Structure that can be unfolded and folded when not in use
Deployable structures are structures that can be unfolded when in use and folded when not in use. In this sense, umbrellas or parasols, which have a long history and are widely known to people, are folding structures, which indicates that the folding structurethoughtIt has existed since ancient times, but the folding structure is used in the field of architecture and forms the correspondingDesignComputational theory has been developed in recent decades
In 1961, the Spanish architect P. Pinero exhibited a small foldable mobile theater, from which people found many advantages of this structure. The foldable structure is generally reusable, and after being folded, it is small in size, easy to transport and storePermanent buildingsCompared withconstructionIt saves time and labor, and can avoid the waste caused by unnecessary reinvestment of funds. With the gradual understanding of the concept of "folding", folding structures have been greatly developed in both computational theory and structural form. This structure has gone out of the laboratory and been widely used in engineering.
Deployable structures are structures that can be unfolded when in use and folded when not in use. In this sense, umbrellas or parasols, which have a long history and are widely known to people, are folding structures, which indicates that the idea of folding structures has existed since ancient times, but folding structures are used forArchitectureAnd form correspondingDesignComputational theory has been a thing in recent decades. In 1961, the Spanish architect P. Pinero exhibited his wound, a small folding and moving theater, from which people found many advantages of this structure. Folded structures are generally reusable and small in size after folding, which is convenient for transportation and storagePermanent buildingsCompared withconstructionIt saves time and labor, and can avoid the waste caused by unnecessary reinvestment of funds. With the gradual understanding of the concept of "folding", folding structures have been greatly developed in both computational theory and structural form. This structure has gone out of the laboratory and been widely used in engineering.
purpose
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In the life field, it can be used for temporary structures such as construction shed, market shed, temporary warehouse, etc;staymilitaryIt can be used for battlefield command, battlefield rescue, assembly repair and field tent, etc. It is of great significance to improve the logistical support ability of the troops and increase their combat effectiveness;In the field of aerospace, folding structure has an irreplaceable position and has been used as solar sail, deployable antenna, etc.According to different standard folding structures, they are divided into different types: according to the type of folding structure elements, they can be divided into bar system elements and plate system elements, and the bar system elements can be divided into shear type elements and telescopic elements;According to the stable balance mode after the structure is unfolded, it can be divided into structural geometry self-locking, structural member self-locking and structural external locking;It can be divided into rigid structure and flexible structure according to whether the cable element is used in the structure composition;According to the driving mode of the structure deployment process, it can be divided intohydraulic pressure(Pneumatic) transmission mode, electric mode, node preloading spring drive mode, etc.
brief introduction
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Geometrically self-locking structure, also known as self stabilizing folding structure, isengineeringA structure that is universally valued by the world.Its self-lockingprincipleIt is mainly determined by the geometric conditions of the structure and the mechanical properties of materials.In this structure, some ribbon cutting elements (referred to as shear hinges) are connected in a certain way to form a lock hinge.Each member in the lock hinge only adapts to the geometric state of the structure when it is folded and fully unfolded. The stress of the member is zero. During the expansion process, the member bends and deforms, stores the external load energy, and finally releases the energy in the opposite direction.The self stable folding structure is easy and fast to deploy, but its members have relatively small bending stiffness, so its bearing capacity is low, and it is only suitable for small span situations.The self-locking mechanism of structural members is mainly to lock the structure by the pin at the hinge automatically sliding into the reserved slot at the end of the bar when the structure is deployed.The external locking structure of the structure is also called additional stable structure. In the process of structure deployment, there is no stress in the bars. The whole structure is a mechanism system. When the structure is deployed to a predetermined span, bars or other constraints are added at the end of the structure to eliminate the mechanism and form a structure.The member stiffness of this structure is relatively large, which can meet the requirements of large span.
The folding structure without elastic iron is called rigid structure, while the flexible folding structure is tensionedunitIs cable element.When the flexible structure is in the storage state, the cable is in a loose state, and the rigid bars can form bundles to facilitate transportation and storage.During deployment, the driving cable can be tensioned to deploy the structure, and the length of the compression bar can also be increased to tension the cable, which can form a whole tensioning system when fully deployed.The structure has light deadweight and large stiffness after being unfolded, and can be used for structures with large spans.
classification
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Folding structures can be divided into two categories according to their motion characteristics in the process of deployment: one is that the motion of each part is rigid body motion, which is called multi rigid body system. Its motion description and internal force analysis are relatively easy to solve;The other is that the components experience large rigid motion in space, and at the same time, they also have their own deformation movement, showing the characteristics of strong coupling between rigid motion and deformation movement.Self stabilizing bar structure belongs to the latter type, in which the design of locking hinge is the basis of the design of the whole self stabilizing folding structure, which directly affects the rationality of the structure and the convenience of use.The ideal self-locking condition is that in the process of stacking and unfolding, internal forces are generated in the bars that make up the locking hinge. The internal forces change slowly and sharply, and the rate of change shows the characteristics of large range of slow variables and small range of fast variables.This kind of motion characteristic must be described by nonlinear theory, which is exactly the difficulty of this kind of structure calculation.
Node design
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For anyspaceStructure and node design occupy a very important position. Folding structures are no exception, and there are some special requirements: the nodes of folding structures must be able to ensure that the members can move freely during the deployment process, and there is no large friction or deformation easy to bend at the joints between the members and nodes;When the structure is in the storage state, it can ensure that the rods are tightly bundled for storage;People have enough strength to bear the tension, compression, local bending, shearing, friction and other effects of the bar.The hub node is widely used, and the node material can be metal orhigh polymerMaterial Science.
