The usage of Fiber reinforced composites in the modern engineering structures have been developed since the past few decades. Because of their low density, the strength to weight ratios and modulus to weight ratios, these materials were marked to be better than metallic materials in various fields of applications. For such reasons traditional materials are being replaced by them in many weight-critical components in Aerospace, Automotive, Power generation, civil structures etc. Among the different fiber reinforcements, Glass Fiber reinforced composites have become very prominent in the global markets because of their exceptional mechanical properties a lower economical value compared to the others. Because of their applications in various industries where they could undergo a considerable amount of vibrations which they might not be able to resist. In order to improve the damping properties of these composites, the research groups of Politecnico di Milano developed a Hybridised architecture; embedding a Shape Memory Alloy (SMA) into GFRP plates. The structure was developed based on the amplitude dependent damping exhibited during the numerical investigations conducted using ABAQUS. In this thesis work, the damping properties of the developed structure were experimentally investigated in Time and Frequency domains. Using a Logarithmic decay approach the dependency of the damping properties of the Hybrid structure on the strain induced in the material was investigated. Various boundary conditions and geometries for the structure were numerically investigated in order to improve the strain experienced by the embedded SMA. Non-dimensional Damping ratio was the parameter that was used to comment on the damping properties of the structure and as it depends not only on the Amplitude but also on the Frequency of excitation, the effects of the hybridization on the Modal parameters of the structure were also experimentally investigated. With the help of empirical results the dependency of the contribution of the SMA to the damping properties of the structure, on the excitation parameters and the boundary conditions of the structure was inferred.
L'uso di compositi rinforzati con fibre nelle moderne strutture ingegneristiche è stato sviluppato negli ultimi decenni. A causa della loro bassa densità, della resistenza al peso e dei rapporti modulo / peso, questi materiali sono stati contrassegnati come migliori dei materiali metallici in vari campi di applicazione. Per tali motivi i materiali tradizionali vengono sostituiti da essi in numerosi componenti critici in ambito aerospaziale, automobilistico, della produzione di energia, strutture civili ecc. Tra i diversi rinforzi in fibra, i compositi rinforzati con fibra di vetro sono diventati molto importanti nei mercati globali a causa della loro eccezionale proprietà meccaniche un valore economico inferiore rispetto alle altre. A causa delle loro applicazioni in vari settori in cui potrebbero subire una notevole quantità di vibrazioni alle quali potrebbero non essere in grado di resistere. Al fine di migliorare le proprietà di smorzamento di questi compositi, i gruppi di ricerca del Politecnico di Milano hanno sviluppato un'architettura ibrida; incorporare una lega a memoria di forma (SMA) nelle piastre GFRP. La struttura è stata sviluppata in base allo smorzamento dipendente dall'ampiezza mostrato durante le indagini numeriche condotte utilizzando ABAQUS. In questo lavoro di tesi, le proprietà di smorzamento della struttura sviluppata sono state studiate sperimentalmente nei domini del Tempo e della Frequenza. Utilizzando un approccio di decadimento logaritmico è stata studiata la dipendenza delle proprietà di smorzamento della struttura ibrida dallo sforzo indotto nel materiale. Varie condizioni al contorno e geometrie per la struttura sono state studiate numericamente al fine di migliorare la deformazione subita dalla SMA integrata. Il rapporto di smorzamento non dimensionale era il parametro utilizzato per commentare le proprietà di smorzamento della struttura e poiché dipende non solo dall'ampiezza ma anche dalla frequenza di eccitazione, gli effetti dell'ibridazione sui parametri modali della struttura erano anche investigato sperimentalmente. Con l'aiuto di risultati empirici è stata dedotta la dipendenza del contributo di SMA alle proprietà di smorzamento della struttura, ai parametri di eccitazione e alle condizioni al contorno della struttura.
Experimental investigations on SMA based hybrid structure to assess its damping properties
RAVULAPALLI, VINEETH
2018/2019
Abstract
The usage of Fiber reinforced composites in the modern engineering structures have been developed since the past few decades. Because of their low density, the strength to weight ratios and modulus to weight ratios, these materials were marked to be better than metallic materials in various fields of applications. For such reasons traditional materials are being replaced by them in many weight-critical components in Aerospace, Automotive, Power generation, civil structures etc. Among the different fiber reinforcements, Glass Fiber reinforced composites have become very prominent in the global markets because of their exceptional mechanical properties a lower economical value compared to the others. Because of their applications in various industries where they could undergo a considerable amount of vibrations which they might not be able to resist. In order to improve the damping properties of these composites, the research groups of Politecnico di Milano developed a Hybridised architecture; embedding a Shape Memory Alloy (SMA) into GFRP plates. The structure was developed based on the amplitude dependent damping exhibited during the numerical investigations conducted using ABAQUS. In this thesis work, the damping properties of the developed structure were experimentally investigated in Time and Frequency domains. Using a Logarithmic decay approach the dependency of the damping properties of the Hybrid structure on the strain induced in the material was investigated. Various boundary conditions and geometries for the structure were numerically investigated in order to improve the strain experienced by the embedded SMA. Non-dimensional Damping ratio was the parameter that was used to comment on the damping properties of the structure and as it depends not only on the Amplitude but also on the Frequency of excitation, the effects of the hybridization on the Modal parameters of the structure were also experimentally investigated. With the help of empirical results the dependency of the contribution of the SMA to the damping properties of the structure, on the excitation parameters and the boundary conditions of the structure was inferred.| File | Dimensione | Formato | |
|---|---|---|---|
|
2019_10_RAVULAPALLI.pdf
accessibile in internet solo dagli utenti autorizzati
Descrizione: Master's Thesis text of Vineeth Ravulapalli_876323
Dimensione
4.35 MB
Formato
Adobe PDF
|
4.35 MB | Adobe PDF | Visualizza/Apri |
I documenti in POLITesi sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
https://hdl.handle.net/10589/149740