Low Rolling Research Articles

On the Elastohydrodynamic Film-Forming Properties of Metalworking Fluids and Oil-in-Water Emulsions

Oil-in-water (O/W) emulsions are water-based lubricants and used as fire-resistant hydraulic fluids and metalworking fluids (MWFs) in industry. The (elasto-)hydrodynamic film-forming properties of O/W emulsions have been studied extensively in literature. Typical elastohydrodynamic lubrication (EHL) behaviors are revealed at low rolling speeds followed by a starved EHL regime at elevated speeds. These emulsions are self-prepared and mostly stable only for a limited time ranging from hours to several days. By contrast, the film-forming behavior of water-miscible commercial MWFs (long-term stable O/W emulsions) has rarely been reported. This restricts the understanding of the lubrication status of many tribological interfaces in manufacturing processes, e.g., the chip-tool contact in cutting. In this work, the (elasto-)hydrodynamic film-forming property of two commercial MWFs is investigated by measuring the film thickness on two ball-on-disc test rigs using different optical interferometry techniques. For comparison, two self-prepared simple O/W emulsions with known formulation have also been investigated. Experimental results from the two test rigs agree well and show that the two self-prepared emulsions have typical EHL behaviors as reported in literature. However, for the two commercial MWFs, there is almost no (elasto-)hydrodynamic film-forming ability over the whole range of speeds used in this study. This could be explained by the cleaning and re-emulsification effects of the MWFs. The lubrication mechanism of the two MWFs is mainly boundary lubrication rather than hydrodynamic lubrication.Graphical

Natural Rubber Composites Reinforced with Green Silica from Rice Husk: Effect of Filler Loading on Mechanical Properties

Natural rubber (NR) composites filled with silica are typically used for tire tread applications owing to their low energy consumption and low rolling resistance. Tire tread properties vary broadly depending on the compound formulation and curing conditions. Silica loading is recognized as a critical factor influencing the mechanical properties of the composites. In this work, we aim to investigate the effect of silica loading (10–50 phr) on the mechanical properties of NR composites. Silica was prepared from rice husk waste via chemical treatment and subsequent calcination at 600 °C. Prior to the compound mixing process, silica was modified by a silane coupling agent to improve compatibility with the NR matrix. The NR compounds reinforced with silane-modified silica from rice husk were prepared using a two-roll mill machine. The scorch and cure times increased as the silica loading increased. The mechanical properties of the NR composites, including tensile strength, elongation at break, modulus, hardness, and abrasion loss, were examined as a function of silica loading. Tensile strength increased and reached the maximum value at 20 phr but decreased at high loading owing to the agglomeration of silica in the NR matrix. With increasing silica loading, hardness and modulus increased, whereas elongation at break and abrasion resistance decreased slightly. These results indicate that NR composites filled with silica are stiffer and harder at a higher silica loading due to the strong interaction between silica and the NR matrix, inhibiting the segmental mobility of rubber chains. We anticipate that the compound formulation presented in this work could potentially be adapted to tire tread applications.

Unveiling the rolling texture variations of α-Mg phases in a dual-phase Mg-Li alloy

LZ91 Mg-Li alloy plates with three types of initial texture were rolled by 70% reduction at both room temperature and 200 °C to explore the rolling texture formation of α-Mg phase. The results showed that the rolling texture is largely affected by the initial texture. All the samples exhibited two main texture components as RD-split double peaks texture and TD-split double peaks texture after large strain rolling. The intensity of the two texture components was strongly influenced by the initial orientation and rolling temperature. Extension twinning altered the large-split non-basal orientation to a near basal one at low rolling strain. The basal orientation induced by twinning is unstable, which finally transmitted to the RD-split texture. The strong TD-split texture formed due to slip-induced orientation transition from its initial orientation. The competition between prismatic 〈a〉 and basal slip determined the intensity and tilt angle of the TD-split texture. By increasing the rolling temperature, the TD-split texture component was enhanced in all three samples. Limitation of extension twinning behavior and the promotion of prismatic slip at elevated temperature are the main reasons for the difference in hot and cold rolling texture.

