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Testing of elastic modulus of plywood and MDF wood-based panel

Elastic modulus in general, the elastic body will be deformed when the force is applied to the elastic body. “Elastic modulus” is often defined as the ratio of the stress under the action of one-way stress to the strain of the object in that direction. In the stage of elastic deformation, the stress and stress of the material become proportional, i.e. follow Hooke’s law, and its proportional coefficient is the elastic modulus.

“Elastic modulus” is a physical quantity describing the elasticity of a material. It is a general term. The expression method can be “Young’s modulus”, “bulk modulus”, etc. it is an indicator of material stiffness.

The elastic modulus is an important performance parameter of engineering materials. From the macro perspective, the elastic modulus is a measure of the resistance of an object to elastic deformation. From the micro perspective, it is a reflection of the bonding strength between atoms, ions or molecules. All the factors affecting the bonding strength can affect the elastic modulus of materials, such as bonding mode, crystal structure, chemical composition, microstructure, temperature, etc. The young’s modulus of metal materials may fluctuate by 5% or more due to different alloy compositions, different heat treatment states, and different cold plastic deformation. However, generally speaking, the elastic modulus of metal materials is a mechanical property index insensitive to the structure. Alloying, heat treatment (fiber structure), cold plastic deformation, etc. have little influence on the elastic modulus, and external factors such as temperature and loading rate have little influence on it. Therefore, the elastic modulus is taken as a constant in general engineering applications.

The elastic modulus can be regarded as an index to measure the difficulty of elastic deformation of materials. The greater its value, the greater the stress that causes certain elastic deformation of materials, that is, the greater the stiffness of materials, that is, the smaller the elastic deformation under certain stress. Elastic modulus E refers to the stress required by the material to produce unit elastic deformation under the action of external force. It is an index reflecting the ability of materials to resist elastic deformation, which is equivalent to the stiffness of ordinary springs.

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Elastic modulus, also known as young’s modulus, is one of the most important and characteristic mechanical properties of elastic materials. It is a representation of the difficulty of elastic deformation of an object. It is often expressed by E. It is defined as the ratio of the stress to the corresponding strain when the ideal material has small deformation. E with σ The force per unit area is expressed in. The nature of the modulus depends on the nature of the deformation. The modulus during shear deformation is called shear modulus and expressed by G; The modulus during compression deformation is called the compression modulus and expressed by K. The reciprocal of the modulus is called compliance and is expressed in J.

The yield limit and strength limit obtained in the tensile test reflect the bearing capacity of the material to the force, while the elongation δ Or section shrinkage ψ, It reflects the ability of plastic deformation of the material. In order to indicate the difficulty of the material to resist deformation within the elastic range, in the actual engineering structure, the meaning of the elastic modulus E of the material is usually reflected by the rigidity of the part. This is because once the part is designed and shaped according to the stress, the rigidity is judged by the deformation amount generated by the load in the service process within the elastic deformation range. Generally, the load causing unit strain is the stiffness of the part. In order to improve the rigidity of the parts, that is, to reduce the elastic deformation of the parts, the materials with high elastic modulus can be selected and the bearing cross-sectional area can be appropriately increased. The importance of the rigidity is that it determines the stability of the parts when they are in service, and it is particularly important for the slender bars and thin-walled members. Therefore, for the theoretical analysis and design calculation of components, the elastic modulus E is an important mechanical performance index that is often used.

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