基于非平稳非高斯随机振动的航天结构疲劳寿命分析

随机振动试验是考核结构疲劳强度的常用方法，通常假定振动信号符合高斯分布。实际使用中存在非平稳非高斯随机振动环境，非平稳非高斯振动中的结构疲劳寿命分析有助于试验技术的提高。通过介绍非平稳非高斯随机振动的特征和生成方法，分析了跌宕周期对非平稳非高斯信号时域波形的影响。建立典型试件的有限元模型，按照波形再现振动试验的加载方法和时域疲劳寿命分析方法，研究了峭度和跌宕周期对疲劳寿命的影响。结果表明峭度和跌宕周期对疲劳寿命有显著的影响。研究结果对于提高环境试验真实度、改善疲劳寿命试验技术具有参考意义。     

基于等效寿命的航空铆接疲劳特性试验研究

通过二级变幅载荷谱试验与Elber模型相结合分析搭接铆接结构疲劳特性,讨论铆接参数对疲劳断口特征及疲劳寿命的影响。结果表明:疲劳裂纹萌生于搭接板内的多个位置,裂纹源及断裂截面位置受铆接参数及疲劳载荷水平影响;对于较大铆接力下疲劳载荷影响更显著,使用基于Elber裂纹张开应力模型的等效裂纹扩展速率能较好反映铆接工艺及第二弯曲效应影响下的结构疲劳寿命;通常情况下增大铆接力有利于提高疲劳寿命,但其变化规律依赖于疲劳载荷的水平;Smax=100 MPa时,增大铆接力对于4 mm铆钉试件提高疲劳寿命效果显著,但Smax=150 MPa时,较高的铆接力会导致疲劳寿命的增益出现衰减。     

输送管位移的工程计算方法与有限元快速计算方法

在已知波纹管轴向刚度、弯曲刚度的条件下,基于卡氏定理总结出一套输送管平面位移的工程近似计算方法,能够准确计算水平力和竖直力作用下输送管在作用力方向上的位移。并且,在已知波纹管轴向、径向、弯曲刚度的条件下,提出一种基于有限元软件的输送管位移快速计算方法,建模简单,运算时间短,具有很好的实用价值。     

表面完整性对高强度钢疲劳寿命影响的试验研究

研究了高强度钢34CrNiMo6 的加工表面完整性对弯曲疲劳寿命的影响规律。疲劳试件的加工采用不同的切削参数,对加工表面完整性相异的试件进行疲劳试验。研究结果表明:残余应力是影响试件弯曲疲劳寿命的主要因素,残余压应力可获得高疲劳寿命;当表面粗糙度Ry >10 滋m 时,表面粗糙度对疲劳寿命的影响显著;加工硬化对高强度钢疲劳寿命有不利影响,疲劳寿命随表面硬度的增加而降低;采用小刀尖半径和低进给速度可提高高强度钢的疲劳寿命。     

膜片式金属膜盒充放气过程结构仿真分析

为了研究保险阀膜片式金属膜盒在充放气过程中的受力情况及作用机理,并分析各因素对其疲劳特性的影响,基于Abaqus结构仿真软件开展二维轴对称仿真研究.通过静力分析得到充放气单个循环破裂位置的应力变化曲线,使用雨流计数法分解为多个子循环,基于应力疲劳分析方法计算寿命试验次数下破裂位置的疲劳损伤.计算结果表明,限位行程为0～2mm的膜盒疲劳寿命低于限位行程0～4mm状态;相对于拉伸校型,压缩校型使得膜盒疲劳寿命降低更加明显.在工程应用中,适当增大限位行程、避免膜片组校型可以提高金属膜盒疲劳寿命.     

飞机中外对接件的结构疲劳寿命预测

为得到飞机中外对接件在载荷状态下的应力分布情况,合理的对其寿命进行估算,采用ANSYS软件对飞机中外对接件进行有限元分析并与试验值对比,得到应力分布情况,应用局部应力应变法做寿命的估算,其结果为结构细节改进和评价构件的疲劳分析提供依据。     

基于神经网络的结构疲劳可靠性优化设计

研究了人工神经网络在结构疲劳可靠性分析和结构优化设计中的应用。结构的疲劳寿命与各影响因素之间呈高度的非线性关系,或隐函数关系,传统的结构可靠度分析方法计算困难。采用神经网络响应面法模拟结构的极限状态函数及其偏导数,从而进行疲劳可靠性分析,在此基础上采用神经网络法对结构进行疲劳可靠性优化设计,通过算例说明其适用性及可行性。     

