泡沫夹层复合材料的低速冲击损伤及剩余强度的数值模拟

基于渐进累积损伤理论和数据传递分析方法,对泡沫夹层复合材料的低速冲击以及冲击后的压缩破坏过程提出了一种全程数值分析方法,即对泡沫夹层复合材料的冲击以及冲击后损伤的泡沫夹层复合材料在压缩载荷下损伤扩展的全过程进行数值模拟分析。结果表明:由于该方法避免了以往学者对冲击后夹层板损伤状态所做的人为假设,把冲击后的预测损伤直接传递用于剩余强度的研究,从而提高了最终破坏载荷和剩余强度的预测精度,数值模拟结果与已有试验结果吻合较好。     

夹层玻璃的冲击破坏仿真分析研究

在一特种夹层玻璃铝弹撞击实验的基础上，建立了夹层玻璃及其相关部件的有限元模型，应用非线性有限元软件LS-DYNA，对整个铝弹撞击过程进行了数值模拟。使用相邻单元节点固结和破坏评价方法，再现了冲击破坏过程中玻璃碎片的飞散现象；从夹层玻璃破坏过程和PET材料的变形状况来看，获得了与实验基本一致的仿真结果。     

汽车玻璃的静力学特性和冲击破坏现象

应用试验和数值仿真方法对汽车玻璃的静态特性和破坏机理进行了研究.首先,使用有限元法对汽车玻璃梁受集中载荷下的静力响应进行分析.通过与一般叠层板理论的比较,揭示出汽车玻璃与一般叠层复合材料板完全不同的静力学弯曲特性.然后,设计了汽车玻璃梁冲击破坏试验,使用高速照相机并结合光弹试验装置,记录了冲击点附近的裂口发生和发展过程,并从应力波传播的角度,对试验结果进行了分析.最后,应用离散元法对这一冲击破坏过程进行模拟,通过考察冲击点附近的裂口发生和发展过程并与试验结果相比较,验证离散元法分析汽车玻璃冲击破坏现象的有效性.     

基于内聚力模型的夹层玻璃冲击破坏仿真分析

夹层玻璃冲击破坏特性的研究对于风挡玻璃设计、行人保护及交通事故再现具有重要意义。针对传统有限元方法不能有效描述脆性材料冲击破坏的问题,在介绍双线性内聚力模型基本理论的基础上,建立适用于夹层玻璃冲击破坏现象的有限元模型,使用已嵌入内聚力模型的有限元软件LS-DYNA仿真分析夹层玻璃的冲击破坏过程。同时,设计简易夹层玻璃板落锤试验装置,以评价仿真分析结果。夹层玻璃板的裂纹分布和冲击加速度的仿真与试验结果的良好一致性,验证了内聚力模型与仿真分析方法的有效性。     

鸡蛋结构的有限元模型和碰撞动力学模拟

为尽可能逼真地模拟鸡蛋模型的碰撞,利用三维建模软件建立一个鸡蛋的基本模型导入到ABAQUS,建立一个标准鸡蛋的FEM模型,模拟一个尽可能逼真的有限元模型。围绕鸡蛋的内容物对鸡蛋壳冲击破坏中的影响而展开,利用有限元软件ABAQUS分析研究鸡蛋的破坏特性,为鸡蛋包装结构设计提供一定的理论依据。     

ASME规范碳钢及低合金钢材料(母材)低温冲击豁免的判断

介绍了材料低温脆性破坏的危害性，强调了低温冲击的重要性，简单地对按GB150与ASEM规范设计的材料进行冲击试验的条件加以区分，着重并较系统地论述了按ASME规范判断材料免除冲击试验的方法。     

夹层玻璃的冲击破坏仿真分析研究

在一特种夹层玻璃铝弹撞击实验的基础上,建立了夹层玻璃及其相关部件的有限元模型,应用非线性有限元软件LS-DYNA,对整个铝弹撞击过程进行了数值模拟.使用相邻单元节点固结和破坏评价方法,再现了冲击破坏过程中玻璃碎片的飞散现象;从夹层玻璃破坏过程和PET材料的变形状况来看,获得了与实验基本一致的仿真结果.     

利用ANSYS确定开关柜承受的最大爆炸冲击载荷

阐述了板结构在爆炸冲击作用下的破坏情况及其材料破坏的断裂准则，介绍了利用AN—SYS软件对薄板结构在冲击载荷下有限元计算的方法，并对某开关柜板的四周薄板结构在15KA故障电流下发生爆炸时的引起的冲击载荷作用下进行了瞬间动态应力分析，并利用其程序设计语言APDL确定出该板可承受的最大冲击载荷的峰值。     

Nomex蜂窝复合材料冲击损伤及剩余剪切强度试验

Nomex蜂窝复合材料在航空航天中的应用越来越广泛,但其对低速冲击损坏较为敏感,针对Nomex蜂窝复合材料冲击损伤问题,研究了蜂窝材料在冲击作用下的损伤行为,并进行了剩余剪切强度试验,观察试验件应变值变化,得出试验结构件破坏载荷和最大破坏应变,并与未进行冲击试验的试验件进行对比。结果表明:冲击损伤后,破坏载荷的保持率为69.0%左右,破坏最大应变的保持率为78.8%,即冲击损伤使蜂窝复合材料的力学性能恶化,且影响较大。     

管件和管接头耐冲击试验压力的形成及其动态分析

本文对液压冲击试验台冲击压力的形成作了概略性的分析。它是在一定的假设条件下,利用集中参数的方法,把液压系统回路模拟成相似电路进行的,旨在简化问题的分析,得出了工程上计算的方法,并把理论分析和实验的结果作了列表对此,说明理论分析和试验结果基本相符。该课题目前还在进一步深入研究中。     

Numerical simulations of impact flows with incompressible smoothed particle hydrodynamics

A 2D incompressible smoothed particle hydrodynamics (SPH) method is implemented to simulate the impact flows associated with complex free surface. In the incompressible SPH framework, pressure Poisson equation (PPE) based on the projection method is solved using a semi-implicit scheme to evaluate the correct pressure distribution. In this procedure, the PPE comprises the divergence-free velocity condition and density-invariance condition with a relaxation parameter. To test the accuracy and efficiency of the proposed incompressible SPH method, it was applied to several sample problems with largely distorted free surface, including 2D dam-break over horizontal and inclined planes with different inclination angles, as well as the water entry of a circular cylinder into a tank. We mainly focused on the time history of impact pressure on various positions of the solid boundary and temporal evolution of free surface profiles. The results showed reasonably good agreement with experimental data. However, further improvement is needed for extremely high impact flow.     

Optimal design of spaced plates under hypervelocity impact

This paper presents a bumper shield design for protection of a satellite structure system subjected to hypervelocity impact (above 6 km/s) from space debris. Especially, this study is focused on the optimization of the spaced plates (the so-called Whipple shield) design using the coupled SPH and Lagrangian FEM methods. This is because the SPH is a meshless method and it is efficient in hypervelocity impact analysis involving debris caused by fragmentation and penetration under hypervelocity impact. The Whipple shield is composed of multiple spaced plates where the first bumper plate is modeled as particles for SPH simulation while the rear wall is modeled as elements for FEM. The appropriate smoothing length and mesh size were determined taking into account computational cost and accuracy and the erosion scheme is adopted to avoid numerical error due to large deformation. After verification for the comparison with previous experimental works, the optimal plate structure is proposed considering multi design objectives based on parameter optimization.     

光滑粒子动力学方法及其应用

光滑粒子动力学(Smoothed Partic le Hydrodynam ics,SPH)方法是近年来得到广泛发展和应用的无网格方法的一个重要分支,它是一种纯Lagrangian方法。本文对现有的光滑粒子动力学方法进行了综述,介绍了该方法的理论基础、连续介质守恒方程、方法稳定性的改善等,重点阐述了边界条件的处理,并给出了SPH方法的算例。最后,介绍了SPH方法的最新进展状况。     

Numerical Study of Impact Behaviors of Angular Particles on Metallic Surface Using Smoothed Particle Hydrodynamics

Modeling and studying the impact behaviors of angular particles is critical in understanding the mechanisms of erosive wear on solid surfaces. This article focuses on effective mesh-free model based on the smoothed particle hydrodynamics (SPH) method to simulate impacts of angular particles on metallic surfaces. The predicted results are compared with the available experimental data, and good agreement has been achieved. Our simulations under different incident conditions successfully reproduce the general impact behaviors of angular particles, including rotating behavior and rebound behavior, which enables detailed examinations of erosion mechanisms. We find that the rotating behaviors are mainly determined by initial orientation and impact angle, whereas impact velocity has little effect. For backward impact involving a prying-off action, there generally exsits a critical impact velocity below which the cutting process would never be finished, which may result in a rebound angle greater than 90°. Further, multiple and overlapping impacts are simulated to reveal the effect of a pre-created crater on the subsequent impact. The results demonstrate the ability of the present model to handle the extremely deformed surface by overlapping impacts. The proposed SPH model and the present study could be useful in the study of erosive wear on the surface of metal devices that carry granular substances.     

