Full-scale structural testing of of aircraft structures has been and still is the task of the aircraft industry when new aircrafts are developed. The NLR performs structural testing of aircraft structures for certification, this is done using structural test setups. Structural testing consists out of static testing (ultimate load) and fatigue testing (lifetime). The NLR is developing a new structural testing methodology whereby the testing behaviour is predicted using computational models before the certification test is actually performed, called virtual testing. This has the advantage of performance prediction as well as a reduction in costs and risks. This thesis covers the development of a virtual testing methodology for structural test setups, to simulate its static and dynamic behaviour.
Structural test setups consist out of three main systems, the hydraulic system, mechanical system and control system. Currently design of the mechanical system and hydraulic system takes place in separate processes. Controller parameters are tuned when the test setup is built and in operation. As a result the total system performance is currently only known if the test setup is actually built. To improve design and performance of structural test setups a virtual testing methodology has been developed. The virtual testing methodology combines mechanical, hydraulic and control system in a simulation model to simulate the system performance of the test setup before it is built, called virtual testing.
To develop and to verify the proposed virtual testing methodology a demonstration test setup is developed. This demonstration test setup is derived form the general architecture of structural test setups. Assumptions regarding the modelling where made to obtain a demonstration test setup which represents the essence of a general structural test setup.
Reference signals used in fatigue tests are interpolated sinusoidal signals, therefore dynamic modelling of the demonstration test setup is applied. To obtain a measure of the bandwidth of fatigue reference signals, the frequency content of fatigue profiles where analyzed. This analysis obtained a maximum bandwidth of 5 [Hz].
Dynamic models of the three main systems, the hydraulic system, mechanical system and control system were developed and coupled, describing the system behaviour of a demonstration test setup. The control architecture as presently used is implemented in the model. Using the simulation models it is possible to obtain controller parameter and provide also the possibility to investigate non-linear effects, such as play and friction. The simulation models obtain physical knowledge of the system behaviour, which can be analyzed in the time domain or frequency domain.
Measurements on the demonstration test setup where performed to verify the simulation models. Each component of the demonstration test setup was measured and verified individually. Coupled system measurements where performed for verification of the coupled mechanical, hydraulic and control system. The coupled system response is verified up to 40 [Hz], compared with the linear frequency response of the model. The simulation model proved to predict the frequency response of the demonstration test setup.
This thesis proved the ability of virtual testing of structural test setups before they are actually build. Using these simulation models it is possible to investigate system performance and non-linear effects. Further research is needed on extending these models to full scale structural test setups.