Analysis of the most common performance nouns in material mechanical properties testing

In the fatigue test, a graph of stress (S) relative to the number of cycles (N) from the sample to failure is called the S-N graph. The curve in the S-N diagram is composed of a set of data points that determine their fatigue life under different alternating stresses. Stress coordinates can represent stress amplitude, stress or small stress. Coordinates of a certain logarithmic scale are often used to represent N and sometimes to represent S.
1. Elongation:
Measurement of material ductility measured in tensile tests. It is the gauge increment (measured after breaking) divided by the original gauge length. Higher elongation indicates higher ductility. Elongation cannot be used to predict the properties of the material when it is subjected to burst loads or repeated loads.
2. Volume elastic modulus:
The ratio of stress and volume change when a material is subjected to axial load is called the volume elasticity modulus. The following equation shows the relationship between the volumetric elastic modulus and the elastic modulus (E) and the Poisson's ratio (r): the volumetric elastic modulus K=E/3(1-2r).
3. Impact strength:
In the impact test, the energy required for the sample to break under impact load. In addition, it can also be called impact energy, impact value, impact resistance, and energy absorption value. It is an indicator of material toughness.
4. Impact energy:
In the impact test, the energy required for the part to break under impact load. Other names include impact value, impact strength, impact resistance, and energy absorption value.
5. Yield strength:
Without causing plastic deformation, the stress value that the material can withstand becomes the yield strength of the material. Under this stress, the material is specified to produce a certain amount of deformation, and this stress is also an approximation of the actual elastic limit of the material. The conditional yield strength can be determined by stress-strain diagram. It is the stress value corresponding to the intersection of the stress-strain curve and a line parallel to the straight part of the stress-strain curve. (called the specified yield strength) For metals, deformation is usually specified to be 0.2%, that is, the sub-intersection point of the specified line and the 0 stress axis are at 0.2% strain. For plastics, this strain value is usually 2%.
6. Yield strength elongation:
The strain at the yield strength of the material is a representation of the material's ductility.
7. Stiffness:
It refers to the measurement of plastic bending resistance. Both plasticity and elasticity are included, so the stiffness is only the apparent value of the elastic modulus rather than the true value (ASTMD-747 standard).
8. Rigid modulus:
It means that the strain of the sample with shear or torsional load is a function of stress, and the rigid modulus is the rate of change of strain to stress. It is the elastic modulus measured in the torsion test, that is, the elastic modulus in the torsion test and the shear test. Apparent rigidity modulus is a method of plastic stiffness measured in torsional tests (ASTMD-1043). The reason why it is called "appearance" is that the sample may deflect and the sample has exceeded its proportional limit. The calculated value cannot represent the true elastic modulus within the material's elastic limit range.
9. Hooke's Law:
Stress is directly proportional to the strain. Hookeslaw is a condition that assumes that the material is completely elastic. It does not take into account the plasticity or dynamic loss characteristics of the material.
The above are some of the data and terms that may be used in material mechanics testing, and I hope it can help you!