Measuring the deformation of a ferrogel sphere in a homogeneous magnetic field

TL;DR

This study investigates how a ferrogel sphere deforms under a uniform magnetic field, demonstrating elongation, vibration, and creep behavior that align with theoretical models, and calculates its Poisson's ratio.

Contribution

It provides experimental validation of theoretical predictions for ferrogel deformation in magnetic fields and introduces a model for time-dependent elongation and vibration behaviors.

Findings

Ferrogel sphere elongates along magnetic field lines as predicted.

Deformation dynamics follow a damped harmonic oscillator model.

Poisson's ratio of the ferrogel is calculated from deformation measurements.

Abstract

A sphere of a ferrogel is exposed to a homogeneous magnetic field. In accordance to theoretical predictions, it gets elongated along the field lines. The time-dependence of the elastic shear modulus causes the elongation to increase with time analogously to mechanic creep experiments, and the rapid excitation causes the sphere to vibrate. Both phenomena can be well described by a damped harmonic oscillator model. By comparing the elongation along the field with the contraction perpendicular to it, we can calculate Poisson's ratio of the gel. The magnitude of the elongation is compared with the theoretical predictions for elastic spheres in homogeneous fields.