基于修正Corten-Dolan模型的机体结构延寿方法研究

针对机体延寿工作的复杂性,从疲劳损伤积累的角度研究机体结构的延寿方法。利用剩余强度衰减退化修正的Corten-Dolan模型计算机体结构疲劳关键件的疲劳损伤累积量,推导了载荷服从正态分布时的疲劳可靠度和k级载荷下剩余疲劳寿命估算公式。根据疲劳损伤的积累量,将疲劳寿命折算成日历寿命。提出机体结构延寿分析流程并进行案例分析,寿命加速实验结果表明各关键件均达到延寿要求,说明该方法具有一定的参考价值。     

开缝衬套冷挤压孔疲劳寿命仿真模型建立及验证

利用有限元分析软件Abaqus和疲劳分析软件MSC.Fatigue联合仿真,建立冷挤压孔疲劳寿命仿真模型,研究冷挤压工艺对7050铝合金带孔试件疲劳寿命的强化效果。在有无衬套情况下,研究疲劳载荷及挤压量对冷挤压疲劳增寿效果的影响。仿真结果表明:带衬套挤压寿命强化效果好于无衬套挤压强化效果;在一定挤压范围内,挤压量越大,强化效果越好;经开缝衬套冷挤压后,7050带孔试件的疲劳寿命可提高2~8倍。将仿真结果与试验结果作比较,验证了该仿真模型的有效性。     

基于Swellam应力指数Ki的电阻点焊疲劳性能研究

为研究301L不锈钢电阻点焊不同板厚组合对疲劳寿命的影响,对9组不锈钢电阻点焊拉剪试样进行疲劳试验,获得不同厚度不锈钢点焊的载荷疲劳寿命曲线及其疲劳强度。利用Swellam应力因子分析疲劳结果时发现:应力因子K_i对于预测同种板厚组合的电阻点焊寿命较为准确;而对于异种板厚组合,两侧板厚的厚度差越大,寿命预测的准确性越差。通过有限元分析发现,厚板对整个试样的应力集中程度有显著影响,采用薄板预测其疲劳强度会产生较大的偏差,采取板厚修正的方法提高其寿命预测的准确性,修正板厚与板厚差满足y=0.357x+0.659的线性关系,修正后的K_i-N曲线可以较好地评价点焊疲劳试样的疲劳寿命。     

Expert Systems Aimed at General Design of Projectiles

Expert systems aimed at the general design of projectiles can implement a series of intelligent designs, such as the design of HE shell, the scheme expounded and proved, the emulation analysis and calculation, etc. Aiming at the product design feature, the expert system adopts the object-oriented knowledge representation and all kinds of inference control engines to describe and reason the relevant knowledge regarding the product through the microcomputer. It embodies the foundation of emulation analysis and simulated manufacturing of the shell. It makes use of the method that knowledge expression is combined with condition of inference to carry out the overall design and emulation and reference.The paper gives the ways through which the functions can be achieved, gives the modularization of reference and the design methods of systematization, puts forward the method of knowledge expression and working interface, and supplies a platform for similar products of the shell category that can be quickly designed.     

Parameter Identification for the Valve Control Cylinder System of a Hydraulic Manipulator

In mechanical, hydraulic and electronic systems, the determination of system parameters is often challenging because liquid parameters often change significantly, due to variations in working and environmental conditions. Therefore, it is of significant practical importance to identify those parameters through experimental procedures. A systematic approach to identifying parameters in the valve controlling cylinder system of hydraulic manipulators is provided. It first derives the transfer function of the system, and then uses P control of PID control to predict system parameters. The predicted parameters are further validated using PID control. The prediction through simulation using MatLab language is utilized, which agrees well with experimental results.     

Three-dimensional Numerical Simulation of Combustion Field in the Combustion Chamber

In order to study the effect of rotation on the combustion in the underwater vehicle, a two-phase turbulent combustion process is described with Reynolds stress turbulence model, eddy-dissipation turbulent combustion model, P-1 radiation model and particle tracking model of liquid. The flow in the rotating combustion chamber is simulated at two different working speeds, 0 r/min and 1 000 r/min by Fluent software. The temperature, gas velocity, static pressure of wall and fuel concentration are computed and compared. The results show that the combustion in rotating combustor is faster and more effective.     