Incremental rolling forming process to fabricate surface micro-grooves

The fabrication of functional micro-structures at sheet surface has a wide range of applications in noise reduction, friction reduction, heat and mass transfer, etc. By integrating the conventional rolling forming and the incremental sheet forming process, a flexible and widely applicable incremental rolling forming process was proposed in the present work to fabricate surface micro-grooves. First, a rolling tool which has hemispherical ring convex on the roller and the convex height is much higher than the height of forming groove was designed and manufactured. Then, a series of incremental rolling tests on titanium alloy (TA1) were carried out by using self-designed rolling tools, with varying roller size, rolling depth and feed rate. The results show that continuous micro-grooves with good dimensional consistency were prepared on the surface of the plate. Furthermore, by investigating rolling force and groove size after rolling, it was found that the rolling depth have significant effects on the micro-groove formation and only localized material flow is occurred at the grooved region. Compared with the traditional rolling process, the incremental rolling process has the advantages of low rolling force and adjustable groove spacing, which is conducive to the subsequent processing of the sheet.

The dynamics of cylinder-wake/boundary-layer interaction revealed by turbulent transports

The flow past a cylinder near a plane wall for small gap ratios (G/D=0.1, 0.3, and 0.9) and fixed ReD = 1000 is numerically studied. The fundamental flow features are characterized by the instantaneous and mean fields. Then, the dynamics of cylinder-wake/boundary-layer interaction are revealed by the turbulent momentum transport and kinetic energy production. The turbulent fluctuations caused by the secondary vortex (SV) (at G/D=0.3, 0.9) and the novel tertiary vortex (TV) (at G/D=0.9) can be observed in the distributions of Reynolds stresses. For G/D=0.1 and G/D=0.3, the wake/boundary-layer interaction is dominated by ejection and sweep events, which are related to the generation of the hairpin vortex. These two bursting events lead to the momentum transport between the high- and low-speed sides. For G/D=0.9, the ejection event is not found in the interaction region because the head of the hairpin vortex is entrained into the wake. The upper roller (RU) helps to transport high-momentum fluid toward the wall in this case, although it does not take part in the interaction directly. The shedding of RU, the lower roller (RL), SV (at G/D=0.3 and 0.9), and KH (Kelvin–Helmholtz) vortex (at G/D=0.1) and the generation of the hairpin vortex are crucial to turbulent kinetic energy (TKE) production. The RU, KH vortex, and SV transfer ⟨u′u′⟩ out to ⟨v′v′⟩ and ⟨w′w′⟩ resulting redistribution of the TKE. While RL, surviving for a shorter time, transfers ⟨v′v′⟩ out to ⟨u′u′⟩ and ⟨w′w′⟩, helping explain why it disappears quickly, TV only transfers out ⟨v′v′⟩ out to ⟨u′u′⟩, and its TKE comes from other terms rather than the production term. The redistribution of TKE due to the generation of the hairpin vortex can result in the slower growth rate of the secondary disturbance growth stage, promoting the wall boundary layer transition.

Readiness study of environmentally friendly motor vehicle tire industry and its supporting infrastructure in implementing tire labeling regulation

Tire labeling is a label on tire products that have met specific rolling resistance, wet grip, and noise emission requirements. It aims to increase road transport’s safety and economic and environmental efficiency by promoting fuel-efficient and safe tires with low external rolling noise. Indonesia has many tire industries and is a significant global market for motor vehicles; they may consider applying tire labeling. The implementation of tire labeling in Indonesia requires a study of the readiness of the tire industry and its supporting infrastructure, including the necessary testing facilities and end-user awareness. The study was carried out by conducting literature studies and distributing questionnaires. The study results showed that the tire industry has sound capabilities, but it is necessary to increase the readiness of an independent testing laboratory. End-user acceptance of tire label products is good, but awareness of tire labels needs to be improved. The application of tire labels in Indonesia is projected to reduce CO2 emissions significantly.

