复合材料π接头渐进失效分析

针对复合材料π接头复杂的失效形式,采用材料刚度退化的方法模拟结构的渐进失效过程,用Abaqus建立某复合材料π接头的三维有限元模型;采用三维Hashin失效准则和Ye分层准则判别复合材料层合板的5种失效形式,将理想弹塑性材料模型应用于胶层材料来模拟胶层材料的失效,在Abaqus中建立考虑复合材料层合板和胶层失效的分析子...     

基于Abaqus的复合材料板冲击特性分析

基于Hashin准则,用Abaqus建立玻璃纤维/环氧树脂复合材料板的冲击仿真计算模型,分析材料在不同冲击能量、冲击质量与冲击速度影响下的初始损伤和损伤演化特性.通过对比发现仿真计算结果与试验结果吻合较好,表明该仿真计算模型对此材料的冲击预测有效.     

含孔复合材料层合板累积损伤仿真分析

针对面内静拉伸纤维增强复合材料含中孔层合板,发展了一种参数化三维逐渐损伤模型,并结合有限元三维逐渐损伤分析技术即应力分析、失效判定准则及损伤过程中材料性能退化等,对含孔层合板损伤扩展进行了仿真分析.本模型可以模拟含中孔层合板损伤起始、发展及最终结构破坏整个过程,并能较好地预测含孔层合板的破坏模式和破坏强度.该文同时对含孔层合板的损伤基本机理、类型及其相互关联作用进行了分析探讨,该文计算结果与文献实验结果非常吻合.     

连续纤维增强复合材料商用车车轮的抗冲击性能仿真

为实现车轮的轻量化,采用碳纤维增强树脂基复合材料、基于国标要求的轮辋与轮辐截面尺寸设计一款商用车车轮,并根据层合板设计原则设计其铺层结构。为验证车轮的抗冲击性能,基于车轮30°冲击试验标准,在Abaqus软件中建立车轮冲击试验的有限元仿真模型,分别基于蔡 吴准则和Hashin准则对车轮冲击过程的受力状态进行模拟,根据仿真结果改进车轮的铺层方式,从而提高车轮的抗冲击性能,使其满足冲击试验要求。与同等规格的铝合金车轮相比,复合材料车轮取得约25.3%的轻量化效果。     

基于APDL的层合板破坏过程分析

为研究层合板的破坏过程,用APDL编程,自定义复合材料的单元破坏判据,分析[90°/±45°/0°],铺排方式的层合板破坏过程.建立层合板宏观和微观的ANSYS模型,分析对比其破坏应力.结果表明:宏观模型破坏应力与微观模型破坏应力略有差别,但微观模型能更直观地给出层合板破坏的动态过程.APDL编程方法可拓展ANSYS有...     

基于ABAQUS的高磷铸铁激光淬火温度场分析

论文利用Abaqus有限元分析软件模拟仿真高磷铸铁激光淬火过程.模拟激光淬火温度场主要包括三维模型的建立、高磷铸铁热物性参数的计算、模型网格的划分、载荷的施加方法、移动热源的程序设计、淬硬层深度确定等.激光淬火试验选取激光扫描功率P=1100W和扫描速度v=25mm/s验证模拟仿真结果,结果显示仿真淬硬层层深与激光淬火...     

负泊松比超材料减振结构设计与实验验证

旋转机械的转子部件发生故障时,振幅会迅速增大甚至发散,此时需要一种轻质高效的吸能减振结构,快速控制转子部件的振动幅值.本文基于负泊松比材料概念,提出了一种针对转子系统的负泊松比弧形超材料减振结构,可以实现很好的故障转子减振效果.首先,通过释放自由度提出了负泊松比非对称星形胞单元,设计了针对转子的超材料减振结构,并给出了相应的能量吸收指标.然后,基于有限元模型进行了动力学仿真,讨论了不同冲击速度、不同冲击角度对能量吸收性能的影响.结果表明,低速冲击下,材料主要产生弹性变形吸能.随着冲击速度增加,材料变为弹塑性变形混合吸能模式,有效吸能率会明显增大.特别是在冲击速度较大时,减振结构的吸能率会迅速增加,这对于转子突发故障的减振十分有利.最后,设计了验证实验,对故障转子进行了负泊松比减振结构的验证实验.实验结果证明,对于转子的不平衡故障响应,设计的减振结构能够起到很好的抑制转子振动与吸收振动动能效果.     

