PSI - Issue 80

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ScienceDirect

Procedia Structural Integrity 80 (2026) 195–202 Structural Integrity Procedia 00 (2023) 000–000 Structural Integrity Procedia 00 (2023) 000–000

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© 2025 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 Ferri Aliabadi Abstract Leakage in bolted pipe flange connections, particularly those involving materials with dissimilar sti ff ness like high-density polyethylene (HDPE) and steel, is a persistent challenge in infrastructure systems. This study investigates a computational frame work for evaluating and improving the leak-tightness of HDPE flange assemblies by employing the tetra-parametric assem bly method (TAM), which iteratively calculates non-uniform bolt load distribution. The approach accounts for key time- and temperature-dependent phenomena, including viscoelasticity and stress relaxation in HDPE, using a calibrated non-linear three network (TN) constitutive model. Finite element analysis (FEA) is used to simulate the long-term mechanical response of HDPE connections under various isothermal conditions (23 ◦ C , 40 ◦ C , 60 ◦ C , and 80 ◦ C ), revealing increased susceptibility to leakage at elevated temperatures due to loss of bolt preload. To reflect real-world operating conditions, an annual temperature profile rep resentative of an above-ground piping system was applied to the model, enabling prediction of leak-tightness over a full year of service. The results highlight the importance of accounting for thermal and mechanical degradation over time and inform several bolt re-torquing strategies to mitigate leakage risks. The proposed framework o ff ers practical guidelines for optimizing HDPE flange connection performance and provides engineers with a robust tool for improving the reliability of thermoplastic piping systems. © 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of Professor Ferri Aliabadi. Keywords: Bolted connections; HDPE; Elastic interaction; Relaxation; Thermal loads. Abstract Leakage in bolted pipe flange connections, particularly those involving materials with dissimilar sti ff ness like high-density polyethylene (HDPE) and steel, is a persistent challenge in infrastructure systems. This study investigates a computational frame work for evaluating and improving the leak-tightness of HDPE flange assemblies by employing the tetra-parametric assem bly method (TAM), which iteratively calculates non-uniform bolt load distribution. The approach accounts for key time- and temperature-dependent phenomena, including viscoelasticity and stress relaxation in HDPE, using a calibrated non-linear three network (TN) constitutive model. Finite element analysis (FEA) is used to simulate the long-term mechanical response of HDPE connections under various isothermal conditions (23 ◦ C , 40 ◦ C , 60 ◦ C , and 80 ◦ C ), revealing increased susceptibility to leakage at elevated temperatures due to loss of bolt preload. To reflect real-world operating conditions, an annual temperature profile rep resentative of an above-ground piping system was applied to the model, enabling prediction of leak-tightness over a full year of service. The results highlight the importance of accounting for thermal and mechanical degradation over time and inform several bolt re-torquing strategies to mitigate leakage risks. The proposed framework o ff ers practical guidelines for optimizing HDPE flange connection performance and provides engineers with a robust tool for improving the reliability of thermoplastic piping systems. © 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of Professor Ferri Aliabadi. Keywords: Bolted connections; HDPE; Elastic interaction; Relaxation; Thermal loads. Fracture, Damage and Structural Health Monitoring Assessing Bolt Assembly in Thermoplastic Flange Connections Under Realistic Service Conditions Sherif Ezzeldin a , Rehan Umer b , Imad Barsoum a,c,d, ∗ a Department of Mechanical and Nuclear Engineering, School of Engineering, Khalifa University, Abu Dhabi P.O Box 127788, UAE b Department of Aerospace Engineering, School of Engineering, Khalifa University, Abu Dhabi P.O Box 127788, UAE c Advanced Digital and Additive Manufacturing (ADAM) Center, Khalifa University, Abu Dhabi P.O Box 127788, UAE d Department of Engineering Mechanics, Royal Institute of Technology – KTH, Stockholm P.O Box 100 44, Sweden Fracture, Damage and Structural Health Monitoring Assessing Bolt Assembly in Thermoplastic Flange Connections Under Realistic Service Conditions Sherif Ezzeldin a , Rehan Umer b , Imad Barsoum a,c,d, ∗ a Department of Mechanical and Nuclear Engineering, School of Engineering, Khalifa University, Abu Dhabi P.O Box 127788, UAE b Department of Aerospace Engineering, School of Engineering, Khalifa University, Abu Dhabi P.O Box 127788, UAE c Advanced Digital and Additive Manufacturing (ADAM) Center, Khalifa University, Abu Dhabi P.O Box 127788, UAE d Department of Engineering Mechanics, Royal Institute of Technology – KTH, Stockholm P.O Box 100 44, Sweden

1. Introduction 1. Introduction

Ring-type joints (RTJ) are widely used in high-pressure, high-temperature environments—such as o ff shore oil and gas—due to their reliable sealing performance. While metallic flanges are traditionally preferred for their rigidity, high-density polyethylene (HDPE) is increasingly adopted for its corrosion resistance and flexibility. However, HDPE Ring-type joints (RTJ) are widely used in high-pressure, high-temperature environments—such as o ff shore oil and gas—due to their reliable sealing performance. While metallic flanges are traditionally preferred for their rigidity, high-density polyethylene (HDPE) is increasingly adopted for its corrosion resistance and flexibility. However, HDPE

∗ Corresponding author. Tel.: + 971 2 312 3436. E-mail address: imad.barsoum@ku.ac.ae ∗ Corresponding author. Tel.: + 971 2 312 3436. E-mail address: imad.barsoum@ku.ac.ae

2452-3216 © 2025 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 Ferri Aliabadi 10.1016/j.prostr.2026.02.019 2210-7843 © 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of Professor Ferri Aliabadi. 2210-7843 © 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of Professor Ferri Aliabadi.