Статті в журналах: "Polyethylene Stresses"

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Huang, Chang-Hung, Yung-Chang Lu, Lin-I. Hsu, Jiann-Jong Liau, Ting-Kuo Chang, and Chun-Hsiung Huang. "Effect of material selection on tibial post stresses in posterior-stabilized knee prosthesis." Bone & Joint Research 9, no. 11 (November 1, 2020): 768–77. http://dx.doi.org/10.1302/2046-3758.911.bjr-2020-0019.r2.

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Aims The material and design of knee components can have a considerable effect on the contact characteristics of the tibial post. This study aimed to analyze the stress distribution on the tibial post when using different grades of polyethylene for the tibial inserts. In addition, the contact properties of fixed-bearing and mobile-bearing inserts were evaluated. Methods Three different grades of polyethylene were compared in this study; conventional ultra high molecular weight polyethylene (UHMWPE), highly cross-linked polyethylene (HXLPE), and vitamin E-stabilized polyethylene (VEPE). In addition, tibial baseplates with a fixed-bearing and a mobile-bearing insert were evaluated to understand differences in the contact properties. The inserts were implanted in neutral alignment and with a 10° internal malrotation. The contact stress, von Mises stress, and equivalent plastic strain (PEEQ) on the tibial posts were extracted for comparison. Results The stress and strain on the tibial post for the three polyethylenes greatly increased when the insert was placed in malrotation, showing a 38% to 56% increase in von Mises stress and a 335% to 434% increase in PEEQ. The VEPE insert had the lowest PEEQ among the three materials. The mobile-bearing design exhibited a lower increase in stress and strain around the tibial posts than the fixed-bearing design. Conclusion Using VEPE for the tibial component potentially eliminates the risk of material permanent deformation. The mobile-bearing insert can help to avoid a dramatic increase in plastic strain around the tibial post in cases of malrotation. The mobility allows the pressure to be distributed on the tibial post and demonstrated lower stresses with all three polyethylenes simulated. Cite this article: Bone Joint Res 2020;9(11):768–777.

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Fisher, H. P., R. K. Eby, and R. C. Cammarata. "Surface stresses in paraffin and polyethylene." Polymer 35, no. 9 (January 1994): 1923–30. http://dx.doi.org/10.1016/0032-3861(94)90982-2.

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Swieszkowski, W., P. Bednarz, and P. J. Prendergast. "Contact stresses in the glenoid component in total shoulder arthroplasty." Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 217, no. 1 (January 1, 2003): 49–57. http://dx.doi.org/10.1243/095441103762597737.

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Several studies of retrieved glenoid components from total shoulder arthroplasty show an erosion of the rim, surface irregularities, component fracture and wear resulting from polyethylene deformation in vivo. Particles resulting from polyethylene wear might be one of the reasons for the very high rate of glenoid component loosening found clinically. Because wear can be the result of high contact stresses, the aim of this study is to find out whether or not contact stresses are high enough to cause wear of the glenoid component and what influence the component type and geometry have on polyethylene contact stresses for different humerus abduction angles. Elasticity theory is used in a parametric study of contact stresses in several glenoid component designs. A finite element method is used to confirm the accuracy of the analytical solution. The analysis shows that the peak stress generated in glenoid components under conditions of normal living can be as high as 25 MPa; since this exceeds the polyethylene yield strength, wear and also cold flow of the components can be expected. It is predicted that more conforming components have lower contact stresses, which might result in lower wear rate and less cold flow. It is also found that a metal-backed component promotes higher contact stresses than an all-polyethylene component with the same total thickness, therefore it can be expected that metal-backed components have inferior wear properties.

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Masayuki, Nishida, Hanabusa Takao, and Yasukazu Ikeuchi. "X-Ray Stress Measurement of Fiber Reinforced Plastics Composite Material." Key Engineering Materials 353-358 (September 2007): 2423–26. http://dx.doi.org/10.4028/www.scientific.net/kem.353-358.2423.

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X-ray stress measurement with sin2ψ method is one of useful tools to detect residual stresses in manufactured products. In this study, the residual stresses in the tungsten fiber reinforced polyethylene composite were examined by X-ray stress measurement technique. The transmission diffraction method was employed in residual stress measurement of polyethylene matrix. The X-ray elastic constant of high density polyethylene (HDPE) which formed matrix of the composite was estimated before residual stress measurement. The results of sin2ψ diagram with transmission method show good linearity under the several tensile loading. After that the residual stresses in the composite were investigated for HDPE matrix phase. From the measurement results, the tensile residual stresses existed in fiber longitudinal direction and compressive ones in transverse direction for HDPE matrix.

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Serebrennikov, Anatoly, Daniil Serebrennikov, and Zufar Hakimov. "Polyethylene Pipeline Bending Stresses at an Installation." American Journal of Engineering and Applied Sciences 9, no. 2 (February 1, 2016): 350–55. http://dx.doi.org/10.3844/ajeassp.2016.350.355.

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Bilgin, Ömer. "Modeling Viscoelastic Behavior of Polyethylene Pipe Stresses." Journal of Materials in Civil Engineering 26, no. 4 (April 2014): 676–83. http://dx.doi.org/10.1061/(asce)mt.1943-5533.0000863.

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Kandemir, Göksu, Simon Smith, and Thomas J. Joyce. "The influence of contact stress on the wear of cross-linked polyethylene." Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 232, no. 10 (August 23, 2018): 1008–16. http://dx.doi.org/10.1177/0954411918796047.

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Generation of wear debris and wear particle-induced osteolysis are the main limitations of metal-on-polyethylene artificial joints. Cross-linked polyethylene has been recently used, particularly in hip replacements, as an alternative material to conventional ultrahigh molecular weight polyethylene due to its superior wear resistance. This study focused on the wear behaviour of cross-linked polyethylene under different contact stresses in order to make interpretations of its long-term in-vivo performance. A 50-station SuperCTPOD (pin-on-disc) machine was used to investigate the influence of contact stress on the wear of cross-linked polyethylene pins which were articulated against cobalt chromium discs. It was found that the wear rate of cross-linked polyethylene was lower at higher contact stresses.

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Triwardono, Joko, Agung Shamsuddin Saragih, Fuad Abrar, Muhammad Satrio Utomo, Ika Kartika, Yudan Whulanza, and Sugeng Supriadi. "Finite Element Analysis Contact Stresses on Tibiofemoral Joint and Post Polyethylene Components Used to Evaluated Predesign Knee Implant." Journal of Biomimetics, Biomaterials and Biomedical Engineering 55 (March 28, 2022): 46–55. http://dx.doi.org/10.4028/p-uv1qax.

