Добірка наукової літератури з теми "Aluminum-steel pair"

A type of new environmentally friendly lube additive---boron-nitrogen modified soybean oil was synthesized and characterized by infrared spectrum. Its effect on the friction and wear behavior of steel-steel and steel-aluminum alloy systems were investigated with a four-ball machine and an Optimol SRV friction and wear tester respectively. The morphographies of the worn surfaces were analyzed by means of scanning electron microscopy (SEM).The worn surfaces of the 2024Al alloy block were analyzed by means of X-ray photoelectron spectroscopy (XPS).The results show that the type of modified soybean oil as additives can obviously decrease the wear rate and friction coefficient of steel pair and steel-aluminum frictional pair. Its lubrication mechanism is inferred that a high strength adsorption film and/or tribochemistry reaction film on the worn surface of the Al alloy due the carrier effect of a long chain soybean oil, high reaction activities of nitrogen, electron-deficient of boron and their synergisms.

When using light-alloy drill pipes (LAIDP) with steel tool joints, the development of contact corrosion is observed under certain operating conditions. The value of corrosion mainly depends on the difference in electrochemical potential (ECP) of the contacting metals. One of the effective methods for increasing the corrosion resistance of aluminum alloys is the micro-arc oxidation (MAO) method. This is an electrochemical process in combination with micro-arc-discharges phenomena at the anode-electrolyte border, which allows forming ceramic coatings of aluminum oxides on the surface, including its high-toughness and wear-resistant phase - α-Al2O3 (corundum). MAO-technology is a highly efficient and environmentally friendly process. At the forming of such a coating on the threaded part and in the tool joint zone of the pipe, a barrier for contact corrosion between the steel tool joint and the surface of the aluminum pipe is created. In this work, contact corrosion on samples in a pair of 1953T1 aluminum alloy - 40KhN2MA steel in a 5% NaCl solution at 80 °C was investigated. The data obtained showed the effectiveness of using protective MAO-coating to reduce contact corrosion and increase the reliability of the tool joint threaded connection of LAIDP.

This paper presents the design and development of miniature coils for wireless power and data transfer through metal. Our coil has a total size of 15 mm × 13 mm × 6 mm. Experimental results demonstrate that we can harvest 440 mW through a 1 mm-thick aluminum plate. Aluminum and stainless-steel barriers of different thicknesses were used to characterize coil performance. Using a pair of the designed coils, we have developed a through-metal communication system to successfully transfer data through a 1 mm-thick aluminum plate. A maximum data rate of 100 bps was achieved using only harvested power. To the best of our knowledge, this is the first report that demonstrates power and data transfer through aluminum using miniature coils.

Aluminum alloys are widely used in mechanical engineering due to their physical and mechanical properties. However, their low wear resistance and burr resistance limit their use in friction nodes. In this regard, parts made of aluminum alloys operating under conditions of sliding friction require surface strengthening, which determines the friction wear parameters. Research works in this direction allow increasing the reliability and service life of friction nodes. Ensuring the compatibility of friction pairs allows reducing the coefficient of friction and, as a result, to increase wear resistance. One of the effective methods of forming wear-resistant coatings on aluminum alloys is the method of micro-arc oxidation (MAO). The use of micro-arc discharges as highly concentrated energy sources to create conditions for high-temperature electrotechnical processes and phase transformations in the surface layer makes it possible to form structures based on high-temperature oxides on the surface of metals, which provides qualitatively new surface properties: high hardness, wear resistance, corrosion resistance in various environments. However, the use of oxide coatings in bearings is mainly due to their high wear resistance and corrosion resistance. Information on the antifriction properties of aluminum oxide-based coatings is limited. The purpose of this work is to determine the coefficient of friction of MAO-coatings on D16 aluminum alloy in a pair with cast iron, steel and MAO-coating under conditions of oil and water lubrication, and to find out the feasibility of using MAO technology to create sliding bearings. The formation of MAO coatings was carried out in an alkaline-silicate electrolyte in the cathodic-anodic mode. The structure and morphology of the working layer of the MAO-coating surface, which works in friction pairs with cast iron, steel and MAO-coating under conditions of oil and water lubrication, was investigated. The benefit of the available porosity of the working layer of the MAO coating, which is 5-10% and contributes to the retention of lubricant in the friction zone, is shown. The phase composition, hardness of the coatings were studied and the coefficient of sliding friction was determined on the SMC-2 friction machine according to the "disk-pad" scheme when using water and oil as lubricants; the load varied from 0.2 to 2 kN, the nominal pressure from 1 to 11 MPa. It was established that the MAO coating has a crystalline structure, the phase composition is high-temperature modifications of aluminum oxide (α-Al2O3 and γ- Al2O3), and the hardness is 18000-20000 MPa. It was established that the coefficient of sliding friction of gray cast iron - MAO-coating, steel - MAO-coating and MAO on MAO decreases to the value of 0.01 - 0.013 under lubrication conditions. It was found that in a pair of MAO-coating - MAO-coating, anti-friction properties are manifested both under conditions of lubrication with oil and water. The low coefficient of friction for the coating-coating pair in the case of water lubrication is explained by the high hydrophilic properties of the oxide contacting surfaces, which makes it possible to recommend them for use in sliding bearings (liners) of hydroturbines. A conclusion was drawn regarding the reasons for the low coefficient of friction of the studied samples. Keywords: D16 aluminum alloy, cast iron, steel, micro-arc treatment, coating, phase composition, crystal structure, aluminum oxides, coating thickness, coating hardness, friction coefficient, antifriction properties

