基于Workbench的机轮轮毂静力强度分析方法探究

本文运用ANSYS Workbench建立了机轮轮毂、轮胎、轴的一体化模型,将载荷直接作用于轴以及轮胎上,对机轮轮毂的静强度应力分布和变形分布进行了分析。结果显示:本模型克服了已有模型所产生的胎圈座部位的应力集中问题,与试验结果相比,径向载荷产生的变形误差由之前的18.0%下降为10.5%,径侧向载荷产生的变形误差由之前的7.7%下降到3.3%。对于轮毂的强度校核以及结构优化具有实际参考价值。     

航空机轮设计和制造技术现状及发展

航空机轮的主要功用是减小飞机在地面运动的阻力,并吸收飞机着陆触地和地面运动时的撞击动能,一般由轮毂、刹车装置、轮胎组成,可分为刹车机轮和无刹车机轮两类,刹车机轮按刹车结构形式又分为弯块式、软管式和盘式三类。轮胎一般由轮胎承制厂单独生产。最初的飞机上,...     

某歼击机前起落架着陆瞬间有关参数的试验研究

 以某歼击飞机前起落架为例, 用落震试验的方法, 通过分析起落架有关参数随机轮转速变化的情况,来研究飞机着陆瞬间起落架的状况。研究结果表明, 在飞机着陆过程中, 当起转水平载荷达到最大值时, 起落架逆航向的弹性变形还未结束; 当起落架逆航向的弹性变形达到最大值时, 机轮从滑动转为滚动。     

航空机轮和刹车装置状况监控技术的发展

航空机轮和刹车装置状况监控技术包括机轮温度监控、轮胎压力监控、刹车间隙 /寿命监控和无损检测。作为飞机着陆系统的重要组成部分，航空机轮应用监控技术是十分必要的。本文综述了该装置状况监控的进展，并以期推动其进一步完善和发展。     

某型航空机轮热/固耦合中热场对轮毂强度的影响

本文针对机轮轮毂在热场和径侧向联合载荷作用下的静强度应力分布行研究,通过使用Ansys Workbench软件建立机轮的有限元模型,采用间接热/固耦合方法进行数值模拟分析。模拟结果显示:刹车热场使机轮轮毂的受载环境更加恶劣,机轮轮毂在刹车热场作用下各点应力值均有显著增加,对轮毂的应力强度要求至少提高10 MPa,应力上升幅度大于19.6%。     

航空轮胎改进方法

本文以某机为例,试述为满足飞机的某些性能要求,不得不在已有的航空轮胎基础上进行改进的方法。 航空轮胎是飞机机轮的组成部分,供飞机起飞、着陆滑跑及地面滑行之用,并缓冲和吸收部分运动动能,阻尼飞机在地面运动中其重心垂直运动。     

起落架轮轴偏角对轮毂结构强度影响分析

在飞机结构设计图纸上各类零部件都以静态刚体的形式表达,起落架机轮轮轴通常设计成与地面水平的形式,在地面载荷计算与结构强度分析时也通常以图纸为准进行计算分析,但在真实的地面使用物理场景中机体结构和起落架都会在受载后产生变形,轮轴轴线将与地面产生一个偏角,或者由于制造偏差和装配偏差等原因也会产生偏角,这些因结构柔性或者制造偏差原因造成的偏角对轮轴结构强度分析过程中准确性的影响有多大,在飞机设计精确化发展趋势的今天有较大的意义。本文基于有限元方法研究了典型地面载荷工况下,通过分析相同载荷状态、不同偏角状态下,某型民用飞机主起落架轮轴轮毂结构强度的变化情况,判断计算分析中是否应考虑轮轴偏角,为后续民机相关的结构强度设计提供参考。     