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At the time of prayer, most Muslims kneel with fully extended limbs (between 150° and 165°). Meanwhile, incidents such as hyperflexion in total knee arthroplasty (TKA) implant outside their designated configuration can lead wear or fracture of the polyethylene component. In this study, polyethylene component of posterior-stabilized right knee joint implant have been developed to facilitate higher range of motion (ROM). Finite element analysis (FEA) was used to analyze contact stresses on the polyethylene component. FEA was used to simulate weight-bearing condition at 0°, 30°, 60°, 90°, 120°, and 150° of knee flexion. Modified polyethylene component results in better performance in terms of contact stresses, especially at 120° of knee flexion. Current result shows contact stresses above 120 MPa were measured at the posterior post polyethylene, when 4000 N force was applied. Minimum contact stress on the medial condyles was 630 KPa at 120° of knee flexion, while on the lateral condyles, the minimum contact stress was 250 KPa at 150° of knee flexion. With this finding, the current polyethylene component design is expected to accommodate deep knee flexion movement in daily activities and can reduce potential of wear or fracture of the polyethylene component during deep knee flexion.

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Miller, M. C., P. Smolinski, S. Conti, and K. Galik. "Stresses in Polyethylene Liners in a Semiconstrained Ankle Prosthesis." Journal of Biomechanical Engineering 126, no. 5 (October 1, 2004): 636–40. http://dx.doi.org/10.1115/1.1798011.

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A finite element model of a semiconstrained ankle implant with the tibia and fibula was constructed so that the stresses in the polyethylene liner could be computed. Two different widths of talar components were studied and proximal boundary conditions were computed from an inverse process providing a load of five times body weight appropriately distributed across the osseous structures. von Mises stresses indicated small regions of localized yielding and contact stresses that were similar to those in acetabular cup liners. A wider talar component with 36% more surface area reduced contact stress and von Mises stresses at the center of the polyethylene component by 17%.

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D???Lima, Darryl D., Peter C. Chen, and Clifford W. Colwell. "Polyethylene Contact Stresses, Articular Congruity, and Knee Alignment." Clinical Orthopaedics and Related Research 392 (November 2001): 232–38. http://dx.doi.org/10.1097/00003086-200111000-00029.

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Hütter, Markus, Pieter J. in 't Veld, and Gregory C. Rutledge. "Polyethylene {201} crystal surface: interface stresses and thermodynamics." Polymer 47, no. 15 (July 2006): 5494–504. http://dx.doi.org/10.1016/j.polymer.2005.05.160.

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Berg, Ryan R., and Rudolph Bonaparte. "Long-term allowable tensile stresses for polyethylene geomembranes." Geotextiles and Geomembranes 12, no. 4 (January 1993): 287–306. http://dx.doi.org/10.1016/0266-1144(93)90006-a.

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13

Martinelli, Nicoló, Silvia Baretta, Alberto Bianchi Castagnone Prati, Francesco Malerba, Carlo Corrado Bonifacini, and Fabio Galbusera. "Contact Stresses in a Fixed-Bearing Total Ankle Replacement." Foot & Ankle Orthopaedics 2, no. 3 (September 1, 2017): 2473011417S0002. http://dx.doi.org/10.1177/2473011417s000284.

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Category: Ankle, Ankle Arthritis, Basic Sciences/Biologics Introduction/Purpose: Third-generation ankle implants with good clinical results continued to increase the popularity of total ankle arthroplasty (TAA) to address end-stage ankle osteoarthritis preserving joint movement. Newer TAA used fixed-bearing designs, with a theoretical increase of contact stresses leading to a higher polyethylene wear. The purpose of this study was to investigate the contact stresses in the polyethylene component of a new third-generation TAA, with a fixed-bearing design, using 3D finite element analysis. Methods: A three-dimensional finite element model was developed based on the Zimmer Trabecular Metal Total Ankle (ZTMTA) and a finite element analysis was employed to evaluate the contact pressure, contact area and Von Mises stress in the polyethylene articular surface in the stance phase of the gait cycle. Results: The peak values were found at the anterior regions of the articulating surface, where reached 19.8 MPa at 40% of gait cycle. The average contact pressure during the stance phase of gait was 6.9 MPa. The maximum von Mises stress of 14.1 MPa in the anterior section was reached at 40% of the gait cycle. For the central section the maximum von Mises stress of 10.8 MPa was reached at 37% of the gait cycle, whereas for posterior section the maximum of 5.4 MPa was reached at the end of the stance phase (60% of the gait cycle). Conclusion: Although, the average von Mises stress was less than 10 MPa, high peak pressure values were recorded. Advanced models to quantitatively estimate the wear are needed to assess polyethylene and metal component survivorship.

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Giddings, Virginia L., Steven M. Kurtz, and Avram A. Edidin. "Total Knee Replacement Polyethylene Stresses During Loading in a Knee Simulator." Journal of Tribology 123, no. 4 (August 31, 2000): 842–47. http://dx.doi.org/10.1115/1.1330735.

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We investigated the stresses and kinematics of a total knee replacement during the duty cycle of a knee simulator. Finite element models were constructed of the tibial and the femoral component of a commercially available cruciate retaining total knee replacement. Time dependent flexion/extension, axial loading, and anterior/posterior loading were applied to the components of the arthroplasty to match those generated by the knee simulator. We evaluated the effect of varying the stiffness of a spring-loaded bumper system for anterior-posterior constraint on the joint kinematics as well as on the stresses within the polyethylene tibial component. Both the joint kinematics and the stresses and strains subjected to the polyethylene tibial component, were found to be comparatively insensitive to the stiffness of the spring bumper system for this design. When the stiffness of the bumper system was increased by two orders of magnitude, the maximum contact stresses, von Mises stresses, and von Mises strains in the polyethylene tibial component varied by only 15 to 59 percent. In general, increasing the stiffness of the bumper system decreased the displacements of the base plate, but the relationships were nonlinear, possibly due to the added constraints imposed by the tibiofemoral contact interaction. The long-term goal of this research is to develop a validated structural model to predict the stresses, kinematics, and ultimately, the wear, of total joint replacement components in a contemporary knee joint simulator.

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Schipper, Oliver N., Mehul A. Dharia, Justin S. Hertzler, and Jeffrey E. Bischoff. "Fatigue Strength of Highly Crosslinked Polyethylene in Total Ankle Arthroplasty." Foot & Ankle Orthopaedics 4, no. 4 (October 1, 2019): 2473011419S0037. http://dx.doi.org/10.1177/2473011419s00373.

