Coupled thermo-mechanical analysis of stresses generated in impact ice during in-flight de-icing

Abstract

Before the phase change of ice on the aircraft surface occurs during an electrothermal de-icing process, the stresses developed in impact ice may have certain influence on the shedding of ice. To effectively improve the control accuracy of inflight de-icing, a numerical study on the thermo-mechanical coupling effect caused by aerodynamic force and electric heating is carried out. Based on the fundamental rules of elastic mechanics and heat transfer, this multi-physical process involving fluid-structure interaction and thermal-structure coupling is numerically investigated, with the stress distribution developed across the entire structure predicted. To further evaluate the contribution to ice detachment, the stresses generated under typical conditions are quantitatively compared with the fracture strength of ice. Results show that the effect of the heat flux is much more significant than that of the aerodynamic force on ice failure. Under the action of electric heating, the maximum shear stress is determined at 2.84 MPa, which is 5.6 times the shear strength of ice (0.51 MPa) and will cause ice detachment along the ice-airfoil interface. Besides, the peak principal stress reaches 5.94 MPa after 5 s of heating time and has exceeded the compressive strength of ice (5 MPa), developing local fracture inside the ice. The combined effect of these two aspects weakens the overall adhesion and may eventually lead to ice shedding. Contributions of this study can effectively guide the optimization of aircraft thermo-mechanical de-icing systems.