The present invention refers to a mass damper for reducing vibrations of a structure with a pendulum mass and a damping means, wherein the mass damper has at least three bearings with which the pendulum mass is movably supported on the structure such that it can execute pendulum movements and each of the bearings has at least one pendulum plate with a concave bearing surface and a sliding shoe arranged movably thereon with a convex counter surface. In accordance with the invention, the bearing surfaces and the associated counter surfaces are curved with a constant radius of curvature R and all bearings have a lowest possible friction between the counter surface and the bearing surface. The invention also extends to a structure with such a mass damper and a method for adjusting the natural frequency of a mass damper, in which the natural frequency of the pendulum mass can be adjusted independently of one another in both main directions by displacing and/or rotating the pendulum plates. The invention also extends to the damping means, which can be implemented with linear viscous passive damping, with square viscous passive damping or with controlled damping, in order to tune this damping together with the friction damping of the bearings to the optimum damping of the mass damper.

An aircraft comprises an aircraft component, a sensor, and a multiple frequency vibration absorber (absorber). The sensor is operable to detect a frequency of a vibration of the aircraft component. The absorber is coupled to the aircraft component and configured to absorb the vibration. The absorber comprises a beam element, a fluidic flexible matrix composite (FFMC) tube, a valve, and a controller. The beam element is attached to the aircraft component. The fluidic flexible matrix composite (FFMC) tube is coupled to the beam element and is operable to absorb the vibration based on a stiffness of the FFMC tube. The valve is fluidically coupled to the FFMC tube and is to control the stiffness of the FFMC tube based on regulating a flow of a liquid through the FFMC tube. The controller can actively control absorption of the vibration via the FFMC tube based on opening and/or closing the valve.

A wind tunnel sting comprising a support member and a wind tunnel sting damper. The support member having a first support-member end configured for coupling with a wind tunnel, and a second support-member end configured for coupling with a balance. The wind tunnel sting damper having a reactive member, and a viscoelastic member disposed between the reactive member and the support member wherein, the reactive member is sized relative to the support member so as to radially compress the viscoelastic member against the support member.

There is provided a device for mitigating physical shock to an object to which it is attached. The device includes a body having a through-bore extending from one end to another. A sliding mass is positioned within the bore hole such that it can slide within the through-bore. A first end cap is slidingly disposed in said body hollow volume at one end of the body, and a second end cap is slidingly disposed at the other. End cap and body combination is filled with a liquid. Responsive to an impact along the body axis, one of the end caps is partially displaced into the body and at least a portion of the liquid changes phase from a liquid phase to a vapor phase.

A damper for a semiconductor metrology or inspection system includes a pair of parallel plates with a fluid with a variable viscosity retained between plates. At least one wire is disposed between the plates, which may include one or more sets of lands and grooves. In some implementations, both plates include intermeshed lands and grooves. A controller is configured to provide a current to the at least one wire in order to adjust an electromagnetic field or a current through the fluid. The fluid may be a magnetorheological fluid or an electrorheological fluid in which the viscosity of the fluid is variable based on the electromagnetic field or current through the fluid. The controller varies the current applied to the wire to adjust the viscosity of the fluid to alter the damping of the semiconductor metrology or inspection system based on movement of the stage.

The invention provides an acoustic material structure and an assembly method of the acoustic radiation structure. The acoustic material structure comprises acoustic units which can be attached onto surfaces of acoustic radiation structures. Each acoustic unit comprises a thin sheet, an air cavity between the thin sheet and the surface of the sound radiation structure, and openings penetrating through the acoustic unit with one end connected to the cavity. The openings can reduce the spring effect of the fluid medium in the cavity, so that the acoustic units attached onto the surface of the sound radiation structure can provide low-frequency sound insulation effects. The acoustic unit may also include support bodies, mass blocks, and constraint bodies. The working frequencies of the acoustic unit can be regulated by the support bodies, mass blocks and constraint bodies. The acoustic material structure can effectively suppress sound radiation from low- and middle-frequency sound waves which have relatively larger wavelength under costs of small weight and space. Moreover, the acoustic material structure can enhance the exchange rate of the heat from the attached structure surfaces by the vibration of the thin sheet.

A directional vibration control apparatus, which includes a tunable vibration absorber (TVA) for a vibratory compactor machine is provided. The TVA includes a frame mounting structure that is configured to mechanically interface with a frame of the vibratory compactor to provide a fixed attachment of the TVA to the frame of the vibratory compactor, a TVA carrier that extends from the frame mounting structure into an interior portion of a drum of the vibratory compactor machine, a resilient element that includes a first portion that is fixedly attached relative to the TVA carrier and a second portion that includes a degree of freedom of movement relative to the TVA carrier, and a mass that is attached to the second portion of the resilient element and that includes the degree of freedom of movement relative to the TVA carrier.

An active composite variable damping rotational control device includes a variable damping module and a power module. The variable damping module includes a magnetorheological fluid tank and a rotational inertia wheel. The rotational inertia wheel is arranged in the magnetorheological fluid tank fully filled with magneorheological fluid. The power module includes a device tubular cavity, a driver, an encoder and a speed changer. The driver is fixed on the inner wall of the device tubular cavity. The driver, the encoder and the speed changer are coaxial. A driving shaft of the driver passes through the speed changer and extends into the magnetorheological fluid tank to be fixed perpendicularly at the center of the rotational inertia wheel. The control effect of the present invention may not be greatly affected by the change of a structural form and the change of an external load.

A wind tunnel sting comprising a support member and a wind tunnel sting damper. The support member having a first support-member end configured for coupling with a wind tunnel, and a second support-member end configured for coupling with a balance. The wind tunnel sting damper having a reactive member, and a viscoelastic member disposed between the reactive member and the support member wherein, the reactive member is sized relative to the support member so as to radially compress the viscoelastic member against the support member.

A system or structure subject to external mechanical dynamic loading excitations propagated within the system or structure comprising a fluid filled structure and a fluid volume operable to facilitate fluid flow about at least part of the structure. Excitations within the structure can be propagated throughout. The system can further comprise a tuned mass damper (TMD) located within the fluid volume. The TMD can leverage the viscous properties of the fluid to attenuate the excitations within the structure. The TMD can comprise a mass and a spring operably connected to the mass. The TMD can further comprise a fluid resistance facilitating fluid flow about the mass and the spring for damping and a secondary tuning device operably connected to at least one of the mass and the spring and the supporting fluid-filled structure.