Simulation of Service Loading Processes From Fatigue and Reliability Point of View 785008

To estimate the service fatigue life of dynamically loaded components and structures, laboratory fatigue tests with simulated loads must be carried out. The paper presents various methods of on-line simulation of service loading processes, representing inputs of computer controlled fatigue machines. Omitting the fictitious sinusoidal loading, reproduction of any service process can be based either on the probability density of amplitudes, or on the power spectral density, or both of them, depending on the fatigue damage hypothesis and philosophy of testing accepted.
The starting step of the simulation is generation of random numbers /representing as usually uniformly distributed white noise/, which are further transformed into the required probability density shape. If the simulated process is stationary, this transformation does not represent a principal problem /even when it is non-linear/. There is, however, no general method available, which would reproduce the non-stationary /time-dependent/ probability density and at the same time the non-stationary /time-dependent/ power spectral density of non-stationary processes. A partial success can be gained by simulating each of them separately or supposing the process is Gaussian.
Examples of some simulated processes are shown, having been programmed for the MTS fatigue machine, equipped with PDP8/e computer.


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