A feasibility study was conducted to demonstrate that vibration control by confinement (VCC) is a viable approach to today’s noise and vibration problems. Two types of structures were examined. First, a finite beam carrying a critical component on one side and subjected to harmonic disturbances on the other side was simulated. In this part of the investigation, the vibration suppression criterion was to minimize vibrations transmitted to the critical component. The VCC approach was compared with current passive methods, such as tuned isolators, vibration absorbers, and two cases of layered damping. As the second example, a plate, resembling the panel section of a car door, was investigated. The plate was subjected to transient and harmonic excitations. The objective was to determine the degree of improvement on the effectiveness of layered damping materials when used in conjunction with VCC. The results of the computer simulation combining VCC with layered damping materials covering 100% and 63% of the plate were of interest in this study. The finite element method was used to model both structures. Results clearly show that VCC can be used as a stand-alone mechanism to suppress or isolate vibrations, or combined with layered damping materials to significantly improve performance. [Work supported jointly by QRDC, Inc., 3M, and the Department of Defense.]
The work reported in this paper is focused on an effective and efficient solution, namely Smart Isolation Mount for Army Guns (SIMAG), to the weapon stabilization and fire control issues facing U.S. Army guns. SIMAG is composed of the optimum integration of two innovative technologies, Vibration Control by Confinement and smart sensor/actuator/active control systems. The combined approach may a1o be applied to a gun barrel to reduce its undesired vibratory motions excited by external and internal disturbances, such as gun firing action. SIMAG reconfigures the distribution and propagation of excess vibration energy and confines vibrations to certain non-critical regions or modes within a structure. Concentrated passive, active, or smart damping elements or cancellation techniques may be applied to more effectively dissipate or cancel the trapped vibrations and to prevent an energy build up in the assembly. As the active elements, an array of collocated, PZT-based sensor-actuator sets is recommended for incorporation in SIMAG. Part of the active elements is used for spatially managing excess vibration energy while the other part is utilized for energy dissipation and cancellation. The preliminary results of our feasibility work on the SIMAG concept is demonstrated via computer simulations. It is shown that the insertion of a preliminary version of SIMAG in a 30mm gun system onboard an attack helicopter reduces the fluctuating loads and deformations measured across the helicopter bottom shell by 40 to 50%. SIMAG makes significant progress towards solving the firing control problems with affordable weight and power penalties by compensating for all errors in one of the two places, the turret-aircraft interface or gun barrel. Even though the initial target application of SIMAG is airborne guns, a modified version can be incorporated into ground armors, such as tanks and humvees.
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