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Category: Ankle Introduction/Purpose: Highly crosslinked polyethylene (HXLPE) was developed for its superior wear properties in comparison to conventional polyethylene (CPE). The higher dose irradiation required for HXLPE may also cause embrittlement, which reduces fatigue resistance and leads to surface cracking or fracture of the polyethylene bearing. Concern over fatigue resistance has prevented widespread adoption of HXLPE for use in in total ankle arthroplasty (TAA). The aim of this study was to determine whether HXLPE has sufficient fatigue strength for total ankle arthroplasty under simulated physiologically relevant motion profiles and loading in the ankle. Methods: A bicondylar, semi-constrained HXLPE TAA design was subjected to 10 million cycles (Mc) of fatigue testing under loading conditions representative of a walking gait. Kinetics and kinematics of gait were incorporated into a computational model (Dassault Systemes / SIMULIA, Johnston, RI), for prediction of peak stresses on the HXLPE insert. Based on predicted peak stresses, worst case component size and loading configuration were identified. Ten samples were tested on a closed loop servohydraulic test frame (MTS Systems Corp., Minneapolis, MN) for 10Mc. Testing was conducted to a peak load of 5600 N (1259lbs), representing approximately 5 times body weight for a 240 lb individual. Following testing, all samples were evaluated for evidence of polyethylene fracture or surface cracking. Results: Peak stresses in the HXLPE insert occurred during heel off, closely corresponding to both peak axial force and dorsiflexion during gait. The smallest sized component had the highest polyethylene insert stresses, whereas larger sized components had more material to bear the same load, resulting in up to a 30% decrease in stress. All 10 specimens completed 10Mc of testing at 5 times body weight without fracture or surface cracking of the polyethylene insert. Conclusion: HXLPE has sufficient fatigue strength to withstand 10Mc of loading at 5 times body weight at the point of peak stresses during gait in total ankle arthroplasty, and therefore, may be mechanically strong enough to withstand the demands of the ankle. Further clinical evidence is necessary to determine if these results translate to adequate fatigue strength with clinical use of HXLPE.

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Qayyum, M. M., and J. R. White. "Effect of stabilizers on residual stresses in weathered polyethylene." Polymer Degradation and Stability 39, no. 2 (January 1993): 199–205. http://dx.doi.org/10.1016/0141-3910(93)90096-2.

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Bakalov, Valery, Victor Kuzmenko, and Igor Yarish. "STUDY OF THE DEPENDENCE OF SHEAR STRESSES OF POLYETHYLENE ON TEMPERATURE AND SHEAR VELOCITY." Technical Sciences and Technologies, no. 2(28) (2022): 96–102. http://dx.doi.org/10.25140/2411-5363-2022-2(28)-96-102.

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Polyethylene is increasingly used in various industries such as light, medical and others as a variety of packaging and structural materials. Rheological properties of polyethylene affect products quality. Therefore, knowledge of these properties affects the calculation methods of equipment that produces materials from polyethylene, as well as the control system of technological processes of such industries.When designing equipment for processing polyethylene, namely the forming channels of extruders, flat slotted heads, the question of accurate determination of its rheological properties depending on the temperature and shear rate arises. Depending on the specified rheological properties the geometrical sizes of the specified channels change. These rheological properties are usually determined on the basis of experiments conducted at certain shear rates and temperatures. When designing, there is a need to calculate the geometric dimensions of the forming channels at shear rates and temperatures other than experimental. Therefore, there is a problem of developing a method of calculating these dimensions on the basis of experimental data obtained at other shear rates and temperatures. On the basis of the conducted research, the equation of the dependence of the shear stress of polyethylene on its shear rate and temperature was obtained. In the equation, the shear stress is directly proportional to the conditional viscosity and the shear rate gradient in power, which is the flow index. It is shown that the conditional viscosity of polyethylene is well described by the Arrhenius equation, and the flow index has a quadratic dependence on temperature. The obtained generalized equation of shear stress of polyethylene from its shear rate and temperature will allow to more accurately calculate the geometric dimensions of the forming channels of extruders, slotted heads, as well as to improve control systems for these devices.

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Bischoff, Jeffrey E., Mehul A. Dharia, Justin S. Hertzler, and Oliver N. Schipper. "Evaluation of Total Ankle Arthroplasty Using Highly Crosslinked Ultrahigh-Molecular-Weight Polyethylene Subjected to Physiological Loading." Foot & Ankle International 40, no. 8 (May 15, 2019): 880–87. http://dx.doi.org/10.1177/1071100719847645.

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Background: Highly crosslinked polyethylene (HXLPE) was developed for its superior wear properties in comparison to conventional polyethylene (CPE). Concern over fatigue resistance has prevented widespread adoption of HXLPE for use in total ankle arthroplasty (TAA). The aim of this study was to determine whether HXLPE has sufficient fatigue strength for total ankle arthroplasty under simulated physiologically relevant motion profiles and loading in the ankle. Methods: Physiologic load and motion profiles representative of walking gait were incorporated into a computational model of a semiconstrained, fixed-bearing TAA to determine the loading state with highest stresses in the HXLPE bearing. Subsequent fatigue testing to 10 million cycles (Mc) at 5600 N was performed to assess bearing strength. Results: Peak stresses in the bearing were predicted at peak axial load and peak dorsiflexion during gait, occurring near heel off. All samples withstood 10 Mc of fatigue loading at that orientation without polyethylene bearing fracture. Conclusion: HXLPE had sufficient fatigue strength to withstand 10 Mc of loading at more than 5 times body weight at the point of peak stresses during simulated gait in total ankle arthroplasty. Clinical Relevance: HXLPE may be mechanically strong enough to withstand the in vivo demands of the ankle. Improvements in wear afforded by HXLPE can be obtained without compromising sufficient polyethylene strength properties in total ankle arthroplasty.

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Khosravipour, Ida, Shabnam Pejhan, Yunhua Luo, and Urs P. Wyss. "Customized surface-guided knee implant: Contact analysis and experimental test." Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 232, no. 1 (November 30, 2017): 90–100. http://dx.doi.org/10.1177/0954411917744586.

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Contact pressure and stresses on the articulating surface of the tibial component of a total knee replacement are directly related to the joint contact forces and the contact area. These stresses can result in wear and fatigue damage of the ultra-high-molecular-weight polyethylene. Therefore, conducting stress analysis on a newly designed surface-guided knee implant is necessary to evaluate the design with respect to the polyethylene wear. Finite element modeling is used to analyze the design’s performance in level walking, stair ascending and squatting. Two different constitutive material models have been used for the tibia component to evaluate the effect of material properties on the stress distribution. The contact pressure results of the finite element analysis are compared with the results of contact pressure using pressure-sensitive film tests. In both analyses, the average contact pressure remains below the material limits of ultra-high-molecular-weight polyethylene insert. The peak von Mises stresses in 90° of flexion and 120° of flexion (squatting) are 16.28 and 29.55 MPa, respectively. All the peak stresses are less than the fatigue failure limit of ultra-high-molecular-weight polyethylene which is 32 MPa. The average contact pressure during 90° and 120° of flexion in squatting are 5.51 and 5.46 MPa according to finite element analysis and 5.67 and 8.14 MPa according to pressure-sensitive film experiment. Surface-guided knee implants are aimed to resolve the limitations in activities of daily living after total knee replacement by providing close to normal kinematics. The proposed knee implant model provides patterns of motion much closer to the natural target, especially as the knee flexes to higher degrees during squatting.

