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Fracture mechanics at very high load and different type of loads
2008 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

In this report, data from fatigue crack growth programmes NASGRO and Franc2D is analyzed. Results are correlated with reports written on Volvo Aero, simulations performed in NASCRAC, another crack growth programme, and also another degree project previously performed at Volvo. For some case real test data will be used for comparison. To evaluate the function of these programmes is essential since Volvo in the future will rely on them to a high extent. The different crack geometries used during the execution of this project are through, surface and corner cracks. Since Franc2D is an entirely two dimensional programme there were no possibilities to simulate surface or corner cracks with it and hence these crack geometries were only applied in NASGRO. Cases used in this project originate from parts found in turbines, built by Volvo Aero to the European Ariane rocket. However, presented results may also be used to draw general conclusions concerning the functionality of the programmes. This report may in many aspects be used as a handbook which helps the user to choose certain parameters before a simulation is initiated. A variety of simulations, originating from several cases, indicated that NASGRO and Franc2D handle stresses in two different ways. In NASGRO no height need to be stated for a case because the stress is used along the crack extension. In Franc2D which is a mesh based programme however, the height must be stated and the stress is applied at the top of geometry. Two different approaches and the case simulated should decide which approach is most truthful. For the through crack both programmes give satisfying results and many results correlate well with both older results as well as expectations. Results were also received for surface and corner cracks, some good, but in many aspects these geometries need further development. Franc3D, which operates in a similar manner to Franc2D but is based on three dimensions, could be used in future simulations concerning surface and corner cracks. The elastic-plastic module in NASGRO was also used in this project but a range of simulations indicated that it does not work well enough for cases presented in this project.

Place, publisher, year, edition, pages
Keyword [en]
Technology, Fracture mechanics, Crack propagation, Fatigue simulations
Keyword [sv]
URN: urn:nbn:se:ltu:diva-56746ISRN: LTU-EX--08/145--SELocal ID: d7ef926d-adfa-4496-944a-607264d6fd34OAI: diva2:1030133
Subject / course
Student thesis, at least 30 credits
Educational program
Space Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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