Simplification of Complex Time-Domain Loads for the Frequency-Domain in Fatigue Structure Analysis
The time domain is the most widely chosen alternative in mechanical fatigue tests to completely represent random events across multiple simultaneous channels, such as an interaction between vehicle suspension and the ground. The reason for this is the possibility of a complete reproduction of these physical events on a test bench, without any additional math, simplification and / or post-processing. That is, the load/displacement input set obtained in the field test is the same as that performed in laboratory test equipment. The main disadvantage of this approach is the long test duration and the high cost of the equipment. The hardware required for these tests is complex, composed of servo actuators, in order to incite a certain amount of charge in a window of time. The time required to complete the test is also long, as it consists of the same duration of the test multiplied by the number of repetitions to achieve fatigue performance. Frequency fatigue bench tests, on the other hand, are potential alternatives to overcome these disadvantages. That is, they require less sophisticated equipment, since they require only simple actuators instead of servo actuators and the test duration is reduced, as the total length of the event is replaced by constant repetitions and constant damage. This work proposes and explores a new method that uses the result of structural fatigue as a starting point and, through the solution of an optimization problem, it determines which loads/displacements caused them in the frequency domain. The objective is to assist future developments in fatigue tests, supplanting tests in the time domain without losing the correlation with physical events.