Multi-objective iterative optimization algorithm based optimal wavelet filter selection for multi-fault diagnosis of rolling element bearings

Rolling element bearings (REBs) play an essential role in modern machinery and their condition monitoring is significant in predictive maintenance. Due to the harsh operating conditions, multi-fault may co-exist in one bearing and vibration signal always exhibits low signal-to-noise ratio (SNR), which causes difficulties in detecting fault. In the previous studies, maximum correlated kurtosis deconvolution (MCKD) has been validated as an efficient method to extract fault feature in the fault signals. Nonetheless, there are still some challenges when MCKD is applied to fault detection owing to the rigorous requirements of multiple input parameters. To overcome limitation, a multi-objective iterative optimization algorithm (MOIOA) for multi-fault diagnosis is proposed. In this method, correlated kurtosis (CK) is taken as a criterion to select optimal Morlet wavelet filter using the whale optimization algorithm (WOA). Meanwhile, to further eliminate the effect of the inaccurate period on CK, the update process of period is incorporated. After that, the simulated and experimental signals are utilized to testify the validity and superiority of the MOIOA for multiple faults detection by the comparison with MCKD. The results indicate that MOIOA is efficient to extract weak fault features even with heavy noise and harmonic interferences.     

Drag Power Loss Investigation in Cylindrical Roller Bearings Using CFD Approach

In high-speed rolling element bearings, the drag forces can be prominent and it is demonstrated in this investigation that the classical models may not be appropriate for correctly estimating this power loss contribution. A modification of the models is thus proposed, including the usual drag forces formulation relying upon the drag coefficient to be evaluated from a numerical computational fluid dynamics (CFD) approach. A three-dimensional approach that considers both the rings and the cylinder ends seems the only adequate approach to be used because a two-dimensional approach predicts a drag coefficient value that is too low. When using the former computed drag coefficient for the evaluation of the total power losses, high values of oil volume fraction must be employed to recover the measured power losses.     

基于旋滚比的电主轴轴承预紧力优化研究

为研究不同工况下轴承预紧力对电主轴轴承动力学的影响规律，基于外轨道控制理论,建立了一种以旋滚比可优化的轴承预紧力动力学模型。通过分析高速状态下滚动体载荷和特征参数动态变化过程，构建综合考虑滚动体滚动、自旋转、陀螺运动和离心力的轴承动力学分析模型，在此基础上，计算旋滚比动态变化结果；研究Jones发现的阈值与旋滚比之间的动态定量映射关系；以轴承滚动体打滑状态为优化目标，使用MATLAB仿真分析不同工况下轴承最佳预紧力。建模分析表明，轴承旋滚比大小可以反映轴承预紧效果，也可实现轴承预紧力动态定量优化。     

滚动轴承可靠性设计计算方法

从滚动轴承的可靠性设计理论出发，研究了在不同的目标可靠度要求时滚动轴承奉行命与目标可靠度间的关系；额定动载荷与目标可靠度间的关系。通过对ＸＹ—２型钻机轴承寿命与可靠度的计算，找出了该钻机中可靠度低的轴孢，提供用户注意维护与检修。     

EBH-120型掘进机回转台的设计与应力分析

对EBH-120型掘进机的重要部件回转台进行了结构设计,选择较小的径向滚动轴承和大型平面轴承相结合,将回转齿轮和平面止推轴承盘设计成整体结构,并经过对平面止推轴承盘的应力分析与校验,确定了其设计的合理性。     

基础隔震建筑中应用变刚度保护装置的地震反应分析

长周期的地面运动会使隔震建筑物发生类共振而导致隔震支座失稳破坏。在这种情况下,可以利用附加的弹簧改变建筑物的周期,减小隔震层的变形,使之限制在允许的范围内,同时使上部结构的层间剪力不明显增大。按照多质点结构分析模型推导了不发生附加、右侧附加、左侧附加弹簧的运动方程,编制了相应的分析程序。通过对模型实例分析,论证了变刚度保护装置在限制支座大变形中的作用,讨论了在工程设计中如何选取变刚度保护装置的适宜参数。     

隔震橡胶支座保护方法

在基础隔震建筑中 ,隔震橡胶支座保护上部结构 ,其自身也应该被保护而不发生失效。本文对隔震橡胶支座提出了三种保护措施 :软碰撞保护、变刚度保护和软着陆保护 ,并对工作原理进行了分析。     

屋盖结构柱顶隔震技术的研究

根据屋盖结构的特点,提出柱顶隔震技术;随之,建立串联弹簧模型理论用于初步确定隔震垫参数,再使用非线性动力时程分析法进行详细设计。算例表明,屋盖隔震技术不仅大大降低了屋盖本身的反应,也有效保护了柱和基础等下部结构,而且屋盖侧移和隔震垫变形正常,因此柱顶隔震技术应用于屋盖结构是可行的。     

Finite element analysis of the stability of multilayer elastomeric bearings

The stability of multilayer elastomeric bearings is considered within the framework of two-dimensional finite elasticity. For this purpose, simple constitutive equations which generalize those of a transversally isotropic linear elastic solid are considered. A finite element formulation is discussed which is capable of accounting for very general boundary conditions. For moderate deflections and classical boundary conditions this formulation leads to numerical results in close correspondence with those obtained by Haringx's one-dimensional treatment. It is shown that the presence of boundary conditions in the form of unilateral constraints explains a softening effect which has been experimentally observed during the testing of this type of composite column. Experimental results are also presented which indicate that this softening effect is not produced by a form of material instability. These experimental results provide further justification for the simple constitutive model adopted.     

铅芯夹层橡胶隔震垫基本力学性能研究

本文详细地研究了中国铅芯夹层橡胶隔震垫的基本力学性能。基本力学性能主要包括隔震垫的竖向、水平特性及极限承载能力。竖向性能方面研究了隔震垫的竖向刚度及变形特性;水平性能的研究包括水平有效刚度和阻尼特性;极限承载能力研究包括隔震垫的压缩破坏、拉伸破坏及水平剪切破坏性能。试验研究结果与中国《夹层橡胶垫隔震技术规程》(草案)(1998年)及日本隔震构造协会(1996年)颁布的标准进行比较,结果表明:中国生产的铅芯夹层橡胶隔震垫的基本力学性能完全符合中国和日本隔震协会所颁布的标准。