Untypical cases and incorrect results of vibration tests

The vibration analysis is the study of the behaviour and dynamic properties of mechanical structures under actuation by harmonic vibration forces. The aim of resonance tests of the structures is the experimental delimitation of frequencies and the modes of resonance vibrations. vibration analysis, or more precisely experimental vibration analysis, is the field of measuring and analyzing the dynamic response of mechanical structures when excited by a mechanical input. The broadly applied method of research relies on the harmonic actuation of vibrations and the measurement of respective parameters. Examples would include measuring the vibration of an aircraft load bearing structure when it is attached to an electromagnetic force actuator. Current vibration testing systems are composed of actuators set with their control and powering circuits, the vibration measurement transducers (typically accelerometers), an analog-to-digital converter to digitize analog instrumentation signals) and a system host computer to analyze the data and view it. The result of researcher own accumulated experiences and those experiences knownfrom the literature create the possibility for design o f a stochastic frame model describing, what type of resonances are possible to expect in the given or other type of structure. The cases submitted below became perceived and tested in the course of research of several aircraft, glider and helicopter designs in the Resonance Tests Program of the Institute of Aviation