飞行器机身结构耐撞性分析与设计

耐撞性不仅是飞行器设计中的重要问题,而且还是其取得适航证的必要条件。该文对美国、欧盟和日本等在耐撞性研究方面的研究进行了总结,阐述了耐撞性设计中采用的数值模拟和试验研究方法及其主要问题。主要针对各种飞行器结构耐撞性设计方法进行介绍,对比了轻型固定翼飞机、直升机和大中型民用飞机的耐撞性设计特点。能量吸收结构是耐撞性设计的关键问题之一,对提高飞行器机身能量吸收能力的机身底部结构、机身加强框和客舱地板撑杆结构等设计方法进行详细介绍,总结了飞行器耐撞性可靠性分析和优化设计方法。最后对飞行器结构耐撞性设计的发展作了展望。     

机械冲击耐撞性与稳健设计

碰撞冲击是机电产品损坏失效的常见原因,轻则造成产品外形丧失美观,重则造成产品内在功能失效,甚至机毁人亡,因而机械产品的耐撞性受到日益广泛的关注。本文从产品跌落冲击和运载工具碰撞两个领域论述了机械系统碰撞动力学和耐撞性设计研究的发展、两领域耐撞性研究的阶段性和特点,分析了机械冲击耐撞性中的冲击参数到性能参数传递过程中的不确定性,进而探讨了机械系统产品耐撞性稳健设计优化框架。     

飞机风挡夹层结构耐撞性数值分析

用LS-DYNA3D软件,建立了由钢化玻璃和PU、PVB塑料薄膜组成的风挡夹层结构鸟撞数值模型。鸟体采用ALE格式和与应变率相关的随动硬化材料模型,夹层结构用Lagrange格式和双线性材料模型,对11种风挡夹层结构进行了数值计算,分析了撞击过程的损伤和应力,讨论了夹层结构耐撞性的评估方法,为风挡夹层结构设计提供理论依据。     

PBM算法在近场爆炸数值模拟中的运用研究

为探究爆炸粒子算法(PBM)在近场爆炸问题中的适用性,分别采用PBM法及任意拉格朗日-欧拉算法(ALE&S-ALE),开展AL-6XN不锈钢板近场爆炸的仿真模拟.结合T B?rvik的试验结果,对比了ALE、S-ALE和PBM方法的计算精确度和运算效率;采用PBM算法对不同爆心距的钢板近场爆炸工况进行仿真计算,分析了粒...     

某焦煤车间钢梁的耐撞性分析

利用非线性有限元动力分析软件ANSYS/LS-DYNA研究了某焦煤车间制动梁的耐撞性问题,通过计算机数值模拟计算,分析了装煤钢方斗对制动梁的影响。结果表明:装煤钢方斗的作用为类矩形脉冲荷载;梁的下翼缘的应力很大,被撞区和支座处的腹板和加劲肋应力也很大,这表明可以适当加大下翼缘和腹板的厚度和减小上翼缘的厚度。     

A型不锈钢地铁车体耐撞性研究

轨道车辆车体基本性能的研究需要考虑多方面的因素,车体耐碰撞性是重要指标之一。以A型不锈钢地铁车体为研究对象,基于LS-DYNA碰撞仿真平台,分析了车辆在不同碰撞速度下车体的耐撞性能;然后,采用逼近法,获取了该型地铁车的最大碰撞安全速度,为车体的耐撞性设计提供了理论支撑。     

响应表面法在薄壁构件耐撞性优化设计中的应用研究

汽车结构的耐撞性及碰撞吸能优化是现代汽车工业重要的研究内容。耐撞性的优化涉及材料与结构的众多参数。传统的设计、碰撞仿真及试验往往只能在一定程度上改善结构的碰撞性能而无法达到限定条件下的最优状态。利用国际上近年来新发展起来的一种优化理论方法--响应表面法,结合传统的优化手段以及非线性有限元程序对薄壁构件的耐撞性问题进行了优化研究。耐撞性优化的结果表明,该方法具有较高的精确性和有效性。     

典型薄壁结构抗鸟撞动响应试验及数值模拟研究EI北大核心CSCD

设计满足鸟撞适航条款要求的飞机薄壁结构,必须进行典型薄壁结构抗鸟撞动响应试验及数值模拟研究。对某飞机机头上壁板薄壁结构进行了鸟撞试验,并采用光滑粒子流体动力学-有限元法(smoothed particle hydrodynamics-finite element method,SPH-FEM),基于商用显式有限元分析软件PAM-CRASH,建立了鸟撞上壁板薄壁结构数值计算模型。计算结果表明,上壁板结构损伤模式主要包括蒙皮撕裂和铆钉断裂,计算结果与试验结果良好的一致性验证了该数值计算模型及方法的合理性。在此基础上,建立了鸟撞典型薄壁结构数值计算模型,研究了鸟弹不同撞击角度和速度下典型薄壁结构蒙皮极限厚度值,结果表明,随着撞击速度的增大,蒙皮极限厚度的变化对撞击角度十分敏感。拟合了典型薄壁结构蒙皮极限厚度与鸟弹撞击角度和速度之间的数学关系,为飞机薄壁结构抗鸟撞设计提供技术支撑。     

