Fast fatigue damage calculation tool for hook lifts

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Insinööritieteiden korkeakoulu | Master's thesis
Mechanical Engineering
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Master's Programme in Mechanical Engineering (MEC)
The hook lift, a hydraulic loading machine, incorporates critical welds in its sub-frame that inevitably endure fatigue damage through repetitive operations. Conventionally, predicting this fatigue damage requires employing time-intensive Finite Element Analysis (FEA) software, which is constrained by specific input parameters. Furthermore, the existing digital twin of the hook lift, developed in MATLAB/SIMULINK, presents an opportunity for exploration on how to utilize it for damage calculation purposes. This study presents an innovative and efficient FFDC tool, developed in MATLAB, aimed at predicting fatigue damage in hook lift sub-frames for a wide range of load inputs. The FFDC tool capably handles hydraulic force and load inputs and employs pre-existing finite element stress analysis data to establish robust regression models. It subsequently implements the Manson-Coffin-Morrow strain-life approach, while considering necessary assumptions, for fatigue damage calculation. Moreover, the FFDC tool is thoughtfully designed as a standalone application, facilitating easy sharing via Docker, and it is seamlessly integrated into the existing digital twin of the hook lift. The FFDC tool achieves remarkable efficiency, delivering results in under a minute, a substantial enhancement compared to the lengthy 4-hour requirement of conventional FEA Fatigue Analysis. Additionally, the tool's regression models exhibit an impressive 99% accuracy in predicting maximum equivalent stress at critical weld points. The accuracy assessment of the FFDC tool extends across four distinct damage ranges: minimum, low to medium, medium to high, and maximum. It excels in the low to medium damage range, with an error percentage of 1-21%, and still provides reasonable estimates in the medium to high damage range, where approximately 69% of damage during hook lift operations falls. However, it demonstrates unreliability in the minimum and maximum damage ranges. While the FFDC Tool holds significant potential, additional research is required to improve its accuracy across all damage ranges. Its seamless integration with the digital twin positions it as a platform for future advancements in the field of fatigue analysis.
Viitala, Raine
Thesis advisor
Randelin, Matti
fatigue damage, hook lift, strain-life approach, MATLAB
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