| Author: | Ouyang, Peng |
| Title: | Computational study on the failure mechanisms of the internal epoxy lining in the saltwater pipe |
| Advisors: | Yao, Haimin (ME) |
| Degree: | M.Sc. |
| Year: | 2023 |
| Subject: | Water-pipes -- Corrosion Coatings Water-pipes -- Inspection Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Mechanical Engineering |
| Pages: | ix, 50 pages : color illustrations |
| Language: | English |
| Abstract: | Pipelines play an important role in material transportation in modern industrial society. In 2021, a saltwater pipeline in Hong Kong was corroded and leaked due to the delamination of the coating, which brought huge economic losses and inconvenience. In order to investigate the failure mechanism of the coating, the finite element models were established in this thesis to have the numerical analysis. Numerical analysis requires material properties as input, therefore, in order to obtain the performance between the coating and the pipe, a four-point bending experiment was developed to measure the interfacial energy release rate. And the accuracy of the four-point bending model is checked by J-integral in ABAQUS. After finite element analysis, we give the applicable range of the energy release rate measured by four-point bending under different Young's modulus ratio systems. In addition, we obtained 𝐺 = 231 J/m2 for epoxy/steel system. Traffic loads are an important consideration in pipeline design, and this failed pipeline was located under the fast lane. Therefore, based on measured material properties and some official standards, we established the finite element models under static and dynamic traffic loads, respectively. Static analysis is usually used to study the maximum loading capacity of the coating, while dynamic analysis is used to discuss the effect of different frequencies or amplitudes on the coating. Based on the maximum principal stress criterion, interface strength criterion, and buckling analysis, we proposed three possible failure mechanisms under static loads. Then, based on the assumed dynamic load magnitudes, we calculated the cycles of fatigue-induced failure of the coating. The conclusion of the finite element analysis under static load is that if the epoxy itself has no defects, then the coating will not fail. However, we also found that the coating at the welds was of poor quality and the location of the leak was between the welds. Through dynamic load analysis, we calculated that if there is a pre-crack in epoxy, then the maximum load trucks pass through an average of several times per day, and the coating will have fatigue failure. These results provide a reference for the saltwater pipeline leakage incident. Therefore, in the subsequent pipe welding process, we recommend that the coating be recoated several times to avoid coating quality problems. |
| Rights: | All rights reserved |
| Access: | restricted access |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| 7474.pdf | For All Users (off-campus access for PolyU Staff & Students only) | 1.68 MB | Adobe PDF | View/Open |
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