Hysteretic damping characteristics of a mechanical tensioner: Modeling and experimental investigation

Author(s):  
Hao Zhu ◽  
Yumei Hu ◽  
Yangjun Pi ◽  
Weidong Zhu

The aim of this article is to investigate hysteretic damping characteristics of a typical tensioner used in engine accessory drive systems. An experiment device is developed to measure the friction coefficients of three contact pairs within the tensioner. Statistic results of test data show that the friction coefficient is linearly dependent on normal forces, and thus a linear function is used to describe it. An exact mathematical model and an accurate three-dimensional finite element model are proposed in this study to calculate the relationship of friction torque and rotation angle as well as the damping characteristics of the tensioner. The mathematical model and three-dimensional finite element model are verified through an experiment. Comparison indicates that both the mathematical and finite element model can accurately predict the working torque of the tensioner during operation process, while the finite element model has better accuracy in predicting the damping characteristics than the mathematical model.

Author(s):  
O. E. C. Prizeman ◽  
V. Sarhosis ◽  
A. M. D’Alri ◽  
C. J. Whitman ◽  
G. Muratore

Caerphilly Castle (1268-70) is the first concentric castle in Britain and the second largest in the UK. The dramatic inclination of its ruinous south west tower has been noted since 1539. Comparing data from historical surveys and a terrestrial laser scan undertaken in 2015, this paper seeks to review evidence for the long-term stability of the tower. Digital documentation and archival research by architects is collated to provide data for structural analysis by engineers. A terrestrial laser scan was used to create a detailed three dimensional finite element model to enable structural analysis of the current shape of the tower made by tetrahedral elements. An automated strategy has been implemented for the transformation of the complex three dimensional point cloud into a three dimensional finite element model. Numerical analysis has been carried out aiming at understanding the main structural weaknesses of the tower in its present condition. Comparisons of four sets of data: 1539, 1830, 1870 and 2015 enabled us to determine change albeit between very different methods of measurement.


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