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Engineering design of spot-welded components as well as computational analyses of the local stress in the weld zone require relevant fatigue test data. Those test data, however, are dependent on the applied specimens, on the specimen restraint, on the load introduction into the weld zone as well as on the definition of the specimen failure. The discussion of the advantages and drawbacks as well as of the influence of these factors shows that a deliberate selection of specimens is necessary for different test purposes. For the comparability of the test results it is essential in addition to specify comparable test conditions, e.g., specimen fixturing, load introduction and definition of the specimen failure. On account of the variety of variants, a standardization of suitable specimens and respective test conditions hence constitutes an approach to the determination of relevant and comparable test results.
Risssicherheit von Schweißnähten an Pipelines der Offshore-Industrie aus supermartensitischem Stahl
(2005)
Numerous externally loaded as well as self-restraint hot cracking test procedures have been developed over the years to evaluate soldidification crack phenomena. But the interpretation and the subsequent transfer of test results towards component weldments has still to be regarded as a decisive challenge. Some progress has been achieved by hypothesizing crack / no crack criteria referring to uniform and uniaxial loading of the solidification front during welding. But, as the present results show, solidification cracking significantly depends on the geometry of the solidification front, which has so far not been considered in the respective criteria. In this contribution, the position of solidification cracks is correlated with the positiondependent strain rates along the solidification front and with the positiondependent curvature of the weld pool. Especially at positions of high curvature, an increased rate of shrinkage can be predicted on the basis of a geometrical Rate of Feeding (ROF) Rate of Shrinkage (ROS) model, corresponding to the measured positions of the solidification cracks. The assumption of position-dependent strain and strain rates along the solidification front during Varestraint-Testing has been confirmed by means of numerical simulations.