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Manu, Ioana-Daniela. "The effect of rotating-bending fatigue on high-density polyethylene." Romanian Journal of Petroleum & Gas Technology 3 (74), no. 1 (2022): 71–82. http://dx.doi.org/10.51865/jpgt.2022.01.08.

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External factors, such as main stresses, frequency of the loading, shape and history of loading (hysteresis) have an important effect on the fatigue behavior of high-density polyethylene. HDPE pipes, used in the transport and distribution of water and are required for oscillating loads caused by internal pressure or external loads. These cyclic loads cause the pipe's failure due to fatigue. In a polymer fatigue occurs at stress levels that are low relative to the yield strength [1]. This paper presents results from the assessment of the mechanical behavior of specimen test taken from PE 100 pipe in the case of variable stresses. Thus, compressive and tensile stresses are induced on the specimen test as it is simultaneously bent and rotated. The rotating-bending fatigue test is performed when the specimen test is placed with the extremities on two supports and supports a load applied in four-points placed symmetrically with respect to the supports, at 1/3 of the distance between the supports, according to [2]. The effect of the values of the number of cycles until failure in the case of rotating-bending fatigue stress on mechanical properties of HDPE is also compared with the same factor in the case of axial fatigue stress. The polyethylene pipe may be subjected to random variable stresses. In practice, variable loading patterns as strain rate, temperature, hydrostatic pressure, pressure from to the vehicle wheels, the movement and the variable weights supported by the surrounding soil are causes that could lead to the bending of PE pipe. These loads generate oscillating axial stresses. The bending of the pipe is cause of the cross-section modification (roundness modification) of it.

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DʼLIMA, DARRYL D., PETER C. CHEN, MARK A. KESTER, and CLIFFORD W. COLWELL. "IMPACT OF PATELLOFEMORAL DESIGN ON PATELLOFEMORAL FORCES AND POLYETHYLENE STRESSES." Journal of Bone and Joint Surgery-American Volume 85 (2003): 85–93. http://dx.doi.org/10.2106/00004623-200300004-00010.

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Serebrennikov, A. A., D. A. Serebrennikov, and Z. R. Hakimov. "Justification of indirect methods of bending stresses polyethylene pipes evaluation." IOP Conference Series: Earth and Environmental Science 87 (October 2017): 082044. http://dx.doi.org/10.1088/1755-1315/87/8/082044.

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Olasz, L., and P. Gudmundson. "Prediction of residual stresses in cross-linked polyethylene cable insulation." Polymer Engineering & Science 45, no. 8 (2005): 1132–39. http://dx.doi.org/10.1002/pen.20376.

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Bartel, D. L., A. H. Burstein, M. D. Toda, and D. L. Edwards. "The Effect of Conformity and Plastic Thickness on Contact Stresses in Metal-Backed Plastic Implants." Journal of Biomechanical Engineering 107, no. 3 (August 1, 1985): 193–99. http://dx.doi.org/10.1115/1.3138543.

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Surface damage in polyethylene components for total joint replacement is associated with large contact stresses. An elasticity solution and finite element analyses were used to determine the influence of design parameters on the stresses due to contact in metal-backed components. For nearly conforming contact surfaces, it was found that the stresses in the plastic are very sensitive to clearance, that minimum plastic thickness of 4–6 mm should be maintained for metal-backed components, and that bonding the plastic to the metal backing reduces tensile stresses in the plastic at the edge of the contact zone.

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Minns, R. J. "Wear and Contact Stress Studies of the Minns Meniscal Knee Prosthesis." Engineering in Medicine 17, no. 3 (July 1988): 135–38. http://dx.doi.org/10.1243/emed_jour_1988_017_035_02.

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This paper describes the results of wear testing and contact area studies of a Minns meniscal knee prosthesis and compares the results of previous work on wear and contact stress studies of other knee prosthesis designs. Although stresses that arise at the surface of the polyethylene meniscus components are large, after repetitive loading the contact area rises, as a consequence of plastic flow and creep, and they reduce to a fifth of the initial stress after 1 million cycles. Contact area studies show that asymmetrical loading of the meniscus give proportionally high stresses on the higher loaded meniscus and, at large values of flexion, have similar values to a more conforming but fixed polyethylene tibial component design of knee prosthesis.

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Avrigean, Eugen. "Studies and Research on the Behavior of Polyethylene when Electrofusion Welding Fittings to High Density Polyethylene Pipes." Materiale Plastice 58, no. 1 (April 5, 2021): 85–98. http://dx.doi.org/10.37358/mp.21.1.5448.

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This aim of this paper is to perform a study on the way the material of the fittings that can be welded through eletrofusion on polyethylene pipes withstands. The process is observed by means of the thermal and fast cameras. Also we intend to analyze the way the assembly consisting of the polyethylene fitting and pipe behaves during welding. The stresses caused by the welding process are observed, as well as the concurrent welding of the tapping tee and the branch saddle tee.

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Conard, B. E., R. A. Lohnes, F. W. Klaiber, and T. J. Wipf. "Boundary Effects on Response of Polyethylene Pipe Under Simulated Live Load." Transportation Research Record: Journal of the Transportation Research Board 1624, no. 1 (January 1998): 196–205. http://dx.doi.org/10.3141/1624-23.

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The objective of this paper is to evaluate the deflection response of polyethylene pipes when loaded near their ends. Tests were conducted on pipes loaded at the center and near their ends to simulate loading of a vehicle at the center of a roadway and on the shoulder. The tests were performed on 900-mm (36-in.) and 1200-mm (48-in.) diameter polyethylene pipes with 610-mm (2 ft) cover and a variety of backfills. Loads were applied through a 93 025-mm2 (1-ft2) plate that provides very severe loading conditions. At high contact stresses, the load test plate punched into the soil cover so that the crown of the pipe was subjected to stresses in excess of those that would have occurred if the soil surface were paved or stabilized or a less severe loading condition better representing a truck tire had been used. At contact stresses equivalent to moderate highway tire pressures, pipe deflections are slightly higher near the ends of the pipes than at the center. Except for low-density till, the percent deflections are not excessive and the pipe-soil systems have adequate stiffness. For contact stresses near the upper limit of truck tire pressures and when loaded near the ends, the pipes with sand and till backfills fail by local wall bending. For flowable-fill backfill, the ultimate capacity of the pipes is nearly twice that for the soil backfills.