基于欧拉—拉格朗日方法的复合材料机翼前缘鸟撞模拟

复合材料大面积用于飞机结构后,其鸟撞问题变得更加突出。利用大型通用有限元程序ABAQUS,采用耦合欧拉—拉格朗日方法（CEL）对某型无人机复合材料机翼前缘的鸟撞问题进行模拟,研究了鸟体速度、密度和蒙皮铺层形式等对鸟撞动响应的影响,计算了机翼前缘填充泡沫后的鸟撞损伤,对复合材料蒙皮的鸟撞破坏机理进行了分析,所得结果对工程设计具有参考意义。     

地铁列车双锥内嵌隔板矩形管的耐撞性优化

为设计具有良好耐撞性能的地铁列车吸能结构,将矩形吸能管的一组对称面引入锥度,并在内部嵌入多个隔板.建立该双锥内嵌隔板矩形管和传统矩形管的有限元模型,对两者耐撞性进行对比,通过准静态轴向压缩试验验证有限元分析的准确性.以双锥内嵌隔板矩形管三个部分的厚度为设计变量,进行试验设计并建立代理模型,为最大化比吸能和最小化峰值力,...     

基于细分粒子的刚体破裂动画

为了模拟固体在外力作用下产生的破裂现象,提出一种采用细分粒子的刚体破裂的模拟算法.该算法首先将固体的四面体网格绑定到一系列离散的粒子上;再利用光滑粒子流体动力学（SPH）对线弹性力学方程进行离散求解;并采用粒子细分的算法来进行开裂面的生成和延展.最后实现了多个固体现象的模拟,如砖块碎落、砖墙受力倒塌等.文中算法可适用于刚体脆性破碎的动画应用.     

一种SPH流体仿真边界校正方法

使用光滑粒子流体动力学方法进行流体仿真,并提出一种边界校正方法。使用快速泊松盘采样算法对容器边界进行采样,生成边界粒子,对边界粒子质量进行差值估算,计算边界粒子对流体粒子的作用力,以此来仿真流体与边界的相互作用。该方法可避免穿刺、滞留等现象的发生。通过实验验证了该算法的正确性。     

Virtual and smoothed finite elements: A connection and its application to polygonal/polyhedral finite element methods

We show both theoretically and numerically a connection between the smoothed finite element method (SFEM) and the virtual element method and use this approach to derive stable, cheap and optimally convergent polyhedral FEM. We show that the stiffness matrix computed with one subcell SFEM is identical to the consistency term of the virtual element method, irrespective of the topology of the element, as long as the shape functions vary linearly on the boundary. Using this connection, we propose a new stable approach to strain smoothing for polygonal/polyhedral elements where, instead of using sub‐triangulations, we are able to use one single polygonal/polyhedral subcell for each element while maintaining stability. For a similar number of degrees of freedom, the proposed approach is more accurate than the conventional SFEM with triangular subcells. The time to compute the stiffness matrix scales with the in case of the conventional polygonal FEM, while it scales as in the proposed approach. The accuracy and the convergence properties of the SFEM are studied with a few benchmark problems in 2D and 3D linear elasticity. Copyright © 2015 John Wiley & Sons, Ltd.     

An enhanced cell‐based smoothed finite element method for the analysis of Reissner–Mindlin plate bending problems involving distorted mesh

In this work, an enhanced cell‐based smoothed finite element method (FEM) is presented for the Reissner–Mindlin plate bending analysis. The smoothed curvature computed by a boundary integral along the boundaries of smoothing cells in original smoothed FEM is reformulated, and the relationship between the original approach and the present method in curvature smoothing is established. To improve the accuracy of shear strain in a distorted mesh, we span the shear strain space over the adjacent element. This is performed by employing an edge‐based smoothing technique through a simple area‐weighted smoothing procedure on MITC4 assumed shear strain field. A three‐field variational principle is utilized to develop the mixed formulation. The resultant element formulation is further reduced to a displacement‐based formulation via an assumed strain method defined by the edge‐smoothing technique. As the result, a new formulation consisting of smoothed curvature and smoothed shear strain interpolated by the standard transverse displacement/rotation fields and smoothing operators can be shown to improve the solution accuracy in cell‐based smoothed FEM for Reissner–Mindlin plate bending analysis. Several numerical examples are presented to demonstrate the accuracy of the proposed formulation.Copyright © 2013 John Wiley & Sons, Ltd.     