小鹰-500飞机主起落架静力试验实施技术

介绍了小鹰-500飞机主起落架静力试验实施过程中假机轮的设计，试验件的安装及加载特点。起落架静力试验的所有载荷都作用在机轮或轮轴上，而真实的机轮不能直接加载，必须设计一个假机轮，既要模拟真机轮在飞机上的安装状态，又要便于加载，还要有“刹车装置”。假机轮的加载孔设计成一个能绕轴心摆动的弧形槽孔，以便在试验过程中自动找正加载中心将主起落架在飞机上的三个分布在三维空间的连接点布置在一个由钢框组成的基准面下部以便试件的安装定位。将试件所受的压载用受拉作动筒来实施，避免了有可能出现的系统失稳。延长了加载作动筒根部支点到加载点的距离，从而减小了加载过程中因变形而产生的载荷误差。     

某型飞机机轮可靠性分析

根据外场故障数据统计,对某型飞机机轮LS－16E受力、故障模式和机理进行了分析,进行了可靠性计算,并提出视情检查维修的建议。LS－16E机轮用于某型飞机,是飞机起落架上重要的承力件,在飞机着陆和滑跑过程中,机轮处于复杂的受力状态,一旦发生断裂,将直接危及飞行安全。承制厂给出LS－16E机轮的首翻期为300起落,并没有反映机轮的实际寿命,实际使用中往往超过300起落。但自1998年以来,用户多次发现该机轮轮毂出现裂纹,因此,在保证使用安全的前提下,根据可靠性指标给出更合理的使用寿命,对机轮使用实施有效的管理已成为当务…     

飞机防滑刹车控制技术研究综述综述

机轮刹车系统是飞机上最重要的着陆减速系统,关系到飞机的安全起降,其核心是防滑刹车控制技术。飞机刹车过程包含了众多在控制领域具有挑战的问题(不确定性、强非线性和强时变性),如何在刹车过程中有效克服着陆中所涉及的地面摩擦、刹车盘力矩波动、起落架载荷变化和阵风等具有复杂非线性特征的干扰,实现对地面结合力的可控利用,将对提高飞机地面安全发挥重要作用。本文对飞机防滑刹车控制技术进行综述。简述了飞机机轮防滑刹车系统的作用、发展、基本控制原理和典型架构;从应用需求出发归纳了关键评价指标;以数学模型的形式描述了系统内的典型非线性环节和着陆环境中的扰动;按照飞机防滑控制技术发展的顺序,依次介绍讨论了开关式防滑控制、偏压调制式防滑控制、自适应防滑控制和智能防滑控制中具有代表性的方法。从刹车控制律验证角度介绍了全数字仿真和试验方法。最后,结合刹车控制系统研制所存在的问题与挑战对本领域所涉及的技术研究重点进行了展望。     

基于ANSYS的飞机轮胎分解机效果分析

针对B737系列的飞机子午线轮胎H40x14．5—19,在有限元软件ANSYS中建立了轮胎的胎冠、帘布、胎肩等9种不同的结构层。考虑了轮胎的三重非线性（材料非线性、几何非线性、接触非线性）以及轮胎与轮辋由于长期使用产生的粘合对轮胎分解的影响,利用pilot节点法模拟了拆胎机不同形状压盘的压胎过程。结果表明当压盘β角为40°时,轮胎分解效果最好。该模型对轮胎分解机结构设计、压盘的优化提供了依据。     

薄壁钛管剪应力本构参数识别方法

不同温度下的薄壁钛管剪应力本构参数识别,是研究薄壁钛管差温剪切弯曲过程管材塑性变形行为迫切需要解决的关键问题。提出了一种管材剪切测试的方法。将不同温度下薄壁钛管等温剪切测试、剪切测试过程模拟有限元模型、以及基于距离函数的响应面模型相结合,提出了薄壁钛管不同温度下剪应力本构参数逆向识别方法。采用该方法,识别了TA2薄壁钛管剪应力本构参数。同时建立了TA2薄壁钛管差温剪切弯曲过程模拟3维弹塑性热力耦合有限元模型。分别采用剪应力本构参数和单拉应力本构参数模拟弯管实验过程,评估了有限元模型的可靠性。结果表明：对于剪应力本构参数,温度越高,管材的K值和n值将减小,m值呈现波动的趋势。与单拉应力本构参数相比,剪应力本构参数对温度的变化更敏感,且剪应力本构参数值较小。与单拉应力本构参数相比,使用剪应力本构参数的有限元模型精度较高,模拟精度最大提高了60%。     

