The Influence of Aerodynamic Unsteady Effect on Maneuver Load of Aircraft Horizontal Tail

In this paper, the unsteady effect of airflow is introduced into the calculation of aircraft maneuver load, and the results are compared with those obtained by quasi-steady method. Taking the steep pitch maneuver of an aircraft as an example, two methods are used to calculate the aircraft response after the rudder input is given according to the specifications. The calculation results show that if the peak overload of the aircraft is the same, the horizontal tail load increases by about 1% when the unsteady effect of the airflow is taken into account. If the rudder input of the two methods is the same, the unsteady calculation method will increase more. At the same time, the calculation shows that the bigger the deflection speed of rudder surface is, the bigger the difference between them is. Therefore, in order to improve the design quality of aircraft, it is necessary to introduce the unsteady effect into the calculation of loads in the detailed design stage of aircraft.

考虑自增强影响的Ⅲ型复合材料气瓶连续损伤模拟及渐进失效分析（英文）

目的:成型后的金属内胆复合材料气瓶,即III型复合材料气瓶(以下简称气瓶),需采用自紧工艺来提高疲劳寿命。最佳自紧压力是自紧工艺的重要参数。本文旨在建立确定最佳自紧压力和气瓶渐进失效的有限元方法,研究自紧后气瓶纤维和基体损伤演化规律,并探讨自紧后气瓶复合材料层和金属内衬层的应力变化。创新点:1.建立针对三维气瓶的Hashin失效准则和指数型损伤演化的渐进失效模型,并通过ABAQUSUMAT隐式有限元方法确定气瓶最佳自紧压力;2.通过渐进失效分析,揭示自紧后的气瓶纤维和基体损伤的损伤演化规律,并阐明自紧对气瓶渐进失效的影响。方法:1.基于连续损伤力学,建立三维Hashin失效准则和指数型损伤演化的渐进失效理论模型;2.通过ABAUQS-UMAT二次开发用户子程序实现渐进失效理论模型,并开展气瓶渐进失效计算;3.通过平板拉伸算例以及与气瓶试验数据对比,验证模型的准确性。结论:1.基体损伤首先出现在螺旋层,而纤维损伤首先出现在环向层。2.除了自紧后的泄压阶段和自紧后重新加压至压力值等于自紧压力的升压阶段,有无自紧的气瓶损伤演化规律基本一致;而在上述泄压和升压阶段,基体损伤保持不变,说明经过自紧后的气瓶在工作压力下存在基体损伤。3.当内压压力低于自紧压力时,自紧工艺才会影响气瓶应力分布;且随着压力的升高,基体损伤不变,内衬应力减少,纤维应力增加;此外,经过自紧的气瓶在工作压力下最大环向和轴向内衬应力减少且出现在筒体部分的两端。