Experimental Study of Rheological Behavior of MWCNT-Al2O3/SAE50 Hybrid Nanofluid to Provide the Best Nano-lubrication Conditions

In this study, MWCNT-Al2O3 hybrid nanoparticles with a composition ratio of 50:50 in SAE50 base oil are used. This paper aims to describe the rheological behavior of hybrid nanofluid based on temperature, shear rate ($$\dot{\gamma })$$ γ ˙ ) and volume fraction of nanoparticles ($$\varphi$$ φ ) to present an experimental correlation model. Flowmetric methods confirm the non-Newtonian behavior of the hybrid nanofluid. The highest increase and decrease in viscosity ($${\mu }_{\rm nf}$$ μ nf ) in the studied conditions are measured as 24% and − 17%, respectively. To predict the experimental data, the five-point-three-variable model is used in the response surface methodology with a coefficient of determination of 0.9979. Margin deviation (MOD) of the data is determined to be within the permissible limit of − 4.66% < MOD < 5.25%. Sensitivity analysis shows that with a 10% increase in $$\varphi$$ φ at $$\varphi =$$ φ = 1%, the highest increase in $${\mu }_{\rm nf}$$ μ nf of 34.92% is obtained.

Rheological Characteristics of Tire Rubber-Modified Asphalt following Thermal Variation

In recent years, due to the development of the automobile industry, there are more and more waste car tires, and the reuse of waste tires has become an urgent problem to be solved. In this study, the crushed rubber of waste automobile tires is used to modify asphalt to prepare rubber-modified asphalt, which can not only solve the problem of using waste tires but also effectively improve the performance of asphalt pavement. This study defines four modified asphalts with different rubber powder content, which are defined as 1#, 2#, 3#, and 4#, respectively. The performance difference between the four modified asphalts and the base asphalt was compared through experiments to illustrate the advantages of rubber-modified asphalt. The four selected rubber asphalts and base asphalt are subjected to the viscous toughness test, apparent viscosity test, DSR test, and BBR test to determine the high- and low-temperature characteristics of rubber asphalt. The analysis of experimental data shows that rubber-modified asphalt can effectively improve the low-temperature performance of the asphalt, make the asphalt have better toughness, and also improve the high-temperature shear resistance of the asphalt. Finally, it is determined that adding 10% rubber powder to the base asphalt has the best effect.

Microstructural Evolution and Tensile Testing of a Bi–Sn (57/43) Alloy Processed by Tube High-Pressure Shearing

Tube high-pressure shearing (t-HPS) processing was performed on a eutectic Bi–Sn (57/43) alloy for 0.25, 1, 5 and 20 turns. The selected samples were stored at room temperature for up to 56 days to examine the strain weakening and self-annealing behavior of the alloy. The results showed that t-HPS processing gradually refined the microstructure and led to decreasing of microhardness, but microhardness increased slowly during the subsequent storage at room temperature. Shear localization of the eutectic structure during t-HPS processing was observed as large amounts of narrow dense lamellar zones were visible in the deformed microstructures. The Bi–Sn (57/43) alloy processed by t-HPS exhibited significantly enhanced superplastic properties with elongations up to >1800% in a sample after t-HPS processing for 20 turns. This high elongation is attributed to the breaking of the lamellar structure and the very small grain size.

Experimental Study on the High-Temperature Shear Performance of Asphalt Mixtures

The influence of temperature on the shear performance of asphalt mixtures and the feasibility of using the deformation strength as an index of the high-temperature shear performance of these mixtures were explored in this study. Taking AC-13C and AC-20C asphalt mixtures as the research objects, uniaxial compression, rutting, deformation strength, and uniaxial static load creep tests were carried out at temperatures 40°C, 45°C, 50°C, 55°C, and 60°C. The correlations between the deformation strength and modulus of resilience, compressive strength, dynamic stability, and stiffness of the asphalt mixtures were studied. The test results show that the influence of temperature on the compressive strength, resilience modulus, and deformation strength of the asphalt mixtures decreases significantly as the temperature increased, and the rutting deformation of the two kinds of asphalt mixtures increased as the temperature increased. Strong correlations exist between the deformation strength and the modulus of resilience, the compressive strength, and the dynamic stability of asphalt mixtures, so the deformation strength can be used as an evaluation index of the high-temperature shear performance of asphalt mixtures.

Study of the Influence of SBS and APDDR on the Low-Temperature Properties of Road Bitumen

A comparative assessment of the effect of two modifiers on the low-temperature properties of BND 90/130 bitumen was investigated using Asphalt Binder Cracking Device (ABCD test) and Dynamic Shear Rheometer (DSR 4-mm test). These modifiers are styrene-butadiene-styrene block copolymer (SBS) and active powder of discretely devulcanized rubber (APDDR) - powder elastomeric modifier obtained by high-temperature shear grinding of waste tire crumb rubber. ABCD results of RTFO-aged samples showed clear and gradual decrease of the ABCD cracking temperature (improvement) for all BC as the modifier concentration increases. It is noteworthy that the Bitumen Composites (modified bitumens) were cracking at higher strain and fracture stress values compared to neat bitumen. Results of DSR-4 mm test showed a decrease in the complex shear modulus (G*), storage modulus (G¢) and loss modulus (G²) BC compared to the neat bitumen. It is shown that bituminous composites have no maximum on the Cole-Cole diagram (dynamic vitrification) at T = -28°C which is observed in the neat bitumen.

Methodological Aspects of Evaluating the Particle Size Distribution of Powder Elastomeric Materials

The properties of crumb rubber (CR) of unsorted end-of-life tires and of gas masks face part crushed at ambient temperature, as well as powder elastomeric materials (PEM) obtained by high-temperature shear grinding (HTSG) of CR and high-temperature shear co-grinding of CR with thermoplastic elastomer have been investigated. The methods of dry screening with vibrating sieve, wet laser diffraction, scanning electron microscopy, determination of the specific surface area by the BET method by sorption nitrogen and powder agglomeration were used. The effect of an anti-agglomerating additive on the results of determining the particle size distribution by the methods of dry vibrating sieving and wet laser diffraction has been investigated. Methodological recommendations for determining the particle size distribution of powder elastomeric materials (PEM) obtained by the HTSG have been developed.