INFLUENCE OF BORINATION, BORON CEMENTATION OF STEEL 45 AND VISCOSITY OF A LUBRICANT ON THE PARAMETERS OF ADHESION BOND IN THE STEEL 45 - 40X SYSTEM

In the work, the regularities of changes in the shear strength of the adhesive bond τ and the piezoelectric coefficient β in the metal systems "steel 45 - 40X", "steel 45+В-40Х", "steel 45+ВС-40Х" were obtained during physical modeling of the materials I-20A, Wolf 10W-40, TAD-17i, Litol-24 with distinctive dynamic viscosities using the additional equipment of the SMTs-2 friction machine. It has been established that a twofold increase in the shear rate causes a decrease in the piezoelectric coefficient in the "steel 45+VS - 40X" system by a factor of 1.2-1.6 for Wolf 10W-40, TAD-17i, Litol-24 lubricants and its relative similarity independent of dynamic viscosity. At the same time, a twofold increase in the shear rate in the "steel 45+B-40X" system also causes a decrease in the piezoelectric coefficient by a factor of 1.16-1.38 for all tested lubricants and its alignments, as in the "steel 45+VS" system, does not observed. It was found that the clearly expressed regularity of the effect of the equivalent dynamic viscosity on the strength of the adhesive bond at p = 0 MPa is not revealed, and the nature of the manifestation is predetermined by a possible change in the mechanism of intermolecular interaction, which depends on the structure of the molecules of lubricants. It was determined that the piezoelectric coefficient naturally decreases with an increase in dynamic viscosity in the entire considered range of normal pressures.

Predicted Affinity Ratio between Asphalt Binder and Aggregate

Affinity is a term used to describe the amount of the adhesion bond between asphalt binder and aggregate. Adhesion force may be used as indicator to the amount of energy or work required to breakdown the adhesive bond between asphalt binder and aggregate. In order to study affinity between asphalt binder and aggregate, a modified device is manufacture locally similar to Rolling Bottle Test (RBT) to Predicted the degree of affinity between asphalt binder and aggregate; taking into consideration mineral composition with physical properties of asphalt binder to measure required force to separate asphalt binder from aggregate surface. In this study, suggest new parameters to represent the stripping or affinity phenomena (affinity and stripping ratio) and the time required to make balance between them. From the experimental work result, the affinity ratio of aggregate brought from Dohuk region was 52 % after 24hr of rolling time period which is less than other type because of its mineral composition (high percent of calcite and dolomite which increase ability to resist stripping), pore size and stiffness of aggregate particle. In other hand, the stripping ratio of aggregate brought from al-Taji quarry was 80% after 24hr of rolling time which represent worse case in affinity of aggregate-asphalt binder system due to increased percent of quartz in mineral composition (greater than 80%) and so reduced ability of aggregate to resist stripping

Effects of Asphalt Binder Modifying with Polypropylene on Moisture Susceptibility of Asphalt Mixtures with Thermodynamically Concepts

In this study, the effect of using Polypropylene (PP) as an antistripping additive of asphalt mixtures is investigated. Here, the moisture susceptibility of asphalt mixtures is evaluated by determining the micro-mechanisms using the surface free energy (SFE) concept. The adhesion bond between the aggregate and asphalt binder and the cohesion strength of the asphalt binder are considered as the main factors that affect moisture damage of asphalt mixtures. Test results indicate that the use of PP improves the resistance of asphalt mixtures in both wet and dry conditions. Also, the results of the SFE tests showed that the modifying asphalt binder with PP increases free energy of adhesion that will improve adhesion resistance between asphalt binder-aggregates. The amount of debonding energy in the samples which are modified with PP is lower than the control samples. This shows that by modifying asphalt binders, the tendency of asphalt binder-aggregate stripping can be reduced. The results show the total SFE of the asphalt binders of the modified samples have more free energy rather than the control samples. This phenomenon shows that failure in the asphalt binder film and cohesion failure will be happened more rarely.