Significant Texture Weakening of Al-Cu-Mg Alloy by Low Strain Asymmetric Cross Rolling Process

Significant Texture Weakening of Al-Cu-Mg Alloy by Low Strain Asymmetric Cross Rolling Process

Formation mechanism of the eye-shaped nano-twin bundles in cold rolled 316L stainless steel

The microstructural evolution of a typical coarse-grained 316L stainless steel was explored with the rolling reduction changed from 0% to 80%. The formation mechanism of the novel eye-shaped nano-twin (NT) bundles was clearly revealed. The results show that numerous dislocations were propagated and accumulated around original grain/annealing-twin boundaries at low rolling strain level (20%), which led to a high stress concentration and induced the generation of deformation twin bundles. With the rolling reduction increase to 40%, the number of deformation twin bundles increased and the average thickness of deformation twins decreased. In addition, some micro shear bands were motivated to cut the deformation twin bundles, resulting in the formation of eye-shaped deformation twin bundles. With the further increase of the rolling reduction (60–80%), the average thickness of deformation twins was decreased to nano-scale. Many eye-shaped NT bundles were formed by the cutting activity from the micro shear bands.

Recent progress of elastomer–silica nanocomposites toward green tires: simulation and experiment

AbstractThe concern regarding increasing oil consumption that originates from the high rolling resistance of automobiles has led to the development of green tires. The key enabling technique for preparing green tires involves the utilization of elastomer–silica nanocomposites. Elastomer–silica nanocomposites usually show low rolling resistance because of the intrinsic lubrication characteristics of siloxane and the excellent elastomer‐modified silica interfacial interaction, making them ideal raw materials for a green tire. It is supposed that the comprehensive properties of rolling resistance can be further improved via continually optimizing the microstructures of elastomer–silica nanocomposites. Regulating silica dispersion, understanding the interface between elastomer and silica and building the quantitative correlation between the microstructure and the static/dynamic macro‐mechanical properties are crucial in designing high‐performance elastomer–silica nanocomposites. This review aims to summarize the recent progress of elastomer–silica nanocomposites from the point of view of silica dispersion, the elastomer–silica interface and the microstructure–mechanical connection, combining simulation and actual experimental findings. A short conclusion and an outlook on the current limitations and possible future research directions for constructing high‐performance elastomer–silica nanocomposites for low‐energy green tires are also presented. © 2022 Society of Industrial Chemistry.

Hot Deformation Behavior of C-Mn Steel with Incomplete Recrystallization during Roughing Phase with and without Nb Addition

The objective of the study is to improve understanding of the practical role of niobium (Nb) in the case of industrial inconsistent rolling processes such as the rolling of heavy gauge plates where a lower stored energy rolling practice will result in a less stable and less repeatable static recrystallization (SRX) activation that prevents complete recrystallization. In the current study, these variabilities are validated by comparing the mean flow stress (MFS) indirectly determined from the rolling force measured on a reverse four-high rolling mill stand. The material resistance to deformation and grain size evolution of a C-Mn steel during hot rolling was observed and validated with and without Nb addition. The pre-defined rolling schedule was predicted to exhibit incomplete recrystallization in the roughing phase due to the limited stored energy of deformation that resulted from low rolling loads and a higher number of rolling passes. The prior austenite grain size (PAGS) distribution was predicted and compared to the measured effective ferrite grain (FG) size distribution after the completion of hot rolling and phase transformation achieved using natural air plate cooling. Both the predicted PAG and measured FG distributions revealed the presence of multimodality, and both distributions were used for grain size reduction factor determination for γ → α transformation for the current study with 1.96 for 0 Nb and 1.70 for 240 Nb. The results presented in this paper are not only limited to the rolling schedule used in this paper because instabilities resulting in incomplete austenite conditioning are also observed when evaluating the cross-sections of other heavy plates and various steel grades utilizing different processing routes with comparable compositions such as modern lean abrasion-resistant steels, regular line pipe steels, and other similar grades.