Software Communication Architecture Implementation and Its Waveform Application

This paper attempts to do a research on the development of software defined radio（SDR） based on software communication architecture（SCA）. Firstly, SCA is studied and a whole reference model of SCA3.0 core framework （CF） is realized; Secondly, an application-specific FM3TR waveform is implemented on the platform of common software based on the reference model; Thirdly, from the point of view of real-time performance and software reuse, tests and validations are made on the above realized CF reference model and FM3TR waveform. As a result, the SCA-compliant SDR has favorable interoperability and software portability and can satisfy the real-time performance requirements which are not too rigorous.     

Dynamic Simulation of the Tank Gun Recoil Response

By using the ATV module of MSC. ADAMS, the dynamic simulation of recoil response of tank gun is analyzed.How the recoil force affects the bodywork and the suspension during gun firing, as well as the changing status of the gun muzzle‘s velocity are gained. All results and analyzing methods are offered for the designing basis of optimizing tank vehicle-gun match. The constructive exploration is beneficial to improving the general capability of tank.     

Survey of Controllable Suspension System for Off-road Vehicles

The controllable suspension system can improve the performances of off-road vehicles both on road and cross-country. So far, four controllable suspensions, that is, body height control, active, semi-active and slow-active suspensions, have been developed. For off-road vehicles, the slow-active suspension and the semi-active suspension which have controllable stiffness, damping and body height are more appropriate to use. For many years, some control methodologies for controllable suspension systems have been developed along with the development of modern control theory, and two or more original control methods are integrated as a new control method. Today, for military or civilian off-road vehicles, the R&D of controllable suspension systems is ongoing.     

Finite Element Analysis of Fretting Behavior Between an Engine Cylinder Block and a Main Bearing Cap

The finite element analysis of the fretting behavior between a cylinder block and a main bearing cap is presented. The stresses, relative fretting slip, fretting friction work parameter W and crack initiation location parameter G on the fretting contact surface of the cylinder block are obtained and analyzed. It shows that the fretting fatigue problem of the cylinder block can be quantitatively explained by W or G. The effects of pretightening force, friction factor and material combination of the cylinder block and the main bearing cap are studied. The computational results indicate that the fretting fatigue of the cylinder block can be allayed by increasing the elastic modulus of the cylinder block, but not by changing the other two factors.     

An Efficient Key Agreement Framework to MANET

Protocols for key management are compared and evaluated from the point of view on mobile ad hoe networks （MANET）. The issues of fault-tolerance and efficiency of key distribution protocols for group communications in MANET are addressed. Most key distribution protocols existing today are primarily designed for wlre-line networks. These protocols either fail to work as intended or cannot work at all when they are applied to the demanding environment of MANET. Parameters and performance of different protocols are analyzed, and then a fiat is given out, on which new protocols or existing ones are designed and modified, so that they can be robust, scalable and efficient in MANET.     

A Physical Model of Electromagnetic Force from PEMA Acted on Metal Projectiles

Electromagnetic armor is a new conceptual combat vehicle technology, which improves remarkably the defensive capability and maneuverability of vehicles. The authors present definitely to apply the electromagnetic theory to analyze the electromagnetic armor. Based on electromagnetics, the experienced expression of projectile and the physical model of PEMA （passive electromagnetic armor） are obtained when electric current flows through the system, and a computer sim- ulation is given.     

The Kinematics Analysis of the Hydraulic Mine-clearing Mechanical Manipulator

Through analyzing the kinematics of the hydraulic manipulator operating system, according to the rules for set-ing up the D-H coordinate system, the generalized coordinate of the manipulator system is established. The rotating and moving joints are selected from the mechanism as joint variables. Each generalized transformation matrix of joints is worked out. The kinematics equation at the finger end of the manipulator is calculated. The obverse solution for the manipulator is gained. The geometrical operating parameters and primary technical specification of the manipulator system are simulated through the computer. The simulative result has shown that the manipulator operating system meets the working task requirements. This research provides theoretical basis for optimizing structural parameters of the manipulator operating. So it also is justified the feasibility for mechanical manipulators to be used in the engineering equipment platform of the hydraulic excavator.