How to calculate the subsequent yield force

1.

The yield strength, upper yield strength and lower yield strength can be calculated according to the following formula:

yield strength formula: Re = Fe / so; Fe is the constant force at yield

The formula for calculating the upper yield strength is Reh = FEH / so; FEH is the maximum force before the first drop in the yield stage

The formula of lower yield strength is rel = FEL / so; FEL is the minimum force FEL less than the initial instantaneous effect

In the

test, the constant force when the pointer of the force measuring plate stops rotating for the first time or the maximum force before the pointer rotates for the first time or the minimum force less than the initial instantaneous effect correspond to the yield strength, upper yield strength and lower yield strength respectively

extended data:

the yield limit of metal materials when yielding, that is, the stress resisting micro plastic deformation. For the metal material without obvious yield, the stress value with 0.2% resial deformation is defined as its yield limit

the external force greater than this limit will make the parts permanently invalid and unable to recover. If the yield limit of low carbon steel is 207mpa, when the external force is greater than this limit, the part will proce permanent deformation, and if it is less than this, the part will return to its original state

The external force of

greater than the yield strength will make the parts permanent failure and unable to recover. If the yield limit of low carbon steel is 207mpa, when the external force is greater than this limit, the part will proce permanent deformation, and if it is less than this, the part will return to its original state

2. In general:
yield strength = load at yield / area of specimen
there are three common standards for determining yield strength by prescribing a certain amount of resial deformation in Engineering:

the first is proportional limit, which is the highest stress value in line with the linear relationship on the stress-strain curve σ P means more than σ P, it is considered that the material begins to yield; The second is the elastic limit. The specimen is unloaded after loading. The maximum stress value of the material that can be fully elastic recovered is determined by the standard of no resial permanent deformation σ D means more than σ D, it is considered that the material begins to yield; The third is yield strength, which is based on the specified resial deformation. For example, the stress of 0.2% resial deformation is usually used as yield strength σ 0.2 or σ Ys said

the above definitions are all based on resial deformation, and the difference between them is that the specified resial deformation is different. In the current national standard, the yield strength is specified as the following three cases< (1) specified non proportional elongation stress σ P) During the loading process of the specimen, the non proportional elongation within the gauge length reaches the specified value (expressed in%). For example σ P0.01， σ 05, etc< br />
σ P is usually determined by graphic method. For materials with obvious elastic straight line segment, the automatically recorded load elongation (P) can be used- Δ 50) Curve. From the intersection o of the elastic straight line segment and the extension axis, a segment OC corresponding to the specified non proportional extension is intercepted (OC = NLE) ε p. Where n is the magnification of the drawing, Le is the gauge length of the extensometer, ε P is the specified non proportional elongation), make parallel line CA of elastic straight line section through point C, intersect the curve at point a, the load PP corresponding to point a is the measured non proportional elongation load, and the specified non proportional elongation stress is calculated by the following formula

σ P = PP / S0

(2) specified resial elongation stress σ r) After unloading, the resial elongation of the gauge length part of the specimen reaches the specified proportion σ R0.2, which is the stress value when the specified resial elongation is 0.2%

determination σ R is commonly used unloading method, that is, when the resial elongation obtained after unloading is the specified resial elongation load PR, the specified resial elongation stress is calculated by the following formula

σ R = PR / S0

(3) specified total elongation stress σ t) The stress when the total elongation (the sum of elastic elongation and plastic elongation) of the gauge length part of the specimen reaches the specified proportion. The total elongation is 0.5%, 0.6% and 0.7%, respectively. Accordingly, the total elongation stress is recorded as σ t 0.5， σ 6 and 0 σ t 0.7

determination σ T is also operated and determined by graphic method σ P is the same, the magnification of the horizontal axis of the drawing is not less than 50 times. In P- Δ On the L curve, from the origin o of the curve, the line segment OE corresponding to the specified total elongation is intercepted (OE = n · LE)· ε t. Where ε The load corresponding to point a is the load of specified total elongation. The stress of specified total elongation is calculated by the following formula:

σ T = Pt / S0

in the above yield strength determination, σ P and σ T is measured directly from the stress-strain (load displacement) curve when the specimen is loaded σ R requires unloading measurement. Determination of resial elongation stress by unloading method σ R is difficult and inefficient, so it tends to be used in the evaluation of material yield resistance σ P and σ t σ T is better in the test σ P it's convenient, and it's safe σ P can be used to characterize the yield characteristics of materials σ t. Substitute σ P. Especially in large-scale instrial proction, the use of σ This method can improve the efficiency

for materials with discontinuous yield, i.e. obvious yield point, the yield platform on the stress-strain curve is the sign of material yield deformation. Therefore, the corresponding stress value of the yield platform is the yield strength of this kind of materials σ Ys is calculated as follows:

σ Ys = py / S0

where py is the load at physical yield or the load corresponding to the lower yield point

yield strength is the most widely used performance index. Because any mechanical parts in the working process, are not allowed to have excessive plastic deformation, so in mechanical design, the yield strength as the basis of strength design and material selection.

