Surface film adsorption and lubricity of soybean oil in-water emulsion and triblock copolymer aqueous solution: A comparative study

This paper investigates the surface film adsorption and lubricity of two different types of potential environmentally friendly cold metal forming lubricants: soybean vegetable oil in water VO/W emulsions and triblock copolymer aqueous solutions. The lubricants have different visual appearance, surface film adsorption characteristic, lubricity and surface cleaning behaviour. The effects of concentration, temperature and emulsification ultrasonic energy (for VO/W emulsion) are studied. The result shows that the soybean VO/W emulsions have stronger adsorption, superior lubricity and anti-wear property compared to the copolymer solutions. The effect of temperature is investigated at 30 °C and 65 °C which are below and above cloud point of the aqueous copolymer solutions. Both lubricants show improved friction and anti-wear property at 65 °C. However, tenacious residual film remained on the discs surface after surface cleaning indicates lower cleanability of the soybean VO/W emulsions compared to the copolymer solutions, postulating the need for extra post-processing cleaning operations after cold forming process with VO/W emulsion lubricant

Integrated Condition Monitoring and Prognosis Method for Incipient Defect Detection and Remaining Life Prediction of Low Speed Slew Bearings

This paper presents an application of multivariate state estimation technique (MSET), sequential probability ratio test (SPRT) and kernel regression for low speed slew bearing condition monitoring and prognosis. The method is applied in two steps. Step (1) is the detection of the incipient slew bearing defect. In this step, combined MSET and SPRT is used with circular-domain kurtosis, time-domain kurtosis, wavelet decomposition (WD) kurtosis, empirical mode decomposition (EMD) kurtosis and the largest Lyapunov exponent (LLE) feature. Step (2) is the prediction of the selected features\u27 trends and the estimation of the remaining useful life (RUL) of the slew bearing. In this step, kernel regression is used with time-domain kurtosis, WD kurtosis and the LLE feature. The application of the method is demonstrated with laboratory slew bearing acceleration data

Lubricant as a sticking-scale inhibitor on high temperature sliding contact

Sticking oxide scale is one of the most serious concerns on moving steel surfaces at elevated temperature. However, there has been limited research dedicated to overcoming this issue. In the present work, pin-on-disc testing was carried out to reveal the effects of lubrication on wear characteristics of High Speed Steel sliding against Stainless Steel 316 at 700 °C. Apart from improved friction behavior, the use of inorganic lubricant significantly inhibits material transfer onto the HSS surface which otherwise suffers growing adhered scale during dry sliding contact. In addition, it was found that prolonged exposure to lubrication induces phase transformation of the subsurface iron oxides. The Hematite-to-Magnetite conversion is believed to be a result of complex oxidation and tribological reactions. Multiple characterization techniques were used to thoroughly analyze the worn surfaces, the underlying oxide microstructure and the chemical nature of lubricated interface

Coupled effects of initial orientation scatter and grain-interaction to texture evolution: a crystal plasticity FE study

Grain orientation and neighbourhood are two main factors that determine the in-grain and global texture. The coupled effects of them to texture evolution has not been well understood. In this work, initial orientations scattered from exact Cube at four different levels (2 ° , 5 ° , 20 ° and 45 ° ) were developed, running from near single crystal to polycrystal, which yielded grain-interaction at various grades. A crystal plasticity finite element model was developed and the predicted texture after a 50% and 75% reduction has been validated by experimental observations of both single crystals and polycrystals. When the deviation angles are small, the global texture is similar to that in exact Cube, where crystal rotation about transverse direction is dominant. Initial orientations of large scatter and grains of strong interaction led to high crystal rotations and the formation of rolling texture. To study the grain-interaction to specific grains, the orientations of neighbouring grains were replaced. It was found that texture evolution in the region close to grain boundaries is sensitive to grain-interaction, while crystal rotations in the inner region are basically determined by the initial orientation

Correlation Between Crystal Rotation and Redundant Shear Strain in Rolled Single Crystals: A Crystal Plasticity FE Analysis

The correlation between crystal rotation and redundant shear strain in rolled single crystals was investigated by using the crystal plasticity finite element (CPFE) model in this paper. The deformation in aluminium single crystals of four representative orientations (rotated-Cube, Goss, Copper, and Brass) after rolling and plain strain compression was simulated, and the predictions have been validated by the experimental observations. In the rotated-Cube and Goss, the redundant shear strain and crystal rotation were in the same pattern, alternating along the thickness, while the relation between them was not obvious for the Copper and Brass due to their asymmetrical distributions of activated slip systems. The relations between slip system activation, crystal rotation, and shear strain were investigated based on the CPFE model, and the correlation between shear strain and crystal rotation has been built

Understanding the tribological impacts of alkali element on lubrication of binary borate melt

