Stoßartige Belastung

FKM 2012
Issue number 315
Fracture mechanical strength verification for machine components under impact loads
Project no. 289

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Final report
Abstract:

As part of the research project, a reliable method for the fracture mechanical evaluation of machine components under dynamic loading was derived. For typical materials and component-relevant stress scenarios, the influence of the load velocity on the stress and material toughness was quantified and prepared for a simple calculation.
The focus of the investigations was on shafts and axles with surface defects under mode I loading. Component tests with mixed loading were used to check the transferability of the results derived from mode I loading to mixed-mode loading. On the material side, the influence of the loading rate on the material properties was experimentally investigated and quantified. As an example, two typical mechanical engineering materials with low and high strength and thus different strain rate sensitivities were investigated. In addition to this quantification of the influence of velocity, correlations were established between the characteristic values of the instrumented notched bar impact test and the dynamic fracture toughness in order to make it possible to derive the required
material characteristic values from the instrumented notched bar impact test in a simple manner. The tests were analyzed numerically using the finite element method and an evaluation concept was created based on the master curve concept used for dynamic loading.
Finally, a simplified procedure was proposed for the overall concept of fracture mechanics component evaluation under dynamic loading, which can be used to estimate the influence of dynamic loading on component integrity by providing dynamic fracture toughness values for typical materials and loading rates
. The applicability of the simplified evaluation concept was demonstrated using two example calculations for a symmetrically loaded, cracked shaft.
The objective of the research project was achieved.