典型民机机身段水上冲击数值模拟方法及其耐撞性研究

为了改善民机在紧急迫降情况下的安全性能,对典型机身段水上冲击数值模拟方法及其冲击特性进行了研究。通过合理的简化建立了机身段有限元模型,对有限元方法(FEM)、任意拉格朗日/欧拉方法(ALE)和光滑粒子方法(SPH)水体模型进行了研究,探讨了水体材料模型对机身段结构动态响应特性的影响。在7 m/s垂向冲击速度下,对比分析了水面和刚性地面情况下的机身段结构的耐撞性能。结果表明ALE方法具有最佳计算精度和计算效率。由于忽略了偏应力,采用空材料得到的机身结构响应与弹性流体和弹塑性水体材料有明显不同。在水上冲击过程中,由于水体耗散了大量冲击动能,因此机身加强框变形较小。机身底部蒙皮结构承受较大的均布载荷,因此蒙皮吸能结构吸收了较多的冲击动能,是最重要的吸能结构之一。相对于刚性地面,水面冲击情况下机身具有更小的加速度过载。在紧急迫降情况下,选择湖泊或者江河等水域作为迫降地点可以减小乘员承受加速度过载。

Research on the numerical method and crashworthiness of typical civil aircraft fuselage for water impact

To improve the safety of civil aircraft during emergency loading, the numerical model and impact characteristics of a typical fuselage are investigated for water impact. The finite element model of a civil aircraft is built based on sound simplification. A water model is simulated by Finite Element Method (FEM), Arbitrary Lagrangian-Eulerian (ALE) and Smoothed Particle Hydrodynamics (SPH). The crashworthiness of a typical fuselage with different water materials are discussed. The vertical drop velocity of 7 m/s is adopted, and gravitational acceleration is considered. Finally, the water impact characteristics of a civil aircraft are compared with those under rigid floor impact conditions. Numerical results show that ALE is the best numerical simulation method. The crashworthiness of a civil aircraft for null material is obviously different from that of others for the lack of deviatoric stresses. The deformation of fuselage is small because most of impact kinetic energy is dissipated by water. Skin absorbs large part of impact kinetic energy because it is under large distributed impact load, and it is one of the most important energy absorption structures for water import problems. The acceleration overload with water is smaller than that with rigid floor. The impact load transferred to passengers could be improved if lake or river is chosen as a landing site.