民机电传飞控系统故障检测与容错技术

现代民机广泛采用数字式电传飞控系统,它有利于飞机减重、飞行品质改善、飞机维护性改善等。民机电传飞控系统需满足严格的安全性与可用性要求,保证飞机取证与运营可靠性。故障检测与容错技术是实现高度安全可靠电传飞控系统的关键。该文阐述了已应用于现代民机的故障检测与容错技术,重点介绍了波音、空客公司故障检测与容错技术应用于民机设计的成功案例,对未来民机容错技术发展进行了探讨与展望。     

弹靶作用过程中陶瓷基复合材料的表面驻留行为

为提高陶瓷基复合材料在轻质装甲结构设计中应用的可行性,研究陶瓷基复合材料在抵抗弹体撞击时的表面驻留性能,进而探索其抗弹性能,旨在丰富和完善陶瓷基复合装甲材料的抗弹机理。采用数模模拟方法对弹体撞击SiC-Al陶瓷基复合材料表面驻留过程开展了深入研究,探索了复合材料的表面驻留行为,对比分析了复合材料和陶瓷材料表面驻留过程中应力水平和损伤演化过程。结果表明:复合材料表面驻留耗能为845J,比B_4C、SiC、AD99Al_2O_3陶瓷材料分别提高约46.0%、30.2%、35.7%;完全损伤的复合材料仍具有较一般陶瓷材料更高的承载能力,延长其驻留持续时间;复合材料损伤演化形式与陶瓷材料差异较大,导致损伤耗能占总驻留耗能的比例达到23.9%,比陶瓷材料提高了2倍多。     

含裂口损伤复合材料层合板拉伸试验及数值模拟分析

通过对无损、含损(不同长度的裂口损伤)的碳纤维复合材料层合板进行拉伸试验,研究了裂口损伤形式对碳纤维复合材料层合板拉伸性能的影响。经试验研究,碳纤维复合材料无损层合板的拉伸强度为517.37MPa;且裂口损伤使碳纤维复合材料层合板的拉伸性能显著降低。相比无损层合板的拉伸性能,裂口为5mm的层合板拉伸强度降低26.3%,裂口为15mm的层合板拉伸强度降低23.4%。采用基于三维渐进损伤失效准则编写的子程序对碳纤维复合材料层合板进行拉伸数值模拟分析,模拟了含损层合板的损伤起始过程。通过与试验结果进行比较,验证了模型的合理性。     

Damage characteristics and constitutive modeling of the 2D C/SiC composite: Part Ⅱ–Material model and numerical implementation

In this work, a macroscopic non-linear constitutive model accounting for damage, inelastic strain and unilateral behavior is proposed for the 2D plain-woven C/Si C composite. A set of scalar damage variables and a new thermodynamic potential expression are introduced in the framework of continuum damage mechanics. In the deduced constitutive equations, the material's progressive damage deactivation behavior during the compression loading is described by a continuous function, and different deactivation rates under uniaxial and biaxial compression loadings are also considered. In damage evolution laws, the coupling effect among the damage modes and impediment effect of compression stress on the development of shear damage in different plane stress states are taken into account. Besides, the general plasticity theory is applied to describing the evolution of inelastic strain in tension and/or shear stress state. The Tsai–Wu failure criterion is adopted for strength analysis. Additionally, the material model is implemented as a user-defined material subroutine(UMAT) and linked to the ABAQUS finite element software, and its performance is demonstrated through several numerical examples.     

基于光纤光栅传感的复合材料蒙皮结构修补监测研究

复合材料结构粘接修补是一项被广泛应用的工程技术。采用光纤光栅对复合材料蒙皮结构的损伤和粘接修补结构的全过程进行了实时监测,通过理论分析与试验相结合,发现光纤光栅传感器可对结构损伤进行识别,可对修补结构进行监测,并可评估修补结构的性能。基于光纤光栅传感的修补结构监测对飞机结构的修补评估、保障安全具有实际的工程价值。     

基于最小区域法的形位公差精确算法

最小区域法是真正符合国际形位公差定义的评价方法。针对现有的最小区域法的实现算法存在思路复杂、对初始计算条件要求较高等问题,提出1种逐次逼近算法。详细阐述了依据此算法求解4种常见形位公差的初始计算条件设置和求解步骤,绘制了以圆度计算为例的算法流程图。结果表明:该算法初始计算条件和思路简单,易于编程,对测点坐标分布及运行环境无特殊要求;可以准确有效地实现圆度等形位公差的评定。     

Thermal-structural response and low-cycle fatigue damage of channel wall nozzle

To investigate the thermo-mechanical response of channel wall nozzle under cyclic working loads,the fnite volume fluid-thermal coupling calculation method and the fnite element thermal-structural coupling analysis technique are applied.In combination with the material lowcycle fatigue behavior,the modifed continuous damage model on the basics of local strain approach is adopted to analyze the fatigue damage distribution and accumulation with increasing nozzle work cycles.Simulation results have shown that the variation of the non-uniform temperature distribution of channel wall nozzle during cyclic work plays a signifcant role in the thermal-structural response by altering the material properties;the thermal-mechanical loads interaction results in serious deformation mainly in the front region of slotted liner.In particular,the maximal cyclic strains appear in the intersecting regions of liner gas side wall and symmetric planes of channel and rib,where the fatigue failure takes place initially;with the increase in nozzle work cycles,the residual plastic strain accumulates linearly,and the strain amplitude and increment in each work cycle are separately equal,but the fatigue damage grows up nonlinearly.As a result,a simplifed nonlinear damage accumulation approach has been suggested to estimate the fatigue service life of channel wall nozzle.The predicted node life is obviously conservative to the Miner＇s life.In addition,several workable methods have also been proposed to improve the channel wall nozzle durability.     

SiCp / Al 复合材料低损伤磨削制孔工艺研究

采用研制的椎4 mm 金刚石磨料刀具,研究SiCp / Al 复合材料磨削制孔过程中工艺参数对轴向力和

孔质量的影响规律。结果表明:刀具转速高于6 000 r/ min、进给速度为5 mm/ min 时,可以获得较好的制孔质量。

     

基于Paris解的直升机动部件损伤容限分析

直升机金属动部件是单路传力结构,承受高周疲劳载荷,一般认为不适合采用损伤容限设计,但对多个螺栓连接的大型接头,有较好的损伤容限特性.文章根据线弹性断裂力学Paris理论,提出了一套适合直升机动部件的损伤容限分析方法,通过对某型机尾桨叶接头进行损伤容限分析,得出了具有高可靠度的较长的裂纹扩展寿命.     

中国航空工业疲劳与结构完整性研究进展与展望

随着中国航空事业的发展,航空疲劳与结构完整性成为影响飞机结构寿命、安全性、可靠性的关键问题之一。经过多年来的努力,飞机结构从最初的静强度、安全寿命设计理念逐渐发展成以疲劳与结构完整性为指导的研制理念和方法,并在型号中取得了成功应用,使得新一代飞机结构的使用寿命、可靠性和经济性得到很大的提升。随着技术的发展和新型号的研制需求,这一领域又出现了许多亟待解决的新问题。本文从航空工业角度梳理了自2000年以来中国航空结构疲劳研究的进展和主要成果,重点介绍了在航空材料/结构/工艺、分析评估理论研究、疲劳试验技术以及飞机寿命管理等方面的研究进展和应用概况,在此基础上从型号研制及工程发展角度提出了对中国航空疲劳需要重点关注的研究方向的建议,以期为中国航空结构技术发展提供借鉴。