This research deals with the tribological behavior and corrosion performance of three novel fatty acid anion-based ionic liquids (FAILs): methyltrioctylammonium hexanoate ([N8,8,8,1][C6:0]), methyltrioctylammonium octadecanoate ([N8,8,8,1][C18:0]) and methyltrioctylammonium octadec-9-enoate ([N8,8,8,1][C18:1]), employed for the first time as neat lubricant with five different material pairs: steel–steel, steel–aluminum alloy, steel–bronze, steel–cast iron and steel–tungsten carbide. These novel substances were previously obtained from fatty acids via metathesis reactions, identified structurally via NMR (nuclear magnetic resonance) and FTIR (Fourier-transform infrared spectroscopy) techniques, and then characterized from a physicochemical (density, water solubility, viscosity, viscosity index and refractive index) and environmental (bacterial toxicity and biodegradability) points of view. The corrosion behavior of the three FAILs was studied by exposure at room temperature, while friction and wear tests were performed with a reciprocating ball-on-disc configuration. The main results and conclusions obtained were: (1) Corrosion in the presence of the three FAILs is observed only on the bronze surface; (2) All FAILs presented similar tribological behavior as lubricants for each tested material pair; (3) XPS (X-ray photoelectron spectroscopy) analysis indicated that the surface behavior of the three FAILs in each material pair was similar, with low chemical interaction with the surfaces.

The study objective is to define the influence of various modifiers on the tribotechnical properties of an aluminum and silicon alloy. Determination of the most optimal additives in alloys that would reduce the friction factor and increase the unit load at which friction pairs set in comparison with the starting material, as well as determination of their wear resistance. Research methods are tests conducted for friction and wear of samples based on aluminum and silicon according to the following: plane (test sample) – the sleeve end (steel 40X), as well as conducting tests with the supply of free abrasive into the friction zone according to the following: flat sample - forming surface of a rubber disc. Research results and novelty: the influence of modifiers in the aluminum and silicon alloy composition on wear resistance and friction ratio at different loads and sliding speeds in a friction pair with steel are established. Conclusions: the regularities of changes in the friction ratio from pressure and speed, the load of seizure from the sliding speed are obtained. The wear resistance of samples with various inclusions is higher compared to the base material.

The article presents the assessment of bioelectroproductivity of wetland sedge ecosystems of Carex acutiformis in situ. It was found that it is possible to obtain a bioelectric potential at the level of 864.2-1114.8 mV, depending on external conditions using a pair of electrodes graphite/zinc-galvanized steel and graphite/aluminum. The increase in soil moisture had a positive effect on bioelectric potential parameters. Widespread in Polissya biotopes of sedge have prospects as sources of green plant-microbial energy.

