TWI is able to combine numerical modelling expertise in fatigue with expertise in testing and fatigue design.
Our interdisciplinary approach provides solutions to clients across an array of industries, who manufacture and operate structures at a wide range of scales, from bridges, pipeline and mooring chains down to implantable medical devices.
The use of numerical modelling to support fatigue design of welded structures is now well established. TWI has been instrumental in developing BS7608, 'Guide to fatigue design and assessment of steel products'. The 2014 revision of BS7608 contains new guidance on the use of hot-spot stresses.
Benefits and applications
If fatigue life curves based on weld classes are used then a designer must necessarily make conservative judgements about which weld class is appropriate for a particular joint. The use of hot-spot stress calculations from models of the real geometry and based on actual loads provides increased accuracy of fatigue life prediction. This allows savings to be made in materials cost and component weight, while maintaining adequate margins on the safety and performance of a welded structure.
Our track record
Finite element analysis was used extensively in a joint industry project investigating the use of computer-based fatigue analysis for welded joints. Selected results and findings from this project are available to TWI Members in Industrial Member Reports 955a/2010 and 955b/2010.
This work provided the background to recommendations included in the 2014 release of BS7608 ('Guide to fatigue design and assessment of steel products'). A comparison of approaches to fatigue design, related to life-extension of pressure vessels, is provided here.
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