Analysis of ductile damage under uniaxial cyclic loading
When mechanical parts in vehicles or machines are exposed to repeated actions such as towing, braking, or driving on uneven roads, they experience cyclic loads that can lead to fatigue and failure of the material. It’s hard to predict this kind of damage, especially when it happens bit by bit over t...
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| Tipo de recurso: | tesis de maestría |
| Fecha de publicación: | 2025 |
| País: | España |
| Institución: | Universitat Politècnica de Catalunya (UPC) |
| Repositorio: | UPCommons. Portal del coneixement obert de la UPC |
| Idioma: | inglés |
| OAI Identifier: | oai:upcommons.upc.edu:2117/445631 |
| Acceso en línea: | https://hdl.handle.net/2117/445631 |
| Access Level: | acceso abierto |
| Palabra clave: | Materials -- Fatigue Strength of materials Finite element method Materials -- Fatiga Resistència de materials Elements finits, Mètode dels Àrees temàtiques de la UPC::Enginyeria mecànica |
| Sumario: | When mechanical parts in vehicles or machines are exposed to repeated actions such as towing, braking, or driving on uneven roads, they experience cyclic loads that can lead to fatigue and failure of the material. It’s hard to predict this kind of damage, especially when it happens bit by bit over time because of plastic deformation. In this master’s thesis, we will look at how ductile damage happens under uniaxial cyclic loading. I’ll use afiniteelementapproachtounderstandhowplasticstraincontributestocrackinitiation in metallic structures. Ductile damage models are great for predicting fractures because they show how the material starts to fail by looking at the plastic strain components that develop inside it. But when the loading is cyclic, that is, it repeats loads of times, how plastic strain builds up gets much more complicated. The problem is that the total plastic strain that’s built up can increase a lot, even if each loading cycle is small. If you don’t model it right, you might end up overestimating the damage. The idea is to work out the right plastic strain measures to use in the ductile damage model in these conditions. To do this, I study a simple but typical example: uniaxial cyclic loading. This setup lets me isolate the important variables and understand how the damage changes in a controlled way. I use a finite element model in Abaqus to simulate how the material behaves when it’s loaded and unloaded repeatedly. We pay special attention to how the model builds up plastic strain and how that a!ects the damage evolution. I test and compare di!erent definitions of plastic strain to see which one best reflects the physical damage that occurs in the material. The idea behind the analysis is to get better at predicting when and how cracks start to form, which is really important for components that take a lot of pressure for short periods, like suspension parts or structural joints. This thesis helps engineers and researchers understand how to adapt ductile damage models for situations where there’s repeated loading. It also helps to develop more robust simulation methods that can prevent unexpected failures in real-world applications. It also o!ers a framework that can be used in more complex loading conditions in future research. |
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