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Reinholds, Ingars, Valdis Kalkis, Janis Zicans, Remo Merijs Meri, and Ivans Bockovs. "New Thermoshrinkable Materials of Radiation Modified Polypropylene-Elastomer Composites with Cross-Linking Agents." Key Engineering Materials 604 (March 2014): 134–37. http://dx.doi.org/10.4028/www.scientific.net/kem.604.134.

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In this work, electron beam modified heterogeneous composites of isotactic polypropylene (PP) with chlorinated polyethylene (CPE) have been investigated. The PP/CPE blend composites with an excess of elastomer (30/70 wt%) have been modified with trimethylolpropane triacrylate (TMPTA) and bisphenol-A-dimethacrylate (BPDMA) cross-linking agents and have been irradiated with accelerated electrons up to ionizing radiation doses from 25 to 150 kGy. The internal stresses characterizing the thermoshrinkage properties (TMP) thermorelaxation stresses formed in thermal heating and the residual stresses resulting in the process of full setting and cooling of materials have been investigated for radiation cross-linked oriented (extended up to 100%) composite samples. The dependence of cross-linking efficiency and the TMP characteristics of PP/CPE heterogeneous blends have been compared to properties of a low density polyethylene (LDPE), which has been commonly used as thermoshrinkable material (TSM) in polymer industry. It has been proved that the radiation-chemically modified PP multiphase composites with elastomers and the crosslinking promoters are comparable perspective materials for creation thermoshrinkable materials with higher or similar thermoshrinkage properties compared to currently exploited TSM.

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Dehghani, Samaneh, Mahdi Salami Hosseini, and Ehsan Behzadfar. "Slip behavior of high-density polyethylene at small shear stresses in the presence of esterified polyethylene glycol." Physics of Fluids 33, no. 6 (June 2021): 063101. http://dx.doi.org/10.1063/5.0053461.

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30

Pramualsingha, Sarawuth, and Peerawut Yutthagowith. "Engineering Lifetime Model of Crosslinked Polyethylene under Electrical and Thermal Stresses." Sensors and Materials 33, no. 7 (July 15, 2021): 2445. http://dx.doi.org/10.18494/sam.2021.3310.

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Hopkins, Andrew R., Ulrich N. Hansen, Andrew A. Amis, Lucy Knight, Mark Taylor, Ofer Levy, and Stephen A. Copeland. "Wear in the Prosthetic Shoulder: Association With Design Parameters." Journal of Biomechanical Engineering 129, no. 2 (October 4, 2006): 223–30. http://dx.doi.org/10.1115/1.2486060.

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Total replacement of the glenohumeral joint provides an effective means for treating a variety of pathologies of the shoulder. However, several studies indicate that the procedure has not yet been entirely optimized. Loosening of the glenoid component remains the most likely cause of implant failure, and generally this is believed to stem from either mechanical failure of the fixation in response to high tensile stresses, or through osteolysis of the surrounding bone stock in response to particulate wear debris. Many computational studies have considered the potential for the former, although only few have attempted to tackle the latter. Using finite-element analysis an investigation, taking into account contact pressures as well as glenohumeral kinematics, has thus been conducted, to assess the potential for polyethylene wear within the artificial shoulder. The relationships between three different aspects of glenohumeral design and the potential for wear have been considered, these being conformity, polyethylene thickness, and fixation type. The results of the current study indicate that the use of conforming designs are likely to produce slightly elevated amounts of wear debris particles when compared with less conforming joints, but that the latter would be more likely to cause material failure of the polyethylene. The volume of wear debris predicted was highly influenced by the rate of loading, however qualitatively it was found that wear predictions were not influenced by the use of different polyethylene thicknesses nor fixation type while the depth of wearing was. With the thinnest polyethylene designs (2mm) the maximum depth of the wear scar was seen to be upwards of 20% higher with a metal-backed fixation as opposed to a cemented design. In all-polyethylene designs peak polymethyl methacrylate tensile stresses were seen to reduce with increasing polyethylene thickness. Irrespective of the rate of loading of the shoulder joint, the current study indicates that it is possible to optimize glenoid component design against abrasive wear through the use of high conformity designs, possessing a polyethylene thickness of at least 6mm.

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Wei, Wentao, Huiyuan Wang, Xuqing Liu, Wenjing Kou, Ziqi Liu, Huihui Wang, Yongkang Yang, et al. "Transcriptome Profiling of Stem-Differentiating Xylem in Response to Abiotic Stresses Based on Hybrid Sequencing in Cunninghamia lanceolata." International Journal of Molecular Sciences 23, no. 22 (November 12, 2022): 13986. http://dx.doi.org/10.3390/ijms232213986.

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Cunninghamia lanceolata (C. lanceolata) belongs to Gymnospermae, which are fast-growing and have desirable wood properties. However, C. lanceolata’s stress resistance is little understood. To unravel the physiological and molecular regulation mechanisms under environmental stresses in the typical gymnosperm species of C. lanceolata, three-year-old plants were exposed to simulated drought stress (polyethylene glycol 8000), salicylic acid, and cold treatment at 4 °C for 8 h, 32 h, and 56 h, respectively. Regarding the physiological traits, we observed a decreased protein content and increased peroxidase upon salicylic acid and polyethylene glycol treatment. Superoxide dismutase activity either decreased or increased at first and then returned to normal under the stresses. Regarding the molecular regulation, we used both nanopore direct RNA sequencing and short-read sequencing to reveal a total of 5646 differentially expressed genes in response to different stresses, of which most had functions in lignin catabolism, pectin catabolism, and xylan metabolism, indicating that the development of stem-differentiating xylem was affected upon stress treatment. Finally, we identified a total of 51 AP2/ERF, 29 NAC, and 37 WRKY transcript factors in C. lanceolata. The expression of most of the NAC TFs increased under cold stress, and the expression of most of the WRKY TFs increased under cold and SA stress. These results revealed the transcriptomics responses in C. lanceolata to short-term stresses under this study’s experimental conditions and provide preliminary clues about stem-differentiating xylem changes associated with different stresses.

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Oberbach, Thomas, Sabine Begand, and Wilfried Glien. "Hip Simulator Study of Ceramic-Ceramic and Ceramic-PE-Couplings with Different Head Diameters." Key Engineering Materials 309-311 (May 2006): 1269–72. http://dx.doi.org/10.4028/www.scientific.net/kem.309-311.1269.

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The contact conditions and the resulting contact stresses for ceramic on ceramic pairings with diameter 28, 32 and 36mm were determined. A hip simulator according ISO 14242 was used to measure the wear behaviour of these hard – hard couplings in comparison with the common hard – soft pairing ceramic on polyethylene. It was found that there isn’t a significant dependence of the wear behaviour from articulation diameter for ceramic on ceramic but a strong increase of polyethylene wear with larger hip joint heads.