Effect of rolling temperature on microstructure evolution and mechanical properties of high carbon high manganese steel

The effects of rolling temperature ranging from −55 to 300 °C on dislocation density, twinning behavior and correlative tensile properties of a high carbon high manganese steel were investigated. Results showed that the twinning behavior was enhanced at −55 °C but suppressed at 300 °C. The twin thickness and spacing increase with the rolling temperature. At low rolling reduction of 10%, the dislocation multiplication rate decreased with the increase in rolling temperature. However, the dislocation multiplication rate maintained high level when rolled at high rolling reduction and high temperature. At a given rolling reduction, the samples rolled at −55 °C possessed higher work hardening rate. Especially, the strength of −55°C-rolled-20% sample was higher than that of 300°C-rolled-30% sample and was equivalent to room temperature (RT)-rolled-30% sample. Concurrently, the elongation of the −55°C-rolled-20% sample was higher than the other two. The contributions of dislocation strengthening and twin strengthening to the yield strength of high carbon high manganese steel after rolling at different conditions were calculated by the parameter model. The dislocation strengthening effect played a dominant role under various deformation conditions. Twin strengthening effect showed a temperature sensitivity in the temperature range selected in the present study. Lower rolling temperature showed greater contribution of twin strengthening, whereas the dislocation strengthening effect was insensitive to temperature.

Synthesis of vinyl-based silica nanoparticles by sol–gel method and their influences on network microstructure and dynamic mechanical properties of nitrile rubber nanocomposites

Non-agglomeration and dispersion of silica nanoparticles in polymers and their interfacial interactions to polymer matrix are the most important factors that influence nanocomposites performance. In this work, vinyltriethoxysilane (VTES) as a low VOC emission coupling agent was used for surface modification of silica nanoparticles to prepare better dispersion in nitrile rubber (NBR) and improve its interfacial interactions to silica nanoparticles. The results of X-ray photoelectron spectroscopy, thermogravimetric analysis and Fourier transform infra-red spectroscopy demonstrated successful attachment of VTES molecules on the surface of silica nanoparticles. Dispersion of the modified silica nanoparticles in NBR matrix was studied using field emission scanning electron microscopy and rubber process analysis. Results demonstrated that VTES significantly improved dispersion of nanoparticles in rubbery matrix. The bound rubber content showed that VTES effectively built a bridge between the silica nanoparticles and the rubber matrix that led to promising mechanical performances and strong interfacial interactions. Effect of nanoparticle content on the mechanical performances (static/dynamic) of the NBR was evaluated. It was found that higher modulus and reinforcement indices was obtained at 3 and 5 wt% of nanoparticles. Moreover, these composites had extremely low rolling resistance, the best wet skid resistance and the lowest Heat-Build up.

Design of Experiments for Green Tire Tread Compound Development by Reducing Conventional Carbon with an Eco-Friendly Filler

Several parameters are required to improve Tire dynamic performances like high wet and dry traction (Grip), high wear resistance and high steering performance (handling). These performances depend on the physical properties of tire tread compound, tire construction, tread profile and road conditions. The most influential one is the reinforcing filler, which is responsible for inheriting the tread dynamic properties. Conventionally, carbon black is used as filler but it possesses a major hitch of CO2 emission during manufacturing as well as in service conditions. Its high rolling resistance is responsible for boosting the carbon footprint of a vehicle. In the past few decades, the focus has been shifting on silica fillers, an emerging technology to develop low rolling resistance tires resulting in low CO2 emissions thus contributing in the establishment of a healthy eco system. Design of Experiment (DOE) approach is used therefore, sixteen (16) variants of silica based compounds were prepared and properties of silica based samples were compared with that of carbon black compounds (conventional). The results revealed that this emerging silica filler showed promising results in giving the highest possible wet traction and lowest rolling resistance to minimize CO2 (Greenhouse gas) in the environment.

