Natural frequency of oscillations of a solid surface (without holes) and perforated sieve with holes of complex geometry in the shape of five-petal epicycloid

The experimental determination of the structural function of the frequency response consists in identifying the natural frequencies of oscillation of the test surfaces, for which the laboratory equipment was developed, and the following methodology was used. 

To determine the structural function of the frequency response, it is necessary to obtain two data channels: the input force and the corresponding response of the test object (test surface). In impact measurement, the input force is provided by a modal impact hammer, and the output response of the test object (test surface) is measured using an accelerometer.The basic elements of the scheme are a special impact pulse type hammer PCB 084A17 for creating excitations (oscillations); cables for signals transmission; accelerometer sensor PCB 352V10 with highly sensitive piezoelectric elements for fixing oscillations; signal amplifier SIEMENS model SCADAS Mobile; computer with Simcenter Testlab 2019.1 software for processing and visualization test results.

The study was conducted according to the following algorithms:1. Test setup: boundary conditions; determination of test scheme and parameters; frequency range; determination of excitation source and force level.2. Testing: installation and control of accelerometers; object excitation and frequency response measurement; check of measurement quality and coherence.3. Post-test: modal curve fitting; validation of the modality against the assurance criterion and modal synthesis.The research was carried out using the following algorithm. 

The perforated surface prototype was rigidly fixed to the prefabricated frame. With this type of fixation, the investigated surface at the periphery is fixed and unable to move.The surface of the prototype was marked by overlaying a coordinate grid with the specified step.This data of natural frequency of oscillations of a solid surface under various modes, which are obtained experimentally. The obtained oscillation frequencies are needed to determine the difference between the construction of a solid plate and a perforated surface with holes of complex geometry.