To reduce the herringbone gear transmission vibration and noise, an optimization design method about the meshing vibration of herringbone gear is provided with a controllable sixth-order polynomial function of transmission error. First, the polynomial coefficients of sixth-order polynomial function of transmission error curves can be determined by optimizing the aim at minimum root mean square value of herringbone gear meshing vibration acceleration based on loaded tooth contact analysis method and herringbone gear vibration model. Second, because of the existence of second-order frequency factors in the amplitude of loaded transmission error, the root mean square value of meshing vibration acceleration under the optimization of amplitude of loaded transmission error is worse than the value under the optimization of meshing vibration acceleration in resonant frequency. Third, a numerical simulation of example based on herringbone gear with different order transmission errors is performed, which proves tha...

https://journals.sagepub.com/doi/pdf/10.1177/1687814017704359

Design and analysis of herringbone gear with sixth-order transmission error based on meshing vibration optimization:

This paper is to analyze and identify damage in gear teeth and rolling element bearings by establishing pattern feature parameters from vibration signatures. In the present work, different damage scenarios involving different combinations of gear tooth damage, bearing damage are considered. Each of the damage scenarios are studied and compared in the time domain, the frequency domain, and the joint time-frequency domain using the FM0 technique, the Fourier Transform, the Wigner-Ville Transform, and the Continuous Wavelet Transform, respectively. Results obtained from the three different signal domains are analyzed to develop indicative parameters and visual presentations that measure the integrity and wellness of the bearing and gear components. The joint time-frequency domain obtained from the continuous wavelet transform has shown to be a superior technique for providing clear visual examination solution for different types of component damages as well as for feature extractions used for computer-based machine health monitoring solution.

/pdf/vibration-signature-analysis-and-parameter-extractions-on-4c26lesiit.pdf

Vibration Signature Analysis and Parameter Extractions on Damages in Gears and Rolling Element Bearings

Concrete arch dams have been widely constructed worldwide, and many of these dams are located in areas with high seismic activity. However, strong seismic loading poses a severe threat to concrete arch dams, and dams have the risk of suffering damage and the possibility of an ensuing dam break. In past decades, seismic and structural health monitoring has undergone rapid growth in the context of arch dams to track the operation state of arch dams under strong seismic loading. In fact, arch dams with damage caused by seismic loading normally exhibit nonlinear dynamic behaviors and time-variable dynamic properties. To effectively identify the structural damage state development of arch dams under seismic loading, an online damage identification method using a novel recursive time-variable autoregressive with exogenous (TVARX) input model was presented in this paper. To improve the tracking capability for the time-variable coefficients of the TVARX model, an adaptive adjustment algorithm of variable weighting factors was incorporated into the recursive least-squares method. In the proposed method, the predicted model residual, a damage index named the fit ratio (FR), the difference between fit ratios (DF), and a damage index based on the change in ARX model parameters (CH) were proposed to identify the presence of damage, damage area, and relative damage extent for arch dams. Eventually, the proposed approach was used for the online damage state identification of arch dams in a numerical simulation example and a shaking table test, and the identification results demonstrated the effectiveness of the proposed approach.

Online structural damage state identification of concrete arch dams under dynamic loads using a recursive TVARX approach

Friction and wear tests of a piston ring against the cylinder of a marine diesel engine were conducted on a pin-on-disc tester. The vibration signals under different wear conditions were studied utilizing the discrete harmonic wavelet packet transform (DHWPT). It was shown that the weak friction-induced vibration signals could be extracted using the DHWPT. When the wear behavior is mild, the friction-induced vibration is linear. When the wear behavior is relatively severe, the friction-induced vibration changes from linear to nonlinear. When the wear behavior is more severe, the friction-induced vibration is nonlinear.

Harmonic Wavelet Packet Analysis of Friction-Induced Vibration

In this paper, vibrations and acoustic emissions (AEs) of defective linear-guideway type recirculating ball bearings under grease lubrication were measured. The experimental results show that the vibration and AE amplitudes (the pulse amplitudes, the RMS values) of both the normal and defective bearings have a tendency to be reduced when a grease with higher base oil viscosity is used. Under the same type of grease, the RMS values of the vibrations and AE of the defective bearings increase as the defect angle increases. However, the increases of the RMS values due to increased defect angle are reduced when a grease with higher base oil viscosity is used.Copyright © 2010 by ASME

Effects of Grease Types on Vibration and Acoustic Emission of Defective Linear-Guideway Type Recirculating Ball Bearings

The main objective of this article is to identify single and multiple gear teeth damage based on vibration signatures analysis of experimental results and their comparison with those by numerical simulations. In this study, vibration signals are experimentally acquired for the case with no tooth damage to cases with multiple teeth damage using the controllable wear/damage gear sets in the 75-HP gear test rig. Vibration signatures for cases similar to the experimental studies are numerically simulated based on a two-spool rotor-bearing model connected by a set of meshing gears. The effects of the wear on the gear tooth surface are numerically represented by the phase change in the gear teeth mesh stiffness during both gear mesh engagement and disengagement. Results from both experimental studies and numerical simulations are examined and compared in the time domain, the frequency domain, and the joint time-frequency domain using the Wigner-Ville distribution (WVD). Based on results of this compara...

Identification of single and multiple teeth damage in a gear transmission system

To investigate the efficacy and value of optical genome mapping (OGM) in detecting chromosomal structural variations. In a clinical study about high-precision analysis of genomic structural variation for complex genetic diseases, a retrospective study was performed on the cases with karyotyping at the department of Obstetrics and Gynecology, and Endocrinology of Peking Union Medical College Hospital from January to December 2021. Ten cases with abnormal karyotype was detected by OGM. Partial cases were verified by fluorescence in situ hybridization (FISH), SNP array or CNV-seq. Results of ten cases, nine were detected with abnormality by OGM, including unbalanced chromosomal rearrangements (n=3), translocation (n=5) and paracentric inversion (n=1), and the results were in concordance with other standard assays. However, one case with breakpoint and reconnected at centromere has not been detected. In conclusion, ten samples were comprehensively analyzed by karyotyping, FISH, SNP array or CNV-seq, and OGM, and results demonstrated that optical genome mapping as a new technology can not only detect unbalanced rearrangements such as copy number variants as well as balanced translocations and inversions, but more importantly, it can refine breakpoints and orientation of duplicated segments or insertions. So it can contribute to the diagnosis of genetic diseases and prevent birth defect. However, the current technology is not yet capable of detecting breakpoints of balanced structural variations lying within unmapped regions.

[Efficacy and initial clinical evaluation of optical genome mapping in the diagnosis of structural variations].

Experimental Study of the Rheology of Cellulose Nanocrystals-enhanced C22-tailed Zwitterionic Wormlike Micelles

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Identification of single and multiple teeth damage in a gear transmission system

[Efficacy and initial clinical evaluation of optical genome mapping in the diagnosis of structural variations].

Experimental Study of the Rheology of Cellulose Nanocrystals-enhanced C22-tailed Zwitterionic Wormlike Micelles