Frequency weighting filter design for automotive ride comfort evaluation

Few study gives guidance to design weighting filters according to the frequency weighting factors,and the additional evaluation method of automotive ride comfort is not made good use of in some countries.Based on the regularities of the weighting factors,a method is proposed and the vertical and horizontal weighting filters are developed.The whole frequency range is divided several times into two parts with respective regularity.For each division,a parallel filter constituted by a low-and a high-pass filter with the same cutoff frequency and the quality factor is utilized to achieve section factors.The cascading of these parallel filters obtains entire factors.These filters own a high order.But,low order filters are preferred in some applications.The bilinear transformation method and the least P-norm optimal infinite impulse response(IIR) filter design method are employed to develop low order filters to approximate the weightings in the standard.In addition,with the window method,the linear phase finite impulse response(FIR) filter is designed to keep the signal from distorting and to obtain the staircase weighting.For the same case,the traditional method produces 0.330 7 m · s~(–2) weighted root mean square(r.m.s.) acceleration and the filtering method gives 0.311 9 m · s~(–2) r.m.s.The fourth order filter for approximation of vertical weighting obtains 0.313 9 m · s~(–2) r.m.s.Crest factors of the acceleration signal weighted by the weighting filter and the fourth order filter are 3.002 7 and 3.011 1,respectively.This paper proposes several methods to design frequency weighting filters for automotive ride comfort evaluation,and these developed weighting filters are effective.     

FRFT在转子起停车状态评估中的应用研究进展

转子起停车过程中由传统的等时间间隔采样所获得的机械动态信号已不再保持原有的周期特性,采用经典的基于傅里叶变换的谱分析方法进行信号处理不再有效。针对转子起停车状态评估中幅值、频率的非平稳特性所带来的问题,引入分数阶傅里叶变换研究了基于起停车信息的故障定性分析和定量识别方法,提出了基于分数阶全息原理的转子起停车故障特征提取方法,并在此基础上实现了基于分数阶主分量原理的转子故障特征模式定量分类。实验验证表明,该方法解决了转子起停车过程中瞬变信息的获取问题,能有效提取出起停车过程振动信号中的典型故障特征,可以实现对转子不同故障类型及不同故障程度的准确分类。     

基于深度学习特征匹配的铸件微小缺陷自动定位方法

针对射线实时成像检测中精密铸件微小缺陷自动定位的需要,提出一种基于深度学习特征匹配的铸件缺陷三维定位方法。模拟选择注意机制的中央-周边差算法,提出以视觉显著度为尺度,从射线图像复杂背景中检测出微小缺陷及其区域,以定义的区域中央点为待匹配点;然后,提出构造深度卷积神经网络自动提取微小缺陷区域的深度学习特征,通过深度学习特征矢量的相似度,实现在不同视角下投影图像中的同一微小缺陷点的自动匹配;最后,基于平移视差测距原理计算缺陷匹配点的三维空间坐标。实验表明,基于深度学习特征匹配的方法能够正确搜索平移前后投影图像中的同一缺陷点,以此为基础,利用视差测距原理实现了微小缺陷匹配点的自动准确定位,深度定位误差小于5.52%,能够满足对精密铸件微小缺陷智能评判的需要。     

Measurement of 900 °C Isothermal Section in the Mo-Ni-Zr System

The isothermal section of the Mo-Ni-Zr system at 900 °C was investigated by characterization of eighteen equilibrium alloys. Electron probe microanalysis (EPMA) and x-ray diffraction (XRD) were used to identify the phases and obtain their compositions. The existence of two ternary compounds, Zr₆₅Mo_18?x Ni_16.5+x (τ₁, cF96-Ti₂Ni) and Zr₆₅Mo_27.3Ni_7.7 (τ₂, hP28-Hf₉Mo₄B), was confirmed in the Zr-rich corner, and the compositions of the two phases were determined. The isothermal section of the Mo-Ni-Zr system at 900 °C consists of 15 three-phase regions and 29 two-phase regions. The following three-phase equilibria were well established: (1) (Ni) + Ni₇Zr₂ + Ni₅Zr, (2) MoNi + MoNi₃ + Ni₇Zr₂, (3) Ni₇Zr₂ + MoNi + (Mo), (4) (Mo) + Ni₇Zr₂ + Ni₃Zr, (5) (Mo) + Ni₃Zr + Ni₂₁Zr₈, (6) (Mo) + Ni₂₁Zr₈ + Ni₁₀Zr₇, (7) (Mo) + Ni₁₀Zr₇ + NiZr, (8) (Mo) + Mo₂Zr + NiZr, (9) NiZr₂ + Mo₂Zr + τ₁, (10) τ₁ + Mo₂Zr + τ₂, (11) τ₂ + Mo₂Zr + (Zr)ht, (12) NiZr₂ + τ₁ + (Zr)ht and (13) τ₁ + τ₂ + (Zr)ht. Several binary phases, such as MoNi₃, Ni₇Zr₂ and Mo₂Zr, dissolve appreciable amount of the third component.     

