Design of a test stand for damping measurement
Tutor / director / evaluatorErmanni, Paolo
Document typeMaster thesis (pre-Bologna period)
Rights accessRestricted access - confidentiality agreement
The main objective of this master thesis is the design and building of a stand for damping measurement. The purpose of this stand is to be able to fulfill two different experiments: a material characterization conducted in this Thesis and an interface design. The experiments carried out consist on the application of a sinusoidal force in a range of frequencies varying from 0 to 400 Hz coming from an electrodynamic shaker fixed on the mainframe of the stand. This force is directly applied to a specimen, which is supported by another structure isolated from the mainframe in order to avoid the vibrations from the shaker. The experiments consist on the study of the reaction of different specimens, measuring the strain when the force is applied. The measurement of the strain is done by means of a laser head, connected to an oscilloscope to obtain the response wave. The viscoelastic material such as rubber stores a certain quantity of energy, so not all the applied energy is returned by the sample. In the experiments, the main goal is to characterize the viscoelastic material of the specimen calculating the Loss Factor (∂), a damping parameter that relates the energy stored and lost by the specimen when the force is applied. The mentioned specimens consists of a rubber layer glued to a 200 x 40 mm metal plate in different configurations, as free layer damping or constrained layer damping. The applied force is read with the help of two force transducers integrated in the structure that supports the specimen and are connected to the same oscilloscope which reads the strain. Comparing the waves from the laser and force transducer, a lag between them can be obtained and with this value, the Loss Factor can be calculated. The stand has also been designed to allow other experiments related with interface design to be carried out. For those experiments, the specimen consists on a metal plate of the same size supported by two rubber blocks, one in each side of the plate. The goal is to study the effect that this size change of the viscoelastic material has on the energy dissipating capacity. One of the requirements of the stand is that experiments with different sizes of samples should be performed on it. The range varies from 40 to 400 mm. It has also been checked by means of different simulations of the setup, that the eigenfrecuency of the different structures of which the stand is made is higher than the value of the maximum frequency required for the experiments, 400 Hz, in other to avoid dangerous effects such as resonance which could damage the different parts of the structures. A reinforcement system has also been designed, which allows an increase of the value of the frequency in the experiments of 50 Hz up without any undesirable problem. The resulting stand accomplishes the mentioned requirements thanks to the profiles and standard fasteners used for the construction, which makes the structure stiff and flexible enough. Once finished the construction of the stand, the experiments are carried out and analyzed. The results have been checked with the data sheets from the provider company of the viscoelastic material.
|Alberto Sánchez Cebrián-Report.pdf||Report||2.352Mb||Restricted access|
|Alberto Sánchez Cebrián-Appendix.pdf||Annex||2.565Mb||Restricted access|