THEORETICAL ANALYSIS AND EXPERIMENTAL VERIFICATION ON TERNARY-WAVES METHOD TO COMPILE ACCELERATED SPECTRA

The equivalent damage calculation formulae of fatigue crack formation and growth are established. In order tocompile the fatigue crack formation and growth accelerated load spectra, the main wave shapes and load sequence of theactual load spectrum are kept constant, and the carrier waves are cut off. And secondary waves are put together into newsecondary waves to shorten the test time according to the equivalent damage calculation formulae respectively. Then bythe fatigue cumulative damage calculation of the fatigue crack formation and growth accelerated load spectra, the onecorresponding to the bigger damage is determined as the fatigue accelerated test load spectrum. Therefore in the test process, the fatigue accelerated test spectrum may be applied till fatigue failure, the engineering fatigue crack length of full-scale structure need not be inspected, and the fatigue crack formation accelerated load spectrum need not be transferredinto the fatigue crack growth accelerated load spectrum. Finally, it     

THEORETICAL AND EXPERIMENTAL STUDY ON MAGNETIC FLUID SEALING OF SERRATED FORM

ＴＨＥＯＲＥＴＩＣＡＬＡＮＤＥＸＰＥＲＩＭＥＮＴＡＬＳＴＵＤＹＯＮＭＡＧＮＥＴＩＣＦＬＵＩＤＳＥＡＬＩＮＧＯＦＳＥＲＲＡＴＥＤＦＯＲＭＬｉＤｅｃａｉ，ＳｏｎｇＤｅｎｇｘｕａｎ，ＹｕａｎＺｕｙｉＮｏｒｔｈｅｒｎＪｉａｏｔｏｎｇＵｎｉｖｅｒｓｉｔｙＡｂｓ...     

INVESTIGATION ON COMPRESSIBILITY AND BULK MODULUS OF FLUID

ＩＮＶＥＳＴＩＧＡＴＩＯＮＯＮＣＯＭＰＲＥＳＳＩＢＩＬＩＴＹＡＮＤＢＵＬＫＭＯＤＵＬＵＳＯＦＦＬＵＩＤＣａｏＢｉｎｇｇａｎｇＸｉ＇ａｎＪｉａｏｔｏｎｇＵｎｉｖｅｒｓｉｔｙＡｂｓｔｒａｃｔＴｈｅｐｒｏｂｌｅｍｓｉｎｔｈｅｔｒａｄｉｔｉｏｎａｌｄｅｆｉｎ...     

EQUIVALENT EXCITATION METHOD FOR VIBRATION ISOLATION DESIGN：THEORETICAL ANALYSIS AND EXPERIMENTAL RESULTS

In view of difficulties concerned with direct measurement of excitations inside source equipments and their significant influence on vibration isolation effectiveness, a dynamical model, for vibration isolation of a rigid machine with six-degree-of-freedom mounted on a flexible foundation through multiple mounts, is analyzed, in which the complicated and multiple disturbances inside the machine are described as an equivalent excitation spectrum. And a method for the estimation of the equivalent excitation spectrum according to system dynamic responses is discussed for the quantitative prediction of isolation effectiveness. Both theoretical analysis and experimental results are demonstrated. Further work shows the quantitative prediction of transmitted power flow in a flexible vibration isolation experiment system using the proposed equivalent excitation spectrum method, by comparison with its testing results.     

EXPERIMENTAL INVESTIGATION OF PASSIVE CONTROL ON UNSTABLE CHARACTERISTICS IN AXIAL FLOW FAN

ＥＸＰＥＲＩＭＥＮＴＡＬＩＮＶＥＳＴＩＧＡＴＩＯＮＯＦＰＡＳＳＩＶＥＣＯＮＴＲＯＬＯＮＵＮＳＴＡＢＬＥＣＨＡＲＡＣＴＥＲＩＳＴＩＣＳＩＮＡＸＩＡＬＦＬＯＷＦＡＮ①ＬｉａｎｇＸｉｚｈｉＷｕＨａｉＣｈｉｎｅｓｅＡｃａｄｅｍｙｏｆＳｃｉｅｎｃｅｓＡｂｓｔｒ...     