Melt lubricants have been regarded as an effective class to deliver lubrication on moving mechanical contacts at extreme temperatures. Among the elementary constituents, alkali elements play a critical role in governing the physical-chemical characteristics of the lubricant despite the obscurity regarding their intrinsic roles on the rubbing interfaces. The present study attempts to unfold the effects of sodium on the tribological responses of mating steel pair under borate melt lubrication. It has been found that the involvement of Na inspires a total reversal in lubricating potentials of the lone B2O3melt manifested by remarkable friction reduction, wear inhibition and prolonged load-bearing capacity. These exceptional performances are attributed to the accretion of nanothin Na layers on the contact interfaces. The interfacial occurrences are interpreted from a physico-chemistry perspective while the influences of surface microstructure are also discussed in detail. Multiple characterizations are employed to thoroughly examine the sliding interfaces in multi-dimensions including Scanning Electron Microscopy (SEM), Scanning Transmission Electron Microscopy (STEM) and Atomic Force Microscopy (AFM). In addition, chemical fingerprints of relevant elements are determined by Energy Dispersive Spectroscopy (EDS) and Electron Loss Energy Spectroscopy (EELS)

Insights into the behavior of polyphosphate lubricant in hot rolling of mild steel

Hot rolling with a large reduction is usually performed to produce the fine-grained strips, which leads to a severe wear of work roll and affect substantially the strip quality. As a result, lubricants are usually introduced to reduce these problems, with inorganic polyphosphate glass polymer showing the most promising prospective. This study aims to provide a new insight into the lubrication film at roll/strip interface in hot rolling. A series of lubricated hot rolling tests were performed by a 40wt% sodium metaphosphate aqueous solution under 20-60% reduction, at 950-1150 °C and 0.5 m/s. Thermal behaviors of sodium polyphosphate and the rolled strip samples were analyzed by high temperature laser confocal microscope, Secondary Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDX), Focused Ion Beam (FIB) and Transmission Electron Microscopy (TEM) etc. The results reveal that the lubrication film thickness at the roll/strip interface varied from 0.6 to 4.3 µm with the rolling load being reduced up to 6.1% and friction coefficient up to 16%. FIB and TEM analysis reveal that the polyphosphate film has an amorphous structure which was penetrated through by the oxide scale. It had been found that the polyphosphate lubrication performance was improved at a higher reduction and temperature, which contributes to the friction and oxidation-reduction

Micro Cup Drawing without Wrinkles Using a Bulged Punch

A novel Bulged Punch (BP) was successfully performed for wrinkle elimination in micro cup drawings of AA1235 foils. BP was used to create a specific enlarged gradual punch profile before wrinkles began to occur until the end of the stroke, with fully annealing of AA1235 occurring before accumulative roll bonding (ARB), asymmetric rolling (AR), and stress relieving of a rolled blank, and deep drawing. The research purpose is to create a micro cup without wrinkles. The method was studied via experimentally deep drawing a blank thickness of 300 mm with pairs of dies-BPs supported by a press tool. Blanks were processed under (a) ARB 4 and 6 cycles, (b) combined ARB with AR and (c) post-heat-treatment. The process was selected when a force (F) from the simulation matched with the measured value. The results showed that BP can simultaneously eliminate the occurrence of wrinkles at the cup edge, reduce the earing occurrence, increase cup corner thickness, and decrease the edge thickness. Simulation models were built using the finite element method software LS Dyna, which supports experimental evidence. The findings imply that BP can successfully eliminate wrinkles at the cup edge

Microstructure and mechanical properties of large-volume gradient-structure aluminium sheets fabricated by cyclic skin-pass rolling

Materials of a gradient structure have been shown to possess both high strength and high ductility. To date, materials of a gradient structure can only be produced in small quantities. In this paper, we report a novel \u27cyclic skin-pass rolling\u27 (CSPR) technique capable of producing sheets of gradient structure in large quantities. Both experimental and analytical/numerical investigations are reported. In the experiments on aluminium sheets, the outer layer was subjected to 40 passes of CSPR with a reduction ratio of 1% per pass. After CSPR, the sample surface shows an ultrafine-grained microstructure with a mean grain size of 206 nm, while the annealed microstructure is retained in the core of the sample. Compared with cold-rolled aluminium sheets fabricated with the same total reduction ratio, CSPR-processed aluminium sheets have the same yield stress but improved uniform elongation (2.4 times). The scanning electron microscopy was used to study the fracture surface, and The transmission electron microscopy to examine the microstructure near the fracture end, in order to analyse the improvement in ductility. In addition, the finite element method was used to simulate the roll-sample contact pressure and strain distribution as well as residual stress on the sheet surface during CSPR, and to better understand the mechanism leading to improvement of ductility of the sheets by the CSPR technique

Crystal plasticity modelling of microbands in a rolled aluminium single crystal

In this study, an aluminium single crystal was deformed by roll-bonding, and the through-thickness texture and microstructure were characterized by electron backscattered diffraction (EBSD). Matrix bands and transition bands developed at the macro-scale, and microbands formed at the lower scale. Moreover, the crystal plasticity finite element method (CPFEM) was used to model the experimentally observed macro- and micro-subdivision. Matrix bands were captured in the Globalmodel that had a coarse mesh, and Submodel was adopted to predict microbands by refining the mesh. Two smaller regions of interest were selected from the Globalmodel and they were reconstructed in the Submodel. The Submodel was finely meshed, and it was deformed by the displacement-solution saved in the Globalmodel. One primary set of microbands in matrix bands and two sets of microbands in transition bands were successfully predicted. The deformation history at two points were traced to investigate the formation of microbands. The dominance of microbands in the Submodel was found to be associated with slip activity in the Globalmodel, and the formation and crystallographic nature of microbands were studied