In a recent paper by E. Esmailzadeh and N. Jalili the design of optimal vibration absorbers for Timoshenko beams was discussed. While the paper is interesting, the solution seems to be questionable, because it does not satisfy the governing differential equation of motion. There has been no reference made to the corresponding experimental results, or results obtained through the application of other analytical methods. Therefore, the application of the results presented in the paper seems to be misleading.
The method used in the paper for generating a solution for the optimal design of vibration absorbers for Timoshenko beams, is questionable. The assumption of same modal amplitudes for deflection and section rotation results in a severe contradiction. Since the results obtained by the application of this method have not been compared with any other method or experimental data, one cannot rely on the results presented in the paper.