结冰风洞冰与固壁间剪切黏附应力和强度的初步研究

Preliminary study on ice adhesion stress and strength on solid wall in icing wind tunnel

为研究飞机结冰与固壁间的黏附强度,耦合固体力学实验方法和结冰风洞试验方法,在3m×2m结冰风洞试验段内开展了冰与固壁间的剪切黏附强度测量试验。首先,基于结冰风洞试验段,建立了冰与固壁间剪切黏附强度测量试验装置及其试验模型。然后,通过固定外试验模型、拉伸内试验模型的方式,实现了冰从固壁表面的剥离,并针对此冰层剪切剥离过程建立了相应的计算模型。采用平面弹性力学方程描述该计算模型,采用非结构网格技术对计算区域进行划分,利用有限元方法对控制方程组进行离散,根据不同断裂力学判断准则的适应范围,采用了最大剪切强度准则用于判断剪切拉伸作用对冰层剥离的影响,计算结果表明,随着作用于内试验模型的轴向力载荷增加,冰与固壁间的剪切黏附应力也将增加,由于外试验模型的固定约束,在冰与固壁间的黏附界面两端会出现两个轻微的剪切黏附应力峰值,而在黏附界面中间位置,剪切黏附应力变化比较平缓。结冰风洞试验获得的剪切黏附强度在0.4MPa到1.0MPa之间,与参考文献中的试验结果比较吻合,明冰的剪切黏附强度大、霜冰的剪切黏附强度低,说明本文的试验方法和装置都比较合理,试验结果也验证了计算模型和计算结果的合理性。

Coupled with solid mechanics experiment method and icing wind tunnel experiment method,the ice shear adhesion strength measurement is implemented in test section of 3 m×2 m icing wind tunnel to study the adhesion strength between ice and solid wall of airplane.Firstly,the ice shear adhesion strength test equipment is established on the basis of test section,which is used to measure the shear adhesion strength between ice and solid wall of airplane.Then the peeling of ice from solid wall is implemented by fixing outer test model and stretching inner test model.A computational model is also established to describe the shear peeling process.The plane elasticity equations are adopted to describe the computational model.An unstructured mesh is used to distribute the computational domain.The finite element method is utilised to discrete and solve the equation group.In view of the adaptability of different fracture mechanics criterion,the maximum shear stress criterion is adopted to judge the influence of shear stretching on the peeling of ice from solid wall.It shows that the ice shear adhesion stress increases with the axial forceload on the inner test model.Due to the constrain of the outer test model,there are two slight peaks of shear adhesion stress at two sides of the adhesion interface,and the variation of the shear adhesion stress is slight flat in the middle of the adhesion interface.The ice shear adhesion strength from the present experiment is reasonable from 0.4 MPa to 1.0 MPa,which is in good agreement with the reference experimental results.The shear adhesion strength of glaze ice is larger than that of rime ice.The present experimental method and measurement device are reasonable.Moreover,the computational model and numerical results have been validated by the experimental results.