飞机转顶基座及支架结构静力试验技术研究

根据飞机空中试验用转顶基座及金属支架结构静力试验技术需求,研制了一套试验系统,解决了转顶基座及金属支架结构支持模拟、加载边界模拟等关键问题。对载荷进行等效处理,设计加载假件,采用载荷偏移与力偶施加相结合的方法施加力矩,分别完成了五级风载荷下4种工况的设计载荷试验和极限载荷试验,以及八级风载荷下其中第4工况的极限载荷试验。考核了结构的危险部位应力值及结构安全余量。试验结果表明,该试验系统工作稳定可靠,转顶基座及金属支架在设计载荷试验工况下未发生有害塑性变形,其强度、刚度满足设计要求。上述试验结果可作为该结构强度、刚度性能的评定依据,同时为后续结构研究的有限元建模提供数据支持。     

六自由度静定支持与约束技术在飞机载荷校准试验中的应用

在研究以往飞机载荷校准试验时非静定支持与约束方式的基础上,首次提出了飞机六自由度静定支持与约束方法;根据载荷校准试验得到的飞机受力分析结果,对飞机起落架支持与约束载荷进行了分解和简化,建立了飞机六自由度静定支持与约束工程模型;结合某型飞机的载荷校准试验对该方法进行了试验验证,结果表明:采用该方法可实现对飞机约束载荷的理论计算和实时监控,保证了飞机机翼等复杂结构部件在高载校准工况下试验过程的安全、可控;使飞机机翼的试验载荷量级提高到了限制载荷的43%,机翼载荷建模精度可控制在3%以内。     

作动器/传感器优化配置的研究进展

给出了作动器／传感器优化配置问题的数学描述,综述了作动器／传感器优化配置方法的发展现状．阐述了振动控制和模态试验中作动器／传感器优化配置的关系．并给出需要进一步研究的几个问题      

中央肋对接平尾结构非对称载荷测量技术

针对中央肋对接平尾结构,使用直接测量法和提出的唯象拟合法对其非对称弯矩载荷进行测量。通过先后开展虚拟试验和地面载荷校准试验,分别建立了两种测量方法的非对称载荷模型,并对其适用性和准确性进行研究。地面试验和飞行试验结果显示,唯象拟合法能够有效地完成平尾结构的非对称载荷测量,地面试验验模误差最大值为1.57%;直接测量法由于中央对称面附近连接有对接肋和平尾接头等导致局部传力比较复杂,测量精度较差,地面试验验模误差达到8.11%。     

大型客机后缘襟翼操纵与非对称控制

针对大型客机后缘襟翼操纵与非对称控制的复杂结构及运动机构动力学仿真问题,通过零部件模态综合法建立刚柔混合多体动力学模型,替代传统的有限元法,综合考虑结构柔性、关节轴承摩擦、滑轮架摩擦、机翼盒段变形协调支持边界影响,实现了大型客机后缘襟翼在空中多状态/多工况载荷综合作用下的仿真分析．总体上看,仿真计算的各作动器驱动载荷变化规律与试飞结果一致,驱动载荷最大值误差小于10 %．受内襟翼靠近机身部分的翼面风洞测压数据及机身变形支持边界等不确定因素影响,初始启动和襟翼小偏度时各作动器操纵载荷仿真结果与试飞结果相对误差偏大．通过数值仿真,进行后缘襟翼单作动器脱开故障的非对称控制需求及其交联装置动态冲击过程分析,仿真结果表明内外襟翼交联装置可以有效减小后缘襟翼单作动器脱开故障非对称变形影响．     

跨声速机翼阵风减缓研究

阵风响应分析是大型民用飞机设计必不可少的工作. 利用操纵面的主动偏转实现机翼阵风减缓是未来民用飞行器的一个关键技术. 基于CFD/CSD耦合的气动弹性仿真方法,将阵风视为输入,翼根弯矩作为输出,通过系统辨识方法建立跨音速阵风响应的状态空间分析模型. 而后将副翼作动位移视为系统输入,建立副翼作动对应的机翼响应分析模型. 耦合上述2个模型,通过最优控制方法设计副翼偏转的控制律,实现跨音速机翼的阵风响应减缓. 通过设计状态观测器得到最优控制反馈所需的状态量. 通过数值算例验证了所设计的阵风减缓控制律的有效性,能将翼根弯矩减少60%～80%.      

