The shock absorber includes: a base portion fixed to the attachment target; a shock absorbing portion having flexibility and attached to the base portion so as to be reversibly switchable between a housed state in which the shock absorbing portion is retracted toward the base portion and a protruding state in which the shock absorbing portion protrudes from the base portion; and a drive unit driving the shock absorbing portion to reversibly switch between the housed state and the protruding state. The drive unit, when operating the shock absorbing portion, at least switches the shock absorbing portion from the housed state to the protruding state.

Two or more target points different in amplitude in a natural mode, which exist in a housing of an object to be damped such as an engine, a gearbox, motors, or the like are located. Among these target points, an arm is fixed at a position relatively small in amplitude, and a vibration absorber provided at the free end of the arm is pressed against a position (relatively large in amplitude. When vibrations occur in the object, the vibration absorber holds the target point relatively large in amplitude while the arm is following the vibrations of the target.

A piezoelectric substrate attachment structure including a press section pressed by contact, a piezoelectric substrate provided adjacent to the press section, and a base section provided adjacent to the piezoelectric substrate on an opposite side from the press section. The following relationship Equation (a) is satisfied:
da/E′a<db/E′b  (a) wherein da is a thickness of the press section in a direction of adjacency to the piezoelectric substrate, E′a is a storage modulus of the press section from dynamic viscoelastic analysis, db is a thickness of the base section in the adjacency direction, and E′b is a storage modulus of the base section from dynamic viscoelastic analysis.

A piezoelectric substrate attachment structure including a press section pressed by contact, a piezoelectric substrate provided adjacent to the press section, and a base section provided adjacent to the piezoelectric substrate on an opposite side from the press section. The following relationship Equation (a) is satisfied:
da/E′a<db/E′b  (a) wherein da is a thickness of the press section in a direction of adjacency to the piezoelectric substrate, E′a is a storage modulus of the press section from dynamic viscoelastic analysis, db is a thickness of the base section in the adjacency direction, and E′b is a storage modulus of the base section from dynamic viscoelastic analysis.

A nonlinear mechanical element including a buckling column and hard stops. In one embodiment when the nonlinear mechanical element is subjected to an increasing compressive load, the buckling column buckles at a critical load, resulting in reduced stiffness past the critical load. One or more lateral hard stops may be provided adjacent to the buckling column to prevent the buckling deformation from exceeding a certain extent, and axial hard stops may be provided to shift the load path away from the buckling column when a certain amount of compressive displacement has been reached.

An energy absorber includes a flexible tensile member having lengthwise sections arranged serially along a length of the flexible tensile member. Lengthwise sections define convolutions. Features are provided for both restricting straightening of the convolutions and automatically reconfiguring, in response predetermined tension in the flexible tensile member, to allow straightening of the convolutions.

Devices with internal flexibility sipes, such as slits, provide improved flexibility, improved cushioning to absorb shock and/or shear forces, and improved stability of support. Siped devices can be used in any existing product that provides or utilizes cushioning and stability. These products include human and other footwear, both soles and uppers, as well as orthotics; athletic, occupational and medical equipment and apparel; padding or cushioning, such as for equipment or tool handles, as well as furniture; balls; tires; and any other structural or support elements in a mechanical, architectural, or any other product.

Devices with internal flexibility sipes, such as slits, provide improved flexibility, improved cushioning to absorb shock and/or shear forces, and improved stability of support. Siped devices can be used in any existing product that provides or utilizes cushioning and stability. These products include human and other footwear, both soles and uppers, as well as orthotics; athletic, occupational and medical equipment and apparel; padding or cushioning, such as for equipment or tool handles, as well as furniture; balls; tires; and any other structural or support elements in a mechanical, architectural, or any other product.

[Problem] To provide an active energy ray-curable composition which provides a cured product having excellent transparency as well as superior shock absorption and vibration absorption, and a cured product, a shock-absorbing material, a vibration-absorbing material and a sheet material in which said active energy ray-curable composition is used.

[Solution] An active energy ray-curable composition containing (A) diallyl 1,4-cyclohexane dicarboxylate, (B) a compound having two or more mercapto groups, and (C) a polymerization initiator.

[Problem] To provide an active energy ray-curable composition which provides a cured product having excellent transparency as well as superior shock absorption and vibration absorption, and a cured product, a shock-absorbing material, a vibration-absorbing material and a sheet material in which said active energy ray-curable composition is used.

[Solution] An active energy ray-curable composition containing (A) diallyl 1,4-cyclohexane dicarboxylate, (B) a compound having two or more mercapto groups, and (C) a polymerization initiator.