基于随机顺序吸附法的Csf/Mg周期性体胞模型的建立及其应用

采用随机顺序吸附法建立了Csf/Mg复合材料周期性体胞模型,对Csf/Mg复合材料的拉伸性能进行了有限元模拟。对比拉伸试验结果,验证了该周期性体胞模型的有效性。模拟结果显示:随着Csf/Mg复合材料中纤维体积分数的提高,其拉伸性能不断提高,弹性模量、屈服强度和抗拉强度均随之增加;平行于外载方向的纤维承载了最大的应力,而与外载方向约呈60°角的纤维承受的应力最小;平行于外载方向的纤维,其端面附近的基体也承受了较大应力;在拉伸变形的过程中,基体的塑性变形由纤维附近区域向基体其他区域扩展。     

ABAQUS二次开发在Csf/Mg复合材料微观几何建模中的应用

基于RSA方法构建Csf/Mg微观模型是对其材料性能进行有限元模拟的重要基础。由于Csf/Mg复合材料性能受纤维体积分数、纤维取向分布、纤维长径比等参数的影响,针对不同仿真需求采用手工方法建立其有限元模型工作效率极低,因此采用Python脚本语言对ABAQUS GUI进行二次开发,建立用户自定义图形界面。结果表明,对ABAQUS GUI进行二次开发可以根据用户需求创建图形用户界面,通过输入相关参数可以实现自动创建Csf/Mg复合材料有限元几何模型,同时极大地简化了建模过程。基于RSA方法可实现二维或三维纤维随机取向或定向分布的短纤维增强复合材料的几何建模。     

C_f/Al复合材料横向拉伸微观损伤与力学性能的有限元分析

根据石墨纤维增强铝基复合材料(C_f/Al基复合材料)显微组织特征构建了其代表性体积单元(RVE),通过基体合金的延性损伤模型和纤维的最大应力失效模型,建立了基于内聚力界面模型的细观力学有限元模型并结合试验结果验证了其可靠性,在此基础上分析了纤维含量对复合材料横向拉伸损伤演化与力学行为的影响。结果表明,基于正六边形纤维排布RVE建立的细观力学模型能够准确预测复合材料横向拉伸力学性能。横向拉伸过程中首先发生界面损伤,随应变增加界面损伤累积,引起局部界面失效并诱发附近基体合金的损伤与失效,最终导致复合材料横向开裂,拉伸断口呈现界面脱粘和基体合金撕裂共存的微观形貌。提高纤维含量增加了界面数量和面积,从而降低了复合材料横向拉伸弹性模量和极限强度。     

碳纳米管／金复合材料拉伸力学性能的分子动力学模拟

用分子动力学方法对纳米单晶金和碳纳米管/金(CNT/Au)复合材料在拉伸下的力学行为进行了模拟研究.其中,CNT/Au复合材料根据嵌入到金基体中的碳纳米管的轴向方向与拉伸方向平行和垂直而采用2种不同的模型,即水平嵌入和垂直嵌入.在模拟中,分别用多体紧束缚(TB)势、经验Tersoff势和长程Lennard-Jones(L-J)势描述金原子间、碳原子间以及金原子与碳原子之间的相互作用.计算结果表明:平行嵌入碳纳米管的CNT/Au复合材料的杨氏模量比纳米单晶金的杨氏模量大很多,但是垂直嵌入碳纳米管的CNT/Au复合材料的杨氏模量比金的杨氏模量稍低,且垂直嵌入碳纳米管的CNT/Au复合材料的屈服应力和屈服应变明显低于纳米单晶金的屈服应力和应变.     

真空压力浸渗制备CF/Al复合材料热收缩与残余应力数值模拟与实验研究

针对连续碳纤维增强铝基复合材料(CF/Al复合材料),采用细观力学数值模拟与热性能试验结合的方法,研究了真空压力浸渗制备过程中的热收缩行为和热残余应力分布。结果表明,复合材料的横向热收缩应变量远大于轴向热收缩应变量,且具有横观各向同性,纤维随机分布的单胞有限元模型能够准确地预测复合材料轴向与横向热收缩行为曲线;复合材料制备完成后纤维和基体合金分别处于压应力和拉应力状态,基体和纤维的横向残余应力均小于其轴向残余应力,且均表现出横观各向同性;基体合金在轴向残余拉应力作用下会出现不同程度的损伤现象,特别是纤维间距较小部位过高的残余应力会引发界面的局部失效,从而不利于发挥复合材料承载性能,减少纤维局部偏聚是进一步改善提高复合材料力学性能的重要技术手段。     

TiC颗粒增强钛基复合材料的静动态力学性能

利用伺服式疲劳实验机和杆一杆型冲击拉伸实验机对TiC颗粒增强钛基复合材料TP650和基体钛合金的静动态力学性能进行研究,得到不同应变率下复合材料的应力一应变曲线.结果表明,复合材料和基体材料的屈服应力均随应变率的增加而提高,属于应变率敏感材料;TP650的破坏形式以颗粒附近基体的撕裂以及颗粒与基体合金的脱粘为主,几乎没有发生颗粒破碎现象.假设复合材料的微观结构为非均质单胞在空间的周期性重复排列,利用有限元软件对钛基复合材料的静动态力学性能进行数值模拟研究,计算结果与实验结果吻合良好.进一步通过数值模拟预测了颗粒形状和颗粒体积分数的变化对TiC颗粒增强钛基复合材料静动态力学性能的影响.     