基于SPH算法的驾驶室底部结构对爆炸冲击波响应数值仿真

针对地雷等简易爆炸装置在车辆驾驶室底部非接触爆炸问题,引入无网格光滑粒子流体动力学(Smoothed particle hydrodynamics,SPH)算法模拟爆炸冲击波作用下车辆底部结构的响应。以四边约束靶板为研究对象,分析靶板在爆炸冲击下的能量、应力变化和破坏形态,通过与传统的任意拉格朗日欧拉(Arbitrary Lagrangian-Eulerian,ALE)固流耦合分析法和经验公式计算结果对比,验证SPH算法应用于处理此类问题的可行性;利用SPH算法对爆炸冲击波作用下驾驶室底部结构进行数值仿真,分析车辆底部的油箱、电瓶支架、驾驶室地板、车架等关键结构的冲击响应,并与试验做出对比验证。仿真结果表明,基于SPH算法的爆炸仿真分析具有精度较高、建模简单、耗费计算资源少等优势,能够应用于爆炸冲击波作用下驾驶室底部板壳结构的响应研究,并为驾驶室底部结构抗爆炸设计提供参考。     

A Contact algorithm in the low velocity impact simulation with SPH

The formulation of Smoothed Particle Hydrodynamics (SPH) and a shortcoming of traditional SPH in contact simulation are presented. A contact algorithm is proposed to treat contact phenomenon between two objects. We describe the boundary of the objects with non-mass artificial particles and set vectors normal to the contact surface. Contact criterion using non-mass particles is established in this study. In order to verify the contact algorithm, an algorithm is implemented in to an in-house program; elastic wave propagation is an analysed under low velocity axial impact of two rods. The results show that the contact algorithm eliminates the undesirable phenomena at the contact surface; numerical result with the contact algorithm is compared with theoretical one.     

SPH method applied to high speed cutting modelling

The purpose of this study is to introduce a new approach of high speed cutting numerical modelling. A Lagrangian smoothed particle hydrodynamics (SPH)-based model is carried out using the Ls-Dyna software. SPH is a meshless method, thus large material distortions that occur in the cutting problem are easily managed and SPH contact control permits a “natural” workpiece/chip separation. The developed approach is compared to machining dedicated code results and experimental data. The SPH cutting model has proved is ability to account for continuous to shear localized chip formation and also correctly estimates the cutting forces, as illustrated in some orthogonal cutting examples. Thus, comparable results to machining dedicated codes are obtained without introducing any adjusting numerical parameters (friction coefficient, fracture control parameter).     

复合材料蜂窝夹层板低速冲击损伤模拟及实验研究

复合材料蜂窝夹层板因其良好的力学特性及质量轻等优点在工程中得到了广泛应用,但其抗冲击能力较差。本文研究了复合材料蜂窝夹层板受低速冲击后的变形和损伤情况,采用光滑粒子动力学结合有限元数值模拟方法分析了复合材料蜂窝夹层板受不同能量冲击后的响应,并通过试验和模拟计算结果对比分析,给出了不同冲击能量下复合材料蜂窝夹层板的位移和损伤。研究结果表明:给出的复合材料蜂窝夹层板冲击数值模型能够合理的模拟低速冲击行为,能为工程中复合材料蜂窝夹层板结构受冲击损伤的测定提供参考依据。     

SPH modeling of chip formation in cutting unidirectional fiber-reinforced composite

The machining of composites is of great interest in manufacturing today. To that end, it is necessary to calculate the cutting forces required and to predict the surface quality obtained. In the present work, the cutting zone of a unidirectional fiber-reinforced composite is simulated by the SPH method. The calculation results—specifically, the equivalent stress and the strain distribution—are compared with results obtained previously by the finite-element method and also with experimental data. The good agreement with experimental data indicates that the SPH method may expediently be used in simulating the cutting of composites.