Author(s)

F. Deuble, G. Ferraris, F. Hölig & C. Hofmann

Abstract

Experimental fatigue testing is inevitable during the qualification process of newly developed automotive and aerospace components subjected to dynamic loads. These tests have to cover the whole range of environmental conditions occurring during operation. This includes, besides load specification, also process variables like temperature, pressure and corrosive atmosphere. Furthermore, the reduction to single-axis testing is usually not acceptable. Multi-axial tests require a combination of a controller and an overlaying adaptation algorithm to ensure accurate reproduction of the target signal vector. Furthermore, stop-criteria must be implemented for the case of failure or damage. Both the test-setup and control system must be easily adaptable to the customer specific test case. Once the test is specified, standard mechanical components are assembled to a specific test rig. The mechanical setup depends on amplitude, frequency and type of loading, i.e. the combination of tensile, bending and torsional loads. Analogously, it is desirable to have some kind of 'construction kit' for the control of the experiment. The main reason for this is that implementing the control algorithm in conventional programming languages for signal processors is usually not acceptable concerning the reaction time on customer requests. On the other hand commercially available test rigs often lack the necessary flexibility for customer-specific tests which is inevitable for institutions offering test-services. Rapid control prototyping (RCP) systems provide such a construction kit and are very efficient concerning development time. This paper shows the use of RCP-systems for adaptive environmental testing. Adaptation algorithms are presented and as an application example a multi-channel fatigue-test in liquid nitrogen is shown. Keywords: multi-axial fatigue testing, rapid control prototyping, time waveform reproduction, digital control, test rig control.

Keywords

multi-axial fatigue testing, rapid control prototyping, time waveform reproduction, digital control, test rig control.