Machines and equipment for asphalt pavement milling are widely used throughout the world. With the growth of road construction, the demand for this class of machinery also rises. At the same time, the optimization of design and technological parameters of the milling machines is impossible without a comprehensive study of processes of milling asphalt concrete with the working elements of a cutter. The article provides a brief overview of different approaches to find out the loads on the working bodies of various machines, as well as indicates the advantages and disadvantages of these approaches. We describe the design of a pendulum stand used to study the processes of milling asphalt concrete with a single tooth cutter. We also describe the method of operation of such a stand. The design of the pendulum stand allows us to determine the cutting work, the average, and the instantaneous cutting forces. The work also provides the result of tests of cutting elements during their interaction with samples of asphalt concrete of different grades that are widely used in road construction. We also show the non-linear dependence of cutting resistance forces on the temperature and thickness of penetration of a cutting element. It is noted that working with a slight tooth penetration leads to low energy efficiency of the work process. It is also noted that temperature affects cutting resistance forces significantly less in asphalt concrete containing high amount of gravel.
Introduction. The article is devoted to the research results on cutting resistance of a road asphalt concrete in the process of the removal of worn coatings by the working elements of milling machines. The relevance of the work is due to the occurring of new brands of asphalt concrete alongside with the use of new types of cutting elements, for which it is difficult to predict the load on the working element when solving the problems of designing new ones and substantiation the operating conditions of the current machines. The purpose. The objective of the study of the interaction of a single cutting element of a road mill with a material at the best fit of speed and geometric parameters of a cutting process with real machines is solved.Materials and methods. The experimental work was carried out by determining the tangential component of a cutting resistance strength, as well as the work of this strength on a pendulum desk using a unit recording equipment. Four different types of asphalt concrete were being destroyed. A two-factor experiment was conducted for each type of the material. The tangential components of a cutting resistance strength depending on the thickness of the cut chips and the temperature of the material were evaluated.Results. As a result of the experiment, the data were obtained that make it possible to reasonably determine the loads on the teeth of road milling machines, to determine a power capacity of the process and the drive power of the working element. It was found that the growth of the tangential component to a cutting resistance strength occurs quite intensively alongside with an increase in the thickness of the cut chips, only at the initial stages of the penetration of the cutter. With an increase in the thickness of the cut chips, the growth of the tangential component to a cutting resistance strength does not occur so intensively. In all cases the temperature of the material has an impact on the value of a cutting resistance strength, but this effect is less significant for asphalt concrete with a higher crushed stone content.Discussion and conclusion. The obtained data make it possible not only to determine the tangential strength to cutting resistance on the cutting elements of the working element of the milling machine, but also to find rational ways to place the cutting elements on the working element, as well as to determine the rational operation conditions of the current and new machines. This is possible when using the results in a mathematical model that describes the operation of the milling working element as a whole.Financial transparency: the authors have no financial interest in the presented materials or methods. There is no conflict of interest.
The paper reflects the results of the study conducted to determine how a free rotary instrument cuts narrow joints in asphalt pavements required for road construction. Based on the analysis of strength characteristics of different asphalt concrete grades, we developed a mathematical model of working process, and this model stands as the calculation basis. The mathematical model associates the main parameter — cutting resistance force — with the material strength values and geometrical characteristics of the working body and the working process. The results of experimental confirmation of mathematical model reliability are presented in the paper.
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