Study on uncertainty of ice loads measurement system
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School of Engineering |
Master's thesis
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Date
2024-09-30
Department
Major/Subject
Marine and Arctic Technology
Mcode
Degree programme
Master's programme in Mechanical Engineering
Language
en
Pages
95
Series
Abstract
The vessel’s outer hull is exposed to numerous external environmental forces throughout the ship’s operation. For ice-going ships, the main load impacts come from interaction with ice. To operate safely, it is essential to consider the impacts of ice loads on the structural elements. The thesis aims to present the verification methods that can display the ice-induced loads on ships. The influence coefficient matrix was developed from the finite element model of RRS Sir David Attenborough, where the determined strains were used to analyse the loading on the ship structure. The verification method compares results obtained with different numerical approaches, the finite element method and beam theory. When assessing the correctness of the influence coefficient matrix and a simple beam approach included in the verification process, the influence coefficients are found to under- or overestimate loads with a known magnitude depending on their location. Even though the verification procedures include different approaches, the results are still within allowable limits. The verification methods are selected based on the variations of loads a ship can encounter in the environment. Since the shear strain sensors only measure the shear response directly on the instrumented frame, the loading patch greatly impacts the accuracy of the measurement system. The strain gauge responses gave better results when the applied loads were higher and were centred on the matrix at around ±20%. Based on those discoveries, it has been found that simple approaches could be taken before the sensors are installed, and that can improve the accuracy of the measured load when a ship is in operation. The results also show that a purely numerical approach cannot be valid for verifying the measurement system’s uncertainty.Description
Supervisor
Suominen, MikkoThesis advisor
Hindley, RobKeywords
ice load, influence coefficient matrix, inverse method, measurement uncertainty, shear strain measurement, ship-ice interaction