This paper presents the methodology and results of laser texturing of the surface layer steel 41Cr4, applied to the manufacture of crankshafts and selected aluminum alloy used for the production of slide bearings (bearings) for internal combustion engines. Laser treatment of the surface layer of this material was carried out using Nd: YAG laser with a wavelength of pulsed laser radiation λ-1064 nm. Application of laser ablation micromachining in sensitive zones of the crankshaft and slide bearing, mainly the surface layer of the friction pair, was aimed to formation of a suitable surface texture containing oil microchannels. Applying different parameters ablative laser micromachining (power density, repetition rate, number of pulses in the same area, the overlap area microchannels), a very interesting stereometry of the surface layer steel 41Cr4 and bearing alloy was obtained. The lubricant had characteristic microchannels, very important in the tribological process of the friction pair crankshaft – slide bearing. Laboratory metallographic tests showed the high dispersion microstructure of martensitic steel 41Cr4 in the superficial zone, melted and hardened. The transition zone was found to be of martensitic-bainitic microstructure and bainite. The microstructures are formed by ultrafast phase transformations over time crystallization of alloy Fe-Cr-C from the liquid phase (microhardness in the range of 550-680 HV0.05). The microstructures appear in the adjacent area to the lubricant microchannels produced during laser texturing. The studies of laser texturing the sliding layer of slide bearing made of aluminum alloy, destined to cooperate with tribological function pin engine crankshaft are preliminary results. The positive results: high repeatability of the process texturing regular geometric shape microchannels and ease process control. In the best version, technological preliminary tests showed the following oil microchannels dimensions: depth of about 3.2 microns, width 47 microns; it is a promising result.

Purpose This paper aims to investigate the tribological properties of two protic ionic liquids used as lubricity-improving additives in the water. Their concentration was optimized for different metal friction pairs including bearing steel, stainless steel and aluminum alloy. Design/methodology/approach In this study tribological properties were investigated by using a ball-on-plate reciprocating tribometer. Three different friction pairs were selected: bearing steel-bearing steel; bearing steel-stainless steel; bearing steel-aluminum alloy. To optimize the concentration of investigated protic ionic liquids four concentrations were selected. Wettability was investigated using the droplet method. The corrosiveness of additive-loaded water was investigated using the iron chip method. Findings The results show that by using protic ionic liquids the lubricity of water could be greatly improved. However, the friction pair material and additive concentration play a significant role. The positive tribological effect was attributed to the polarity of the additive molecule which tends to form an adsorption layer. The polarity of molecules also leads to better surface wettability. It was also found that both investigated protic ionic liquids can improve the anticorrosion properties of water. Originality/value To the best of the authors’ knowledge, this is the first study to present a complex investigation of tribological properties of two protic ionic liquids as additives in the water. In this case, three different metal friction pairs and four additive concentrations were investigated. The results could be interesting to those who are working in the field of water-based lubricants and luck for multipurpose lubricity-improving additives.

Les assemblages acier-aluminium de tôles minces (0,8 à 2 mm) ont été beaucoup étudiés au début des années 2000 pour des applications automobiles, dans la perspective d'alléger les véhicules (projet européen Super Light Car). Dans ce contexte, le présent travail est réalisé en vue d'étudier les possibilités d'assemblage hétérogène acier-aluminium par la nouvelle variante du procédé de soudage MIG connue sous l'appellation CMT (Cold Metal Transfer). La première partie de l'étude est consacrée à la compréhension du principe de fonctionnement de ce procédé, en utilisant une plateforme équipée d'un système d'acquisition de données permettant les mesures synchronisées de tension, intensité, vitesse fil et d'images vidéo prises par une caméra rapide. Dans une seconde partie, nous présentons les caractéristiques métallurgiques des assemblages acier/aluminium réalisés en configuration à clin avec des jeux de paramètres couvrant toute la plage étudiée dans la partie précédente. On s'intéresse plus particulièrement à la zone créant la liaison entre l'acier et l'aluminium. Dans une troisième partie, la tenue mécanique des assemblages est évaluée par des essais de traction transverse quasi-statique et sous chargement cyclique. La résistance à rupture de la couche de réaction est aussi évaluée par une technique originale, habituellement dédiée à l'évaluation de l'adhérence des revêtements par choc laser. Enfin, nous proposons une nouvelle méthode pour estimer le rendement du procédé CMT basée sur la simulation numérique par éléments finis de l'évolution des champs de température lors du dépôt d'un cordon d'aluminium sur un substrat d'acier galvanisé, couplée à la modélisation de la croissance de la couche de réaction formée le long de l'interface acier/aluminium
Joining of steel- aluminum thin sheets (0.8 to 2 mm) has been extensively studied in the beginning of 2000 years for automotive applications, in a regard to reduce vehicle weight (European Project Super Light Car). In this context, this work is carried out to study the possibilities of dissimilar steel-aluminum assembly by the new variant of the MIG welding process known as CMT (Cold Metal Transfer). The first part of the study is devoted to understand the operating principle of this process, using a platform equipped with a data acquisition system for synchronized measurements of voltage, current, speed wire feed and video images taken by a speed camera. In a second part, we present the metallurgical properties of steel-aluminum joints made in lap configuration with parameter sets covering the entire range studied in the previous section. We are especially interested in the area creating the connection between steel and aluminum. In the third part, the mechanical proprieties of connections are evaluated by quasi-static transverse tensile tests and under cyclic loading. The breaking strength of the reaction layer is also evaluated by an original technique, usually dedicated to the evaluation of the adhesion of coatings by laser shock. Finally, we propose a new method to estimate the efficiency of the CMT process based on the finite element numerical simulation of the evolution of temperature fields during the deposition of an aluminum weld on a galvanized steel substrate, coupled with modeling of the growth of the reaction layer formed along the steel / aluminum interface

