Scale-induced effects on fatigue properties of a cast steel for bogie frames of China railway rolling wagons

A new method is suggested for measuring scale-induced effect on fatigue properties of grade B cast steel for fabricating bogie frames of China railway rolling wagons. One grouped material and three grouped structure-like specimens are machined and fatigued under same stressing amplitude with scale kinetics. Fracture surface observations reveal that fatigue cracks are initiated from weakest material cast shrinking cavity or hot tear. There are distinct fatigue striations, river-like flowers, and second cracks in perpendicular to the fatigue crack growth path on fracture surfaces. Lots of dimples appear in transient fracture zone to indicate a ductile fracture. And more dimples appear for material specimens. The effect is statistically assessed on a phase of specified fatigue strength by comparing random fatigue lives. Interactive effect of the scale and surface quality are taken into account involving in scale change. And then, this effect is extensively employed to cover entire fatigue strength range and, additionally, to address structural scale kinetics.     

Comparison for the crystal structure,synthesis and microwave dielectric properties of alkaline earth orthophosphates

A₃(PO₄)₂ compounds have different crystal structures when A sites are occupied by Ca or heavy alkaline earth metal atoms (Sr or Ba). The compounds with isomorphous crystal structure were synthesized by solid-state reaction method when the A-site atoms were Sr or Ba, and their crystal structure and microstructure of the sintered ceramics were investigated by X-ray powder diffraction (XRD) and scanning electron microscope (SEM), respectively. The microwave dielectric properties were measured using a network analyzer. It was found that Ba₃(PO₄)₂ could be sintered at 1060 °C, while the α-Sr₃(PO₄)₂ ceramics that has a smaller Sr²⁺ ionic radius, could be sintered at 1200 °C, and higher relative densities were obtained. The dielectric constant (?) of the α-Sr₃(PO₄)₂ is higher than that of Ba₃(PO₄)₂, but Ba₃(PO₄)₂ has a higher Q × f value than that of β-Ca₃(PO₄)₂ and α-Sr₃(PO₄)₂, which could be interpreted by the differences in ionic polarizability and bond strength. The temperature coefficients of resonant frequency (τ_f) for all samples with isomorphous crystal structure have positive values, ranging between +11 and +66 ppm °C⁻¹.     

基于H_∞滤波的电液伺服控制系统鲁棒观测器设计

为了更好地实现电液伺服控制系统的故障诊断,提出一种新的鲁棒状态观测器的设计方法。简化电液伺服控制系统的流量非线性方程,建立系统的线性定常模型;考虑过程噪声与测量噪声,设计系统的鲁棒观测器结构;并运用H∞滤波理论确定观测器设计的性能指标,求解系统的矩阵Riccati方程,计算观测器的反馈增益矩阵。设计实例表明,该方法不仅计算简便、易于工程实现,而且能限制噪声干扰对观测误差的影响。     

ZG230-450铸钢的疲劳可靠性设计Goodman-Smith图

研究铁道车辆ZG230-450车轮铸钢疲劳可靠性设计Goodman-Smith图的绘制方法.图中疲劳寿命单位采用循环数或车辆行驶里程万公里,疲劳强度由中-短与长寿命范围的概率疲劳S-N曲线确定,图中转折点坐标与设计判据采用全概率模式求解.应用文中方法可获得任意可靠性水平下ZG230-450铸钢中短与长寿命范围的疲劳可靠性设计Goodman-Smith图.     

遗传算法和支持向量机在机械故障诊断中的应用研究

提出一种基于遗传算法和支持向量机的故障诊断方法,利用遗传算法对故障特征集和支持向量机的参数同时进行优化,然后把优化选择的故障特征输入支持向量机进行故障识别.既剔除了故障特征的冗余性、减少了计算量,又解决了支持向量机的参数难以选择等问题.诊断实例表明,该方法能利用较少的故障特征得到较高的诊断精度.     

应变疲劳可靠性理论与方法的新进展

介绍概率应变疲劳试验法、评价模型和损伤随机演化机制方面的新进展。突破经典极大似然法在参考试验载荷之外的单试样限制，提出新的广义极大似然疲劳试验法。新发现随机循环应力—应变响应现象并建立其概率模型。新发展概率疲劳应变一寿命模型。概率模型参数由称为广义极大似然法的方法确定，在整体数据层面综合考虑数据分散性规律与样本量对概率评价的影响。考虑随机应力—应变关系反映“随机应变载荷”、随机应变—寿命关系揭示材料的“应变强度”，提出随机应变载荷—强度干涉恒幅可靠性模型，与Keciguliu的递推法结合可进行变幅和应变载荷谱下的可靠性分析，形成了应变疲劳可靠性理论和方法的新体系。进一步根据有效短裂纹准则，揭示疲劳性能随机及演化性的本质原因源于主导有效短裂纹萌生区域及其裂尖区域微观结构扩展条件的差异及演化性；随机疲劳裂纹扩展、应变—寿命和应力—应变关系是3个关联的随机疲劳关系；疲劳损伤是一个由初始混沌状态，到独立无关的随机状态，然后到史相关随机状态的演化过程。     

基于BP网络锌窑渣、水解渣共同熔炼预测系统的研究

本文提出一种基于生产实践样本数据、BP神经训练和嫁接网络对锌窑渣、水解渣共同熔炼进行预测的模型。10组数据所构建的9-16-13-8BP神经网络训练模型,是以锌窑渣、水解渣中各成分作为输入参数,冰铜、烟尘和水淬渣相应成分作为预测目标。建立输入参数和预测目标之间的模拟关系,训练误差为10-4。预测网络是采用训练网络权值、阈值,和相同设计参数,在Matlab的GUI可视化界面中输入各成分的含量,实现各元素成分的预测,误差为10-4,人机交互性强。     

Review:Development of SARS-CoV-2 immuno-enhanced COVID-19 vaccines with nano-platform

Vaccination is the most effective way to prevent coronavirus disease 2019(COVID-19).Vaccine development approaches consist of viral vector vaccines,DNA vaccine,...     

PW200转向架的概率疲劳强度

以包含长寿命范围在内的16MnR钢焊接接头和ZG25钢概率延拓S-N关系为基础，得到材料疲劳强度分布。针对考察的PW200转向架不同关键部位，分别选取适当的表面加工系数、尺寸系数，获得转向架结构细节综合影响系数。在此基础上，通过对材料疲劳强度进行修正，获得转向架各部位的概率疲劳强度，为转向架的疲劳可靠性分析提供参考。     

Effects of polydopamine modification on self-grown CuO cube anodes in lithium-ion batteries

We report the synthesis of Cu O cubes with well-defined size and shape by thermal treatments of Cu2O cubes.Polydopamine(PDA)is introduced to modify the Cu O cubes by the in-situ polymerization of the dopamine precursor.The initial specific capacity of the lithium-ion batteries using the Cu O cubes as anodes increases about 10 times at a 0.5 C rate as a result of the modification of PDA.The overall specific capacity for 100 cycles also increases effectively due to the introduction of PDA.So PDA as surface modifying agent significantly improves the electrochemical performance of the Cu O anodes.