Rationale of acceptable risk of using tractors with operational damages of responsible parts
2020
Voinalovych, O., National Univ. of Life and Environmental Sciences of Ukraine, Kiev (Ukraine) | Aniskevych, L., National Univ. of Life and Environmental Sciences of Ukraine, Kiev (Ukraine) | Motrich, M., National Univ. of Life and Environmental Sciences of Ukraine, Kiev (Ukraine) | Titova, L., National Univ. of Life and Environmental Sciences of Ukraine, Kiev (Ukraine)
For calculating risk and safety indicators of the tractor it is proposed to use the data of defectoscopic control of the array of responsible tractor parts and to analyse the kinetics of accumulation of the total damage in the array of these parts by analogy with the estimation of the boundary elasticity of the surface layer of metal by multi-cycle fatigue. It is established that the dependence of the kinetics of crack accumulation in parts of systems (units) of the tractor with a high degree of reliability can be described by exponential diagrams within the studied range of service life, which is typical for the pattern of monotonic accumulation in model samples of structural materials of scattered fatigue damage. The description of the kinetics of dispersion of the relative number of defective parts using a 4 degree polynomial allowed to establish a certain maximum corresponding to the interval of 1213.5 years of the tractor operating life. This maximum corresponds to the maximum intensity of formation of operational cracks for the studied interval of the duration of operation of the tractor and the probability of accumulation in the array of parts of the critical (limit) number of defects. This can serve as a criterion for discontinuing the tractor, performing part flaws to detect cracks and repairing (replacing) defective parts. On the basis of the kinetic diagram of accumulation of operational defects in the array of tractor parts, the method of estimating the residual life of tractors after certain duration of operation is proposed. This method uses approaches to analyse the kinetics of damage to metallic materials that have undergone mechanical loading, using the Hearst parameter as a criterion, the limiting value of which does not depend on the mechanical loading parameters.
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