激光冲击SiCp/Cu复合材料的有限元模拟

为了探究激光冲击强化对SiCp/Cu复合材料力学性能的影响,采用有限元分析软件ANSYS/LS-DYNA对复合材料单胞模型进行冲击加载,模拟结果显示:在基体金属上存在着广泛的压应力,并且在载荷作用过程中导致了基体的屈服强化,大大提高了基体的强度;在基体与颗粒增强体之间的界面上存在着一定的等效应力值。采用WDW-200微机控制式电子万能试验机对激光冲击强化前后的试样进行拉伸性能对比试验:发现冲击后试样的抗拉强度较未冲击试样的提高了18MPa,且断口呈现韧窝形貌,为微孔聚集形韧性断裂。结果表明:激光冲击强化提高了SiCp/Cu复合材料的力学性能。     

Al_2O_3纤维增强Al合金复合材料界面孔隙率测定及复合材料应力分布有限元计算

利用挤压铸造法制备了 Al2 O3纤维增强 Al合金复合材料 ,对其界面孔隙率进行了测定 ,结合拉伸强度数据 ,讨论孔隙率对复合材料强度的影响 ;并通过有限元计算 ,分析了与拉伸轴平行、成 45°及与拉伸轴垂直的 3种纤维模型 ,得出纤维、基体、界面处应力分布。     

基于细观力学有限元法的碳纤维增强铝合金复合材料横向拉伸行为研究

针对真空压力浸渗制备的碳纤维增强铝合金复合材料（CF/Al复合材料）,分别采用延性损伤本构和内聚力界面本构定义基体合金和界面的损伤演化与失效行为。建立其细观力学单胞有限元模型,数值模拟获得了复合材料横向拉伸变形中基体合金和界面的细观损伤演化和失效过程,通过复合材料横向拉伸应力-应变试验曲线与数值模拟曲线对比,验证所建立细观力学有限元模型的可靠性。结合力学试验和拉伸断口分析,探索CF/Al复合材料横向拉伸变形时断裂力学行为规律及其失效机理。     

SiC_f/TC17复合材料拉伸行为研究

研究了Si Cf/TC17复合材料的室温、高温(773 K)拉伸性能及其断裂机制.结果表明:Si Cf/TC17复合材料室温、高温应力-应变曲线受纤维线弹性变形和基体屈服程度影响呈现不同的形状;室温断裂机制主要是反应层多次断裂、纤维一次断裂和基体脆性断裂等,高温断裂机制主要是纤维多次断裂、基体韧性断裂和大范围的界面脱黏等;纤维累计损伤理论适合于对Si Cf/TC17复合材料断裂强度的估测,其中室温断裂强度符合临界断裂纤维数大于或等于3时的局部承担载荷模型,高温断裂强度符合均匀承担载荷模型.结合断裂机制和强度估算结果,详细论述了Si Cf/TC17复合材料室温、高温拉伸断裂过程.     

Microstructure-Based Numerical Simulation of the Tensile Behavior of SiCp/Al Composites

Modeling and prediction of the damage evolution in particle reinforced composites is a complex problem. Microstructure characters such as the particle morphologies, sizes, and distribution significantly affect the damage evolution in composites. A numerical simulation has been performed to investigate the damage evolution of SiC_p/AA2009 composites. Tensile deformation in SiC_p/AA2009 composites was simulated using the microstructure-based model constructed from the metallograph. Matrix damage, particle cracking, and interface debonding were simulated combining the ductile damage model, the normal stress criterion, and the maximum stress ratio criterion. The simulation results show that under tensile loading, damage initiates at the interface, and then propagates along the weakest direction. The simulation microstructures agree well with experimental results in which interface debonding, particle cracking, and matrix damage co-exist. In addition, the effects of component properties on the damage evolution are examined for various situations.     

碳纳米管/ZM5镁合金复合材料的制备与力学性能研究

采用搅拌铸造法制备了碳纳米管/ZM5镁合金复合材料,研究了搅拌法加入碳纳米管的工艺特点,测试了复合材料的力学性能,并利用扫描电子显微镜和能谱分析对复合材料断口形貌进行了观察和分析.研究结果表明：当搅拌温度接近于ZM5镁合金液相线温度时,碳纳米管能较好的加入到镁合金熔体中.与基体合金相比,复合材料的抗拉强度、弹性模量、显微硬度显著增加,伸长率最大可提高110%,但是碳纳米管加入量过多会导致偏聚,使力学性能下降.碳纳米管能细化复合材料的晶粒组织,并且起搭接晶粒和承载变形抗力的作用.     

