Mechanical properties of steel

Name	Unit	Definition
Tensile strength	MPa (N/mm²)	When the steel is stretched, the ratio of the maximum load it bears before breaking to the original cross-sectional area of ​​the steel specimen is called the tensile strength
The flexural strength	MPa (N/mm²)	The maximum normal stress that the steel bears when the steel is broken under the concentrated load between the two supports.
Compressive strength	MPa (N/mm²)	The maximum normal stress that can be withstood without breaking or cracking just under the pressure
At the yield point,	MPa (N/mm²)	The load no longer increases during the tensile process of the steel, and the phenomenon that the steel specimen continues to deform is called "yield". The stress at which the yield phenomenon occurs is called the yield point or yield limit
Yield strength	MPa (N/mm²)	For some steel materials where the yield phenomenon is not obvious, it is difficult to determine the yield point. The stress that produces 0.2% permanent deformation is often regarded as the yield point, which is called the yield strength or conditional service limit.
Elastic limit	MPa (N/mm²)	Steel can maintain the maximum stress of elastic deformation
Cross-sectional shrinkage rate	%	The percentage of the maximum reduction of the cross-sectional area at the neck of the steel after the steel is broken to the original cross-sectional area
Elongation	%	When the steel material is stretched, after the steel sample is broken, the percentage of the length of the gauge length added to the original gauge length.
Poisson's ratio		For isotropic steel materials, Poisson's ratio means: the ratio of the relative shrinkage in the transverse direction to the relative elongation in the axial direction when the steel specimen is uniaxially stretched
Impact value,	J J/cm²	The resistance of steel materials to impact loads is called toughness, and is usually measured by the impact value. With a sample of a certain size and shape, when the test machine of a specified type is broken by an impact load, the work consumed per unit area at the groove of the sample.
Shear strength	MPa (N/mm²)	The average shear stress of the shear section under the maximum load before the steel specimen is sheared
Endurance strength	MPa (N/mm²)	The stress value that the steel material undergoes when it breaks at a given temperature (T) after a specified time (t)
Creep limit	MPa (N/mm²)	Steel material at a given temperature (T) and within a specified time (t), the steel sample produces a stress value of a certain amount of creep deformation
Fatigue limit	MPa (N/mm²)	The maximum stress that a material can withstand when subjected to a certain number of stress cycles N under symmetric bending stress without breaking. For steel, if the number of stress cycles N reaches 10000000-100000000 times and fatigue fracture does not occur, it can be considered that as the number of cycles increases, fatigue fracture will no longer occur.
Relaxation		Due to creep, under the condition that the total deformation of the steel material is constant, the stress gradually reduced with time is called stress relaxation, referred to as relaxation
Elastic mold	GPa(N/mm²)	In the elastic range, when the steel tensile experiment, the external force and deformation increase proportionally, that is, when the stress and should become a proportional relationship, this proportional coefficient is called the elastic mold, also called positive Modulus of elasticity
Shear die	GPa(N/mm²)	Steel is in the elastic range, when torsion test is performed, the external force and deformation increase proportionally, that is, when the stress and the strain should become proportional, this proportional coefficient is called shear elasticity Mould.
Fracture toughness		The ability of steel to resist crack propagation.
Hardness		Hardness is not a simple physical quantity, but a comprehensive performance index reflecting elasticity, strength, plasticity and so on.