Development of a magnetic cardan suspension coupled with a single actuated axis for gravity assisted pointing of directional devices: A case study of Moon to Earth alignment for a laser ranging reflector

A new class of Lunar Laser Ranging (LLR) experiments has been recently investigated by the international Space Agencies, in order to deploy a set of Next Generation Lunar Reflector (NGLR) on the Moon surface, funded under NASA's Commercial Lunar Payload Services (CLPS) program (Currie et al., 2020). In principle the Cube Corner Reflector (CCR) arrays deployed by Apollo and Lunokhod missions in the 70’s will be flanked (at different locations) by single bigger reflectors, thus removing the systematic errors in the Time of Flight (TOF) measurement induced by the Moon librations (Turyshev et al., 2012).In this paper we describe a mechanism formed by a passive cardan magnetic suspension, dedicated to the alignment of the CCR toward the mean Earth direction. The suspension is able to compensate for the misalignment due to the slope of the landing site that can be different at each site (Zupp, 2013). If proper control of azimuth angle of the spacecraft at touchdown cannot be guaranteed, an additional motor to rotate the magnetic suspension must be provided by the lander, for the alignment toward the mean Earth direction.Once the landing site is defined, the geometry of the retroreflector housing, together with that of the cardan suspension, will autonomously (without human intervention) and passively (without provision of electrical power by the lander) provide the right elevation angle just by gravity, no matter what the morphology of the site is.The mechanical performances of the magnetic suspension have been preliminarily investigated in (Ancillai et al., 2020). The solution presented can be applied to any directional device, requiring pointing capability, like antennas, and can be adopted with low friction rolling bearings as well.

Effect of silica dispersed by special dispersing agents with green strategy on tire rolling resistance and energy consumption

AbstractThe state‐of‐art approach to realize the low rolling resistance of green tires is the high addition of SiO2. However, its dispersion capacity and the interface strength with rubber dominant the final properties of green tires. Here, we systematically study amphiphilic polyoxyethylene sorbitan monooleate, oleylamine, sorbitan monooleate, and oleamide to modify SiO2 through simple hydrogen‐bonded self‐assembly in order to replace the traditional silane coupling agent with low modification efficiency, many side reactions and complex reaction process. The results show that the rolling resistance and processing energy loss of the rubber composite prepared by SiO2 modified with polyoxyethylene sorbitan monooleate and oleylamine are significantly reduced, and other physical and mechanical properties (tensile strength, tear strength, and wear resistance) are also significantly improved compared with the silane coupling agent commonly used in green tire tread. Meanwhile, carbon–carbon double bonds belonging to polyoxyethylene sorbitan monooleate and oleylamine can participate in vulcanization of rubber to strongly improve the dispersion ability of SiO2 and the interface interaction between SiO2 and rubber matrix, so as to develop the fuel‐efficient green tire tread with high performance and low rolling resistance.

Screening of mixing parameters based on their significance on the extent of silanization and energy consumption of silica‐filled S‐SBR elastomer compounds for fuel‐saving tyre application

AbstractIncreasingly stringent in demand for a fuel‐saving tyre with low rolling resistance, the application of silica filler is governing the tyre industry day by day. Unlike carbon black filled rubber compound, silica compound is rather complicated as it demands, a reactive mixing where, mixing parameters of internal mixer play a vital role in the degree of silanization reaction. In this paper, a design of experiments (DOE) is carried out to screen the factors that significantly affect the silanization reaction during mixing. Taguchi method with L18 orthogonal array is employed to determine the significance of mixing parameters on the degree of silanization reaction. To quantify the significance of each mixing parameter on silanization, such as mixing temperature, mixing time, fill factor, feed door condition, ram pressure, and temperature control unit of Banbury mixer are explored. Key properties like Tan δ at 60°C, reinforcement index, and Payne effect (∆G') are considered responses for the DOE. It was observed that the silanization temperature and time were the most influencing factor in silanization using the contribution plot. In contrast, ram pressure and feed door condition have the least significance on the degree of silanization.

Experimental investigation on the effect of roller traverse and rotation speeds on ceramic binder jetting additive manufacturing

The objective of this experimental investigation is to identify the effect of roller traverse and rotation speeds on ceramic binder jetting additive manufacturing. Green and sintered densities were found decreasing with increasing roller traverse speed, and this decrease was more significant at a low roller rotation speed. A high roller traverse speed led to more cavities on the powder bed surface after spreading a new layer on a printed layer. Furthermore, a high roller traverse speed caused more cracks on the powder bed surface after jetting the binder. These defects observed during printing were inherited by the green and sintered parts, which were confirmed by X-ray computed tomography and scanning electron microscopy, respectively. Finally, the sintered flexural strength of the parts printed at a high roller traverse speed was more than 30% higher than that of the parts printed at a low roller traverse speed.