Surface texturing to achieve reduced sliding friction has been a widely studied topic, as seen in contemporary literature. Laser surface texturing, grinding and ion beam milling are popular techniques accepted by researchers today for creating specific surface textures. Among these, grinding is a popular process adopted today in mass manufacturing around the world. In this study, we look at grinding as a method of surface texturing and studying the effect of various grinding parameters on the friction when sliding a relatively softer material against the generated surface. The system chosen was aluminum pins sliding against a stainless steel surface on which specific textures were generated. The specific system was chosen as an aluminum-steel pair is increasingly used in automobiles as weight reduction is a priority for automobile engine manufacturers today. Automobile engine manufacturers are increasingly shifting to aluminum cylinder blocks to make their power-trains lighter. The tribo-system was lubricated with the mineral base oil used in a SAE 30 grade engine oil blends. The tribo-system was in reciprocating sliding motion, driven by a scotch yoke mechanism similar to that used in a reciprocating internal combustion engine. Though aluminum-silicon alloys and steel are widely used in engines, pure aluminum and stainless steel was chosen in this study for a fundamental understanding of the different parameters involved in an aluminum-steel tribo-system. Aluminum being softer than Al alloys will deform at the asperity level and in oxidation will be much lower in stainless-steel, thus avoiding tribo-oxidation mechanisms operating. Different topographies were created on stainless steel using the conventional grinding methods and differentiated for their effect on sliding friction using a reciprocating tribometer. Different surface topographies were created on a lab scale table grinder using coated abrasive sheets. Sliding friction between an aluminum pin and these stainless steel flats under contact pressures not exceeding 7.5 MPa (similar contact pressures existing in an IC engine – This has to be checked) were tested in a s parsely lubricated sliding environment. Certain surface topographies showed an extraordinary reduction in the average coefficient of sliding friction. The average surface roughness of the topographies that showed lower friction was not different from topography of others that showed higher friction. Separate topographies were created on the stainless steel mirror finished countersurface corresponding to P1200, P320 abrasive disc. Group 1 virgin mineral base oils viz. SN500, SN150 and SN60 with viscosities 100, 30 and 12 cSt at 40 deg C were used. The topographies when tested for cycle average coefficient of friction revealed that P1200 finished surface showed an exceptionally low value under 0.02. In a scotch yoke mechanism, the velocity varies according to a sine curve with maximum velocity occurring at the center and with zero velocities at the ends. This would mean that the lubrication regimes, as given by the Stribeck curve would change from boundary lubrication at the ends to a possible hydrodynamic lubrication when the velocity reaches a maximum. Therefore, it was decided to understand the evolution of the frictional force response of these topographies for each reciprocating cycle. When the individual cycle friction force response was examined in greater detail along with other components in the tribo-system, it was found that the behavior of these plots was significantly different from those predicted by classical Stribeck principles. For the mirror finished stainless-steel flat surface while sliding with the aluminum pin at 1Hz or 40 mm/s average sliding velocity showed a frictional force plot as shown in figure I below. The alternating “M” and “W” patterns corresponded to the frictional force variations when the velocity of sliding varied in a sinusoidal manner corresponding to the velocity profile of the scotch yoke follower mechanism. This variation could be explained well using the classical Stribeck curve where coefficient of friction is expected to reduce as the velocity is increased from zero at the extremes of the track to a maximum at the center of the track, which is defined by the amplitude and frequency of reciprocation. When a P1200-finished surface was tested for 1800 cycles at the same average velocity, the frictional force was as shown below in figure II. The plots showed extremely low frictional force. Frictional force corresponding to the accelerating region was the only response visible and the rest of the cycle approached near zero frictional force. Different average velocities of sliding, viz. 12 mm/s, 40 mm/s, 80 mm/s and 200 mm/s corresponding to 0.3Hz to 1Hz, 2Hz and 5Hz reciprocating frequencies respectively were tested. The tests were carried out for the same number of cycles for a P1200 finished surface. As the sliding velocities were increased from 1 Hz to 5Hz, faster transitions to a steady state was observed. At 1Hz, the system reaches a steady state at about 1000 cycles. At 2Hz, the steady state was reached after around 500 cycles and at 5Hz, the system seemed to reach the steady state from the initial few cycles. It was felt that there were some modifications happening on the aluminum pin surface and/or stainless steel flat countersurface as the test progressed. This change happens at a faster rate and the system reached a steady state faster when the relative velocities of sliding were higher. Thus, for the test conducted at the lowest frequency of 0.3Hz there was no change in the shape of the frictional force plots till the end of the test and friction remained high. The above tests were also done for other topographies viz. mirror and P320 finished surfaces. At velocity corresponding to 5Hz, even the mirror finished surface exhibited extremely low friction and showed nearly flat friction response curves. At low velocities corresponding to 0.3Hz, the adherence to the Stribeck curve phenomenon was seen for all three topographies. It was also observed that a critical film thickness had to be exceeded for this phenomenon of friction reduction to take place. It was found that either an increase in sliding speed or an increase in the oil viscosity enabled the tribo-system to achieve this minimum critical film thickness. Critical three-dimensional areal surface parameters were found out for these topographies using an optical profilometer, and a few parameters governing the shape of these frictional plots were identified. It was found that surface parameter ratio Spk/Sk, where Spk is the reduced peak height and Sk is the core roughness depth, could predict the shape and magnitude of the frictional Fx forces under sliding reciprocating motion for the above tribosystem. Conventionally Spk/Sk ratio is used to distinguish surface topographies which cannot be distinguished by the characteristic average surface roughness and root mean square surface roughness parameters. Spk/Sk highlights the importance of peak structures on a topography. The volume occupied by the peaks in relation to the core roughness and the symmetry in the texture amplitude increased with increase in this surface parameter ratio. Three different types of topographies generated using the same abrasive disc: P320, by using different amounts of grinding fluid (here water) were studied. Conventional surface parameters like average surface roughness and root mean square roughness could not distinguish these three surfaces. However, using the ratio Spk/Sk, it was found that two of these surfaces had Spk/Sk ratio less than 1, and the other surface had this ratio greater than unity. Where the ratio Spk/Sk was less than 1, the frictional force plots did not reduce with the number of cycles and showed adherence to classical Stribeck curves with alternating “M” and “W” shapes. Where Spk/Sk ratio was greater than 1 the friction force reduced with the number of cycles, as seen in figure I and almost became flat and near zero at steady state. It was found that the topography of the stainless-steel countersurface had an influence on the evolution of the aluminum pin topography during sliding. Where the friction force curves resembled figure I, the pin topographies got modified as the Spk/Sk value shifted to a value greater than 1; it was also observed that an evenly spread layer of iron was dispersed on the pin face after the system reached steady state. Where the friction force curves did not reduce with the number of cycles (figure II), there was neither a change in the pin topography nor formation of any tribo-layer as noted above. It was also found that this progressive tribo transfer layer was selectively formed on the pin surface when the friction was extremely low. Some physical explanations have been developed for why the value of the Spk/Sk parameter is important in determining friction in this mating combination. The importance of the pin topography and tribo-layer was evident from different shapes of the frictional force plots with changing pin topographies. When a mild abrasive was used to abrade the pin face after the system reached the steady state, the tribo-layer formed on the pin face was removed and the topography also changed. An immediate shift in the shape of the force plots when the test resumed. Here it was also found that rubbing such a pin on a “used” flat face did not bring the system back to steady state even after continued sliding in successive tests. However, shifting the pin to a “virgin” flat face on the same topography brought the system back to steady state. The sharp tipped peaks on “virgin” stainless-steel flat topography fractured while in sliding contact with the pin and contributed to the quick reformation of the tribo-layer on the countersurface of the pin. It was also found that wear debris did not have any contribution to the shape of the Fx plots. It follows that a combination of the pin topography observed at steady state and the tribo-layer is responsible for reduction in sliding friction to such a low level for certain topographies

