Hardness is one of the measures of resistance of solid materials against plastic deformation
In general, the meaning of hardness is a state of matter that resists the change of position. In other words, it means the resistance of a material against the force that causes the change of shape (change of location) of that material, which means preventing the change of shape (change of location). And I also said, the principle of the concept of hardness is summarized in the following relationship, which is related to the hardness of a spring according to Hooke’s law.
F=k.delta-> k=F/delta
F force
K hardness
Delta changed location
Theoretically, the ratio of the amount of force that causes a change in shape in the material to the amount of change in shape created in the material (change in location) indicates the hardness of that material against the applied force. That is, assuming for example the existing material against n tons of force, the hardness It has n tons per square centimeter (that is, the resistance of the existing material against the deformation of that force is equal to n tons per square centimeter).
When such a relationship is established for a material, it can be said that the material has a linear behavior and if we display the results on a graph, we will see that the results are obtained as a straight line, I will send the related image below.
Hardness types of solid materials and calculation relationships:
Axial stiffness EA/L
Flexural stiffness EI/L
Torsional hardness GJ/L
Shear hardness GA/L
G=E/2(1+v) shear modulus
A= cross-sectional area
I= Moment of inertia
E= modulus of elasticity
For example, suppose we have a sponge and a wooden board.
If we apply the same axial force to both, we can see that the wooden board needs more force to change its shape due to its high hardness compared to the sponge, so the hardness of this material or the wooden board is very high against changing its shape.
The hardness of a material depends on its geometry and material.
Nair sponge is deformed due to not having enough hardness in small forces.
The same example can be said in relation to the structure and the hardness of one floor of it. Assume one floor of a structure, the bigger and stronger the beams and columns of that floor are, in other words, the overall hardness of that floor against the change of location. drift) is more.
@shirichannel structural calculations channel
This post is written by MOJTABA_SHIRI