Abstract
Residual stresses in welded joints are often of extended interest in order to evaluate unexpected failures or distortions. Since the possibilities to calculate residual stresses in welds are still strongly limited, the measurement techniques are still of great importance. Several measurement techniques with particular possibilities and limitations are available today where especially the different diffraction methods are used mostly. The material, weld type, and the size of the components are important for the quality of the results obtained with different methods as well as the environment where the measurements have to be carried out. The paper shall give an overview of the results of a round robin test on the application of XRD on butt welded joints which has been carried out in cooperation of different experienced laboratories. The results show the high reliability of XRD measurements in welds, if the measurements are performed under well-defined boundary conditions. The experiences can be used as a recommendation about useful measurement conditions the expectable quality of the results.
Highlights
Future developments of fatigue design rules will be forced to consider increasingly high-strength steels
As the resulting average profiles with the resulting scatterband reveal (Fig. 10b), the scatter range in the base material and in the heat-affected zone is between ± 25 N/mm2 and ± 40 N/mm2
Experiences with larger numbers of specimen of the same series have shown that the variation of the residual stresses in welds may vary between ± 20 and ± 80 N/mm2 even if the specimen have been produced under comparative laboratory conditions
Summary
Future developments of fatigue design rules will be forced to consider increasingly high-strength steels The use of these materials depends strongly on the application of improved fabrication techniques which take into account the necessarily much higher quality requirements. The further development of the design rules must take into account explicitly known residual stresses in welds due to different sources. This necessarily requires the Recommended for publication by Commission XIII - Fatigue of Welded Components and Structures. Mechanical techniques like the hole drilling, deep hole drilling, or the ring-core method use a locally restricted access to the material in order to measure the released strains which can be used to calculate the initial residual stresses. The focus was fixed on butt welds with different weld geometries which already represents a non-trivial challenge for the accurate determination of residual stresses
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