Finite Element Solutions for Magnetic Field Problems in Terfenol-D Transducers

Area of Science:

• Materials Science
• Magnetism
• Acoustics Engineering

Background:

• Giant magnetostrictive transducers utilize Terfenol-D (Terbium-Dysprosium-Iron alloy) rods for optimal magnetostriction.
• Achieving desired magnetostriction requires precise control over magnetic fields and minimization of energy losses.

Purpose of the Study:

• To investigate an optimal magnetic design for Terfenol-D rods in giant magnetostrictive transducers.
• To reduce eddy current losses in Terfenol-D rods and enhance their magnetostriction capabilities.
• To demonstrate the practicability of the designed transducer for underwater applications.

Main Methods:

• A segmented stack configuration using Terfenol-D rods and NdFeB permanent magnets was designed and simulated using the finite element method.
• Bias magnetic field distributions were analyzed to determine optimal configurations for long stacks.
• A digital slot configuration was introduced in Terfenol-D rods to mitigate eddy current losses, with simulations estimating induced currents and losses.
• A prototype transducer was manufactured and tested for its transmitting current response.

Main Results:

• The segmented stack configuration effectively produces desired bias magnetic fields, particularly for long stacks.
• The digital slot configuration reduced eddy current losses in Terfenol-D rods by 78.5% compared to a rod with only a hole.
• A prototype transducer achieved a maximum transmitting current response of 185.4 dB at 3.75 kHz.
• The manufactured transducer demonstrated practical performance for underwater projector applications.

Conclusions:

• The segmented stack configuration is an effective method for optimizing the magnetic design of Terfenol-D rods.
• Digital slots significantly reduce eddy current losses, improving the magnetostriction ability of Terfenol-D transducers.
• The developed Terfenol-D transducer prototype shows high performance and practicality for underwater acoustic applications.