Determination of the Residual Life of the Spraying Boom of a Field Sprinkler in the Maneuvering Loading Mode
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DETERMINATION OF THE RESIDUAL LIFE OF THE SPRAYING BOOM OF A FIELD SPRINKLER IN THE MANEUVERING LOADING MODE O. E. Andreikiv,1,2 A. V. Babii,3 I. Ya. Dolinska,4 and Yu. Ya. Matviiv5
UDC 539.375
We propose a computational model for the evaluation of the residual service life of spraying booms of the field sprinklers in the maneuvering loading mode (stationary oscillations of sections of the boom together and separate shocks caused by the irregularities of the field surface). This model is based on the energy approach earlier developed by the authors. A scheme of maneuvering load is proposed. The proposed model is used to determine the residual service life of a wide-sweep spraying boom made of St.3 steel and operating in the maneuvering loading mode for specific values of the parameters. Keywords: maneuvering loading mode, wide-sweep spraying boom, field sprinkler, residual service life, kinetic diagram of fatigue crack growth, period of subcritical growth of fatigue cracks.
Introduction The normative acts regulating the numerical analyses of the spraying booms of field sprinklers do not take into account the characteristics of low-cycle fracture resistance and, in particular, the characteristics of resistance to maneuvering loads. The analysis of the operating conditions and fractures of the booms under the action of complex bending loads reveals a significant number of failures caused by the exhaustion of their resistance to the indicated variable loads. The fracture processes are initiated by nearly invisible stress concentrators (similar to cracks). The maneuvering mode of operation (i.e., operation under the action of complex multifrequency loads with variable amplitudes) is one of the most dangerous causes of failures of the spraying booms of field sprinklers due to the initiation and propagation of fatigue cracks. Therefore, in order to prevent their unpredicted failures and other emergency situations, it is necessary to be able to determine their residual service life with regard for the in-service factors. For this purpose, in what follows, we formulate a computational model. Computational Model Consider a wide-sweep spraying boom oscillating in the process of operation. As a result, some elements of the boom undergo the action of bending cyclic loads (Fig. 1a). 1 2 3 4 5
I. Franko Lviv National University, Lviv, Ukraine.
Corresponding author; e-mail: [email protected].
Pulyui Ternopil Technical University, Ternopil, Ukraine.
Karpenko Physicomechanical Institute, Ukrainian National Academy of Sciences, Lviv, Ukraine. Lutsk National Technical University, Lutsk, Ukraine.
Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 56, No. 1, pp. 106–111, January–February, 2020. Original article submitted February 12, 2019. 112
1068-820X/20/5601–0112
© 2020
Springer Science+Business Media, LLC
DETERMINATION OF THE RESIDUAL LIFE OF THE SPRAYING BOOM OF A FIELD SPRINKLER
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Fig. 1. Loading scheme of a boom element weakened by a surface crack (a) and the variations of loads applied to the boom el
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