NDTnet 1998 Aug, Vol.3 No.8

Abstract

The real piano hammer is a rather complicated object. The relationships of dynamic force versus hammer deformation show the significant influence of hysteresis characteristics, so the loading and unloading of the hammer are not alike. Furthermore, the force-compression characteristics of the hammer are essentially nonlinear, and the slope of the dynamic force-compression characteristics is strongly dependent on the hammer velocity. The model of the hammer that takes into account all the dynamical features of the hammer and used the real hammers' parameters that are independent on the hammer velocity was derived in the article: A. Stulov, "Hysteretic model of the grand piano hammer felt", J. Acoust. Soc. Am. v. 97 (4), 2577-2585,1995. According to this model the piano hammer possesses history-dependent properties or just, in other words, is made of the material with memory. In this case two additional hereditary parameters are involved to describe the hysteretic behaviour of the hammer.

The unknown elastic and hereditary values of the hammer parameters were obtained by means of numerical simulation of the dynamical experiments. In these measurements the hammer struck the piece of string fixed on the force sensor, and the force compression relationships of the hammers were obtained. The mathematical model of this experiment was run again and again, each time with different values of hammer parameters, until the prediction from the model gave good agreement with the experimental data.

The hysteretic model is a very powerful instrument as for the piano hammers matching, and for their manufacturing. By numerical simulation of the hysteretic model it is possible to calculate the hammer parameters that provide the needed spectrum of the string vibrations. On the other hand, the numerical simulation of the hysteretic hammer model may significantly simplify the process of the good hammers manufacturing. By means of the dynamical experiments it is possible to find the dependencies of the hammer parameters on the technological conditions during their manufacturing. The combination of the experimental piano hammer testing and the hysteretic hammer model together is the good practical way to improve the hammer quality and thus. the piano voicing.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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