形状记忆合金作动器的设计及优化

采用Ｂｒｉｓｉｏｎ［１］等提出的ＳＭＡ材料的本构关系，分析了形状记忆合金作动器在三种热交换方式（自然冷却、强制冷却和采用半导体热泵技术）下的动力特性，同时研究了ＳＭＡ丝在恒载和载荷变化时对完成正逆相变所用时间的影响，并简单讨论了影响作动器响应的几个因素和改进方法     

基于能量密度等效的超弹性压入模型与双压试验方法

针对超弹性材料压入问题, 本文基于能量密度中值等效原理, 提出了描述球、平面、锥3类压头独立压入下载荷、深度、压头几何尺寸和Mooney-Rivlin本构关系参数之间关系的半解析超弹性压入模型(semi-theoretical hyperelastic-material indentation model, SHIM), 进而提出了球、平面、锥压入组合的双压试验方法(indentation method due to dual indenters, IMDI). 正向验证表明, 基于系列超弹性材料的本构关系参数, 由SHIM分别预测的球、平面、锥3类压入下的载荷-位移曲线与有限元分析(finite element analysis, FEA)结果之间密切吻合; 反向验证表明, 基于系列超弹性材料的FEA条件本构关系下3类压入的载荷-位移曲线, 由双压试验方法预测的Mooney-Rivlin本构关系与FEA条件本构关系密切吻合. 针对3种超弹性橡胶, 完成了球、平面、锥压入试验, 应用双压试验方法获得的3组Mooney-Rivlin本构关系均与单轴拉伸试验结果吻合良好.      

基于能量密度等效的超弹性压入模型与双压试验方法

针对超弹性材料压入问题,本文基于能量密度中值等效原理,提出了描述球、平面、锥3类压头独立压入下载荷、深度、压头几何尺寸和Mooney-Rivlin本构关系参数之间关系的半解析超弹性压入模型(semi-theoretical hyperelastic-material indentation model, SHIM),进而提出了球、平面、锥压入组合的双压试验方法 (indentation method due to dual indenters, IMDI).正向验证表明,基于系列超弹性材料的本构关系参数,由SHIM分别预测的球、平面、锥3类压入下的载荷-位移曲线与有限元分析(finite element analysis, FEA)结果之间密切吻合;反向验证表明,基于系列超弹性材料的FEA条件本构关系下3类压入的载荷-位移曲线,由双压试验方法预测的Mooney-Rivlin本构关系与FEA条件本构关系密切吻合.针对3种超弹性橡胶,完成了球、平面、锥压入试验,应用双压试验方法获得的3组Mooney-Rivlin本构关系均与单轴拉伸试验结果吻合良好.     

绳驱桁架结构伸展臂的主动振动控制

伸展臂由于受到空间温度变化和卫星机动动作的影响,不可避免地会产生振动。在阻尼较低的空间环境中,这种振动衰减较慢,影响伸展臂的正常工作。因此,合适的振动控制方法对于伸展臂的正常工作至关重要。本文采用拉绳作为作动器的空间桁架结构伸展臂,研究其作动绳上铰链串联顺序的优化和模型预测控制律的设计,这两部分内容均考虑了作动绳的单边约束和饱和约束。首先,通过ANSYS软件获取结构的模态信息;然后结合系统可控性原理和遗传算法计算出作动绳上铰链串联最优顺序;最后,在数值仿真中,通过设计的控制率对一个由四个单元组成的桁架结构伸展臂的振动控制过程进行仿真分析。结果表明,提出的作动绳串联铰链的方式能够有效抑制伸展臂的振动。     

民用飞机发动机吊挂静力试验技术研究

根据民用飞机发动机吊挂部段静力试验技术需求,研制了一套用于吊挂部段静力试验的试验系统,解决了吊挂支持模拟、加载边界模拟等关键技术;采用载荷偏移与力偶施加相结合的方法施加力矩;设计了加载杠杆施加试验小载荷.顺利完成了吊挂应急着陆、航向侧移相关的三种危险工况试验.试验结果表明,试验系统工作稳定可靠,吊挂在应急着陆等工况下未发生有害塑性变形,其强度、刚度满足设计要求.试验结果可作为该吊挂部段强度、刚度性能的评定依据,同时为有限元建模提供数据支持.     

Experimental and numerical investigation of combined isotropic-kinematic hardening behavior of sheet metals

To prevent a sheet specimen from buckling subjected to a tension-compression cyclic loading, a new fixture has been developed to use with a regular tensile-compression machine. The novelty of this device lies in 4-block wedge design with pre-loaded springs. This design allows blocks to freely move in the vertical direction while providing the normal support to the entire length of the specimen during the tension-compression cycle. The entire test is easy to setup, which is another advantage of this design. In order to measure the strain accurately, the transmission type laser extensometer was utilized together with the implementation of double-side fins in the specimen. Experimental results of tension-compression tests are presented followed by a review of existing testing methods. In order to describe the accurate cyclic tension-compression behavior, the combined isotropic-kinematic hardening law based on the modified Chaboche model and the practical two-surface model based on Dafalias-Popov and Krieg models have been modified in this work, considering the permanent softening behavior during reverse loading and the non-symmetric behavior during reloading. Through tension-compression tests, the material characterization has been performed for three base materials, BH180, DP600 steels and AA6111-T4 sheets.     

某发动机热试车的振动环境预示方法研究

发动机热试车试验在新型运载器的研制过程中起到重要作用,可用于预测运载器在飞行中的振动环境.由于载荷不等效,试验数据量有限,使得难以直接通过试验数据建立同一结构在不同系统下的映射关系模型.本文提出了一种基于试验数据的振动环境预示方法,以某发动机两次热试车试验数据为对象,分别提取了反映结构特性的动力学模型,基于载荷等效原则...     

