Laboratory for Dynamics of Machines and Structures 
Harmonic Equivalence of the Impulse Loads in Vibration Fatigue
 P. Ogrinec, J. Slavič and M. Boltežar
Journal of Mechanical Engineering 65(2019)11-12, 631-640

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In vibration fatigue, three unique types of loads are typical: random, harmonic and impulse. In an application any of these loads are possible. A fatigue-life analysis is possible in the time and frequency domains using the frequency-response function of a structure. Recent studies demonstrated that the impulse loads influence the accuracy of a fatigue-life prediction in the frequency domain. The focus of this research is a theoretical study of an equivalent harmonic load to the impulse load on a single-degree-of-freedom system in order to investigate the feasibility of impulse loads in vibration testing. This research shows that there is a relationship between the impulse and harmonic loads that is related to the underlying dynamic properties (e.g., damping, natural frequency). Based on a theoretical analysis an experimental procedure was developed for both cases of excitation, which was able to confirm the theoretical analysis. Using the modal decomposition the single-degree-of-freedom approach can be generalized to multiple-degrees-of-freedom systems.

Primož Ogrinec, PhD



Janko Slavič, PhD

  Ladisk, Faculty of Mechanical Engineering, University of Ljubljana
  +386 1 4771 226
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Miha Boltežar, PhD

  Ladisk, Faculty of Mechanical Engineering, University of Ljubljana
  +386 1 4771 608
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