2024-T3铝合金动力学实验及其平板鸟撞动态响应分析

通过电子万能试验机和分离式霍普金森拉杆（SHTB）拉伸试验分别获得2024-T3铝合金材料准静态和高应变率两种应变率下的应力-应变曲线。铝合金材料的本构关系由能够反映材料硬化效应和应变率强化效应的Johnson-Cook材料模型描述,方程中的4个参数通过不同应变率下的应力-应变曲线拟合得到。基于瞬态动力学软件PAM-CRASH,结合材料动态力学性能试验所获得的2024-T3铝合金Johnson-Cook模型方程,耦合光滑粒子流体动力学（SPH）方法和有限元（FE）方法建立2024-T3铝合金平板的鸟撞数值模型,数值计算所得动态响应与鸟撞试验结果吻合较好,表明建立的鸟撞数值计算模型是合理、可靠的,整个分析流程从材料动态力学性能试验、鸟撞数值计算到最终的鸟撞试验验证为飞机结构的抗鸟撞设计与分析提供了有力的参考。     

鸟撞45#钢平板动响应试验研究

采用动态数据采集系统,对45#钢平板在不同撞击速度下的鸟撞动响应全过程进行了详细研究,得到了撞击过程中平板上三个点位移和四个点的应变、撞击方向4个支反力等物理量随时间变化历程,同时利用高速摄像系统记录了鸟撞过程中鸟体及平板动态变形的全过程。对重复试验的结果进行比较,二者良好的一致性表明试验结果的可靠性,在此基础上分析了平板动响应及鸟体破碎随撞击速度的变化规律。发现,位移及撞击支反力峰值随撞击速度的提高而线性增大;撞击速度越高,鸟体的流体特性越明显,表明高速撞击数值模拟中鸟体应采用描述流体行为的本构模型。该试验结果对建立合理的鸟体本构模型及验证鸟撞有限元计算方法具有重要意义。     

复合材料雷达罩鸟撞破坏的流固耦合动响应分析

建立了鸟撞复合材料雷达罩有限元模型,用壳单元模拟雷达罩,在鸟体周围附加用于模拟空气的欧拉流动域,利用显示动力分析软件LS-DYNA对鸟撞复合材料雷达罩的过程进行了数值模拟,对雷达罩的破坏响应进行了分析。结果表明,在撞击的过程中,应力的峰值主要出现在被撞击区域的周围;部分区域的不同材料层间会承受不同的应变趋势。     

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。     

民用飞机平尾前缘鸟撞数值分析及试验验证

用电子液压拉伸试验机与分离式霍普金森拉杆(SHTB)装置进行2024-T3、7075-T6铝合金材料不同应变率的拉伸试验,拟合出反映两种材料应变率强化效应的Johnson-Cook本构方程。通过SHTB动态拉伸试验获得7种铆钉的极限拉伸、剪切载荷。基于瞬态动力学软件PAM-CRASH,利用元件级材料试验获得铝合金本构方程及连接件动态失效参数,耦合光滑粒子流体动力学(SPH)方法与有限元方法建立民机平尾前缘鸟撞数值模型进行试验并验证数值计算结果。计算、试验结果的一致性表明,所建鸟撞数值计算模型合理、可靠。整个积木式试验、分析流程可为民机结构抗鸟撞设计提供有力参考。     

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。     

飞机撞击特大型LNG储罐全过程仿真分析

采用数值模拟方法对飞机撞击特大型LNG储罐的全过程进行仿真分析。分析中采用LS-DYNA有限元程序,考虑罐体、储液与保温层间的相互问题,建立了F-15战斗机的SPH模型,对飞机材料的选择和参数确定进行了详细分析,并以Riera法为依据,对F-15战斗机SPH模型撞击刚体所产生的荷载进行了对比验证,对比结果证明了SPH模型的可靠性和实用性。分析结果表明：撞击角度越大,外罐所承受的撞击能量越大,相应的内罐破坏越小,因此垂直撞击为最不利撞击角度;撞击高度对整体工况计算结果影响不大,储罐在经受215m/s撞击速度撞击下均出现了严重破坏;112m/s撞击速度时内罐尚有安全余量,160m/s撞击速度时内罐撞击中心区域内材料已达到极限应变,因此可认为目前设计方法设计的储罐所能承受的最大撞击速度为160m/s。     

飞机驾驶舱后观察窗抗鸟撞试验及数值模拟研究

为了对飞机驾驶舱后观察窗玻璃进行抗鸟撞设计,进行了后观察窗玻璃抗鸟撞试验,试验中测量了观察窗玻璃上两个点的应变时间历程。利用大型商用碰撞分析软件PAM-CRASH建立了全尺寸鸟撞后观察窗玻璃有限元计算模型,对鸟撞后观察窗试验过程进行了数值模拟,比较了应变及位移时间历程曲线的计算结果和试验结果,二者良好的一致性表明计算模型的合理性。在此基础上分析了内外层玻璃厚度及中间空气层厚度对后观察窗结构抗鸟撞动响应的影响规律,为飞机驾驶舱后观察窗玻璃的抗鸟撞设计提供技术指导。     

基于SPH方法的叶片鸟撞数值模拟研究

基于显式碰撞动力分析软件PAM-CRASH及其提供的SPH方法,建立了鸟撞平板叶片数值分析模型.通过SPH方法、Lagrange方法结果和实验结果三者对比,指出SPH方法比Lagrange方法的数值计算结果更贴近试验结果.还应用SPH方法,研究了圆柱体、两端带半球的圆柱体、椭球体三种不同几何构型的鸟体对计算结果的影响.最后,计算了实验条件下易出现损伤的叶片根部不同时刻的应变分布及应力分布.     