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Manu, Ioana Daniela. "Internal Pressure Test on HDPE Pipe Ring." Materiale Plastice 59, no. 3 (October 3, 2022): 21–30. http://dx.doi.org/10.37358/mp.22.3.5603.

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The purpose of experiment was the highlight of the creep of ring from polyethylene pipe subjected to internal pressure. To create the internal pressure in the HDPE pipe ring, a weight of 4.5 kg was superimposed on it, in the form of a cylindrical plate. In order to evaluate the strains of the elastic element subjected to the tensile stress, respectively compression, tensometric marks 1 and 2 are placed on the outside, in the case of the circular section. The internal pressure test was performed to evaluate the strains of the material of a PE 100 polyethylene ring in two directions: one axial (longitudinal) and the other transverse (circumferential) in order to highlight the creep of the pipe material due to its structure. In a polyethylene pipe stressed at internal pressure, due to the symmetry the tangential stresses are zero. The axial strain initially showed a positive increase, followed by a decrease, reaching negative values towards the end of the experiment, while the circumferential strain recorded positive values, about 300 times higher than the initial ones. The principal stress changed approximately linearly. The circumferential stress recorded the maximum value of σ1=0.33 MPa (3.3 bar) after two and a half hours of experiment. Based on such this test could be calculate Poisson s ratio ν.

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35

Revjakin, Oleg, Janis Zicans, Martins Kalnins, Valdis Kalkis, and Robert D. Maksimov. "Thermomechanical Properties of Radiation-Modified Polyethylene/Ethylene-Propylene-Diene Copolymer/Liquid-Crystalline Copolyester Blends." Collection of Czechoslovak Chemical Communications 64, no. 7 (1999): 1180–92. http://dx.doi.org/10.1135/cccc19991180.

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Radiation-modified blends of high-density polyethylene (PE) with ethylene-propylene-diene copolymer (EPDM; 10-65 wt.%) and thermotropic liquid-crystalline polymer (LCP; 10 wt.%) were investigated. The LCP was a liquid-crystalline copolyester of 40% poly(ethylene terephthalate) with 60% 4-hydroxybenzoic acid. The constituents were blended using a circular extruder, the specimens were prepared by compression molding and irradiated by 60Co γ-radiation up to 200 kGy. Mechanical, thermal, and morphological properties in wide temperature range were investigated for the irradiated and non-irradiated specimens. The effects of irradiation on the thermomechanical behaviour of the PE matrix are discussed. The LCP addition significantly affected the stress-strain behaviour of PE at temperatures above its melting point resulting in some anomalies in kinetics of formation of thermorelaxation stresses, which arise if the material is previously oriented. Thermosetting properties (thermorelaxation stresses and residual setting stresses under conditions of isometric heating and cooling) of the PE/EPDM/LCP blends crosslinked by irradiation and then oriented were also established. The results obtained suggest that such ternary blends improve the application properties of irradiated polyethylene and obtain useful thermosetting materials.

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36

Kazerooni, Elham Ahmed, Sajeewa S. N. Maharachchikumbura, Abdullah Mohammed Al-Sadi, Umer Rashid, Il-Doo Kim, Sang-Mo Kang, and In-Jung Lee. "Effects of the Rhizosphere Fungus Cunninghamella bertholletiae on the Solanum lycopersicum Response to Diverse Abiotic Stresses." International Journal of Molecular Sciences 23, no. 16 (August 10, 2022): 8909. http://dx.doi.org/10.3390/ijms23168909.

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This study examined the efficiency of fungal strain (Cunninghamella bertholletiae) isolated from the rhizosphere of Solanum lycopersicum to reduce symptoms of salinity, drought and heavy metal stresses in tomato plants. In vitro evaluation of C. bertholletiae demonstrated its ability to produce indole-3-Acetic Acid (IAA), ammonia and tolerate varied abiotic stresses on solid media. Tomato plants at 33 days’ old, inoculated with or without C. bertholletiae, were treated with 1.5% sodium chloride, 25% polyethylene glycol, 3 mM cadmium and 3 mM lead for 10 days, and the impact of C. bertholletiae on plant performance was investigated. Inoculation with C. bertholletiae enhanced plant biomass and growth attributes in stressed plants. In addition, C. bertholletiae modulated the physiochemical apparatus of stressed plants by raising chlorophyll, carotenoid, glucose, fructose, and sucrose contents, and reducing hydrogen peroxide, protein, lipid metabolism, amino acid, antioxidant activities, and abscisic acid. Gene expression analysis showed enhanced expression of SlCDF3 and SlICS genes and reduced expression of SlACCase, SlAOS, SlGRAS6, SlRBOHD, SlRING1, SlTAF1, and SlZH13 genes following C. bertholletiae application. In conclusion, our study supports the potential of C. bertholletiae as a biofertilizer to reduce plant damage, improve crop endurance and remediation under stress conditions.

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37

Starostin, NP, and RS Tikhonov. "Thermoelastic state during electrofusion welding of polyethylene pipes at different ambient temperatures." IOP Conference Series: Earth and Environmental Science 991, no. 1 (February 1, 2022): 012011. http://dx.doi.org/10.1088/1755-1315/991/1/012011.

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Abstract The problem of welding polyethylene pipes used in the mining industry at low ambient temperatures is considered The numerical solution of a thermoelastic problem revealed the distinctive features of thermal and stress-strain states of weld connections of polyethylene pipes using embedded heater couplings at different ambient temperatures. It is found that in low-temperature conditions, the size of the melted zone is considerably smaller than during welding at permissible temperatures. In this regard, the pressure insufficient for high-quality welding is created between the coupling and the pipe. It is also shown that at the time of melt crystallization, the maximum values of stresses and strains during welding at low temperatures are higher than during welding in the permissible temperature range, which causes high values of residual stresses. The results obtained can be used in the development of low temperature welding technology.

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38

Blake, T. J., E. Bevilacqua, and Janusz J. Zwiazek. "Effects of repeated stress on turgor pressure and cell elasticity changes in black spruce seedlings." Canadian Journal of Forest Research 21, no. 9 (September 1, 1991): 1329–33. http://dx.doi.org/10.1139/x91-187.

