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An ideal elastomer
An object that returns completely to its original state after the removal of external forces
Elastomer generally refers to materials that can recover after the removal of external forces, but elastic materials are not necessarily elastomers. Elastomer deformation is significant only under weak stress, stress relaxation can quickly return to the original state and size of the material.
An ideal elastomer is an object that can completely return to its original state after the removal of external forces.
- Chinese name
- An ideal elastomer
- Foreign name
- perfect elastic body
- definition
- An object that returns completely to its original state after the removal of external forces
- Law of obedience
- Hooke's law
- Action time
- Instantaneous, independent of external action time
- Application field
- elasticity
When a material deforms due to an external force, when the deformation is proportional to the external force (in accordance with Hooke's law), the material is considered to be an ideal elastomer or Hooke elastomer.
In fact, any material has an inertial effect and does not obey Hooke's law. However, within a certain range, the relationship between stress and strain can meet the requirements of Hooke's law and can be treated as an ideal elastomer. The deformation and recovery deformation of an ideal elastomer are instantaneous and do not depend on the duration of external force.
According to elasticity, the ideal elastomer must satisfy four conditions: (1) assume that the body is continuous; (2) Suppose that the body is completely elastic; (3) The object is assumed to be isotropic; (4) The object is assumed to be uniform. After these conditions are satisfied, the body can be said to be an ideal elastic body. But there are no actual ideal elastomers, only relative ideal elastomers. We have to be realistic when we think about whether an object is an ideal elastic body, so some non-ideal cases in order to simplify the calculation or operation can also be treated as an ideal elastic body in a non-strict case.
Under the action of stress, the strain behavior of the actual body deviates from the ideal elastomer in three main cases:
(1) High order elasticity. When the stress is large, the stress-strain relationship deviates from linear, but still has the properties of ideal elastomer (1), (2), (3);
(2) Inelastic. In the process of loading and unloading, the strain response of the non-elastic body has different strokes, and the stress and strain are neither one-to-one correspondence nor proportional, but it still has the third feature of the ideal elastic body.
(3) Plasticity. This object does not have any of the four characteristics of an ideal elastomer.
The higher order elasticity, inelasticity and plasticity mentioned above are not isolated in the experiment, they are often characteristic at different stages of stress development, although they may not all be observed in the measurement of stress-strain relationship of the same sample
[1]
.
Elasticity is also known as "elasticity theory". The study of ideal elastomers in solid materials and of mechanical problems in the elastic deformation phase of solid materials. It's a branch of solid mechanics. Its theoretical basis is Newton mechanics plus elastic physical relations, that is, the method of theoretical mechanics and material mechanics is applied to the general elastic body. Its basic assumptions are: (1) continuity hypothesis; (2) Complete elasticity hypothesis; (3)
Uniformity hypothesis
; (4) Isotropic hypothesis; (5)
Small deformation hypothesis
; (6) the object has no initial stress. There are linear elastic mechanics, nonlinear elastic mechanics, mathematical elastic mechanics, applied elastic mechanics and so on. Based on the above six basic assumptions, linear elasticity is developed early, rigorous in theory and complete in system, and has been widely used in engineering practice. Nonlinear elasticity does not assume small deformation, the deformation of the object is not very small, so that it forms a geometric nonlinear or physical nonlinear relationship of the material. Mathematical elasticity applies energy analysis to study and summarize the theoretical problems in elasticity. In addition to the above six assumptions, applied elasticity also refers to certain supplementary assumptions, such as the geometric deformation assumptions and stress distribution assumptions similar to those used in curved beams for thin plates (or shells). Elasticity is widely used in engineering design, such as determining the stress distribution in turbine impellers, high pressure vessels and other components to solve their strength problems
[2]
.
