Session: SYMP 2-1: Magneto-Responsive Materials Modeling, Optimization, and Performance

Paper Number: 140384

140384 - Transient Magnetostriction of Magneto-Active Elastomeric Cylinders 

Magnetostriction (MS) is commonly defined as a dimensional change of the material in the a uniform external magnetic field. Magneto-active elastomers (MAEs), which consist of an elastic polymer matrix and micrometer sized ferromagnetic particles, also exhibit this property. In contrast to conventional solid ferromagnets, MS in MAEs is caused mainly by the form effect, accompanied by the  movement of the filler particles toward magnetic field lines in chain-like structures. Due to the form effect, a soft composite material elongates in a uniform magnetic field to minimize the demagnetizing energy. Most previous publications were devoted to quasi-static behavior of MS where the deformation has reached its stationary state. However, its well known that rheological response of MAE materials in time varying magnetic field results in complex transient behavior, which can be characterized by several time constants. Direct measurements of the dynamics of macroscopics deformation of MAE material in time varying magnetic fields are still missing in the literature, which would be a particular interest due to understanding of the dynamics of nonlinear soft actuators for creation of controllable soft robots.

In this work, we systematically investigate the transient behavior of macroscopic deformation in magneto-active elastomers as a response to the trapezoid-shaped rising and falling of the field excitation with four different slew rates of the magnetic field, and three different maximum values of the magnetic field. We introduce four characteristic times: two for the delay of the transient response during increasing and decreasing magnetic field as well as two for rise and fall times. The comparison between different magnetic field rates is made easier by normalizing these characteristic times on the rise time of the magnetic field ramp.

The delay times for the magnetostrictive strain response for both increasing (ascending) and decreasing (decreasing) parts of magnetic fields were different. For the two higher magnetic field slew rates (505 kA/(s·m) and 757 kA/(s·m)) and otherwise the same experimental parameters, the delay time for the falling part of the magnetic field was lower than the delay time for the rising magnetic field. Typically, for isotropic samples, the normalized delay time for the rising magnetic field was about 0.2, and the normalized delay time for the rising falling magnetic field was roughly 0.7. Introduced Measured rise and fall times of the magnetostrictive strain response for the increasing (ascending) and descending (decreasing) parts of magnetic fields were different as well. Typically, for isotropic samples, the normalized rising time for the rising magnetic field was about 0.8, and the normalized fall time for the falling magnetic field was roughly 0.5.

The dependencies of the normalized characteristic times on the aspect ratio, the magnetic field slew rate, maximum magnetic field values, initial internal structure (isotropic versus anisotropic specimens) and weight fraction of the soft-magnetic filler are presented and discussed in detail.

Presenting Author: Mikhail Shamonin OTH Regensburg

Presenting Author Biography: Mikhail Chamonine is a Professor in the Faculty of Electrical Engineering and Information at the Ostabyerische Technische Hochshule Regensburg in Regensburg, Germany.

Authors:

Gašper Glavan
Inna Belyaeva
Paris Von Lockette
Mikhail Shamonin