Publication: Screw coupling analysis within the offshore platform fire water pump
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Date
2024-07-01
Authors
Tong Wai How
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Abstract
This Final Year Project was conducted to interpret the fracture of screw coupling failure in the offshore platform fire water pump under the combined load condition. When overtightening torque was applied to the shafts initially in contact within the T&C connection, this torque generated axial tension within the coupling structure, primarily concentrating in the venting hole region. Additionally, accounting for shaft misalignment in the simulation revealed that combined loading exerted on the coupling body significantly increased the likelihood of fracture. The methodology employed to examine the failure scenario of the screw coupling involved two primary approaches: a 3D static simulation of the assembly screw coupling and threaded shaft, and the use of Digital Image Correlation (DIC) to measure the strain on the specimen. The results obtained from each approach were compared to validate the model. In the simulation, the maximum von Mises stress was observed at the venting hole, attributed to the stress riser characteristics from the hole and thread profile. The crack initiation was most likely to occur at the tip of the venting hole along the vertical direction, with the crack propagating at 45 degrees. This phenomenon was due to the highest shear stress being localized at the tip of the venting hole leading to failure occurred at 45 degrees. Moreover, the DIC technique captured the surface strain contour of the specimen, revealing that the strain field was only concentrated and maximized solely around the venting hole, with minimal strain observed in other regions of the specimen. The maximum in-plane shear strain obtained from the simulation, 𝛾max𝑖𝑛 𝑝𝑙𝑎𝑛𝑒 =3.396×10−4 was compared with the experimental strain value 𝛾𝑒𝑥𝑝𝑒𝑟𝑖𝑚𝑒𝑛𝑡= 312.5 𝜇m/m (3.125×10−4). The percentage error between the simulation results and experimental results was 8.67%, indicating successful validation of the SolidWorks simulation, despite being conducted in a static (linear) rather than a dynamic (non-linear) approach.