On computing upper and lower bounds on the outputs of linear elasticity problems approximated by the smoothed finite element method

Verification of the computation of local quantities of interest, e.g. the displacements at a point, the stresses in a local area and the stress intensity factors at crack tips, plays an important role in improving the structural design for safety. In this paper, the smoothed finite element method (SFEM) is used for finding upper and lower bounds on the local quantities of interest that are outputs of the displacement field for linear elasticity problems, based on bounds on strain energy in both the primal and dual problems. One important feature of SFEM is that it bounds the strain energy of the structure from above without needing the solutions of different subproblems that are based on elements or patches but only requires the direct finite element computation. Upper and lower bounds on two linear outputs and one quadratic output related with elasticity—the local reaction, the local displacement and the J‐integral—are computed by the proposed method in two different examples. Some issues with SFEM that remain to be resolved are also discussed. Copyright © 2010 John Wiley & Sons, Ltd.     

A face‐based smoothed finite element method (FS‐FEM) for 3D linear and geometrically non‐linear solid mechanics problems using 4‐node tetrahedral elements

This paper presents a novel face‐based smoothed finite element method (FS‐FEM) to improve the accuracy of the finite element method (FEM) for three‐dimensional (3D) problems. The FS‐FEM uses 4‐node tetrahedral elements that can be generated automatically for complicated domains. In the FS‐FEM, the system stiffness matrix is computed using strains smoothed over the smoothing domains associated with the faces of the tetrahedral elements. The results demonstrated that the FS‐FEM is significantly more accurate than the FEM using tetrahedral elements for both linear and geometrically non‐linear solid mechanics problems. In addition, a novel domain‐based selective scheme is proposed leading to a combined FS/NS‐FEM model that is immune from volumetric locking and hence works well for nearly incompressible materials. The implementation of the FS‐FEM is straightforward and no penalty parameters or additional degrees of freedom are used. The computational efficiency of the FS‐FEM is found better than that of the FEM. Copyright © 2008 John Wiley & Sons, Ltd.     

A saturated discrete particle model and characteristic-based SPH method in granular materials

Based on the discrete particle model for solid-phase deformation of granular materials consisting of dry particulate assemblages, a discrete particle–continuum model for modelling the coupled hydro-mechanical behaviour in saturated granular materials is developed. The motion of the interstitial fluid is described by two parallel continuum schemes governed by the averaged incompressible N–S equations and Darcy's law, respectively, where the latter one can be regarded as a degraded case of the former. Owing to the merits in both Lagrangian and mesh-free characters, the characteristic-based smoothed particle hydrodynamics (SPH) method is proposed in this paper for modelling pore fluid flows relative to the deformed solid phase that is modelled as packed assemblages of interacting discrete particles. It is assumed that the formulation is Lagrangian with the co-ordinate system transferring with the movement of the solid particles. The assumed continuous fluid field is discretized into a finite set of Lagrangian (material) points with their number equal to that of solid particles situated in the computational domain. An explicit meshless scheme for granular materials with interstitial water is formulated. Numerical results illustrate the capability and performance of the present model in modelling the fluid–solid interaction and deformation in granular materials saturated with water. Copyright © 2007 John Wiley & Sons, Ltd.     

Modelling of Bird Strike on an Aircraft Wing Leading Edge Made from Fibre Metal Laminates – Part 2: Modelling of Impact with SPH Bird Model

Fibre Metal Laminates with layers of aluminium alloy and high strength glass fibre composite have been reported to possess excellent impact properties and be suitable for aircraft parts likely to be subjected to impacts such as runway debris or bird strikes. In a collaborative research project, aircraft wing leading edge structures with a glass-based FML skin have been designed, built, and subjected to bird strike tests that have been modelled with finite element analysis. In this second part of a two-part paper, a finite element model is developed for simulating the bird strike tests, using Smooth Particle Hydrodynamics (SPH) for modelling the bird and the material model developed in Part 1 of the paper for modelling the leading edge skin. The bird parameters are obtained from a system identification analysis of strikes on flat plates. Pre-test simulations correctly predicted that the bird did not penetrate the leading edge skin, and correctly forecast that one FML lay-up would deform more than the other. Post test simulations included a model of the structure supporting the test article, and the predicted loads transferred to the supporting structure were in good agreement with the experimental values. The SPH bird model showed no signs of instability and correctly modelled the break-up of the bird into particles. The rivets connecting the skin to the ribs were found to have a profound effect on the performance of the structure.     

基于有限元与光滑粒子耦合的弹丸挤进过程分析

基于有限元（FEM）与光滑粒子（SPH）耦合算法,建立弹丸身管耦合系统动力学模型。通过对某大口径火炮弹丸挤进过程进行数值模拟,弥补弹丸挤进过程有限元分析方法无法有效模拟弹带大变形缺陷,成功模拟出弹丸挤进阶段弹带塑性流动过程,在此基础上深入研究弹带的应力应变变化规律。分析弹丸初始装填角、弹炮间隙、弹丸装填不到位等因素对挤进过程中弹丸动力响应影响。结果表明,仿真与实弹射击的弹带变形一致性较好。