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Influence of loads in the process of laying on the resource of sea pipelines

100%

Poberezhnyi L. , Tregubenko S. , Poberezhna L. , Hrytsanchuk A. , Stanetsky A.

tom Vol. 96, nr 2

63--72

Purpose: In the process of laying on the bottom of the sea material of the pipeline undergoes single-cycle alternating load. The purpose of the work is to determine the effect of pre-operational loads on the resource of marine pipelines. Design/methodology/approach: The influence of the method of construction of pipelines on their stress-strain state is analysed. According to the real modes of packing of sea pipelines, the loading regime is programmed and the laboratory modelling of the pipelaying process by the S-method has been programmed. Findings: According to the results of one-cycle shift load were obtained characteristics of the hysteresis loop. It is proposed to simplify the mathematical description of the hysteresis loop of the pipeline laying cycle in the given form. It was shown that the preload during the construction process negatively affects the durability of the pipeline material due to the exhaustion of its plasticity resource, reducing it to 70%. Research limitations/implications: In the future, investigations into the effect of overloading and overloading during the repair of pipeline sections on their durability and on the safe exploitation of resources should be continued. Practical implications: The developed method of estimation of influence of preoperational loads in the process of pipeline laying on its safe exploitation resource is used in gas-extraction enterprises. Originality/value: To forecast the deformation behaviour of the pipeline material in the laying cycle, it is efficient to use diagrams of a sign-changing single-cycle bend, which were built considering the creep. The fatigue life capability of a steel pipeline depends on the history of the pipeline load in the laying cycle. Ratio σ*0.2c / σ* 0.2t and εyc / ε yt can use as power and deformation criteria for evaluating Bauschinger effect. It is suggested that fatigue damage is determined by the width of the hysteresis loop.

Numerical simulation of the stress state of an erosion-worn tee of the main gas pipeline

86%

Doroshenko Y. , Zapukhliak V. , Grudz Y. , Poberezhny L. , Hrytsanchuk A. , Popovych P. , Shevchuk O.

2020

tom Vol. 101, nr 2

63--78

Purpose: To investigate the strength of tees with regard to their erosion wear, it is necessary to consider the complex three-dimensional geometric shape of the erosion worn inner surface of the tee. In addition, the study of the strength of the erosion worn tees of the main gas pipelines is complicated by the occurrence of additional stresses caused by changes in the direction of movement of the gas stream, resulting in an uneven pressure distribution in the inner cavity of the tee, and the temperature difference in its walls. Design/methodology/approach: Methodology for complex numerical three-dimensional simulation of the stressed state of tees of the main gas pipelines, taking into account the gas-dynamic processes that occur in the places of these defects, erosion wear of the tee wall, temperature difference in the tee walls. Findings: The acceptable parameters of erosion defects of tees of gas pipelines, and residual life of tees with erosion defects of the wall should be determined. Research limitations/implications: The developed model does not take into account internal corrosion and corrosion products as an additional erosion factor. Further studies plan to develop a model of corrosion-erosion wear of pipeline elements. Practical implications: The developed technique allows determining the location of erosion defects, estimating the strength and determining the residual life of tees with erosion wear of the wall in order to ensure their reliability, to rank such defects according to the degree of danger, to determine which of them are critical and need an immediate repair. Originality/value: Based on the gas-dynamic processes occurring in the internal cavity of the main gas pipelines’ tees, the complex three-dimensional geometric form of wall erosion defects, and temperature difference, the technique of three-dimensional simulation of stress state of the main gas pipelines’ tees is developed

Simulation of thermomechanical processes in disc brakes of wheeled vehicles

72%

Hrevtsev O. , Selivanova N. , Popovych P. , Poberezhny L. , Sakhno V. , Shevchuk O. , Poberezhna L. , Murovanyi I. , Hrytsanchuk A. , Romanyshyn O.

tom Vol. 104, nr 1

11--20

Purpose: Ensuring the required operational reliability of disc brakes by forecasting their technical condition taking into account thermomechanical processes. Design/methodology/approach: Differential equations of rotation of a rigid body around a fixed axis are solved, it is established that the equations of motion and the equations of thermal conductivity are indirectly related. The use of these analytical dependences provides a better understanding of thermomechanical transients. Findings: The solution is obtained on the basis of the differential equation of thermal conductivity of the hyperbolic type, which does not allow an infinite velocity of propagation of temperature perturbations in contrast to the differential equation of thermal conductivity of the parabolic Fourier type. The obtained analytical dependences provide a better understanding of thermomechanical transients and develop a theoretical basis for determining stresses and heat fluxes in solving problems of reliability and durability of disc brakes. Research limitations/implications: The work uses generally accepted assumptions and limitations for thermomechanical calculations. Practical implications: It is shown, that transients in a mechanical system - a brake disk at impulse loadings cause emergence of thermal effects which arise under the influence of external loadings. Originality/value: The application of these analytical dependences provides a better understanding of thermomechanical transients and develops a theoretical basis for solving problems of reliability and durability of disc brakes.