MAGNETOMECHANICAL DEFORMATION OF THIN FERROMAGNETIC SHELLS IN EXTERNAL MAGNETIC FIELDS: A COUPLED MAGNETOELASTIC FINITE-ELEMENT AND EXPERIMENTAL STUDY

This study presents a coupled theoretical, numerical, and experimental investigation of the deformation of thin ferromagnetic cylindrical shells subjected to externally applied magnetic fields. A magnetoelastic constitutive framework is formulated by decomposing total strain into elastic and magnetostrictive components and by incorporating magnetostatic field equations, Maxwell-type tractions, and field-dependent magnetization. The shell kinematics are described through the Kirchhoff-Love hypothesis, while the coupled boundary-value problem is solved by a finite-element procedure that links shell elements to a three-dimensional magnetic domain. A mesh-convergence study identifies a 1,200-element discretization as an efficient numerical compromise, yielding a peak radial displacement within 0.1% of the refined solution. The model is evaluated against measurements from annealed Co-Fe-V cylindrical shells exposed to axial magnetic flux densities of 0.25, 0.50, and 1.00 T. The predicted peak radial displacements are 18.4, 46.2, and 88.3 µm, compared with experimental values of 17.9, 44.7, and 84.3 µm, corresponding to relative errors of 2.8-4.7%. Parametric analysis indicates that deformation increases as the shell becomes thinner, depends strongly on field orientation, scales approximately with saturation magnetostriction, and decreases with elastic modulus. The results demonstrate the importance of simultaneously representing nonlinear magnetic response, shell curvature, free-edge effects, and magnetostrictive eigenstrain when designing shell-based magnetic actuators and sensors.

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