高速列车风阻制动风翼抗鸟撞分析

对研制的复合材料高速列车风阻制动风翼建立有限元模型。据接触-碰撞基本理论利用非线性动力分析软件LS-DYNA对鸟撞制动风翼过程数值仿真,将计算结果与实验数据对比验证仿真过程的合理性。结果显示,该制动风翼能承受500 km/h鸟体撞击,极限能达625 km/h,满足要求设计。鸟撞过程中制动风翼变形具有冲击波传递特征,应力峰值主要出现在被撞击区域,与底座相连部分及摇臂附近也会出现应力集中。     

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.     

Modelling of Bird Strike on an Aircraft Wing Leading Edge Made from Fibre Metal Laminates – Part 1: Material Modelling

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 from objects such as runway debris or birds. 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 first part of a two-part paper, a material model developed for FML suitable for use in impact modelling with explicit finite element analysis is presented. The material model is based on a recent implementation in the commercial finite element code PAM-CRASH/SHOCK of a Continuum Damage Mechanics (CDM) model for composites, incorporating anisotropic strain rate effects. Results from the model are compared with experimental results on FML at variable strain rates and the model is shown to be capable of capturing most of the complex strain rate dependent behaviour exhibited by these materials.     

Rigid body water impact-experimental tests and numerical simulations using the SPH method

Statistics show that water impact of an aircraft in emergency is likely to have tragic consequences and therefore new researches on this topic are recommendable. In 2005, the GARTEUR AG15 was established to improve the SPH method for application to helicopter ditching. As a contribution, water impact drop tests using rigid bodies were performed at the Politecnico di Milano LAST Crash Lab to collect data and validate the numerical models. During the tests, impact decelerations were measured and suitably pressure transducers were developed to measure the impact pressures. Numerical simulations were carried out by adopting the SPH method to model the fluid region. A close experimental-numerical correlation was obtained. Findings are reported and guidelines for further investigations are proposed.     

飞机尾翼前缘结构鸟撞仿真与改进设计

基于疏散鸟体动能的防鸟撞策略,以提高结构刚度和抑制变形为目标,采用光滑粒子流体动力学(SPH)方法对现有飞机尾翼前缘结构鸟撞过程进行了数值研究。根据模拟结果,通过增加单向斜支板结构和采用纤维/金属复合材料,实现了从结构和材料两个方面对尾翼前缘结构进行改进设计。结果表明,前缘增加的单向斜支板结构可以通过疏散鸟体动能来降低鸟撞冲击对尾翼内部结构的破坏,而采用纤维金属复合材料则减轻了前缘曲翼约10%的质量,且提高了整体刚度,并使结构在鸟撞过程中最大变形降低到原始构型的25%。通过分析不同铺层方式下材料的破坏模式和吸能效果,发现合理的铺层设计可显著提高尾翼前缘结构的抗鸟撞性能。     

Thermo-optic coefficient of barium gallogermanate glass

Barium gallogermanate (BGG) glasses are currently being explored as a viable low cost material for numerous U.S. defense and commercial visible-infrared window applications. These glasses are transparent from 0.4 mum to beyond 5.0 mum and can be easily made in large optics and complex shapes with high index homogeneity. For high-energy laser (HEL) applications, knowledge of the thermo-optic coefficient (dn/dT) of the window material is important in determining the optical path distortion. The dn/dT measurements were made on BGG glass at 633 and 3390 nm and compared with the values for multispectral ZnS. The dn/dT for BGG glass was approximately 1/5 the value for multispectral ZnS, giving BGG glass a clear advantage for HEL applications.     

风致飞掷物冲击建筑浮法玻璃试验和数值模拟

通过试验和有限元数值模拟的方法研究风致飞掷物对建筑浮法玻璃的冲击破坏效应。首先进行钢球冲击浮法玻璃面板的破坏试验,然后基于LS-DYNA建立与试验对应的飞掷物冲击浮法玻璃有限元模型,并通过对比试验和数值模拟的结果验证有限元模型的可靠性。最后基于验证后的有限元模型,以板状飞掷物为代表,研究风致飞掷物的冲击位置、冲击姿态和外形等特性对其冲击效应的影响。结果表明,建筑浮法玻璃在风灾中非常容易受到飞掷物的冲击而破坏。采用JH-2作为浮法玻璃的本构模型并以SIGP1=75 MPa作为失效准则,能够较准确地模拟浮法玻璃在冲击荷载下的破坏特性。板状飞掷物的冲击位置对其冲击效应影响不大,但其冲击姿态和边厚比对冲击效应有较大的影响。     

Numerical implementation of strain rate dependent thermo viscoelastic constitutive relation to simulate the mechanical behavior of PMMA

In this work, a nonlinear viscoelastic constitutive relation was implemented to describe the mechanical behavior of a transparent thermoplastic polymer polymethyl methacrylate (PMMA). The quasi-static and dynamic response of the polymer was studied under different temperatures and strain rates. The effect of temperature was incorporated in elastic and relaxation constants of the constitutive equation. The incremental form of constitutive model was developed by using Poila–Kirchhoff stress and Green strain tensors theory. The model was implemented numerically by establishing a user defined material subroutine in explicit finite element (FE) solver LS-DYNA. Finite element models for uniaxial quasi-static compressive test and high strain rate split Hopkinson pressure bar compression test were built to verify the accuracy of material subroutine. Numerical results were validated with experimental stress strain curves and the results showed that the model successfully predicted the mechanical behavior of PMMA at different temperatures for low and high strain rates. The material model was further engaged to ascertain the dynamic behavior of PMMA based aircraft windshield structure against bird impact. A good agreement between experimental and FE results showed that the suggested model can successfully be employed to assess the mechanical response of polymeric structures at different temperature and loading rates.