Calibration of nonlocal damage model from size effect tests

The calibration of nonlocal models which contain an internal length has been among the major issues conditioning the implementation of this kind of failure models. Direct calibration from uniaxial testing, where the state of strain remains homogeneous throughout the specimen, is impossible. The softening law is not directly accessible because the strains cannot remain homogeneous during the entire test. In the absence of local information on the displacement field and on micro cracking in the fracture process zone, the calibration has to rely on inverse analysis. This paper presents such a procedure based on three point bend size effect tests on notched specimens. The complete load deflection curves are used for the identification of the constitutive relations. Manual calibration is discussed first. It is emphasised that calibration on the load deflexion curve from a single experiment is not objective. We show that Bazant's size effect law, which is related to peak loads only, may serve as a helpful guide to reach the closest fit. Then, automatic calibration is described. An optimal set of model parameters can be obtained within a reasonable number of iterations.     

飞机模型高速撞击钢筋混凝土载荷特性实验研究

为得到大型商用飞机撞击的冲击载荷特性及其计算方法,基于火箭橇加载试验平台,搭建了飞机模型撞击钢筋混凝土运动靶体测试系统,开展了两种不同尺寸飞机模型的撞击试验,利用高速摄影技术获得了飞机模型撞靶前的姿态、着速及飞机模型撞靶的破坏过程。采用加速度测试系统和激光干涉测速系统,分别得到撞击过程中运动靶体的加速度和速度历史,据此得到靶体受到的冲击载荷-时间曲线,二者吻合,验证了测试系统的可靠性。通过飞机模型上安装的机载存储过载测试系统,获得了撞击过程中飞机模型的负加速度-时间曲线,由此确定了修正的Riera理论模型中的静载荷项,并进一步计算得到靶体受到的冲击载荷-时间曲线,与通过测试靶体的加速度或速度得到的结果一致,验证了使用修正的Riera理论模型计算飞机模型冲击载荷的合理性及计算方法的正确性,同时确定了适合于本试验中飞机模型的修正系数α。     

A Device for Biaxial Testing in Uniaxial Machines. Design,Manufacturing and Experimental Results Using Cruciform Specimens of Composite Materials

The present study deals with the design and manufacturing of a mechanical device to perform biaxial testing in universal (uniaxial) testing machines. A review of previous definitions of similar devices is carried out and a new device is conceived and developed. The main improvement with the present device is that it allows different types of biaxial loadings (tension-compression) to be performed with few manipulations. The device allows variable displacement ratio to be used in each loading direction, giving then rise to variable loading ratios. Biaxial tension-tension tests on cruciform specimens made of composite material were carried out using very brittle samples in which the fibre direction was perpendicular to the loading plane. Strain gages were used to monitor the percentage bending parameter so that the correct alignment of the loading could be checked. Values below 5% for the bending parameter were achieved at the moment of failure.     

The in-situ fatigue testing of a cast aluminum-silicon alloy

The study reported in this paper deals with the experimental determination of the effect of the two-phase microstructure of an aluminum-silicon alloy on the propagation of fatigue-induced fracture. The work involved the use of a computerized apparatus which applied four-point bending loads to test specimens inside the vacuum chamber of a scanning electron microscope (SEM). The use of the SEM allowed for the in-situ monitoring of the progression of the fatigue crack with respect to the microstructure of the material.A constant load amplitude fatigue test was established for the experimental system and an analytic model is proposed to predict the growth of the crack in the specimen using compliance measurements. In-situ tests were performed on a variety of test aluminum-silicon alloy specimens. Preliminary results show that a relationship exists between the silicon phase in the aluminum matrix and propagating fatigue crack. Data from these tests were used to evaluate both the model mentioned above and an analytic relation for the stress intensity factor for a beam containing a crack subjected to four-point bending.     

Four-Point Bending Test of Determining Stress-Strain Curves Asymmetric between Tension and Compression

A method of determining both uniaxial tension and compression stress-strain curves from the result of a single four-point bending test was demonstrated. Stress-strain curves of magnesium showing tension-compression asymmetry due to twinning deformation and those of an S45C steel due to the Bauschinger effect were calculated. The Mayville-Finnie equation was modified slightly for this calculation. The calculation is sensitive to small change in the slope of bending curve, revealing an aspect of inverse problem.     

Novel load cell for measuring axial force,shear force,and bending movement in large-scale structural experiments

This paper describes the design, construction and testing of a load cell to measure the axial force, shear force, and bending moment at the end of a structural beam. The capacities of the load cell are 780 kN in axial load, 350 kN in shear, and 200 kNm in bending. These magnitudes, together with the requirement that the load cell should be kept as slim as possible, necessitated a novel design comprising three steel double-spring elements machined with semicircular channels to provide localized strain amplification. The load cell was designed with the aid of detailed finite element analysis and was machined from grade 55 steel. After strain gaging, it was subjected to an extensive series of calibration tests. Results from these tests are reported, together with those from some early experiments in which two load cells were used to measure the behavior of structural steel knee elements.