EXPERIMENTAL INVESTIGATION ON SURFACE INTEGRITY OF END MILLING NICKEL-BASED ALLOY— INCONEL 718

Inconel 718 is a typical difficult-to-machine material, and its high speed end milling process has wide applications in manufacturing parts from aerospace and power industry. Surface integrity of these parts greatly influences the final characteristics. This paper presents an experimental investigation to evaluate surface integrity behaviors in high speed end milling of Inconel 718 with finishing cutting parameters in terms of surface topography, surface roughness Ra, residual stresses, subsurface microstructure, and microhardness. The results show that abraded marks can be observed on the machined surfaces, and high cutting speed is advisable to get better surface topography and roughness quality. Due to high cutting temperature, residual stress is mainly high tensile stress. After increasing the cutting speed beyond 80m/min, the cutting forces hardly increased and the chips take away more cutting heat, which leads to that the residual stress barely increases. Microstructures in subsurface layers have only slight deformations after high speed milling, and there was also no obvious difference when the cutting speed increased beyond 80m/min against the microhardness in subsurface increases together with the cutting speed.     

FINITE ELEMENT ANALYSIS AND EXPERIMENTAL STUDY OF THE METAL MULTIDIE IRONING PROCESS

ＦＩＮＩＴＥＥＬＥＭＥＮＴＡＮＡＬＹＳＩＳＡＮＤＥＸＰＥＲＩＭＥＮＴＡＬＳＴＵＤＹＯＦＴＨＥＭＥＴＡＬＭＵＬＴＩＤＩＥＩＲＯＮＩＮＧＰＲＯＣＥＳＳＦＩＮＩＴＥＥＬＥＭＥＮＴＡＮＡＬＹＳＩＳＡＮＤＥＸＰＥＲＩＭＥＮＴＡＬＳＴＵＤＹＯＦＴＨＥＭＥＴＡＬＭ...     

THE INFLUENCE OF PERIOD VARIATION ON TIME–FREQUENCY ANALYSIS OF THE WESTLAND HELICOPTER DATA

In this work, we address the influence of period variation on the Westland CH-46E helicopter vibration data. The estimation of the time-varying shaft speed by using a newly developed constrained AR(2) estimator and the well-known EKF estimator will be discussed. The influence that the period variation captured by these two estimators have on the periodic time–frequency analysis will be illustrated via numerical simulation. This simulation clearly illustrates a potential spectral smearing if the period variation is not properly accommodated. A data resampling scheme will then be proposed to eliminate the spectral smearing effect. The potential of this scheme will be demonstrated via the analysis of the helicopter vibration data.     

ANALYSIS AND RESEARCH OF COMPUTER-AIDED MODEL OF HIP JOINT BASED ON REVERSE ENGINEERING

Former research work about the modeling of hip joint focus on the upper segment of femoral, and assumes the acetabulum cup is sphere concave, and the acetabulum prostheses is semisphere. A method of acquiring the point data on the surface of the hipbone using the reverse engineering technology is presented. After analyzing the acetabulum surface fitting error, a rotation ellipsoid CAD model is applied to fit the acetabulum surface, and then optimization technique is used to find the geometric parameters of the model. The fitting error between the sphere and rotation ellipsoid is compared and gets the result that the fitting error of rotation ellipsoid is smaller than sphere, and the rotation ellipsoid can describe the shape of the acetabulum better.     

MODAL ANALYSIS OF A LIGHTWEIGHT STRUCTURE—INVESTIGATION OF THE EFFECTS OF THE SUPPORTS ON THE STRUCTURAL DYNAMICS

This study grew out of the use of vibration to modify welding stresses, and the corresponding need to understand the modal vibration properties of the test structures. Supporting the structure is a practical problem in experimental modal analysis. In this study the effect of the supports on the dynamic properties of a lightweight structure were investigated. Thick rubber bungee supports and thin elastic band supports were used in the investigation. The effect of the position of the supports was found to be insignificant if a proper type of support is used. It was observed that with the thick bungees the modes become invisible or obscure on the frequency response function (FRF) curves. On the other hand, the thin elastic band supports provide very clear FRF curves and hence clear mode shapes. It has been suggested that the bungees should be chosen considering the weight of the structure and the requirement of the vibration amplitude in the modal analysis and/or in the subsequent treatments. The position of the bungees should be chosen at the node points of a particular mode of the structure to reduce the support effects further.     

多跨转子-轴承系统振动稳定性试验研究

在一多跨转子-轴承模拟试验台上进行了轴承不对中对系统阻尼及稳定性影响作用的试验研究。采用扩展Prony方法识别了阻尼参数,从非线性系统动力学角度对试验中若干现象进行了定性分析。     

螺旋槽干运行非接触气体密封的理论分析与试验

设计制造了“W ndef 288型”螺旋槽干运行非接触气体密封(线速度111,4 m/s、温度110℃),并进行了动态与稳定性分析、特别是角向半频自激振动及共振振荡的理论分析。工业模拟运行了近3 000 h(100余次起停),上万的测试数据表明了其优异的性能。     

ANALYSIS ON MOTION STABILITY OF A HIGH-SPEED ROTOR-BEARING SYSTEM

A non-linear dynamic model of one type of high-speed rotor system with gas supporting system is set up. The laws between the capacity force and the parameters of bearing, the static equilibrium position and rotating speed are studied on the basis of above model. Then, the failure rotating speed is given in the working state, and the relation between the minimum failure rotating speed and clearance of bearing is also studied. At last, the stability and failure condition are discussed in different working conditions.     

