Research on the mechanical properties of magnetorheological fluid under electromagnetic-thermal coupling

The mechanical properties of magnetorheological fluid are influenced by multiple factors in multi-physical field environments. To precisely characterize the mechanical properties and variations under the influence of multiphysical field coupling, this study analyzes the mechanism of electromagnetic-thermal multi-physical field coupling based on the principles of electromagnetic thermal effects. Furthermore, it derives formulas to describe the changes in resistance of the excitation coil, electric current, and magnetic field strength resulting from the influence of temperature. A physical model of the excitation coil is constructed for conducting numerical simulations, and a test bench is assembled to validate the magnetic field strength generated by the excitation coil. By considering the impact of temperature on both the magnetic field strength and the magnetization rate of the particles in the magnetorheological fluids, an analytical calculation is performed to determine the shear yield stress of the fluid under multi-physical field conditions. The results showed that the magnetic field strength generated by the excitation coil as temperature decreased with increasing, and with an increase in temperature from 30 C-degrees to 80 C-degrees, the magnetic induction strength decreased by 17.1 % from 22.88 mT to 18.96 mT, while the shear yield stress decreases by 29.2 % from 35.9 kPa to 25.4 kPa. These findings have a significant effect on the performance of magnetorheological fluids materials, underscoring the necessity of considering multi-physical field effects when researching their performance and verifying the performance degradation and failure of magnetorheological devices under high-temperature conditions.