TWI Industrial Member Report Summary 412/1990
By P J Tubby
The majority of fatigue data for welded joints are for plate specimens under simple uniaxial direct tension loading, whereas in practice, joints in large structures are frequently subjected to more complex loading. There are very few fatigue results for such conditions and hence design must currently be based on the published design curves for uniaxial stressing. The objective of the present project is to produce fatigue data for joints subjected to complex loading and to evaluate current design recommendations.
This report describes two simple testing methods developed to produce the following stress conditions:
i. biaxial bending;
ii. varying principal stress direction.
Some preliminary results for steel joints under the former stress condition are presented. The testing arrangement to produce a variation in principal stress direction requires further development to increase the angle of stress variation before a test series is undertaken.