This chapter introduces advanced aluminum alloy matrix composites and their manufacturing processes. In the beginning, the state of the art is characterized and the general characteristics of aluminum and its practical applications are presented, starting with the history of aluminum. The current approximate distribution of bauxite resources in the world and the production of bauxite and alumina in the leading countries of the world, as well as the production of primary and secondary aluminum and the range of aluminum end products, are presented. Aluminum alloys intended for plastic deformation and castings, and composite materials in general and with a matrix of aluminum alloys in particular, have been characterized in general. Against this background, a detailed review of the results of the Author’s own research included in numerous projects and own publications on advanced composite materials, their production technology, their structure, and properties were done. The range of aluminum alloy matrices of composite materials was adequately characterized, which include AlSi12, AlSi7Mg0.3, AlMg1SiCu, AlMg3, AlMg5, and AlMg9, respectively. Composite materials tested in terms of manufacturing technology include three groups. The first group includes gas pressure infiltration with liquid aluminum alloys of suitably formed porous preforms. Porous frameworks as a reinforcement for pressure-infiltrated composite materials with a matrix of aluminum alloys are produced by three methods. Al2O3 powder with the addition of 30–50% carbon fibers is uniaxially pressed, sintered, and heated to thermally degrade the carbon fibers and create the required pore sizes. In the second case, the ceramic porous skeleton is produced with the use of halloysite nanotubes HNTs by mechanical milling, press consolidation, and sintering. A third method is SLS selective laser sintering using titanium powders. Another group of manufacturing technologies is the mechanical synthesis of the mixture of AlMg1SiCu aluminum alloy powder and respectively, halloysite nanotubes HNTs in a volume fraction from 5 to 15% or multi-wall carbon nanotubes MWCNTs in a volume fraction from 0.5 to 5%, and subsequent consolidation involving plastic deformation. The third group of analyzed materials concerns composite surface layers on substrates of aluminum alloys produced by laser feathering of WC/W2C or SiC carbides. The structure and properties of the mentioned composite materials with aluminum alloys matrices are described in detail. The chapter summary provides final remarks on the importance of advanced aluminum alloy composite materials in industrial development. The importance of particular groups of engineering materials in the history and the development of the methodology for the selection of engineering materials, including the current stage of Materials 4.0, was emphasized. The importance of material design in engineering design is emphasized. Concepts of the development of societies were presented: Society 5.0 and Industry 4.0. The own concept of a holistic model of the extended Industry 4.0 was presented, taking into account advanced engineering materials and technological processes. Particular attention was paid to the importance of advanced composite materials with an aluminum alloy matrix in the context of the current stage of Industry 4.0 of the industrial revolution. Growth in the production of aluminum, its alloys, and composites with its matrix was compared with that of steel. Despite the 30 times less production, aluminum is important due to its lower density. The challenges posed by the development in the Industry 4.0 stage, including the expectations of the automotive and aviation industry, force constant progress in the development of new materials with the participation of aluminum, including the composite materials with an aluminum alloy matrix presented in this chapter.

