Dynamic response of a magnetizable single fiber in an AC magnetic field for contactless particle detachment in gas-phase filtration

The dynamic behavior of a magnetizable single fiber exposed to a spatially homogeneous alternating magnetic field was investigated experimentally and numerically with the purpose of laying the foundations for subsequent contactless particle removal in gas-phase filtration. A Helmholtz coil arrangement was used to generate a well-defined AC magnetic field, which was characterized by Hall probe measurements and finite element simulations using COMSOL Multiphysics®. A ferritic stainless steel fiber clamped at one end was excited by the aligning magnetic torque induced by the alternating magnetic field with sinusoidal time dependence. High-speed imaging combined with automated MATLAB-based motion analysis enabled the determination of deflection, velocity, and acceleration. The steady-state response exhibits harmonic oscillation at the driving frequency (35–55 Hz) and can be accurately described by the analytical solution of a driven damped harmonic oscillator. A pronounced resonance peak was observed near the theoretically predicted natural frequency (f0,theo. = 49.2 Hz). The transient response reveals a superposition of the natural and driving frequencies, leading to beat phenomena for off-resonant excitation. The experimentally determined frequency response agrees well with the analytical model and confirms the interpretation of the distributed magnetic torque as an effective modal driving force. The results provide a consistent physical framework for magnetically induced oscillations of slender structures and form the basis for future studies on particle detachment from particle-laden magnetizable fibers.