Assessment of a Test Rig for the Measurement of Contact Properties of Bolted Joints

In machinery industry, especially in turbo machinery and automotive, accurate predictions of vibration and noise levels of mechanical systems are very valuable before a prototype is produced. However, in general, the contact properties of multibody structures are not known with acceptable accuracy at the design stage, which makes the theoretical predictions of multibody structures quite unreliable. In theoretical or numerical studies, especially in automotive industry, contact surfaces are usually not modeled and some empirical values are frequently used to represent the dry friction properties. However, in most cases, the use of approximate, linear damping and stiffness values instead of the actual dry friction damping and contact stiffness of structures cannot yield results with acceptable accuracy in terms of vibration amplitude and natural frequency. Thus, accurate predictions of vibration properties of multibody structures require detailed theoretical models including not only the realistic representation of the elastic and inertia properties, but also accurate representation of the damping in the system. In this study, it is aimed to identify the contact properties of a specific bolted joint experimentally. For this purpose, a practical test procedure is selected among those available in the literature and an appropriate test rig is developed in order to identify the contact stiffness and dry friction damping properties of a bolted joint. U sing the measured data, the nonlinear elastic and damping properties of the contact are modelled as amplitude-dependent complex stiffness using the describing function method. The results show that, using the test rig developed, elastic properties of the nonlinear contact can be identified with acceptable accuracy. However, the accuracy of the identification of the damping properties of the contact is found to be somewhat low, hence the test rig and the associated data analyses used in this study can be improved further.