Nonlinear characteristic investigation of magnetorheological damper-rotor system with local nonlinearity

Magnetorheological (MR) dampers show superior performance in reducing rotor vibration, but their high nonlinearity will cause nonsynchronous response, resulting in fatigue and instability of rotors. Herein, we are devoted to the investigation of the nonlinear characteristics of MR damper mounted on a flexible rotor. First, Reynolds equations with bilinear constitutive equations of MR fluid are employed to derive nonlinear oil film forces. Then, the Finite Element (FE) model of rotor system is developed, where the local nonlinear support forces produced by MR damper and its coupling effects with the rotor are considered. A hybrid numerical method is proposed to solve the nonlinear FE motion equations of the MR damper-rotor system. To validate the proposed model, a rotor test bench with two dual-coil MR dampers is constructed, upon which experimental studies on the dynamic characteristics of MR damper-rotor system are carried out. The effects of different system parameters, including rotational speed, excitation current and amount of unbalance, on nonlinear dynamic behaviors of MR damper-rotor system are evaluated. The results show that the system may appear chaos, jumping, and other complex nonlinear phenomena, and the level of the nonlinearity can be effectively alleviated by applying suitable excitation current and oil supply pressure.     

A hierarchical updating method for finite element model of airbag buffer system under landing impact

In this paper, we propose an impact finite element(FE) model for an airbag landing buffer system. First, an impact FE model has been formulated for a typical airbag landing buffer system. We use the independence of the structure FE model from the full impact FE model to develop a hierarchical updating scheme for the recovery module FE model and the airbag system FE model.Second, we define impact responses at key points to compare the computational and experimental results to resolve the inconsistency between the experimental data sampling frequency and experimental triggering. To determine the typical characteristics of the impact dynamics response of the airbag landing buffer system, we present the impact response confidence factors(IRCFs) to evaluate how consistent the computational and experiment results are. An error function is defined between the experimental and computational results at key points of the impact response(KPIR)to serve as a modified objective function. A radial basis function(RBF) is introduced to construct updating variables for a surrogate model for updating the objective function, thereby converting the FE model updating problem to a soluble optimization problem. Finally, the developed method has been validated using an experimental and computational study on the impact dynamics of a classic airbag landing buffer system.     

某航空发动机机匣的动力学模型修正

利用动力学模型修正技术对某航空发动机机匣的有限元模型进行了修正.通过振动模态测试得到了实际机匣的模态数据用以作为有限元模型 修正的基准.利用频率对单元刚度的灵敏度分析选定了修正区域.在此基础上,应用1阶优化方法对机匣的有限元模型进行修正.研究结果表明:修正后机匣有限元模型的前10阶模态的计算值与实际测试的误差都在29%以内,可以应用在后续的发动机整机动力学分析等方面.      

湿滑道面飞机轮胎临界滑水速度计算方法比较

以美国国家航空航天局(NASA)临界滑水速度计算公式为基础,基于耦合欧拉-拉格朗日(CEL)算法建立动流场冲击原地转动轮胎分析模型,并由NASA公式及试验数据验证了模型的正确性及NASA公式在重轴载高胎压范围的适用性。进而考虑实际道面积水状态,建立滚动轮胎冲击静流场模型,探讨实际积水状态对临界滑水速度的影响。通过两类模型对比分析得出:两类模型的轮胎-水膜相互作用机理不同,相同速度和胎压下,后者在轮胎前缘形成的动水压强峰值明显高于前者,表明滚动轮胎冲击静流场模型中轮胎受到动水压强抬升作用更为显著,且相同速度条件下,滚动轮胎冲击静流场分析模型计算的竖向支撑力和临界滑水速度始终低于动流场冲击滚动轮胎的结果,表明该模型计算结果偏于安全,更适用于飞机高速滑行中轮胎-水膜相互作用分析。据此,提出了基于道面积水状态的临界滑水速度计算公式。     

