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《稀有金属材料与工程》2021,(2)
航空/航天器、汽车、轮船等工程设施在服役过程中受到其他物体的冲击时,造成的损伤会引起构件的失效甚至会造成灾难性事故,如何采取有效的措施监测和评定这类活性冲击损伤至关重要。为了实现实时、准确地定位工程结构中的冲击损伤,提出了一种基于扫描式激光多普勒测振仪(SLDV)的非接触式冲击损伤定位方法。将希尔伯特黄变换(Hilbert-Huang transform, HHT)应用于信号处理中,得出最佳响应频率谱,将分离出的本征模函数(IMF1)用于幅值全加和幅值全乘的圆轨迹定位成像中。实验结果表明,HHT方法可用于实现复合材料的非接触式冲击损伤定位中。 相似文献
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为了应对空间碎片的威胁,研制了一种基于声发射技术的用于实时监测空间碎片撞击航天器的在轨感知系统。对平面声发射源精确定位技术提出了需求。声发射信号属于非平稳随机信号,传统的小波变换无法充分获得其中携带的信息。利用HHT技术分析声发射信号波形,改进了AO模态到达时刻的确定算法,提高了线定位精度。在此基础上,将平面定位问题转化为求取函数最小值的优化问题,并利用单纯形法进行求解。在铝合金板上对铅芯折断波源进行了定位试验,结果表明,相对于小波变换,HHT更适于分析声发射信号;改进后的线定位方法和双时标法可有效应用于各向同性板的定位问题。研究结果为空间碎片在轨感知系统的研制提供了参考。 相似文献
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希尔伯特-黄变换能精确描述信号频率和幅值随时间的变化,高阶累积量可以自动地抑制高斯背景噪声。为正确分析机械故障领域所采集的信号,将高阶谱和HHT的优点有机结合,通过EMD分解得出三阶累积量的各个本征模态函数分量,通过Hilbert变换得出相应的时频特性曲线和幅频特性曲线,并根据幅频特性曲线进行故障诊断,然后将诊断结果和原始信号进行比较。比较结果表明,基于高阶累积量和HHT的机械故障诊断方法是可行的和必要的。 相似文献
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针对磁控焊缝跟踪信号的非线性不平稳特点,提出了一种基于Hilbert-Huang变换和Cohen核的磁控电弧传感器焊缝跟踪系统的信号提取分析方法;运用经验模态分解,把周期激励下磁控跟踪信号分解成多个从高频到低频的本征模态函数分量,依据各分量的Hilbert边际谱,采用Cohen核分布的时频变换,能有效抑制交叉项,提取出磁控焊缝跟踪实时信号动态规律. 结果表明,利用此方法有助于更深入地揭示焊缝自动跟踪系统内各种干扰源的时频和频谱特征,为建立有激励源的焊接信号新的非线性模型提供了理论依据. 相似文献
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精确测量空间自由曲面的传统方法是采用三坐标测量机的接触测量或简单的非接触测量,这些测量方法存在工作效率低,自动化程度低等缺点。在深入研究上述方法的基础上,提出了一种自由曲面的非接触自动测量方法,介绍了测量系统的构成,曲面边缘的提取,自动扫描方式的规划以及测头跟踪方式等设计要点。 相似文献
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本文是基于555定时器双稳态触发电路和双向晶闸管组成的电动机无触点开关控制电路,利用双稳态触发电路输出的两种稳定状态(高电平和低电平),通过继电器控制双向晶闸管的通断,实现电动机的启动、停止控制和断相、过载保护。 相似文献
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ZHANG Z Y M. O. W. Richardson 《中国有色金属学报》2004,14(Z2):150-154
Barely visible impact damage (BVID) is developed when polymer matrix composites are subjected to impact loading. The damage has an adverse effect on structural integrity, and potentially leads to catastrophic failure.Thus it is important to employ a variety of advanced non-destructive testing (NDT) techniques in parallel to unambiguously determine the integrity of composite systems. This study deals with damage evaluation using visual inspection, ultrasonic C-scan, electronic speckle pattern interferometry (ESPI), electronic shearography (ES) and optical deformation and strain measurement system (ODSMS). Internal damage was introduced using an instrumented falling weight impact test (IFWIT) machine by controlling the combination of striker mass and releasing height. It was found that different NDT techniques were successfully employed to identify and visualise the impact induced internal damage. Experimental results generated from these techniques show a good agreement in damage identification and determination. The features, capabilities and limitations associated with these techniques were briefly discussed. 相似文献
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Transient thermography (TT) images of impact damaged 3.44, 8.66 and 13.76 mm thick composites, from the impact face and rear face, are compared with the corresponing ultrasonic c-scan (UCS) images. Comparisons of apparent delamination area and size were made using novel image analysis techniques. The defect image sizes were also compared with crack lengths obtained from a selected number of specimens that were sectioned. For all composite thicknesses, the UCS damage areawas proportional to the impact energy. The damage area obtained by TT from the front faces of the specimens did not correlate to the UCS damage areas although there was a correlation for the rear face damage on 3.44 and 6.88 mm thick specimens. Crack lengths obtained from sectioning showed that UCS damage length was equal to the maximum crack length and back and front sub surface cracks corresponded to back and front TT images. 相似文献
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采用专用工件进行切削实验,借助三维受力分析仪和热成像仪分别采集机械和热冲击载荷,从而揭示刀片断裂行为产生的规律;通过电子显微镜观测刀片断口亚微观形貌特征,从而研究刀片破损失效机理;通过将切削速度和进给量进行区域性划分,明确硬质合金刀片安全切削的参数区域。研究数据可为硬质合金刀片的设计以及切削参数的选择提供方法、数据和理论支撑。 相似文献
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《中国有色金属学会会刊》2021,31(12):3929-3942
To evaluate the quality and damage condition of the electrolyzer, wave velocity detection technology and impact echo technology were used to detect the cathode part of the electrolyzer. The experimental results show that wave velocity is linearly related to the porosity, and there is also a linear relationship betweenwave velocity and the square root of reciprocal density in cathode carbon blocks (CCBs) before installation into electrolyzer. Combined with detection results of wave velocity and voltage drop, the large-size CCBs with relatively good quality can be found. Through the impact echo technology on cathode steel rods (CSRs), the results of the on-site detection show that the damage condition of CSRs can be effectively evaluated, and the damage location of CSRs can be determined. This study proposes a novel and quantifiable method for the evaluation of cathode quality and damage, which provides a reference for prolonging the service life of the electrolyzer. 相似文献
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基于连续损伤力学(CDM)的经典损伤理论和不可逆热力学原理,分别对高周和低周疲劳载荷下的损伤演化模型进行了研究,进而推导出一个新的高低周复合疲劳损伤模型;将该模型编写为UMAT耦合到ABAQUS有限元分析软件中,实现了对缺口材料高低周复合疲劳损伤的模拟及裂纹萌生位置和萌生寿命的预测;同时研究了不同的高低周循环比对裂纹萌生寿命的影响.结果表明,裂纹容易在缺口根部应力集中处萌生;该模型考虑了高低周循环的交互作用,模拟计算结果更符合实际情况;同时通过研究发现高的循环比会使裂纹的萌生加速. 相似文献
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以Lee多孔材料屈服模型为基础 ,并假设空穴密度积累到一临界值时 ,材料出现裂纹 ,推导出适用于多孔材料的韧性损伤模型。该模型描述了在应力、应变、密度分布及其积累因素影响下 ,材料的损伤状态。使用该模型可以跟踪整个加载过程中多孔材料各点的损伤状况和破裂过程。 相似文献