VISCOELASTIC MATERIAL SELECTION
The viscoelastic material requirements of the TVA are much different than the viscoelastic material requirements of a surface damping treatment. For example, the inherent damping of the material is usually required to be much lower. Also, in order to ensure that the TVA remains tuned across broad temperature ranges at the application site, it is very desirable that the viscoelastic material has very stable modulus relative to temperature and frequency.
HISTORY AND COMPLICATIONS OF TVA DESIGNS
TVA designs have been utilized for many years in noise and vibration applications. Conceptually, it is a very simple approach. However, with most of these old designs there were numerous problem associated with production of the TVA such that frequency tolerances were unacceptably high. This generally rendered the countermeasure as non-feasible for the production-environment. Often, a provision was built into the design to "tune" the TVA by applying static prestrain to the viscoelastic material, thereby varying its stiffness. Our experience with these designs has been that the long-term time domain variation in modulus as a function of static prestrain (relaxation effects) can cause the TVA to be mis-tuned after some time. In addition, this approach can result in variability of the inherent damping of the viscoelastic material, since loss factor will typically vary as a function of static prestrain. Finally, this approach incurred extreme expense via the necessity to tune each-and-every TVA by hand. Again, under these circumstances, the net results were that the TVA approach was rendered unacceptable for a cost and production standpoint.
TVA FABRICATION AND MATERIAL PROCESSING
Damping Technologies, Inc. has developed proprietary processing techniques to eliminate the concerns described above regarding TVA designs. Damping Technologies has demonstrated the capability to design and produce TVA assemblies to within (1%) to (2%) of the target tuning frequency. This capability has enabled TVA designs to become a powerful tool in the menu of noise/vibration countermeasures.
ENVIRONMENTAL EXPOSURE ISSUES
Correctly designing a TVA is only the first step in successful implementation of the design. The TVA must be produced repeatably, with quality control, and it must also survive the environment to which it is exposed. Damping Technologies can specify its TVA designs for applications periodically exposed to very harsh environments such as:
Damping Technologies has experienced structural dynamics engineers on staff who are available to review your particular noise/vibration issue for TVA applicability. Damping Technologies has a full structural dynamics experimental laboratory which can be utilized for design and development support. The keys to a successful implementation of the TVA countermeasure include: