A crankshaft arrangement for an internal combustion engine includes a crankshaft, a torsional vibration damper having a primary mass and a flywheel, wherein the primary mass is connected fixedly to the crankshaft, and the flywheel and the primary mass are coupled via a viscous fluid. The torsional vibration damper is attached to an output end of the crankshaft. The primary mass is coupled to a secondary coupling via an elastomer coupling ring. The torsional vibration damper is coupled to the secondary coupling via a feedback device. The feedback device has a negative stiffness.

A spring (3, 3′) comprising a plurality of elements (30), each element (3) comprising a rigid portion (31) and a flexible beam (32), the extremities (320, 321) of the flexible beam being supported by the rigid portion (31), the flexible beam (32) having a single stable position, so that the flexible beam can be deformed when a pressure is exerted between said extremities in the direction of the rigid portion (31), and returns to said single stable position when the pressure is released, and wherein the rigid portion (31) of at least one element (30) is in contact with the flexible beam (32) of the next element between said extremities (320, 321) of the flexible beam (32), so that the spring has a negative stiffness over an operating range. The arrangement ensures a pure radial compression/expansion of the spring.

A horizontally arranged six-degree-of-freedom constant-stiffness mechanism is provided, and includes an upper platform, a bottom plate, three composite spherical hinges, spherical hinges, support rods, guide rail slider assemblies, and six electromagnetic adjustable stiffness units. Two ends of a shaft on which a permanent magnet is fixed in each electromagnetic adjustable stiffness unit are fixed to the bottom plate via shaft supports. Axially moving housings of electromagnetic adjustable stiffness units are fixed on sliders of the guide rail slider assemblies via slider backing plates respectively. Guide rail slider assembles are fixed on the bottom plate. Tops of the housings are mounted with the spherical hinges respectively. A bottom of the upper platform is uniformly mounted with the composite spherical hinges. One end of each support rod is threadedly connected to a corresponding one of the spherical hinges, and another end is connected with a corresponding one of composite spherical hinges.

The present invention provides a test device for a quasi zero stiffness isolator, and belongs to the technical field of vibration response tests of isolators. The device comprises a negative stiffness adjusting mechanism, a positive stiffness adjusting mechanism, and a beam-damping block mechanism. The negative stiffness adjusting mechanism and the positive stiffness adjusting mechanism are connected successively and installed on a beam-mass block system. The test device for the quasi zero stiffness isolator can realize smooth longitudinal vibration of a tested system, and can also flexibly adjust the positive stiffness value and the negative stiffness value of an overall mechanism. The present invention is suitable for a vibration model test of the quasi zero stiffness isolator, and solves the problems of complicated use method, impossibility of flexible adjustment of mechanism stiffness and complicated replacement process of stiffness elements in the device for the existing quasi zero stiffness isolator.

A metamaterial system for protecting a payload from external energy flux generated by an energy source includes a mechanical, metamaterial framework configured to circulate the external energy flux between the metamaterial system and the energy source.

In at least one embodiment, a rotational spring is provided with adjustable stiffness and includes at least one beam arranged about an axis between an input tuning port and an output port, wherein the input tuning port is configured to change an effective bending length of at least one beam so as to change a shear stiffness with respect to the input tuning port and the output port.

The invention provides a vibration isolation system (IS), comprising a piston (402) to carry a payload, a connecting member (410), a spring (404) and a flexible member (408). The spring is arranged to support the piston along a direction with a positive stiffness. The flexible member is arranged to apply a force to the piston along the direction via the connecting member with a negative stiffness.

A horizontally arranged six-degree-of-freedom constant-stiffness mechanism is provided, and includes an upper platform, a bottom plate, three composite spherical hinges, spherical hinges, support rods, guide rail slider assemblies, and six electromagnetic adjustable stiffness units. Two ends of a shaft on which a permanent magnet is fixed in each electromagnetic adjustable stiffness unit are fixed to the bottom plate via shaft supports. Axially moving housings of electromagnetic adjustable stiffness units are fixed on sliders of the guide rail slider assemblies via slider backing plates respectively. Guide rail slider assembles are fixed on the bottom plate. Tops of the housings are mounted with the spherical hinges respectively. A bottom of the upper platform is uniformly mounted with the composite spherical hinges. One end of each support rod is threadedly connected to a corresponding one of the spherical hinges, and another end is connected with a corresponding one of composite spherical hinges.

An apparatus includes at least two disk spring washers, at least one ring-shaped outer spacer coupled to the outer edges of one or two of the disk spring washers, and at least one ring-shaped inner spacer coupled to the inner edges of one or two of the disk spring washers. The apparatus also includes a central shaft concentric with the disk spring washers, the outer spacers, and the inner spacers. The apparatus also includes a bottom attachment portion coupled to the bottom of the central shaft to support the at least two disk spring washers, and a top attachment portion configured to slide vertically along the central shaft. The top attachment portion is configured to, with an application of a downward force, compress the at least two disk spring washers.

An apparatus includes a vibration isolator which incorporates at least two disk spring washers. Each disk spring washer has at least one ring-shaped outer spacer coupled to the outer edges of one or two of the disk spring washers, and at least one ring-shaped inner spacer coupled to the inner edges of one or two of the disk spring washers. A bottom attachment portion supports the disk spring washers, and a top attachment portion, with an application of a downward preload force, compresses the disk spring washers. A compression fixture applies and holds the preload force to the top attachment portion, and a second top attachment portion, with application of an additional downward force, further compresses the at least two disk spring washers.