Abstract
When performing extensional ER tests for the characterization of electro-rheological fluids, the time between applying the electric field and triggering the experiment (delay time) plays an important role in ER behaviour of the sample. The current study investigates the delay time effect in extensional ER characterization. The ER sample used in the measurements is a suspension of cornstarch in olive oil with a concentration of 30 wt%. Fixtures adaptable to the commercial version of the Capillary Breakup Extensional Rheometer (HaakeTM CaBERTM, Thermo Scientific) are designed and fabricated to allow the application of an external electric field aligned with the flow kinematics undergone by the fluid sample while the extensional characterization is taking place. An in-house code developed in Matlab is used to process the images and investigate the filament thinning behaviour of the sample under 3 kV applied voltage and at different delay times (0 s, 10 s, and 40 s).
The results show that, under extensional flow, when the voltage is applied, and the delay time between setting the electric field and triggering the experiment is 10 s, the fluid filament breaks. However, if the delay time is increased up to 40 s, then it is observed that the filament does not break anymore. Thus, increasing the time between applying the voltage and triggering the experiment strengthens the structure of the ER sample. According to these results, it can be concluded that the formation of the microstructure due to the presence of the electric field does not occur instantaneously, but instead it is a time-dependent phenomenon.
This is a preview of subscription content, log in via an institution to check access.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
References
Winslow, W.M.: Induced fibration of suspensions. J. Appl. Phys. 20(12), 1137–1140 (1949)
Yin, J., Zhao, X.: Titanate nano-whisker electrorheological fluid with high suspended stability and ER activity. Nanotechnology 17(1), 192 (2005)
Sheng, P., Wen, W.: Electrorheological fluids: mechanisms, dynamics, and microfluidics applications. Annu. Rev. Fluid Mech. 44, 143–174 (2012)
Sadek, S.H., Najafabadi, H.H., Campo-Deaño, L., Galindo-Rosales, F.J.: Extensional Electro-Rheological Fixture (ExERF). Provisional Patent Application Ref. PAT20191000021255/0198 (2019)
Campo-Deaño, L., Clasen, C.: The slow retraction method (SRM) for the determination of ultra-short relaxation times in capillary breakup extensional rheometry experiments. J. Non-Newton. Fluid Mech. 165, 1688 (2010)
Acknowledgements
The authors acknowledge the financial support provided by Fundação para a Ciência e a Tecnologia (FCT), COMPETE and FEDER through projects MIT-EXPL/IRA/0077/2017 and POCI-01-0145-FEDER-030765.
Author information
Authors and Affiliations
Corresponding author
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2020 Springer Nature Switzerland AG
About this paper
Cite this paper
Najafabadi, H.H., Sadek, S.H., Campo-Deaño, L., Galindo-Rosales, F.J. (2020). Time Effect in Extensional Electrorheological Characterization. In: Galindo-Rosales, F., Campo-Deaño, L., Afonso, A., Alves, M., Pinho, F. (eds) Proceedings of the Iberian Meeting on Rheology (IBEREO 2019). IBEREO 2019. Springer Proceedings in Materials. Springer, Cham. https://doi.org/10.1007/978-3-030-27701-7_32
Download citation
DOI: https://doi.org/10.1007/978-3-030-27701-7_32
Published:
Publisher Name: Springer, Cham
Print ISBN: 978-3-030-27700-0
Online ISBN: 978-3-030-27701-7
eBook Packages: EngineeringEngineering (R0)