Abstract The solid-state welding method was applied under atmospheric conditions by using metal powder medium which was interposed in the space between the two solid bars of specimen (i.e., base metal), and was compressed longitudinally and simultaneously current was conducted to generate Joule thermal heat. Some fundamental data on the mechanical and metallurgical properties of the joint were obtained by using resistance welding. In the experiments, the specimen materials used as base metals in this study were pure aluminum, stainless steel and titanium bars of solid, and the powder media were aluminum, nickel and silicon powder. The mixed silicon powder medium increases electric resistance between base metals, moreover, to obtain mechanical properties. Four experiments were conducted with different specimen; The first experiment used two solid aluminum specimen bars with aluminum powder medium. The second, two solid aluminum specimen bars with mixed aluminum and nickel powder media. The third, two solid aluminum specimen bars with mixed nickel and silicon powder media. And the fourth, solid specimen were different materials and had relatively different melting points. Such as solid aluminum and stainless steel (SUS430) with mixed nickel and silicon powder media, and solid aluminum and titanium with mixed aluminum and nickel powder media. Data were obtained with the intent of optimizing the method using powder medium between a pair of solid sample specimen and observation, analysis and assessment were made with microscope. Scanning Electron Microscope (SEM), Energy Dispersive X-ray spectroscopy (EDX). X-ray Diffraction (XRD), tensile strength, Vickers hardness and bending U-shape flexure tests.