基于三维软件辅助的轮胎爆破特定风险评估方法研究

采用偏安全的假设,建立了符合CS25.734及AMC25.734的轮胎爆破三维仿真模型,对中国民用航空规章FAR/CCAR25.729(f)及SAE ARP 4761中提出的轮胎爆破风险给出了安全性评估的方法。用分析的方法支持此适航规章条款的符合性验证工作。     

Thermomechanical coupling effect on characteristics of oxide film during ultrasonic vibration-assisted ELID grinding ZTA ceramics

Ultrasonic vibration-assisted ELID (UVA-ELID) grinding is utilized as a novel and highly efficient processing method for hard and brittle materials such as ceramics. In this study, the UVA-ELID grinding ZTA ceramics is employed to investigate the influence of thermomechanical loading on the characteristics of oxide film. Based on the fracture mechanics of material, the model of internal stress for oxide film damage is proposed. The thermomechanical loading is composed of mechanical force and the thermal stress generating from grinding temperature. The theoretical model is established for the mechanical force, thermal stress and internal stress respectively. Then the finite element analysis method is used to simulate the theoretical model. The mechanical force and grinding temperature is measured during the actual grinding test. During the grinding process, the effect of grinding wheel speed and grinding depth on the thermomechanical force and the characteristics of oxide film is analyzed. Compared with the conventional ELID (C-ELID) grinding, the mechanical force decreased by 25.6% and 22.4% with the increase of grinding wheel speed and grinding depth respectively, and the grinding temperature declined by 10.7% and 12.8% during the UVA-ELID grinding. The thermal stress in the latter decreased by 16.3% and 20.8% respectively, and internal stress reduced by 12.3% and 15.6%. It was experimentally found that the topographies of oxide layer on the surface of the wheel and the machined surface in the latter was better than that in the former. The results indicate that the action of ultrasonic vibration establish a significant effect on the processing. Subsequently, it should be well considered for future reference when processing the ZTA ceramics.     

Experimental,analytical and numerical investigation on tensile behavior of twisted fiber yarns

Stitched composite materials are emerging as a promising material due to their high interlaminar strength, combined performance and light weight. The mechanical properties of stitch yarns are very essential for stitched composite structures. In this study, the tensile behaviors of the twisted fiber yarn in stitched composites were investigated experimentally, analytically and numerically. Two kinds of cross-sectional area of twisted yarn are proposed and discussed. The paper presents an intersecting circle model to describe the cross-section of twisted fiber yarns, and a physics-based theoretical model to predict the effective tensile moduli. The numerical models take into account the cross-sectional characteristic and the twist architecture. The investigation shows that: the sum of each fiber area should be used for experimental analysis; and the cross-sectional area surrounded by the yarn profile should be used for theoretical predictions and finite element (FE) simulations. The relative errors of the prediction method and the FE simulation are less than 2% and 1%, respectively. The friction between the fibers is derived, and the effect of friction on mechanical properties is discussed. The investigation method will serve as a fundamental component of twisted fiber bundle/yarn analysis.     

Determination of thermal expansion coefficients for unidirectional fiber-reinforced composites

In the present work, the coefficients of thermal expansion（CTEs） of unidirectional（UD）fiber-reinforced composites are studied. First, an attempt is made to propose a model to predict both longitudinal and transverse CTEs of UD composites by means of thermo-elastic mechanics analysis. The proposed model is supposed to be a concentric cylinder with a transversely isotropic fiber embedded in an isotropic matrix, and it is subjected to a uniform temperature change. Then a concise and explicit formula is offered for each CTE. Finally, some finite element（FE） models are created by a finite element program MSC. Patran according to different material systems and fiber volume fractions. In addition, the available experimental data and results of other analytical solutions of CTEs are presented. Comparisons are made among the results of the cylinder model,the finite element method（FEM）, experiments, and other solutions, which show that the predicted CTEs by the new model are in good agreement with the experimental data. In particular, transverse CTEs generally offer better agreements than those predicted by most of other solutions.