热/力耦合作用下基于应力分析的冰破坏准则

根据飞机热除冰的物理过程,考虑外部空气动力和蒙皮表面加热的作用,建立了NACA 0012翼型前缘冰层应力计算模型。采用有限元方法和平面三角形单元对控制方程组进行了求解,获得了外部空气动力和蒙皮表面加热对冰层黏附界面应力的影响规律。研究表明:蒙皮表面不加热时,来流速度影响了黏附界面应力的强度,来流攻角影响了黏附界面应力的分布,冰-蒙皮间黏附界面切应力最大值随来流速度呈近似线性增大趋势,但外部空气动力很难造成冰层破坏。蒙皮表面加热时,冰-蒙皮间黏附界面的耦合应力和冰层内部的主应力随着热流密度的增大而增大,很容易超过剪切强度,这是造成冰破坏的关键因素。耦合冰-蒙皮剪切强度随界面温度的变化关系,初步建立了基于应力分析和热/力耦合作用的冰破坏判断准则。外部空气动力产生的界面应力和蒙皮表面加热产生的界面热应力之和，必须大于与蒙皮表面温度相关的剪切强度，则冰层发生破坏，破坏位置是耦合应力超过剪切强度的区域。 

Ice fracture criterion coupled thermal/mechanical effect based on stress analysis

Considering the effect of the external aerodynamic force and skin heating, the computational model of stress inside ice on the leading edge of NACA 0012 airfoil was established according to the thermal de-icing physical process. The finite element method and triangular element were employed to solve the governing equations. The effects of external aerodynamic force and skin heating on the ice adhesion interface stress were obtained. The study showed that, without skin heating, the variation of airflow speed changed the intensity of interfacial stress of ice adhesion interface and the variation of angle of attack changed the distribution of interfacial stress of ice adhesion interface. An approximate linear increasing trend for maximum interfacial shear stress existed along with the increasing airflow speed. But external aerodynamic force contributed little to ice fracture. For skin heating, the coupled stress of ice adhesion interface and principal stress inside ice increased along with the increase of heat flow rate, which can be easily larger than the shear strength of adhesion interface and key factor for ice fracture. The preliminary ice fracture judgement criterion was founded based on the relationship between interfacial stress and adhesion strength related with interfacial temperature. Ice fracture appears when the sum of the interfacial stress generated by the external aerodynamic force and the interfacial thermal stress generated by the skin heating are greater than the shear strength related to the skin surface temperature. The fracture location is the area where the coupled stress exceeds the shear strength.