Development of experimental vibro-acoustic transfer function for a system with combined rolling-sliding motion

2021 ◽  
Vol 263 (5) ◽  
pp. 1505-1515
Author(s):  
Kumar Milind Rewanand Shripad ◽  
Sriram Sundar
Keyword(s):  
Transfer Function ◽  
Noise Exposure ◽  
Acoustic Pressure ◽  
Acoustic Noise ◽  
Contact Forces ◽  
Sliding Contact ◽  
Direct Technique ◽  
Cam Follower ◽  
Acoustic Transfer Function ◽  
Contact Parameters

Combined rolling-sliding contact is present in popular non-linear systems such as cam-follower, gears, clutches, and brakes. These systems produce significant noise due to complex contact between the components during operation. The noise generated is a strong function of the contact parameters and excitation to the system. The objective of this study is to develop a transfer function to quantify the vibro-acoustic noise for various contact conditions. Acceleration, reaction forces, and acoustic pressure measurements are made on a cam-follower setup with combined rolling-sliding contact. Experiments are performed under different conditions of friction, lubrication, load, and speed. Contact forces are back-calculated using the kinematics. The transfer function relating the acoustic pressure to different forces is estimated. It is observed that the contact parameters govern the transfer function and hence the vibro-acoustic systems. The developed transfer function is useful in designing better sub-systems with combined rolling-sliding contact to reduce noise exposure, as a direct technique to relate the contact parameters to the noise does not exist. This study can be extended to other complex systems such as gears and clutches.

Study on Test Method of Interior Noise Caused by Body Panels

2013 ◽  
Vol 365-366 ◽  
pp. 650-653
Author(s):  
Hai He ◽  
Hong Zhou ◽  
Xiang Li
Keyword(s):  
Transfer Function ◽  
Sound Source ◽  
Sound Pressure ◽  
Acoustic Pressure ◽  
Test Methods ◽  
Test Method ◽  
Vibration Velocity ◽  
Acoustic Contribution ◽  
Acoustic Transfer Function ◽  
Vector Sum

This paper introduced four common test methods of acoustic contribution of body panels. The methods using PU sensor to array measure vibration velocity of body panels. Then, the vibration velocity of body panel multiplied by the area of panel to get the value of sound source intensity. Use reciprocity method to measure acoustic transfer function. In the experiment, the vector sum of the product of sound-source intensity and acoustic transfer function is used to compose the sound pressure contribution of the panels. The experiment proves that the composite value of acoustic pressure spectrum of drivers right ear coincide with the measured value. Therefore, this method is proved to be valid.

The elastic contact influences on passive walking gaits

Robotica ◽  
2010 ◽  
Vol 29 (5) ◽  
pp. 787-796 ◽  
Author(s):  
Feng Qi ◽  
Tianshu Wang ◽  
Junfeng Li
Keyword(s):  
Coulomb Friction ◽  
Dynamic Models ◽  
Contact Stiffness ◽  
Contact Forces ◽  
Hertz Contact ◽  
Walking Gait ◽  
Routes To Chaos ◽  
Coulomb Friction Law ◽  
Contact Parameters ◽  
Passive Model

SUMMARYThis paper presents a new planar passive dynamic model with contact between the feet and the ground. The Hertz contact law and the approximate Coulomb friction law were introduced into this human-like model. In contrast to McGeer's passive dynamic models, contact stiffness, contact damping, and coefficients of friction were added to characterize the walking model. Through numerical simulation, stable period-one gait and period-two gait cycles were found, and the contact forces were derived from the results. After investigating the effects of the contact parameters on walking gaits, we found that changes in contact stiffness led to changes in the global characteristics of the walking gait, but not in contact damping. The coefficients of friction related to whether the model could walk or not. For the simulation of the routes to chaos, we found that a small contact stiffness value will lead to a delayed point of bifurcation, meaning that a less rigid surface is easier for a passive model to walk on. The effects of contact damping and friction coefficients on routes to chaos were quite small.

Numerical simulations of flow induced noise from a dual rotor cooling fan used in electronic cooling systems

2021 ◽  
Vol 263 (5) ◽  
pp. 1308-1319
Author(s):  
Sahan Wasala ◽  
Yutong Xue ◽  
Lon Stevens ◽  
Ted Wiegandt ◽  
Tim Persoons
Keyword(s):  
Noise Exposure ◽  
Acoustic Noise ◽  
High Capacity ◽  
Disk Drive ◽  
Air Cooling ◽  
Noise Sources ◽  
Cooling Systems ◽  
Cooling Fan ◽  
Flow Induced Noise ◽  
High Level

Hard Disk Drive (HDD) system enclosures in a data center require effective cooling systems to avoid HDD overheating. These systems often rely on air cooling because of their cost effciency and maintainability. Air cooling systems typically consist of an array of axial fans which push or pull the air through the system. These fans emit high level tonal noise particularly at high tip speed ratios. High-capacity HDDs, on the other hand, are sensitive to high acoustic noise, which consequently increases the risk of read/write error and deteriorates drive performance. Therefore, cooling fan noise adversely affects the function of the HDD enclosure systems which emphasizes the need to understand the noise sources and develop methods to mitigate HDD noise exposure.

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