不同轴截面薄壁筒在轴向冲击下吸能特性研究

针对目前飞行器坠撞安全性问题研究,要减缓碰撞时的冲击载荷和耗散能量,以薄壁筒结构为研究对象,采用非线性有限元理论建立计算模型,采用显式动力学算法进行数值仿真。利用非线性有限元软件ABAQUS仿真了不同轴截面的薄壁筒在受轴向冲击下的变形,通过比较四种薄壁筒在受轴向冲击下的压溃力峰值、平均压溃力及比吸能研究其吸能特性,并与相关的理论解进行了对比。结果表明：冲击动能相同条件下,无论从比吸能方面还是从压溃力峰值方面来考虑,轴截面为梯形的薄壁筒的吸能特性优于轴截面为矩形的薄壁筒;从乘员的安全角度考虑圆台做吸能结构吸能是方台的1.5倍,而压溃力峰值只有方台的75.3%。     

夹层板系统碰撞性能数值仿真分析技术

为促进夹层板系统（Sandwich Plate System,SPS）在船舶耐撞结构设计中的应用,用Abaqus分析SPS在碰撞载荷下的数值模型化技术,包括夹芯层和面板的建模方式、连接形式和网格尺寸．根据该技术研究SPS在碰撞冲击载荷作用下的力学性能,如结构损伤变形、碰撞力和结构吸能等．结果表明,SPS建模采用壳一体混合模型（即上、下面板采用壳单元,夹芯层采用体单元）较合理;夹芯层与面板之间采用绑定连接较合理;SPS具有良好的耐撞性能．     

索杆梁钢结构施工动力学仿真软件研制

充分利用Matlab功能强大的数学函数库和C＋＋的面向对象特性,采用Matlab和C＋＋混合编程求解索杆梁钢结构施工过程中的柔性多体系统动力学问题．研制基于AutoCAD二次开发工具ObjectARX的三维实体索杆梁钢结构施工过程仿真软件系统,该系统能对各种索杆梁钢结构的施工过程进行仿真计算并给出完整计算结果．     

纤维金属层板低速冲击仿真

采用Johnson-Cook模型模拟铝层的力学行为,选用Hashin三维准则对复合材料层内损伤进行判断,采用Camanho-Matthews折减方案进行刚度折减,同时采用粘接元描述复合层板层间失效,采用Abaqus/Explicit结合VUMAT建立玻璃纤维增强铝合金层板冲击有限元模型。结果表明：随着冲击能量的变大,测量点的位移逐渐变大,钢球反弹后的测量点最大塑性变形也逐渐增大;纤维金属层板的玻璃纤维先发生破坏,然后铝合金层出现裂纹;2种层板的抗低速冲击性能基本相同。研究结果可用于玻璃纤维铝合金层板抗冲击性能的对比分析。     

Response of hybrid laminated composite plates under low-velocity impact

The response of hybrid laminated composite plates subjected to low velocity impact was investigated using shear deformation theory. As a result, the fractional energy loss of two hybrid composite plates with the same component ratio has different values according to the stacking sequence. A Graphite-Kevlar-Graphite plate has low energy loss and a Kevlar-Graphite-Kevlar plate much higher energy loss. Contact forces between the impactor and plates, center deflections of the plates and velocity changes of the impactor to time have different values according to the material properties of the impacted surface. Various composite plates with the same material in the impacted surface behaved with a similar response.     

A refinement of Ambartsumian multi-layer beam theory

One of the current problems connected with multi-layer composite structures concerns the analysis of the distribution of the stresses around peculiarities (free edge and loaded edge) and at the interfaces of each layer. This work presents a new shear stress function in the form of the exponential function, to predict the mechanical behaviour of multi-layered laminated composite structures. As a case study, the mechanical behaviour of a laminated composite beam (90°/0°/0°/90°) is examined. The results are compared with the model “Sinus” and 2D finite element method studied. Results show that this new model is more precise than older ones as compared to the results obtained by the finite element analysis [Abaqus]. To introduce continuity on the interfaces of each layer, the kinematics defined by Ossadzow is used with the new exponential model. The equilibrium equations and natural boundary conditions are derived by the principle of virtual power.     