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One-year-old black spruce (Piceamariana (Mill.) B.S.P.) seedlings were preconditioned by exposing them to either one or two dehydration–rehydration cycles by using the osmoticum polyethylene glycol 3350. Preconditioned and unconditioned seedlings were then subjected to a more severe osmotic (water) stress by exposing them to a higher concentration of polyethylene glycol. Effects of repeated dehydration–rehydration cycles on cell-water relations were studied after 3, 7, and 13 days of stress relief using pressure–volume curve analysis. Repeated dehydration–rehydration cycles caused a cumulative increase in turgor potentials at full saturation. In these preconditioned plants there was also a progressive lowering of osmotic potentials and relative water contents at zero turgor, which increased over time with stress relief. The decline in osmotic potentials at zero turgor in osmotically stressed black spruce was associated with increased cell wall relaxation, followed by increased turgor potentials, in preconditioned but not in unconditioned seedlings. Saturated osmotic potentials were not altered by repeated, short-term conditioning stresses, suggesting that tissue elasticity was more important for turgor regulation than osmotic adjustment.

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39

Zamora, Pablo, Susana Rasmussen, Ariel Pardo, Humberto Prieto, and Gustavo E. Zúñiga. "Antioxidant responses of in vitro shoots of Deschampsia antarctica to Polyethylene glycol treatment." Antarctic Science 22, no. 2 (January 22, 2010): 163–69. http://dx.doi.org/10.1017/s0954102009990733.

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AbstractTo understand the adaptability to environmental stresses by Deschampsia antarctica, one of the two vascular plants growing in Antarctica, we analysed the activity of several antioxidant enzymes, including peroxidase (POD, EC 1.11.1.7), ascorbate peroxidase (APX, EC 1.11.1.11), catalase (CAT, EC 1.11.1.6)) and glutathion reductase (GR, EC 1.6.4.2), in shoots subjected to drought stress (PEG-8000, -0.3 MPa). Additionally, levels of total phenolic compounds, flavonoids and ascorbate, were determined. The content of malondialdehyde (MDA), chlorophyll and hydrogen peroxide did not change as a result of PEG-8000 treatment. In addition, treated plants showed higher enzymatic activity of CAT, POD and GR in shoots than control plants. In addition, a high capacity to scavenge free radicals was also detected in stressed plants. These results seem to indicate that in D. antarctica tolerance of drought stress is associated with enhanced activity of antioxidant enzymes and free radical scavenging capacity.

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40

Waldman, S. D., and J. T. Bryant. "Dynamic Contact Stress and Rolling Resistance Model for Total Knee Arthroplasties." Journal of Biomechanical Engineering 119, no. 3 (August 1, 1997): 254–60. http://dx.doi.org/10.1115/1.2796089.

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Problems associated with premature failure of total knee replacements (TKR’s) include: wear, creep, and oxidation of ultrahigh-molecular-weight polyethylene (UHM-WPe) as well as adverse tissue reactions to polyethylene wear debris. These problems are associated in part with the mechanical behavior of UHMWPe. In TKR’s, contact stress analyses have been performed on the UHMWPe tibial component; however, most have employed simplified material properties and not accounted for joint kinematics. A nonlinear viscoelastic rolling model was developed for TKR’s to predict the contact stress and rolling friction for varying rolling speed, conformity, applied load, and tibial plateau thickness. Results indicated that the contact stress increased and rolling friction decreased with increasing rolling speed. Effects of conformity, applied load, and tibial plateau thickness were consistent with previous models. At large rolling speeds, predicted peak contact stresses were almost twice their static value, resulting in a compound fatigue problem in UHMWPe components due to normal cyclic loading, moving point of contact, and velocity-dependent stresses.

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41

Khademi-Zahedi, Reza, and Pouyan Alimouri. "Finite Element Analysis to the Effect of Thermo-Mechanical Loads on Stress Distribution in Buried Polyethylene Gas Pipes Jointed by Electrofusion Sockets, Repaired by PE Patches." Energies 11, no. 10 (October 19, 2018): 2818. http://dx.doi.org/10.3390/en11102818.

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Polyethylene (PE) gas pipes can be jointed together by electrofusion PE fittings, which have sockets that are fused onto the pipe. Additionally, electrofused PE patches can be used to repair defected pipes. When these pipelines are buried under the ground, they can experience sever local stresses due to the presence of pipe joints, which is superimposed on the other effects including the soil-structure interaction, traffic load, soil’s column weight, a uniform internal pressure, and thermal loads imposed by daily and/or seasonal temperature changes. The present contribution includes two cases. At first, stress variations in buried polyethylene gas pipe and its socket due to the aforementioned loading condition is estimated using finite element. The pipe is assumed to be made of PE80 material and its jointing socket material is PE100. Afterward, the effects of aforementioned thermo-mechanical loads on the stress distribution in patch repaired buried pipes are well investigated. The soil physical properties and the underground polyethylene pipe installation method are based on the American association of state highway and transportation officials and American society for testing and material standards. The computer simulation and analysis of stresses are performed through the finite element package of ANSYS Software. Stress concentrations can be observed in both components due to the presence of the socket or the repair patch. According to the results, the electrofusion sockets can be used for joining PE gas pipes even in hot climate areas. The maximum values of these stresses happen to be in the pipe. Also, the PE100 socket is more sensitive to a temperature drop. Additionally, all four studied patch arrangements show significant reinforcing effects on the defected section of the buried PE gas pipe to withstand applied loads. Meanwhile, the defected buried medium density polyethylene (MDPE) gas pipe and its saddle fused patch can resist the imposed mechanical and thermal loads of +22 °C temperature increase.

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Dear, John P., and Nick S. Mason. "The Effects of Chlorine Depletion of Antioxidants in Polyethylene." Polymers and Polymer Composites 9, no. 1 (January 2001): 1–13. http://dx.doi.org/10.1177/096739110100900101.

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For many polyethylene products, their working life-span depends on retention by the material of its antioxidant. In dry air, when the working and environmental stresses remain within defined limits, the life-span of the material can be many decades. Immersed in water, for example, the diffusion and loss of antioxidant from the material's surface can increase. Also, some types of aggressive agents, if in the water, can enter the material's surface and migrate into the material to increase the depletion of the antioxidant population. Researched in this study, is the depletion of antioxidants in polyethylene when exposed to water containing different chlorine concentrations. This research relates to the world-wide use of polyethylene pipes in water treatment and distribution networks.

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43

Ek, C. G. "Correlation between interfacial interactions and internal stresses in filled high density polyethylene." Rheologica Acta 27, no. 3 (May 1988): 279–88. http://dx.doi.org/10.1007/bf01329744.

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44

Pleşa, Ilona, Petru Noţingher, Cristina Stancu, Frank Wiesbrock, and Sandra Schlögl. "Polyethylene Nanocomposites for Power Cable Insulations." Polymers 11, no. 1 (December 24, 2018): 24. http://dx.doi.org/10.3390/polym11010024.

