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HomeFatigue behaviour of welded joints in offshore steel structures
Properties and service performance. Part III, Fracture mechanics
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In this research programme three different aspects of the fatigue behaviour of welded joints are investigated. So the final report includes three parts. Part 1: Fatigue behaviour of thick plates with and without attachments. Earlier fatigue research up to a plate thickness of 76 mm showed that an increase of the plate thickness has a decreasing effect on the fatigue per-formance. Since the plate thickness applied in offshore structures tends to increase with the dimensions of those structures, fatigue research is carried out on thick plates. Part 2: Fatigue behaviour of butt-welded tubular connections with root defects. In the construction of offshore platforms one-side welding is often unavoid-able and so are root defects. To gain better knowledge of the influence of root defects on the fatigue behaviour tests have been carried out on butt-welded tubular joints under axial loading with a constant amplitude. Part 3: Fatigue life estimation on a fracture mechanics approach. The generation of fatigue data for the longer fatigue life of large-scale components is especially troublesome, time consuming and expensive. Application of a fracture mechanics approach may at least partly bypass the difficulties and restrictions. For a further development of the fracture mechanics approach a step-by-step procedure is performed for specimens with an increasing degree of geometrical complexity. Experimental and analytical work has been carried out with regard to the fatigue behaviour of two dimensional geometries with an edge crack and of three dimensional geometries with a semi-elliptical surface crack. Some of the geometries were provided with a weldshape exactly alike a T-shape specimen with a full penetration weld. However, all specimens were manufactured out of one thick plate by machining. So no weld irregularities were present in the specimens. All experiments were carried out in four point bending. The Paris-Erdogan relation was used as a crack growth model. Stress-intensity factors were taken from literature and determinded by finite element calculations. An evaluation was carried out by com-paring the experimental and analytical results. For the specimens with a simple geometry a relatively good agreement was found between calcu-lation and experiment. However, due to the fact that at low D K values the data point are below the da/dn - D K curve, the analytical life time underestimates the experimental lifetime. With regards to the growth of surface cracks in plates with a weld geometry the agreement between calculation and experiment was rather poor. The lifetime calcu-lations gave conservative to very conservative results. Further inves-tigation of the available information will be necessary in the future to solve the remaining questions.
- Published:
- Corporate author(s): Directorate-General for Research and Innovation (European Commission) , Directorate-General for the Information Society and Media (European Commission)
- Edited by: Scholte, H. G ;
- Themes: Industrial research and development
- Subject: metal structure , research report , resistance of materials
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| ISSN 1018-5593 | ISBN 92-826-3625-9 | DOI | Catalogue number CD-NC-13-395-EN-C |
- Released on EU publications website:
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