The present invention belongs to the technical fields of novel structure design and lattice material design, and refers to structures, lattice materials, and lattice cylindrical shells with simultaneous stretch- and compression-expanding property. First, use the local tension-compression asymmetry in the tension modulus and compression modulus generated by the contact nonlinearity of the tension springs to construct a type of 2D structures and lattice materials with stretch- and compression-expanding property. Then by assembling the 2D structures in different directions, 3D structures and lattice materials can be constructed. Meanwhile, a lattice cylindrical shell can also be constructed by using the 2D stretch- and compression-expanding structures as the unit cell. The structures and lattice materials presented in this invention can be used as a specific functional material and has a promising application in the fields of energy absorption, vibration reduction, medical treatment, wave propagation, intelligent components, and so on.

The present invention belongs to the technical fields of novel structure design and lattice material design, and refers to structures, lattice materials, and lattice cylindrical shells with simultaneous stretch- and compression-expanding property. First, use the local tension-compression asymmetry in the tension modulus and compression modulus generated by the contact nonlinearity of the tension springs to construct a type of 2D structures and lattice materials with stretch- and compression-expanding property. Then by assembling the 2D structures in different directions, 3D structures and lattice materials can be constructed. Meanwhile, a lattice cylindrical shell can also be constructed by using the 2D stretch- and compression-expanding structures as the unit cell. The structures and lattice materials presented in this invention can be used as a specific functional material and has a promising application in the fields of energy absorption, vibration reduction, medical treatment, wave propagation, intelligent components, and so on.

A method and system of absorbing the shock force of an impact including a substance which absorbs at least part of the shock force of an impact by changing phase from a first phase to a second phase, and back to the first phase on cessation of the impact force, and a container for the substance for protecting a person from an impact injury.

A main spindle device for a machine tool includes a main spindle, a cushioning member, and an arithmetic unit. The cushioning member is disposed on a position where a vibration displacement of a rotator exists. The arithmetic unit uses data of a tool to be used to analyze a vibration mode in a free vibration of the rotator based on a support rigidity of a bearing, masses of respective parts of the rotator including the tool, an attenuation coefficient, and an equation of motion derived from rigidity and inertia by a rotation. An outer diameter of a sleeve positioned outside the bearing is changed such that a position of an antinode of the vibration or a position on which a vibration displacement exists in the vibration mode matches a position of the cushioning member inside the main spindle to change a preload on the bearing.

A main spindle device for a machine tool includes a main spindle, a cushioning member, and an arithmetic unit. The cushioning member is disposed on a position where a vibration displacement of a rotator exists. The arithmetic unit uses data of a tool to be used to analyze a vibration mode in a free vibration of the rotator based on a support rigidity of a bearing, masses of respective parts of the rotator including the tool, an attenuation coefficient, and an equation of motion derived from rigidity and inertia by a rotation. An outer diameter of a sleeve positioned outside the bearing is changed such that a position of an antinode of the vibration or a position on which a vibration displacement exists in the vibration mode matches a position of the cushioning member inside the main spindle to change a preload on the bearing.