In the present study plate-impact pressure-shear friction experiments were employed to investigate dynamic slip resistance and time-resolved growth of molten metal films during dry metal-on-metal slip under extreme interfacial conditions. By employing tribo-pairs comprising hard tool-steel against relatively low melt-point metals such as 7075-T6 aluminum alloy, interfacial friction stress of up to 300 MPa and slip speeds of approximately 250 m/s have been achieved. These relatively extreme interfacial conditions are conducive to the development of molten metal films at the tribo-pair interface. A Lagrangian finite element code is developed to understand the evolution of the thermo-mechanical fields and their relationship to the observed slip response. The code accounts for dynamic effects, heat conduction, contact with friction, and full thermo-mechanical coupling. At temperatures below the melting point the material is described as an isotropic thermally softening elastic-viscoplastic solid. For material elements with temperatures in excess of the melt temperature a purely Newtonian fluid constitutive model is employed. The results of the hybrid experimental-computational study provide new insights into the thermoelastic-plastic interactions during high speed metal-on-metal slip. During the early part of friction slip the coefficient of kinetic friction is observed to decrease with increasing slip velocity. During the later part transition in interfacial slip occurs from dry metal-on-metal sliding to the formation of molten A1 films at the tribo-pair interface. Under these conditions the interfacial resistance approaches the shear strength of the molten aluminum alloy under normal pressures of approximately 1-4.5 GPa and shear strain rates of ~ 107 s-1. It is interesting to note that the dynamic shear resistance of molten metal films decreases from ~100 MPa to ~50 MPa when the initial slip velocities increase from ~100m/s to ~250 m/s. Scanning electron microscopy of the slip surfaces reveal molten aluminum to be smeared on the tribo-pair interface. Photo-micrographs of the cross-section of the 7075-T6 A1 alloy reveals a thin region of severe shearing deformation in close vicinity of the sliding surface. The shearing deformation manifests itself as severely deformed grains in the direction of the sliding.

This paper presents the design and analysis of a cantilever beam resonator that is driven by a piezoelectric material. The beam is a bimorph structure with Lead Zirconate Titanate (PZT) and stainless steel or aluminum layers. The PZT layer is electroded in segments to form a sensor and actuator pair for feedback to drive the resonator. An additional PZT segment is used, in conjunction with a capacitive shunt circuit, to change the vibration frequency of the resonator. The study is based on an analytical model of the beam and experimental testing.

An electrical resistance welding method was applied under atmospheric conditions by using one of metal powder medium or media mixture which was sandwiched in the space between the two solid metal bars of specimen (i.e., solid specimen material), and was compressed longitudinally by oil pressure servo control electrodes (upper and bottom) and simultaneously current was conducted to generate Joule thermal heat. In the joining experiments, a solid aluminum specimen material was used as a basis material, and was joined to another solid aluminum specimen material or one of four other solid specimen materials with different melting points by using resistance-welding apparatus. Some fundamental data on the mechanical properties of the joint were obtained by material testing. In the experiments, the specimen used as solid specimen materials in this study were pure aluminum, copper, stainless steel, carbon steel and titanium bars of solid specimen, and the powder media were aluminum, nickel and silicon powder. Proper mixed ratios of total amount of the powder media were determined for reliable joining, and material testing was prepared for mechanical properties. The obtained data were examined with the intent of optimizing the method using metal powder media between a pair of specimen materials and were compared with that of the solid specimen material, in terms of tensile strength, Vickers hardness, bending U-shape flexure stiffness. On the tensile strength and Vickers hardness, they were found to be reliable, but on bending U-shape flexure stiffness, they were not definite enough.

The tribological behavior of AA5083 aluminum sheet sliding against tool steel impacts the quality of components manufactured with the Quick Plastic Forming (QPF) process. The effect of boron nitride lubricant thickness on the tribological performance of different coated steel/AA5083 pairs utilizing a recently developed reciprocating flat-on-flat tribological test technique was investigated. In most cases of coated and uncoated steel, the time-to-contact increased by a factor of ten when the BN thickness was increased from 8.4 μm to 14.5 μm. The tribological tests with a low sliding speed method (0.1 Hz) confirmed the previous observations conducted at 0.5 Hz in which nitrocarburizing of the tool surface decreased adhesion of aluminum to the steel during sliding contact.

Abstract Detonation sprayed coatings are nowadays applied on many kinds of heavily loaded sliding pairs and in the case high-speed machines. The basic problem in such applications lies in their durability and their scuffing resistance. Detonation sprayed coatings have a different in comparison with other junction surfaces microstructure and their behaviour in boundary condition let us better estimate possibilities of their application. This paper deals with the findings from experiments with regard to the seizure phenomenon when the friction pairing embodies an element with detonation-sprayed coatings. The progression of seizure is examined and evaluated for a number of aluminum oxide-13 titanium dioxide WC-Co 88/12 coatings that were applied to steel by means of detonation spraying. Paper includes a German-language abstract.