Kinetic energy conservation in 2D vortical flow

In this study, distribution of vorticity in 2D vortical flow is evaluated by using energy conservation law. A variational formula named “SPKE functional” (singular part of kinetic energy functional) is introduced, which explain the relation between the rate of kinetic energy transferred to the fluid by a moving body and the production and distribution of vorticity in the fluid. As an example, high Reynolds number flow past a circular cylinder is considered and numerical calculation for velocity, pressure field, drag force and rate of kinetic energy is provided. Using these results, two important consequences are deduced: first, drag force obtained from solving the momentum equation by using conventional vortex method, is compared with the equivalent drag force caused by the energy transferred to the fluid. This is done by using SPKE functional, and validity of vortex method to satisfy the conservation of energy is verified and approved. Second, a functional for 2D vortical flow is derived which has a physical meaning of equivalent energy transferred to the fluid due to the generation of vorticity. This is a function of kinematical parameters of fluid flow such as stream function and vorticity field. Two aspects of this formulation contain great importance: (i) derivation of a functional for 2D vortical flow and (ii) drag force being calculated directly from the vorticity field. The method presented here is capable of obtaining total drag force directly from the discrete vorticity field, as well as calculating either the pressure field. This is where first derivatives of vorticity (or even second derivatives of velocity) is not required. SPKE functional can be used in variational approach for studying 2D vortical flow field numerically.     

基于内聚力模型的界面破坏分析

界面破坏是材料与结构失效的常见形式,准确分析模拟界面损伤演化和最终破坏对评估材料乃至结构性能至关重要.在简要介绍内聚力模型的基础上,用Abaqus中的内聚力单元分别对均质材料和非均质材料界面破坏过程进行模拟,数值结果与理论结果吻合良好,表明内聚力单元适用于材料界面破坏分析.     

桥梁复合材料防撞护舷的结构设计

采用有限元法对某3 000 t船舶与桥梁防撞护舷碰撞的动力学特性进行分析.通过将护舷试样的碰撞试验与有限元计算结果进行对比,完善该防撞护舷的有限元模型,使其更可靠.用ANSYS/LS DYNA模拟3 000 t船舶撞击3种不同护舷（D型、圆环型和板型）的过程.不同护舷吸能结果表明：对于D型护舷,船舶会碰到桥墩,失去作用;对于板型护舷,船舶变形严重;圆环型护舷的效果最好.     

Stress wave calculations in composite plates using the fast Fourier transform

The protection of composite turbine fan blades against impact forces has prompted the study of dynamic stresses in composites due to transient loads. The mathematical model treats the laminated plate as an equivalent anisotropic material. The use of Mindlin's approximate theory of crystal plates results is five two-dimensional stress waves. Three of the waves are flexural and two involve in-plane extenisonal strains. The initial value problem due to a transient distributed transverse force on the plate is solved using Laplace and Fourier transforms. A fast computer program for inverting the two-dimensional Fourier transform is used. Stress contours for various stresses and times after application of load are obtained for a graphite fiber-epoxy matrix composite plate. Results indicate that the points of maximum stress travel along the fiber directions.     

Estimation of low-velocity impact damage in laminated composite circular plates using nonlinear finite element analysis

Nonlinear finite element analysis is used for the estimation of damage due to low-velocity impact loading of laminated composite circular plates. The impact loading is treated as an equivalent static loading by assuming the impactor to be spherical and the contact to obey Hertzian law. The stresses in the laminate are calculated using a 48 d.o.f. laminated composite sector element. Subsequently, the Tsai-Wu criterion is used to detect the zones of failure and the maximum stress criterion is used to identify the mode of failure. Then the material properties of the laminate are degraded in the failed regions. The stress analysis is performed again using the degraded properties of the plies. The iterative process is repeated until no more failure is detected in the laminate. The problem of a typical T300/N5208 composite [45 °/0 °/ − 45 °/90 °]_s circular plate being impacted by a spherical impactor is solved and the results are compared with experimental and analytical results available in the literature. The method proposed and the computer code developed can handle symmetric, as well as unsymmetric, laminates. It can be easily extended to cover the impact of composite rectangular plates, shell panels and shells.