relationship exist among the output variables. The results of the FBF-NNs and that obtained using the empirical expressions are compared with the real experimental values, which shows that the FBF-NN-based models give better predictions than mathematical models.
Tests of the vacuum brazing joints of WC–Co sinters and age-hardened steels of the 17-4 PH using the Cu solder were carried out. Stresses and strains of the joints have been analysed. The joints have been used in large dimension spinning nozzles of a die for polyethylene granulation, in that considerable strength and ductility of the joints are required. Shearing tests of the joints have been executed on specimens done in the spinning nozzle brazed joint model. The results of mechanical properties of the joint tests were a base for the fooling them numerical investigations. Numerical calculation of tensions and deformations of the joints have been made by means of the finite element method of the ADINA system. Influence of the geometrical parameters of the joints like the connection thickness as well as a fixed load on stresses and displacements of the joints have been analysed. Results of the experimental test were the base for identification and verification of the theoretical model parameters. The thickness of the joints has an essential influence on the values of the local stress and the significant influence on the joint rigidity. In a case of the considered joints the values of the local stress differences have been considerable (a few hundred percent) in dependence of a fixed load manner.
Grinding is an industrial process that produces engineering components with a desired surface finish. Prior to the development of continuous dressing operations, the grinding efficiency of vitrified grinding wheels deteriorates as the sharp cutting edges become blunt due to the formation of wear flats. Dressing is essentially a sharpening operation designed to generate a specific topography on the working surface of the grinding wheel. The use of high power lasers is being explored as a non-contact cleaning and dressing technique. In the present study, a high power laser was used to clean metal chips from the surface of the grinding wheel and to dress the wheel by causing phase transformations to occur on the surface of vitrified grinding wheel. Experimental results indicated that laser modified grinding wheels are comparable in performance to conventionally cleaned and dressed grinding wheels.
Top-cited authors
M.s.J. Hashmi
  • Dublin City University
E. O. Ezugwu
  • National Universities Commission Abuja Nigeria
J. Paulo Davim
  • University of Aveiro
Leszek Adam Dobrzanski
  • Medical and Dental Engineering Centre for Research, Design and Production ASKLEPIOS Ltd in Gliwice, Poland
A. Erman Tekkaya
  • Technische Universität Dortmund