Compreendendo o módulo elástico: 5 fatores que afetam os materiais

Understanding Elastic Modulus: 5 Factors That Affect Materials

1. Relationship between alloying elements and modulus of elasticity of steel

The interatomic force depends on the metal atom itself and the type of network, so the modulus of elasticity mainly depends on the nature of the metal atom and the type of network.

Schematic diagram of the material reinforcement process

4. Influence of cold plastic deformation on the modulus of elasticity

Cold plastic deformation makes the modulus of elasticity slightly lower, generally 4% ~ 6%, which is related to residual stress.

When the amount of plastic deformation is large, the modulus of elasticity is anisotropic due to deformation, and the modulus of elasticity along the deformation direction is larger.

The change in the elastic modulus of the material caused by this cold plastic deformation will affect the cold forming accuracy of precision parts.

5. Effect of temperature on the modulus of elasticity

As the temperature increases, the distance between atoms increases and the modulus of elasticity decreases.

When carbon steel is heated, the modulus of elasticity decreases by 3%~5% for every increase of 100℃, but the modulus of elasticity of steel changes little in the range of –50℃~50℃.

6. Effect of loading rate on elastic modulus

As elastic deformation propagates in the medium at the speed of sound, the speed of sound in the metallic medium is quite large, such as 4,982 m/s in steel;

In the ordinary pendulum impact test, the absolute deformation rate is only 4 ~ 5.5 m/s, and even in the high-speed impact test, the deformation rate is within 10 3 EM.

Under such impact load, elastic deformation can always follow the change of external impact force, so the strain rate has no effect on the elastic behavior and elastic modulus of metal materials.

In modern machines, the strain rate of various parts varies from 10 -6 to 10 6 is -1 .

For example, the strain rate of static tensile test is 10 -5 ~ 10 -2 is -1 (referred to as quasi-static strain rate), and the strain rate of impact load is 10 2 ~ 10 4 is - 1 referred to as high strain rate.

In addition, there are average strain rate tests with strain rate of 10 -2 ~ 10 2 is -1 such as hammer and rotating flywheel.

Practice shows that when the strain rate is in the range of 10 -4 ~ 10 -2 é -1 , the mechanical properties of the material do not show obvious changes and can be treated as static load.

When the deformation load rate is greater than 10 -2 is -1 , the mechanical properties of the material will change significantly, which must take into account a series of changes in mechanical properties caused by the increase in the deformation rate.

In the plastic deformation phase, the deformation increases slowly with increasing loading rate.

Therefore, when the loading rate is too fast, plastic deformation cannot be fully realized, which is manifested as the improvement of elastic limit, yield strength and other plastic microdeformation resistance.

It is also found that the plastic deformation under impact load is concentrated in some local areas, which reflects that the plastic deformation is extremely uneven.

This non-uniformity also limits the development of plastic deformation, making plastic deformation unable to be fully realized, resulting in the improvement of yield strength and tensile strength, and the improvement of yield strength is greater and the improvement of tensile strength it's smaller .

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