电磁轴承系统控制参数与稳定性的关系分析

电磁轴承系统的稳定性是这一新型支承部件的研究和应用中必须解决的问题。系统失稳的因素很多，但使电磁轴承系统稳定工作的关键是其电子控制环节。讨论了在经典ＰＩＤ调节器的基础上，应用Ｒｏｕｔｈ判据分析系统稳定性与控制环节中各参数的关系，并以此确定系统稳定时，控制环节中各参数的取值范围的方法及其频带宽度对上述参数选择范围的影响。     

转子-轴承系统稳定性灵敏度分析的广义能量法

讨论了转子一滑动轴承复合系统中，各轴承及转子的稳定性对其复合系统的稳定性的影响和作用问题。运用大系统稳定性的理论和方法，为各滑动轴承和转子子系统及其集结系统引入了反映其各自稳定性状态的“广义能量”──李雅普诺夫函数。并在此基础上首次导出并定义了各子系统对其集结系统的灵敏度，用以刻划它们对复合的转子一轴承系统运动稳定性的影响大小。给出了实例以验证定义的正确性和方法的实际应用。     

轴承参数对平行转子—轴承系统动力特性的影响

在齿轮耦合的转子-轴承系统中,影响系统动力特性的因素很多,只研究了轴承组合形式、间隙比及宽径比对系统失稳转速、涡动比、临界转速及其分布以及系统阻尼特性的影响.发现在该系统中,存在着系统稳定运行的薄弱环节,当轴承组合形式、间隙比及宽径比产生变化时,系统的失稳转速也将产生变化,并表现出不同的阻尼特性.提出了用最小对数衰减率衡量系统跨越临界转速的能力,用涡动比判断哪个子系统首先失稳.     

非线性转子-轴承系统的耦合动力行为及稳定性分析

运用非线性动力学现代理论对一非线性转子-轴承动力系统进行研究.基于Wilson-θ法并将其改进形成一种求解周期响应的局部迭代方法.针对转子系统具有的局部非线性特征,运用该方法使得非线性响应的迭代求解仅在非线性自由度上进行.运用Floquet稳定性分岔理论,结合Poincaré映射研究系统周期响应的稳定性和分岔形式.数值结果展现系统具有周期、拟周期、多解共存、跳跃等丰富复杂的非线性现象.     

单盘含裂纹转子系统的非线性响应分析与实验研究

建立含裂纹Jeffcott转子的动力学运动方程。针对裂纹深度对转子系统动态响应的影响及转子盘摆振响应的特点进行仿真计算和试验研究。数值仿真表明，对于较浅的裂纹，系统响应为周期性运动，在某些转速下会出现倍周期运动，同时还出现各种倍频分量。此时的摆振运动常包含激振频率的倍频成分。当裂纹较深时，盘的摆振运动与横向振动都会出现各种非协调响应。试验结果表明，当轴上存在裂纹时，盘的横向振动响应和摆振响应中都会出现高次谐波分量，这些分量虽然从频率成分上讲是相同的，但各分量的大小有明显差异。这些结论对于转子裂纹故障的监测与诊断具有新的意义。     

四圆盘扭振系统三重共振的理论与实验研究

建立了具有平方非线性并受简谐激励作用的发电机组转子轴系四圆盘扭振模化系统的模型,应用非线性振动的改进平均法,研究系统的固有频率双重内共振关系ω３≈２ω２,ω２≈２ω１且Ω≈ω１时的三重共振问题,求得系统三重共振的一次近似解及稳态响应曲线,并进行了实验验证,实验结果与理论结果相符。     

小孔式动静压轴承的特性分析与试验研究

从理论和试验两方面,对小孔式动静压轴承的性能进行了研究。根据机理和数学模型,推导出计算公式,编制了可在IBM-PC/AT,XT及其兼容机上运算的静、动特性分析计算和优化设计程序,以Auto CAD为图形编辑器,研制成接口软件,实现了参数化绘图,完成从分析计算、优化设计到计算机绘图的CAD全过程。在试验研究方面,设计、制造和调试成一台通用的动静压轴承试验台,对小孔式动静压轴承进行了静、动特性测试,获得一批有价值的试验数据,为这种新型轴承的推广应用提供了可靠的依据。