According to Battelle between 80-90% of all structural failures occur through a fatigue mechanism with a total cost of 4.4% GDP to the world’s economy. Fatigue is defined as: “the progressive weakening of a material caused by cyclic or otherwise varying loads, even though the resulting stresses are well within the static strength limits.”
In many cases fatigue failures occur suddenly with little prior warning and so it is important to design structures to resist fatigue failure.In this short presentation we consider how material fatigue properties used in FE simulation are determined from laboratory tests. Starting with the very first ‘rotating-bend’ test invented by August Wöhler in 1852, we introduce the popular ‘load-control’ and ‘strain-control’ test procedures used today. Particular consideration is paid to the effect of ‘characterising the material’ to derive properties for the ‘design curve’. The design curve accounts for statistical scatter in the test results and is derived for a particular reliability target and confidence interval.
This webinar will help to answer important question like:
- How many samples should I test?
- Can I safely replace material A with material B?
- And, how do I compare the performance of materials from different suppliers.
At the end of the webinar, the engineer should have a good understanding of the process of fatigue testing, material characterisation and the effect of statistical analysis on the results.Topics covered, include:
An introduction to metal fatigue and fatigue testing:
- Material characterisation accounting for statistical reliability and confidence,
- How many specimens to test?
- How to validate replacement materials?
- How to compare the performance of materials from different suppliers?
|Halfpenny. A Goyder. H
|13th December 2016
|Cranfield University and HBM Prenscia