Finite Element Simulation and Experiments of Laminated Cu Cladding Fe Sheet During Cold Rolling Bonding

ABAQUS was used to simulate the laminated Cu cladding Fe sheet during cold rolling, combining theoretical calculations, and the orthogonal test method was adopted. Meanwhiles, the rolling stress was taken as a consideration index to investigate the cold rolling processing rate, rolling speed, friction factor (upper roller), and friction factor (lower roller) 4, the best process parameters of layered metal copper/steel cold-rolled composite are selected. The results show that the cold-rolling processing rate is 52%, the rolling speed is 75 m/min, and the roller friction factor is 0.2 is the best process parameter. At this time, the rolling stress is small, and the bonding quality is the best. Cu cladding Fe sheet of the above-mentioned production process was taken into annealing experiments, SEM and an energy spectrometer were applied to photograph the surface morphology and the element distribution. The interface thickness was calculated by the diffusion distance of Fe and Cu elements, and the interface morphology and mechanical properties were combined for judgment. The results show that the annealing temperature is [Formula: see text]C and the bonding condition is the best under the condition of 4[Formula: see text]h heat preservation.

Green Routes toward Cross-Linkable and Robust Elastomers Derived from Biobased Fumaric Acid

In the rubber industry, the substitution of traditional engineering rubbers derived from fossil resources with novel biobased elastomers is considered for sustainable development, which largely relies on a straightforward and environmentally friendly synthesis procedure and the availability of material properties. In the research, semi-biobased elastomers, poly(dibutyl fumarate-co-butadiene)s (PDBFBs), were prepared by redox emulsion polymerization of dibutyl fumarate obtained from fumaric acid esterified with n-butanol and partially petroleum-derived butadiene. The microscopic structures of PDBFBs were verified by FTIR, NMR, and GPC analyses. The Tg values of PDBFBs were in the range of −73 and −58 °C. Additionally, the reactivity ratios of two comonomers in PDBFBs were evaluated by two methods: the Fineman–Ross and Kelen–Tüdös methods. The macroscopic properties of semi-biobased elastomers, such as thermal and mechanical performances, were meticulously regulated via molecular design. To achieve the desired properties, silica was incorporated into the PDBFBs to prepare strong nanocomposites. These nanocomposites displayed adequate tensile strength (14.3–31.6 MPa), adequate elongation at break (338–457%), low rolling resistance, and excellent thermoresistant oxygen aging performance. These results showed that PDBFB nanocomposites possessed quite good properties and had the potential for practical applications. This work provides a facile, efficient, solvent-less green synthesis route to design new-generation promising sustainable engineering elastomers for the rubber industry.

Optimizing mechanical property of spray formed Al-Zn-Mg-Cu alloy by combination of homogenization and warm-rolling

Effect of homogenization and warm-rolling on the mechanical properties of Al-11.38Zn-2.45Mg-1.1Cu-0.13Zr-0.1Fe (wt. %) alloy fabricated by spray forming technology was studied by scanning electron microscopy (SEM), electron back-scatter diffraction (EBSD), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). The results indicate that the combination of homogenization and warm-rolling exhibit significantly potential for increasing the mechanical properties of the spray formed alloy. The introduction of two-step homogenization process can promote the precipitation of substantial amount of Al3Zr dispersoids, which provide the Orowan strengthening and inhibit recrystallization of the alloy. The warm-rolling at 200 °C produces a large number of dislocations, which not only provide strain hardening, but also promote the precipitation of η’ phase during aging treatment. Besides, the relatively low temperature rolling combined with Al3Zr dispersoids can avoid dynamic recrystallization and thus maintain fibrous microstructure of the alloy. An ultrahigh strength (YS = 868.9 ± 1.6 MPa, UTS = 878.6 ± 2.8 MPa, respectively) is achieved for the alloy due to synergistic effect of homogenization and warm-rolling.