This Modal Analysis applications note was provided by our partners DEWESoft.
Introduction of Modal Analysis on a HEAD Tennis Racket
HEAD® is a leading global manufacturer of premium sports equipment. Their products are used by many top athletes.
During a tennis game, a tennis racket is exposed to vibrations. When we hit the tennis ball, the racket is excited and freely vibrates with its own frequency. Because of that, tennis racket manufacturers such as HEAD® have to monitor the frequency response of a racket and modify the structure in accordance with findings.
Measurement Set Up
To gather measurements to be used in their analysis, the HEAD®company is using an 8-channel SIRIUS DAQ device with 7 ACC modules (for accelerometers and impact hammer) and one MULTI module that is used as a function generator. They are using Dewesoft X2 software with a DSA package (Modal test) and FGEN option.
As illustrated below, the tennis racket is hanging in the air, attached with two thin strings.
The triaxial accelerometer is glued on the racket, measuring the vibrations in all three directions.
The racket is struck with a modal hammer on multiple points along its head.
Using the FGEN option in Dewesoft in MULTI module on SIRIUS, the shaker is excited for modal analysis.
Test are being conducted with a Photron SA3 highspeed camera with Photron plugin in Dewesoft.
For the analysis, HEAD® technicians are monitoring the frequency response spectrum (transfer functions) of all the points as well as the MIF (mode indicator function) function.
With the markers included in our Dewesoft functionality, it is easy to search for maximum peaks (amplitude) and their position in frequency domain. With modal circle visual control, the resonant peak can be examined in detail, offering a more exact measurement of the frequency and damping factor of the peakwith the circle fit procedure.
Geometric parameters of the racket is defined in the geometry editor (utilising a Cartesian Coordinate System) and can be animated at each frequency.
Results are compared with one of the most accurate finite element models on the market.
Another test involves a mobile data logger on the player. This is where the technicians import the TXT files and analyse them using Dewesoft to determine.
In conclusion, with monitoring the frequency response, the manufacturer can improve the tennis racket. By shifting the weight to where the user needs it the most for a faster game.
As displayed below, HEAD®’s most recent development is the new racket named GRAPHENE XT.
Therefore, for further information on the DEWESoft System, please contact us