Safety device with negative thermal expansion characteristic

The utility model discloses a safety device with a negative thermal expansion effect. The safety device comprises a negative thermal expansion structure and an external circular tube arranged outside the negative thermal expansion structure, the negative thermal expansion structure is formed by curling a negative thermal expansion plane structure into a circular tube shape, buckles are arranged at the positions, connected with inclined rods, of the negative thermal expansion structure, and the negative thermal expansion plane structure is obtained by conducting space translation on a plane and connecting a plurality of negative thermal expansion cell elements. Each negative thermal expansion cell is formed by oppositely connecting two same microstructures sharing one bottom edge, and each microstructure is an isosceles triangle formed by one bottom edge and two bevel edges; a clamping groove is formed in the pipe wall of the outer circular pipe, and the buckle of the negative thermal expansion structure is ar