Theoretical models and MD simulation studies suggest that dissolved salts tend to alter the surface tension at liquid vapor interfaces and affect the stability of the free liquid film between adjacent bubbles. Recent modeling of the Leidenfrost phenomenon also indicates that bubble merging is a key mechanism affecting the Leidenfrost transition conditions. This investigation summarizes the results of an investigation of the effects of dissolved salts on liquid film stability and bubble merging in the aqueous solution. The interaction of pairs of bubbles injected into solution with different dissolved salt concentrations was studied experimentally to determine the probability of merging from statistics for ensembles of bubble pairs. The results of these experiments indicate that very low dissolved salt concentrations can strongly reduce the tendency of adjacent bubbles to merge, implying that the presence of the dissolved salt in such cases strongly enhances the stability of the free liquid film between adjacent bubbles. The trends are compared to predictions of free liquid film stability by wave instability theory and MD simulations. These trends are also compared to experimental data indicating the effects of dissolved salt on the Leidenfrost transition. These comparisons indicate that the suppression of merging due to the effects of some dissolved salts can significantly alter the Leidenfrost transition conditions. The implications of this in quenching of cast aluminum or steel parts using water of variable hardness are also discussed.

Simulation accuracy of large strain deformation of sheet metals, such as that which occurs during hemming and vehicle crash situations, is limited because existing hardening laws (true stress vs. true strain relationships) are extrapolated from uniform elongation data and applied for post-uniform deformation. In this paper, a reverse-engineering method was developed to predict metal hardening laws at large strains beyond uniform elongation for sheet metals. The method required a standard uniaxial tensile test and finite element analyses (FEA), and was implemented as a custom computer code called GMSS (General Motors Stress-Strain). The true stress vs. true strain data pairs are determined when the load and displacement history of a tensile test specimen matches the FEA results using GMSS. Test cases showed that the true stress vs. true strain relationships at very large strains (75% for AA6111 aluminum, and 85% for DP600 steel) could be automatically generated using GMSS. This reverse-engineering method will provide General Motors with an easy-to-use tool for generating very accurate metal hardening laws for post-uniform deformation that can greatly improve the accuracy of FEA for formability (including hemming), and crashworthiness simulations.

Due to the long-term durability and the excellent resistance to aging degradation, metal gaskets are expected to endure a longer life compared to conventional polymer gaskets. However, the nature of high elastic modulus of the metal reduces the sealing performance at interface. The authors have paid attention to the super elasticity of the shape memory alloys like Nickel-Titanium (Ni-Ti) alloy and evaluated its applicability to a gasket. In the process, leakage tests of the flange connections with Ni-Ti alloy gaskets were done and the sealing performance was evaluated with the new gasket constants and the tightness parameter proposed by PVRC (Pressure Vessel Research Council, ASME). The results revealed that Ni-Ti alloy gaskets showed a superior sealing performance to the conventional aluminum gasket. However, the thermal expansion coefficient of Ni-Ti alloy is smaller than that of stainless steel of which the flange is made. The increase in temperature of the flange like 20 °C to 40 °C accordingly induced a slight degradation of the sealing performance. In this paper, the effect of the change in temperature on the sealing performance of the pipe flange connections with Ni-Ti alloy gasket was numerically evaluated with the measured thermal expansion coefficient. Moreover, the effect of the clamped temperature on the sealing performance was evaluated taking into account the temperature dependence of the mechanical properties of Ni-Ti alloy.

Friction Stir Welding (FSW) has been widely commercialized to join aluminum alloys, but is yet to be broadly applied to structural steels. The primary difficulty in welding steels relates to severe loads and temperatures experienced at the interface between the FSW tool and the base material. These conditions are challenging even for the most advanced and expensive tool materials. However, within the last five years, tool advancements have begun to enable FSW of steels. Polycrystalline boron nitride (PCBN), tungsten-rhenium alloys, and mixtures thereof appear to be capable of producing sound welds in steel. This paper describes the results of a continuing study on the FSW of pipeline steels. Pipe grades from API X65 to X120 were subjected to FSW. Strength and toughness measurements using the crack tip opening displacement test were performed. The weld microstructure was evaluated using optical, scanning electron, and transmission electron microscopy. A computational fluid dynamics model was developed to better understand the effect of process parameters on thermal cycles, strain rates and strain experienced by material in the weld stir zone. The results indicate that the microstructure and properties of the welds have little dependence on the tool material, while significant variations in properties were observed between steels produced by different manufacturers. In general, obtaining high levels of toughness on par with gas metal arc mechanized girth welds appears difficult when using the FSW process. The results emphasize the need for a better understanding on the role of process parameters on microstructural evolution and weld quality during FSW of pipeline steels. As a full-scale demonstration of FSW on pipeline steels, several circumferential girth welds were produced in 762 mm (30 inch) diameter X80 pipe. The results of these efforts are discussed.