Approach for Calibrated Measurement of the Frequency Response for Characterization of Compliant Interface Elements on Vibration Test Benches

Abstract

In vibration tests, the behavior of the structure depends on its mechanical boundary conditions, which are represented in physical tests by connecting elements with mechanical properties. Adjustable impedance elements are machine elements fulfilling the task of an adjustable connection on a vibration test bench and therefore represent a variety of properties. Their mechanical properties must be known over wider ranges than comparable compliant structures tested in the literature. This paper is dedicated to vibration testing of the adjustable impedance elements themselves, taking the influences of fixtures and measuring devices of the test bench into account. Different approaches for measuring the frequency response functions are applied to freely vibrating masses at a hydraulic and an electrodynamic test bench. Mass cancellation and the frequency-dependent measurement systems function have shown their usefulness in characterizing the biodynamic response of hand–arm models before. This measurement method is extended to be transferable to machine elements to obtain reliable results under a wider range of test conditions. The necessity for dynamically calibrated measurement of the frequency response functions is demonstrated for different free vibration masses and for two compliant elements on two different test benches to provide results over a wide range of test conditions.

A compact adjustable hydraulic damper with symmetric high load behavior enabled by selective laser melting

“…Vibration-resistance. One criterion for use for dampers in dynamic testing is reliable mechanical behavior over wide frequency ranges 10,11 . For this purpose, it must be ensured that the elements are vibration-resistant over the frequency range in which they are used.…”

“…In these test series, the frequency is increased from 3 to 23 Hz with a sweep rate of 0.1 Hz/s at a constant displacement amplitude of 2 mm. The dynamic calibration is performed according to the approach for calibrated measurement of the FRF 11 . The performed calibration is based on the approach of Dong et al 39 , the mass cancellation of Ewins 38 and the measurement systems FRF of McConnell 40 .…”

“…Each data point represents the behavior of the belonging oscillations at the given frequency. The FRFs are derivatives of each other and their representations each have advantages in evaluating different properties of the elements under investigation 11 . The plot in Figure 15(a) of the apparent mass shows parabolic curves as they are typical for mechanical damping 43 .…”

“…AIEs are comparable to adjustable compliant structures, which are more frequently investigated in research 11 . Adjustable compliant structures are commonly known by different terms such as adjustable, controllable or variable - stiffness, damping or compliant - connection, mechanism, actuator, or element 11 .…”

“…AIEs are comparable to adjustable compliant structures, which are more frequently investigated in research 11 . Adjustable compliant structures are commonly known by different terms such as adjustable, controllable or variable - stiffness, damping or compliant - connection, mechanism, actuator, or element 11 . Vanderborght et al 12 , van Ham et al 13 , Tagliamonte et al 14 , and Wolf et al 15 show with their review papers the wide field of application of these elements.…”