Ahaltsov H.M. Determination of the temporal characteristics of the elastic elements of machines taking into account the damage developing in them

Details

Parent Category: Geo-Technical Mechanics, 2020

Category: Geo-Technical Mechanics, 2020, Issue 151

Geoteh. meh. 2020, 151, 128-137

DOI: https://doi.org/10.15407/geotm2020.151.128

Determination of the temporal characteristics of the elastic elements of machines taking into account the damage developing in them

¹Ahaltsov H.M.

¹Institute of Geotechnical Mechanics named by N. Poljakov of NAS of Ukraine

UDC 678.4.06:621.81

Language: Russian

Abstract.

An algorithm for determining changes in the basic physical and mechanical characteristics of elastic elements of machines operating under long-term cyclic loads in conditions of mining and metallurgical production is considered. Such loads lead to a significant change in the structure of the material during operation. Ultimately, this leads to the accumulation of damage and to a change in the macro-characteristics of the material: shear modulus G and dissipation coefficient y.

These machines include screens, feeders, knock-out screens, centrifuges, headers, vibrating machines for agricultural production, etc. The mechanical properties of the rubber elements of such machines do not remain constant during loading, and their changes usually lead to a change in the vibration parameters of the moving parts of the machines, and sometimes to a change in the technological process. In this case, the accumulation of damage in the mass of the rubber part is very important.

Damage to the material is the root cause of the loss of any product’s performance, which ultimately leads to its failure. In this regard, the formation of characteristics of rubber structural elements, as a function of developing damage, is an urgent task of scientific and practical interest.

To solve it, the Walpole method developed for composite materials is used, which makes it possible to determine the effective (averaged over a certain volume of a rubber mass) characteristics taking into account the damage developing in the material.

The calculation uses the following fatigue failure model. The investigated rubber element is represented by a set of material points (or characteristic volumes), each of which is endowed with the properties of the initial material. The process of accumulation and development of microdamages in the material under the action of external loads is interpreted as the formation in the initially homogeneous material of some areas that have, due to their isolation, the nature of inclusions. It is assumed that the properties of all inclusions are identical to each other, but differ significantly from the properties of the starting material.

Based on this model, two main informational macroscopic characteristics of rubber were determined: shear modulus and loss modulus (dissipation coefficient) depending on the function of material damage. The paper considers an algorithm for determining the durability of rubber elements based on the generalized fracture criterion; this criterion makes it possible to combine the micro and macro characteristics of the material into a single whole. An equation for the criterion of structural stability of rubber elements under long-term cyclic loads is obtained. It is shown that the theoretical data are in good agreement with the experiment: for a specific system of vortex mixers of sinter plants, the time for the stiffness characteristics to go beyond the permissible values was obtained within 10-12 years, which is in good agreement with practice.

Keywords:

dissipation, Walpole method, microdamages, generalized fracture criterion, elastic elements

References:

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2.   Walpole, L.I. (1966), “On bounds for the overall elastic moduli of inhomogeneous system – II”, Journal of the Mechanics and Physics of Solids, vol. 14, no. 5, pp. 289-301.
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7.   Dyrda, V., Kobets, A., Bulat, Ie., Slobodian, S., Lysytsia, M., Sokol, S., Lapin, V. and Ahaltsov, H. Present problems of vibration isolation in heavy mining machines at long-term cyclic loads. E3S Web Conf. 2020. 168. 00042.
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About the authors:

Ahaltsov Hennadii Mykolaiovych, Master of Science, Junior Researcher of Department of Elastomeric Component Mechanics in Mining Machines, Institute of Geotechnical Mechanics named by N. Poljakov of National Academy of Science of Ukraine, Dnipro, Ukraine, This email address is being protected from spambots. You need JavaScript enabled to view it.

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