共查询到19条相似文献,搜索用时 62 毫秒
1.
为了研究转子压缩机摩擦噪声的形成机理,基于摩擦耦合引起摩擦系统自激振动的理论,建立了全尺寸的转子式空调压缩机摩擦噪声的有限元模型,模型中的接触对有:曲轴与上下法兰接触形成主副轴承,曲轴偏心部与滚子接触形成轴颈轴承,曲轴下偏心部端面与下法兰接触形成止推轴承.定义各个接触对的接触属性为库伦摩擦.利用复特征值分析法研究了该系... 相似文献
2.
本文对刹车时发出的尖叫摩擦噪声的机理进行了研究。通过对不同工况下摩擦噪声及振动的测量和频谱分析,以及对刹车装置动力学模型的分析与研究表明:尖叫摩擦噪声是由摩擦引发的高频自激振动所致。同时还探讨了这种噪声产生的原因及不同工作条件对其影响的规律。 相似文献
3.
依据国标规定,对某车车内噪声进行测试。利用傅立叶变换对在不同转速工况下测得的噪声信号进行频谱分析,得到其关键频率。在对急加速工况分析的过程中发现虽然傅立叶变换可以分析出整体的变化规律,但不能得到其细节信息。由此采用小波分析对其进行补充,利用小波变换的“自适应变化”的时频窗结构得到信号的细节,并加以处理得到更多的频率信息。 相似文献
4.
5.
6.
7.
应用Olgac直接法对单自由度时滞摩擦噪声模型的稳定性进行了分析,建立了无摩擦尖叫噪声的稳定区域.对模型的自然频率、阻尼和接触摩擦综合系数对摩擦尖叫噪声的影响进行了数值分析.结果显示,摩擦力时滞的数值对摩擦噪声的发生有重要的影响.随着摩擦力时滞数值的增大,模型无摩擦噪声的稳定区和有摩擦噪声的不稳定区交替出现.模型的自然频率越高,就越容易发生摩擦噪声.模型的阻尼越小,也越容易发生摩擦噪声.模型的接触摩擦综合系数越大,也越容易发生摩擦噪声.对模型进行了非线性仿真分析,仿真结果显示,法向振动引起的接触分离是摩擦振动受限的一个非线性因素. 相似文献
8.
噪声(通俗地叫噪音)是最常遇到的音响系统问题之一,无论是在录音制作还是扩音演出等活动中,噪声无处不在,如何尽量减小和避免噪声的干扰,认识噪声的来源和解决方法又有哪些呢? 相似文献
9.
高速工况下,车内噪声信号具有随机性和波动性的特征。将一种基于经验模态分解(EmpiricalModeDecomposition, EMD)和反向传输(Back Propagation, BP)神经网络的算法,用于重构车内乘员耳侧噪声信号。首先通过对车内乘员耳侧噪声贡献量分析,确定关键噪声源信号;其次对选择的噪声源信号进行EMD分解,得到有限个相对平稳的固有模态函数(Intrinsic Mode Function, IMF)分量;然后采用极值点划分法,按各个分量的波动情况进行重新划分,将信号分量重构为高频、中频和低频3个分量;最后对不同频段的部分建立相应BP神经网络模型,并将不同频段分量的重构结果叠加作为原信号的重构结果。以在某轿车采集到的5个噪声信号源为基础,利用该方法进行乘员耳侧噪声信号重构,并对其进行分析。结果表明:提出的噪声重构方法可以实现高速工况乘员耳侧噪声信号的重构,并具有良好的性能。 相似文献
11.
12.
13.
Abstract: The dependability of railway points (turnouts or switches) is a key part of any railway system; the Potters Bar crash (10 May 2002) in the UK, which led to seven fatalities is a key example of a failure of this subsystem. Present maintenance of points involves overly frequent inspection by maintenance staff. A remote condition monitoring approach would lead to more efficient inspection routines and directed anticipatory maintenance trips. To assist the creation of a suitable fault-detection algorithm, the authors analysed existing force and current data for the 'as commissioned' case of a turnout and for situations with different fault conditions. Signal processing of this data revealed several different methods that can be used to distinguish between fully functioning points, and different fault conditions of the points. Specifically, clustering of statistical parameters and their application to wavelet levels and coefficients, provided clear discrimination of most critical faults. This demonstrates a good first step towards a condition monitoring-based maintenance regime for points that is both safer for passengers and maintenance personnel and that has the potential to be more effective and economical. 相似文献
14.
15.
The paper presents new approach to Barkhausen noise signal processing for detection of fatigue crack. Barkhausen noise signal from mild steel samples under axial fatigue is investigated using fractal signal processing, particularly wavelet variance method. Based on repeatability analysis new algorithm is developed and applied to acquired signals. The influence of fatigue on fractal characteristics of Barkhausen noise is analyzed. Signal analysis reveals significant and repeatable changes in wavelet variance, spectral parameter and estimated Hurst exponent just after crack initiation. The results demonstrate high potential of fractal analysis of Surface Barkhausen noise applied to fatigue crack initiation detection. 相似文献
16.
超声衍射时差(TOFD)方法因具有普通超声检测和射线检测的优点而被广泛应用于中厚板的焊缝检测与缺陷定量中。TOFD技术检测的是相对微弱、指向性差的衍射波信号,被检测材料所产生的结构噪声也会降低检测信号的信噪比,影响了TOFD检测的精度。将分离谱技术用于超声TOFD检测信号的处理,采用线性平均、极值阈值、极值阈值+最小值、最小值等四种恢复算法进行比较,并在最小值算法的基础上引入最小值选中次数加权算法恢复信号。结果表明:与传统的滤波方法相比,该方法能有效地提高了回波信号的信噪比,减小了TOFD检测中的缺陷定量误差。 相似文献
17.
18.
Digital image processing is a mechanism for analysing and modifying the image in order to improve the quality and also to manage the unwanted involvement of noises. In image processing, noise is characterized as an unwanted disturbance which occurs while capturing the actual image thus affecting the quality of the image. Hence, noise formation is considered as a perilous issue and the reduction of noise is considered as an awkward process. Nowadays, almost in all fields of science and technology, digital image processing is increasing rapidly, so there arises the need for de-noising to cure the noised image. The main objective of this paper is to overcome the issue of noise and also to increase the quality and pixel value of the image. An advanced methodology known as collaborative filtering and Pillar K-Mean clustering is discussed in this paper to overcome the abovementioned problem. Initially, distinct pure images are taken as the dataset and three types of noises are added to the corresponding image to make it as a noised one. Hence, the unspecified noise is resolved on the basis of a hybrid combination of algorithms of collaborative filtering with the image inpainting method. Sequentially, the low-density noises, such as random noise and poison noise, are recovered by the implementation of collaborative filtering, and the high-density salt and pepper noise are recovered by the image inpainting method. Based on the GLCM (Grey Level Co-occurrence Matrix) feature, the normal image and the noised image are used for the clustering process. Then the de-noised image is evaluated to find the efficiency on the basis of few parameters such as SNR (Signal to Noise Ratio), MSE (Mean Square Error), PSNR (Peak Signal to Noise Ratio) and SSI (Structural Similarity Index). Accordingly, the evaluated images are further withstood for clustering to differentiate the noises by applying the proposed clustering methodology. Then the evaluated images are verified on the basis of a few parameters such as Silhouette Width, Davies–Bouldin Index and Dunn Index. The proposed methodology is run on the platform of Mat Lab. Finally, the proposed methodology is considered as an efficient method for settling the issue in digital image de-noising. 相似文献