复合材料机翼结构的气动弹性优化设计与风洞颤振试验

本文介绍了一种用于复合材料机翼结构设计与优化的气动弹性剪裁方法。该方法应用所谓的双线性拉格朗日(Lagrange)形函数来创建用于复合机翼结构气动弹性剪裁的设计变量。目前常用的基于单元设计变量的方法使得蒙皮/翼梁/肋板的厚度分布不光滑,可能导致制造问题或应力集中。而形函数方法假设机翼蒙皮或沿着翼梁/肋板的厚度分布可以通过一组形状函数叠加。这样,设计变量就变成形函数的系数。在应用优化算法求解这些系数之后,可以通过将形函数叠加来确定每个单元的厚度,可保证相邻单元间厚度分布的平滑度。此外,应用基于计算流体力学(CFD)的颤振分析方法可精确地捕获跨声速颤振边界,并且在优化过程中可用作颤振约束。为了验证本文所介绍的气动弹性优化方法,优化设计了一个民用飞机复合机翼结构。其次,以优化后的机翼结构为基础,设计并制作了风洞缩比颤振模型,并进行了高速风洞颤振试验,以验证优化机翼结构的颤振特性。最后,风洞颤振试验成功验证了本文所提出的气动弹性优化设计方法的有效性。

Evaluation of reclaimed asphalt pavement binder stiffness without extraction and recovery

A new testing procedure to estimate the low-temperature stiffness of the reclaimed asphalt pavement （RAP） binder was developed. In the testing procedure, the SuperpaveTM Bending Beam Rheometer （BBR） with special modifications and binder blending charts by Asphalt Institute were utilized. Modifications involved the development of a new kind of sample mold and different testing parameters were made to BBR testing procedure to capture the theological properties of bitumen mortars produced by mixing fresh binder with fine RAP materials or RAP aggregate. The stiffness relationship between binder and bitumen mortar was established based on the BBR test results. The blended binder stiffness in bitumen RAP mortar was estimated from the RAP mortar stiffness based on the binder-mortar relationship. And finally, the RAP binder stiffness was estimated from the blended binder and fresh binder stiffness based on the blending charts by Asphalt Institute. The results indicate that the new procedure can capture the rheological properties of bitumen mortar and can be used to estimate the low temperature stiffness of RAP binder without binder extraction and/or any chemical treatments.