Multiscale modeling of failure in metal matrix composites

A multiscale approach to composite failure, in which detailed information on small-scale micromechanics is incorporated approximately yet accurately into larger-scale models capable of simulating extensive damage evolution and ultimate failure, is applied to the deformation and failure of a Ti–matrix composite. The composite is reinforced with SiC fibers under conditions of matrix yielding and interfacial sliding via Coulomb friction. Specifically, a fully three-dimensional finite element model is employed to investigate the load transfer from broken to unbroken fibers as a function of applied stress and interface friction coefficient. With a von Mises matrix yield criterion, constraint effects permit the matrix to carry some of the transferred load near the fiber break, a feature not captured in previous composite models. The single-break results for stress concentrations are then used as the discrete Green's functions for load transfer in the full composite, and the predicted load transfer around a seven-fiber-break cluster is shown in good agreement with finite element results. The Green's function model is then used to predict overall damage evolution and composite failure for an IMI-834 Ti/SCS-6 SiC system for various interface friction coefficients. The composite tensile strength is rather insensitive to the friction coefficient and, for values of μ comparable to those measured experimentally, the predicted tensile strength is in excellent agreement with the measured value. Analytic models for scaling of the tensile strength to very large sizes are then shown to agree well with strengths obtained from simulations. These results suggest that the hierarchical coupling approach used here may be useful for approaching a wide variety of damage and failure problems in fiber composites.     

Influence of pre-plastic deformation on thermal residual stress and yield st rength of SiCw/Al composites

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Effect of low temperature treatment on tensile yield strength of SiCw/6061 Al alloy composites

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2.5维织物C_f/Al复合材料制备及其经纬向拉伸变形力学行为研究

以石墨纤维2.5维机织物为增强体,铝合金ZL301为基体材料,采用真空辅助压力浸渗法制备了2.5维织物Cf/Al复合材料,研究了3种织物预热温度下制备的复合材料相对致密度和微观组织形貌,分析了其界面产物组成与界面结构特征,测试了其经、纬向准静态拉伸变形力学行为并分析了其断口形貌。结果表明:复合材料织物的细观结构完整,内部纤维分布均匀,致密度随预热温度提高而略有上升,界面棒状产物为Al4C3相,其相对含量随预热温度的提高而增加,从而引起复合材料经向和纬向力学性能的下降。复合材料经向拉伸强度高于纬向拉伸强度,且其应力-应变行为呈现出显著的非线性特征,复合材料经向和纬向拉伸变形过程均可划分为3个阶段:初始弹性变形阶段、中间弹塑性变形阶段和最终损伤与断裂阶段。     

Indentation-induced localized deformation and elastic strain partitioning in composites at submicron length scale

Three-dimensional spatially resolved strains were mapped in a model NiAl/Mo composite after nanoindentation. The depth-dependent strain distributed in the two phases and partitioned across the composite interfaces is directly measured at submicron length scale using X-ray microdiffraction and compared with a detailed micromechanical stress analysis. It is shown that indentation-induced deformation in the composite material is distinct from deformation expected in a single-phase material. This difference arises in part from residual thermal strains in both phases of the composite in the as-grown state. Interplay between residual thermal strains and external mechanical strain results in a complex distribution of dilatational strain in the Mo fibers and NiAl matrix and is distinct in different locations within the indented area. Reversal of the strain sign (e.g., alternating tensile/compressive/tensile strain distribution) is observed in the NiAl matrix. Bending of the Mo fibers during indentation creates relatively large ～1.5° misorientations between the different fibers and NiAl matrix. Compressive strain along the 〈0 0 1〉 direction reached ?0.017 in the Mo fibers and ?0.007 in the NiAl matrix.     

SiCp/6061Al合金复合材料循环变形行为的有限元模拟

在细观分析模型的基础上,利用ABAQUS有限元程序对T6热处理后不同体积分数的颗粒增强SiCp／6061Al合金复合材料的单调拉伸行为和单轴循环变形行为进行了有限元数值模拟;同时,通过与相应的实验结果的比较对模拟效果进行了评价．模拟结果表明：由于采用了能够描述基体循环棘轮行为的新的本构模型,利用有限元法模拟可对颗粒增强金属基复合材料的循环变形行为,特别是循环棘轮行为进行合理的描述．模拟结果还揭示了复合材料循环变形行为在细观层次上的不均匀性和复杂性．     

Finite element polycrystal model simulation of cold rolling textures in deformation processed two-phase Nb／Al metal-metal composites

The finite element polyerystal model (FEPM) was extended and applied to simulate the development of the cold rolling textures of matrix aluminum in deformation processed two-phase 10% and 20% Nb/Al(in volume fraction) metal-metal composites on the basis of slip deformation of individual grains. This simulation method can assure the continuity of stress and displacement at the boundary during heterogeneous deformation and take arbitrary boundary conditions into consideration. The starting hot-extruded textures, as initial input condition, were taken into account in the FEPM simulation. The simulation results show that the main texture components and their evolution after various cold rolling reductions in 10% and 20% Nb/Al metal-metal composites are well qualitatively in agreement with the experimental ones. The initially extruded textures are rather weak, so they have no much influence on the simulated final cold rolling textures of the matrix aluminum for Nb/Al composites.