PSI - Issue 42

Halyna Krechkovska et al. / Procedia Structural Integrity 42 (2022) 1406–1413 Halyna Krechkovska / Structural Integrity Procedia 00 (2022) 000 – 000 l / t t l I t it i ( )

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fatigue endurance of samples with steel and fiberglass sucker rods in the technological environment of reservoir water were constructed with different probability of their non-destruction P ( N ). Fatigue endurance of samples with steel, fiberglass and hybrid sucker rods was compared. © 2022 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the conference Guest Editors Keywords : sucker rods; fatigue cracks growth; steel; composite. 1. Introduction Sucker rods are designed to connect and transmit reciprocating motion from the rocking machine to the plunger of the rod well sucker. The length of the sucker rod columns can reach up to 2000 m and it is composed of separate rods 8 m long and d0 to 28 mm in diameter, which are connected to each other with threaded couplings. Sucker rods are non-rigid cylindrical rods with heads at both ends. The maximum tensile stresses in their cross-section occur during the upward movement of the plunger, and they depend primarily on the depth of the well. In addition, the performance of sucker rods is affected by corrosive-active environments, inertial vibration forces, axial pulsating of the same sign with an asymmetric cycle, and sign-changing loads (cyclic loads caused by longitudinal bending due to the loss of stability of the rods) Kret et al. (2020) and Kopey 1 et al. (2020). All these operational factors can cause a sucker rod break, which will lead to long-term downtime of the equipment and reduce the productivity of the oil production process. Therefore, depending on the operating conditions, the sucker rods must have the properties necessary to ensure their efficiency (fatigue resistance, corrosion resistance, wear resistance, durability). The fatigue limit in air (σ -1 ) of the steels used for the manufacture of sucker rods usually increases almost proportionally to the strength limit (σ UTS ) of the steels, while the conditional limit of corrosion fatigue of these same steels is low and practically does not depend on their strength. To predict the fatigue life of sucker rods, it is important to evaluate the influence of technological environments under different load schemes on the conditional fatigue limit of the steels used for their manufacture (in particular, such as 20N2M steel) and compare these properties with modern prototypes of steel rods, in the form of hybrid rods with metal heads and fiberglass rod (Sutherland at al. (2004) and (Kopei (2019 2 , 2021 3 ). Their main advantages compared to traditional steel sucker rods are as follows: 4 times lower density (1400/2000 / 7850 kg/m 3 ), 3 times lower modulus of elasticity (50 – 70 GPa), 20 times lower roughness coefficient (0.0015 / 0.03), higher corrosion resistance, as well as the inability to plastically deform. As part of the column, hybrid steel composite sucker rods make it possible to reduce its total weight, reduce amplitude and dynamic loads, and increase the duration of trouble-free operation by 5-6 times. At the same time, it is necessary to substantiate the ability of these rods to be operated under the combined influence of cyclic loads and corrosive active technological environments. But so far the freely available research results are insufficient for such justification. 2. Materials and methods The features of corrosion-fatigue failure of samples 250 mm long, cut from steel sucker rods from the side of their heads, were studied. The samples were tested under cyclic loading by circular cantilever bending at a frequency of 15 Hz in an environment saturated with an aggressive hydrogen sulfide component, and for comparison in air (Kopei (2019 4 ). Corrosion tests were carried out in a chamber with a 3% NaCl aqueous solution, which was periodically (once a day) saturated with hydrogen sulfide to the limit concentration (~2500 mg/l). In addition, 19 mm diameter and 220 mm long steel and hybrid carbon fiber core and fiberglass jacketed sucker rod samples were compared for fatigue life in a formation water environment. To determine the growth rate of fatigue cracks, samples made of rods were cyclically loaded with stresses of 80...140 MPa, and the length of the crack was monitored by the echo-impulse method using the DUK-6V flaw detector. For analysis and laboratory research, rods of three diameters (19, 22 and 25 mm) of 20N2M steel were selected (the content of chemical elements in the rods of the selected standard sizes did not exceed the regulated limits, mass %: 0.19...0.23 С; 0.24...0.33 Si; 0.45... 0.62 Mn; 1.65...1.83 N i; 0.031 S; 0.033 P; 0.21 Cr; 0.22...0.27 Mo; 0.18 Cu). In addition, to compare the patterns of crack growth in the rods, samples from hybrid and fiberglass l it t l i l i t t l i l i t i t t t it i t ilit t i t ti . ti l it t l, i l i . t . li LSEVIER B.V. This is an open ti l t li tt :// ti . /li / / . 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This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the 23 European Conference on Fracture – ECF23 ti