3.

The formula of yield strength is re = Fe / so; Fe is the constant force at yield

The formula for calculating the upper yield strength is Reh = FEH / so; FEH is the maximum force before the first drop in the yield stage

The formula of lower yield strength is rel = FEL / so; FEL is the minimum force FEL less than the initial instantaneous effect

The force collet displacement diagram was drawn with automatic recording device ring

test. It is required that the stress represented by the ratio of force axis per mm is generally less than 10N / mm and 178;, The curve should be drawn at least to the end of the yield stage. The constant force Fe of the yield platform, the maximum force FEH before the first drop of the force in the yield stage or the minimum force FEL less than the initial instantaneous effect are determined on the curve

extended data

the internal factors that affect the yield strength are bond, microstructure, structure and atomic nature

If the yield strength of metals is compared with that of ceramics and polymers, it can be seen that the effect of bonding bond is fundamental. From the influence of microstructure, there are four strengthening mechanisms which can affect the yield strength of metal materials, namely:

(1) solid solution strengthening

(2) deformation strengthening

(3) precipitation enhancement and dispersion enhancement

(4) grain boundary and subgrain strengthening

precipitation strengthening and fine grain strengthening are the most commonly used means to improve the yield strength of instrial alloys. Among these strengthening mechanisms, the first three mechanisms not only improve the strength of the material, but also rece the plasticity. Only refining the grain and sub grain can improve the strength and increase the plasticity

The external factors influencing yield strength are temperature, strain rate and stress state

with the decrease of temperature and the increase of strain rate, the yield strength of the material increases, especially the BCC metal is particularly sensitive to temperature and strain rate, which leads to the low temperature embrittlement of the steel

The influence of

stress state is also very important. Although the yield strength is an essential index reflecting the internal properties of materials, the yield strength values are different with different stress states. The yield strength of materials generally refers to the yield strength under uniaxial tension

4.

Calculation method of steel yield strength:

calculation formula of yield strength: σ= F / s,

where σ Is the yield strength, unit is "MPa",

for reinforcement, f is the force when the plastic deformation of reinforcement is 0.2% of the original length, unit is "n",

s is the cross-sectional area of reinforcement, unit is "m ^ 2"

extended data:

yield strength is the yield limit of metal materials when yielding, that is, the stress resisting micro plastic deformation. For the metal material without obvious yield, the stress value with 0.2% resial deformation is defined as its yield limit, which is called conditional yield limit or yield strength

the external force greater than this limit will make the parts permanently invalid and unable to recover. If the yield limit of low carbon steel is 207mpa, when the external force is greater than this limit, the part will proce permanent deformation, and if it is less than this, the part will return to its original state

(1) for materials with obvious yield phenomenon, the yield strength is the stress (yield value) at the yield point

(2) for the material with no obvious yield phenomenon, the stress when the limit deviation of the linear relationship between stress and strain reaches the specified value (usually 0.2% of the original gauge length). It is usually used as the evaluation index of the mechanical properties of solid materials, and is the actual use limit of materials. Because the necking occurs when the stress exceeds the yield limit of the material and the strain increases, the material is damaged and cannot be used normally

5. There are four stages from tensile to fracture: 1 proportional stage, 2 yielding stage, 3 strengthening stage and 4 necking stage
in the proportional stage, the stress becomes proportional to the stress; Yield stage: because of the metal grain sliding, it temporarily loses the ability to resist failure, and the up-down wave pattern can be seen from the tensile diagram, which is called yield platform; In the strengthening stage, the grain sliding is completed and the material recovers its ability to resist damage; Necking stage: the material completely lost the ability to resist damage
it can be seen from the tensile diagram that there are two yield points: the upper and the lower. The lower yield point is used in engineering, that is, the lowest value ring the yield period, regardless of the initial instantaneous effect
yield strength calculation: divide the value of lower yield point force (n) read from tensile test by the cross-sectional area of the test piece (mm & sup2;), The yield strength is obtained. Unit n / mm & sup2;

6. The yield strength of steel bar is the mechanical property index of steel bar. It is the "physical property" and the nature of specified steel bar. It is not calculated, but detected by tensile test. Is the stress obtained by dividing the measured yield tension of the specimen by the sectional area of the specimen
in design calculation, only the design value of tensile strength is used, not the standard value, nor the "indivial value" or average value detected.