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This review represents a comprehensive study of nanocomposites for power cables insulations based on thermoplastic polymers such as polyethylene congeners like LDPE, HDPE and XLPE, which is complemented by original results. Particular focus lies on the structure-property relationships of nanocomposites and the materials’ design with the corresponding electrical properties. The critical factors, which contribute to the degradation or improvement of the electrical performance of such cable insulations, are discussed in detail; in particular, properties such as electrical conductivity, relative permittivity, dielectric losses, partial discharges, space charge, electrical and water tree resistance behavior and electric breakdown of such nanocomposites based on thermoplastic polymers are described and referred to the composites’ structures. This review is motivated by the fact that the development of polymer nanocomposites for power cables insulation is based on understanding more closely the aging mechanisms and the behavior of nanocomposites under operating stresses.

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45

Phares, B. M., T. J. Wipf, F. W. Klaiber, and R. A. Lohnes. "Behavior of High-Density Polyethylene Pipe with Shallow Cover." Transportation Research Record: Journal of the Transportation Research Board 1624, no. 1 (January 1998): 214–24. http://dx.doi.org/10.3141/1624-25.

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In this investigation, a testing program was initiated to gain some understanding of the nature of high-density polyethylene (HDPE) as a structural material and as a buried structure. The testing program consisted of a series of parallel plate tests, a sequence of flexural tests, and field tests of buried pipes under varying backfill conditions. Parallel plate tests were conducted in accordance with ASTM D2412. The flexural testing consisted of applying two point loads to simply supported beam specimens. The field tests completed in this investigation were developed to study the response of large-diameter HDPE to concentrated loads under shallow cover. From the testing, it seems that in cases where high longitudinal stresses may be present (concentrated loads with shallow cover, uneven bedding, uplift, etc.) the pipeline designer should consider the longitudinal strength of HDPE pipes in addition to the circumferential and backfill properties. In addition, the designer must realize that when stresses exist in both directions, the Poisson’s ratio effect must be considered. This finding is supported by the longitudinal failure strains measured during the flexural tests and the field tests. In both types of tests, the pipes failed at approximately the same longitudinal strain level, approximately 1,300 microstrain. On the other hand, in the field tests, the pipes never reached the magnitude of strain associated with failure in the laboratory parallel plate tests.

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46

Werner, Krzysztof, and Wlodzimierz Baranowski. "The Critical Size of Defect in Polyethylene Pipes because of their Cracking." Key Engineering Materials 598 (January 2014): 249–54. http://dx.doi.org/10.4028/www.scientific.net/kem.598.249.

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In the work the possibility of the rapid crack propagation was analyzed in pipe made from polyethylene with the internal defect about the shape of the elliptical fissure. Pipes made from polyethylene are applied to the building of water-pipes. Critical dimension of such fissure was calculated because of the possibility of rapid cracking the pipe in low temperatures. Calculations were carried out for the nominal pressure during the exploitation of the pipeline and for raised pressure in the test of the tightness of the pipeline. Residual stresses resulting from the production engineering of pipes were also considered in the analysis.

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47

Koloskova, G. M. "Modelling of stresses and strains in two-layer combined materials at their formation." Archives of Materials Science and Engineering 1-2, no. 97 (May 1, 2019): 12–19. http://dx.doi.org/10.5604/01.3001.0013.2866.

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Purpose: The aim of the represented study was to model the behaviour of two-layer combined material during its manufacturing. Design/methodology/approach: The model of material layers joining by means of calender method is built in LS-DYNA software on the basis of finite element method. Using the developed model the study of stress and strain condition changes is carried out. Numerical modelling was carried out for two types of two-layer combined materials in similar conditions. First combination was of high-density polyethylene top layer and aluminium foil bottom layer. Second combination was of high-density polyethylene top layer and low- density polyethylene bottom layer. Joining materials had equal thicknesses. Findings: During formation of two-layer combined materials the primary strain always occurs at the bottom plate of the bottom layer. However, the maximum plastic strain will be represented for the layer with lower elastic modulus value. At the point of the highest loading applied to the two-layer combined material the elasticity condition is changed to the plasticity one and the yield process is registered. Practical implications: Multi-layer combined materials are some of the most advanced types of materials. The quality of the joining of the layers, the strains and the stresses arising in their manufacturing process are the main causes of low interlayer strength. It leads to easy exfoliation and destruction of the material. The results of the study may be used to improve the quality of multi-layer combined materials. Originality/value: For the first time the model was developed for the determination of strains and stresses arising during the formation of multi-layer combined materials by means of calendering method. The calculations of the stresses and strains distribution dynamics for two-layer combined materials are represented for polymer-metal and polymer-polymer layers combinations. The results of the study may be of interest to specialists in the field of multi-layer combined materials designing and manufacturing.

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48

Lei, Chu, Muthukumar Bagavathiannan, Huiyong Wang, Shaun M. Sharpe, Wenting Meng, and Jialin Yu. "Osmopriming with Polyethylene Glycol (PEG) for Abiotic Stress Tolerance in Germinating Crop Seeds: A Review." Agronomy 11, no. 11 (October 30, 2021): 2194. http://dx.doi.org/10.3390/agronomy11112194.

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Abiotic stresses such as drought, extreme temperature, and salinity can negatively impact seed germination and plant growth and have become major limitations to crop production. Most crops are vulnerable to abiotic stress factors during their early growth phase, especially during seed germination and seedling emergence. Rapid crop seed germination and seedling establishment is known to provide competitive advantages over weeds and improve yields. Seed osmopriming is defined as a pre-sowing treatment in which seeds are soaked in osmotic solutions to undergo the first stage of germination, but radicle protrusion has not occurred. The process of osmopriming involves prior exposure of seeds in low-water-potential solutions. Osmopriming can generate a series of pre-germination metabolic activities, increase the antioxidant system activities, and prepare the seed for radicle protrusion. Polyethylene glycol (PEG) is a popular osmopriming agent that can alleviate the negative impacts of abiotic stresses. This review summarizes research findings on crop responses to seed priming with PEG under abiotic stresses. The challenges, limitations, and opportunities of using PEG for crop seed priming are discussed with the goal of providing insights into future research towards effective application of seed priming in crop production.

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49

Hao, W. F., X. W. Chen, Y. N. Yuan, and Y. J. Ma. "Analysis of Residual Stresses in Blow Molded Polyethylene Terephthalate Bottles Using Creep Model." International Polymer Processing 30, no. 5 (November 30, 2015): 534–41. http://dx.doi.org/10.3139/217.3036.

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50

Nakamura, S., F. Murabayashi, K. Iida, G. Sawa, and M. Ieda. "Degradation of Dielectric Properties of Polyethylene by Combined Y-Irradiation and Thermal Stresses." IEEE Transactions on Electrical Insulation EI-22, no. 6 (December 1987): 715–20. http://dx.doi.org/10.1109/tei.1987.298932.

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