Ultra-high strength Mg-9Gd-4Y-0.5Zr alloy with bi-modal structure processed by traditional extrusion

It is usual to observe that multi-scale structures can lead to combined strength and ductility both in aluminum alloys and steels, but related research has been seldom reported yet in magnesium alloys. In this study, applying traditional one step extrusion, we have successfully obtained a bimodal (Mg-9Gd-4Y-0.5Zr) alloy capable of ultra-high strength. The characterized sample reveal a bi-modal microstructure with two constitutions, i.e. stretched coarse-grain region with strong basal fiber texture and recrystallization fine-grain region. The bi-modal structured sample exhibit excellent mechanical properties with an ultimate strength 508 MPa and elongation 8% via 400 °C extrusion and subsequently 200 °C-60 h peak aging process. Ultra-high strength can be attributed to its strong extrusion texture in stretched coarse grains and dispersed nano-scale precipitates. This unique bimodal structure could be produced easily by one step extrusion, which is quite reliable and low costs in industrial applications of magnesium alloys with ultra-high strength as well as ideal ductility.     

Oxidation and Hot Corrosion Behavior of Plasma-Sprayed MCrAlY–Cr<Subscript>2</Subscript>O<Subscript>3</Subscript> Coatings

The oxidation and hot corrosion behavior of two atmospheric plasma-sprayed NiCoCrAlY–Cr₂O₃ and CoNiCrAlY–Cr₂O₃ coatings, which are primarily designed for wear applications at high temperature, were investigated in this study. The two coatings were exposed to air and molten salt (75%Na₂SO₄–25%NaCl) environment at 800 °C under cyclic conditions. Oxidation and hot corrosion kinetic curves were obtained by thermogravimetric technique. X-ray diffraction analysis and scanning electron microscopy with energy-dispersive x-ray spectrometry were employed to characterize the coatings’ microstructure, surface oxides, and composition. The results showed that both coatings provided the necessary oxidation resistance with oxidation rates of about 1.03 × 10^?2 and 1.36 × 10^?2 mg/cm² h, respectively. The excellent oxidation behavior of these two coatings is attributed to formation of protective (Ni,Co)Cr₂O₄ spinel on the surface, while as-deposited Cr₂O₃ in the coatings also acted as a barrier to diffusion of oxidative and corrosive substances. The greater presence of Co in the CoNiCrAlY–Cr₂O₃ coating restrained internal diffusion of sulfur and slowed down the coating’s degradation. Thus, the CoNiCrAlY–Cr₂O₃ coating was found to be more protective than the NiCoCrAlY–Cr₂O₃ coating under hot corrosion condition.     

Synthesis and dynamic mechanical study of core–shell structure epoxy/polyacrylate composite particle

A material with high damping property and based on epoxy/polyacrylate (EP/PA) composite particles was synthesized by two-stage emulsion polymerization. Transmission electron microscopy (TEM) showed that the composite particles have a spherical morphology, a core–shell structure and a diameter of 100 nm–130 nm. Fourier transform infrared spectra (FTIR) indicated the cross-linking between EP groups in the core layer and carboxyl groups in the shell layer of the composite particles during film formation. The cross-linking reaction improved the dynamic mechanical property by the interaction of core and shell polymers. The effects of the cross-linking agent and ratio of the two polymers on the damping capacity were studied by dynamic mechanical analysis (DMA). DMA results revealed that a certain amount of acrylic acid could markedly enhance the loss factor (tan δ) and slightly widen the damping temperature range. When the EP/PA ratio was 1:7, peak values for tan δ of the composite materials could reach 2.10, exceeding the value for most damping materials. The result implies that the EP/PA composites have great potential application in damping steel surface coatings.     

Dynamic analysis for the energy storage flywheel system

A subcritical or supercritical rotor is often employed to improve the energy storage efficiency of flywheel systems. Consequently, it is necessary to introduce Squeeze film dampers (SFD) in the rotor-bearing system to suppress the lateral vibration of the rotor. Although the dynamic behavior of the rotor-bearing system can be investigated in a timely manner with ANSYS software, it is difficult, if not impossible, to directly solve the unbalance responses by the Full method (FM) offered by ANSYS package. The reason is because the stiffness and the damping coefficients of the SFD, which are required in the computation, are in fact functions of eccentricity ratio determined by the unbalance responses. In this paper, the model of the flywheel system was firstly analyzed by QR damped method. Campbell diagram and critical speeds were then obtained from the results. Natural frequencies and their corresponding mode shapes at the rotational speed of 0.1rad·s^-1 were also calculated. Then, the unbalance responses of rotor-bearing system with SFD support were solved through iteration and through the FM with ANSYS Parametric design language routine. The comparison between the calculated unbalance responses and the experimental responses indicates that the dynamic model is valid.