7.

The calculation formula is as follows: σ= FB / so

where: FB -- the maximum force on the specimen when it is pulled to break, n (Newton); So -- original cross-sectional area of sample, mm & # 178

in the tensile process, the material enters the strengthening stage after the yield stage, and then the maximum force (FB) is obtained by dividing the original cross-sectional area (so) of the sample with the decrease of the cross-sectional size σ， It is called tensile strength or strength limit σ b) And the unit is n /

8.

Yield strength: 72.5 * 1000N / (16 & # 178; π/ 4mm²= 360.77 MPa

tensile strength: 108 * 1000N / (16 & # 178; π/ 4mm²)= 537.4mpa

elongation: (96-80) / 80 = 20%

yield strength:

is the yield limit of metal materials when yielding, that is, the stress resisting micro plastic deformation. For the metal material without obvious yield, the stress value with 0.2% resial deformation is defined as its yield limit, which is called conditional yield limit or yield strength

the external force greater than this limit will make the parts permanently invalid and unable to recover

tensile strength:

is the critical value of metal transition from uniform plastic deformation to local concentrated plastic deformation, and is also the maximum bearing capacity of metal under static tensile condition

characterizes the resistance of the maximum uniform plastic deformation of the material. The deformation of the tensile specimen is uniform before the maximum tensile stress, but after the maximum tensile stress, the metal begins to shrink, that is, the concentrated deformation

elongation:

refers to the percentage of the elongation of the hardened body of the sealing material in the original length under the tensile force (unit:%)

extended data

yield point

low yield point steel is used as the manufacturing material of main components in energy dissipation seismic design. Its research and development has been widely concerned since the 1990s, and remarkable progress has been made in the research and engineering application of steel grades

the composition design of low yield point steel is close to that of instrial pure iron. By coarsening grains and adding a small amount of Ti and Nb to fix C and N atoms, the hindrance of dislocation movement can be reced. Ti can form tin → ti4c2s2 → tis and tic successively in the steel, and all excess Ti (ti-3.42n-1.5s) can form tic finally

The results show that when the excess Ti content reaches 0.03% or the ratio of Ti to 3.99c is 2, the grain size of ferrite increases significantly. It is considered that more ti coarsens the grains of tin, tis and tic, thus losing the role of grain boundary pinning

The yield strength of

low yield point steel can be divided into 100MPa, 160MPa and 225MPa

Practical significance of tensile strength:

2. For brittle metal materials, once the tensile force reaches the maximum, the material will break rapidly, so σ B is the fracture strength of brittle materials. When it is used in proct design, the allowable stress is less than 1 σ B is the criterion< br />

3、 σ The strength depends on the yield strength and strain hardening index. When the yield strength is constant, the larger the strain hardening index is, σ B is also higher

Tensile strength

4 σ B and Brinell hardness HBW, fatigue limit

9. Yield strength, also known as yield limit, is the critical stress of material yield

(1) for materials with obvious yield phenomenon, the yield strength is the stress (yield value) at the yield point< (2) when the limit deviation of the linear relationship between stress and strain reaches the specified value (usually 0.2% of the permanent deformation) for the material with no obvious yield phenomenon. It is usually used as the evaluation index of the mechanical properties of solid materials, and is the actual use limit of materials. Because the necking occurs when the stress exceeds the yield limit of the material and the strain increases, the material is damaged and cannot be used normally

when the stress exceeds the elastic limit and enters the yield stage, the deformation increases rapidly. At this time, in addition to the elastic deformation, part of the plastic deformation occurs. When the stress reaches point B, the plastic strain increases sharply and the stress and strain fluctuate slightly. This phenomenon is called yield. The maximum and minimum stresses at this stage are called upper yield point and lower yield point respectively. Because the value of lower yield point is relatively stable, it is called yield point or yield strength (REL or Rp0.2) as the index of material resistance

some steels (such as high carbon steel) have no obvious yield phenomenon. Usually, the yield strength of the steel is the stress at the time of slight plastic deformation (0.2%), which is called yield strength

therefore, if other external and internal conditions are the same, increasing the inner diameter by 0.1 mm has no effect on the yield strength