Test rig configuration

Test rig trials are an essential part for designing structural components of an excavator, but performing such trials is complex and expensive. Methods for deriving simplified tests developed at Fraunhofer ITWM have been successfully applied in projects with excavator components.

Derivation of simplified tests

Wheel mounts
© Photo ITWM

Wheel mounts

When testing vehicle components on servo-hydraulic test rigs, it is necessary to ensure that the excitation is as close as possible to the excitation of the component in the driving vehicle. This should be accomplished using a rig configuration which is as simple as possible, i.e. a configuration that needs as few actuators as possible and time series as short as possible.

The mathematical modeling and simulation of the component and the rig configurations enable the application of optimization methods to solve the problem. A rig configuration consists of mounting points, positions of actuators and excitation signals.

The Fraunhofer ITWM has developed suitable methods to get an optimal rig configuration without the effort of repeated finite elements computations for different mountings.
 

Challenge optimization goals

For the optimization of damage values on defined points of the component, the excitation signals consist of block loads with different amplitudes. This allows also for a short length of the excitation signals. To reproduce also stresses for defined critical points, more complex excitation signals are necessary.

The task is always to find a good compromise for the different competing optimization goals. This is supported by the automated calculation and assessment of different solutions.

The approach is developed further in corporation with the Fraunhofer ITWM department for optimization and has been successfully applied in various industry projects so far.

Sample application project

Excavator boom
© Photo ITWM

Excavator boom

Optimizing the test rig configuration
© Photo ITWM

Optimizing the test rig configuration

Optimizing test rig configuration and excitations for excavator booms

The physical test of structural components is an essential step in the durability analysis of an excavator. Especially for large components such tests are complex and expensive. To keep the effort for testing low, the number of actuators should be small and the excitation time series as short as possible.

The methods for the derivation of simplified tests developed at ITWM are applied successfully in a project with Liebherr to an excavator boom. Reference loads consist of 20 load components a t8 application points. Damage optimized as well as stress optimized excitation time series for different configurations of the test rig are derived and compared to each other.

Details of the method as well as results for example signals are presented in:
A.Marquardt, M.Obermayr: Optimizing test rig configuration and excitations for excavator booms, Prodeedings of the 3rd Commercial Vehicle Technology Symposium (CVT 2014).