What are the two types of strength theories? Please write the equivalent stress expression for the t

There are two different forms of failure of materials under the action of external forces: one is the sudden fracture when no significant plastic deformation occurs, which is called brittle failure; The second is the failure that can not continue to be carried due to significant plastic deformation, which is called plastic failure. The causes of the destruction are complex.

The Fourth Strength Theory is also known as the Maximum Shape Change Specific Energy Theory.

It's Poland. m t.

Huber improved it in 1904 from the theory of total strain energy. German rvon Mizers in 1913, H

Hench further studied and elaborated on this theory in 1925. This theory applies to plastic materials. The conditions for judging plastic failure derived from this theory are:

In the two-way stress state, 3=0, so the bad condition is:

Strength theories are divided into two broad categories, one is the expression of softness and one hardness theory. It should be equal to just one at w.

The strength is divided into two categories, and the corresponding applicable expressive force of the theory of maximum shear stress.

What are the two types of strength theory, I think you can directly send his kind of primary, so that it should be able to explain more specifically, it should be a little better

If you want to take care of things, just use your own imagination and say what you want to express.

Many theories are divided into two, and you can take a look at some of the actual situations about theories.

The four strength theories refer to the theory of maximum tensile stress, the theory of maximum elongation line strain, the theory of maximum shear stress, and the theory of shape change specific energy, which are four theories related to strength.

The four strength theories and their equivalent stressUnder normal temperature and static load, the four commonly used strength theories are divided into two categories, including: maximum tensile stress theory and maximum elongation line strain theory, the second type of strength theory, the second type of strength theory, the second type of strong field ingenuity theory——— taking the yield phenomenon as a sign of failure, the occurrence of yield phenomenon as a sign of failure, including: the maximum shear stress theory and the specific energy theory of shape change, the first type of strength theory, the first type of strength theory, the first type of strength theory, the ——— of brittle fracture as a sign of failure, and the brittle fracture as the symbol of failure of Changji calendar.

When the external force acting on the component is too large, the material at the danger point will be brittle fracture along the cross-section where the maximum tensile stress is located.

1. The first strength theory - the maximum tensile stress theory r=0 The second strength theory - the maximum elongation line strain theory o,2=[oi-v(oz+03)].

The second type of strength theory (1, maximum tensile stress theory:

This theory holds that the factor that causes the brittle fracture failure of the material is the maximum tensile stress, and no matter what the stress state, as long as the maximum tensile stress 1 at the point of random leakage in the component reaches the ultimate stress b in the unidirectional stress state, the brittle fracture of the material will occur. Therefore, the conditions for brittle fracture failure of components in complex stress states at dangerous points are: 1= b.

b s=[ So the strength condition established according to the first strength theory is: 1 [

Qi Peichang 2, maximum elongation line strain theory:

According to this theory, the maximum elongation line strain is the main factor causing fracture, and as long as the maximum elongation line strain 1 reaches the limit value u in the unidirectional stress state, the material will undergo brittle fracture failure, regardless of the stress state. εu=σb/e；ε1=σb/e。by generalized Hooke's law.

Get: 1=[ 1-u( 2 + 3)] e, so 1-u( 2 + 3)= b. According to the second intensity theory, the strength condition established is: 1-u( 2 + 3) [.]

3. Maximum shear stress theory:

According to this theory, the maximum shear stress is the main factor causing yield, and no matter what the stress state, as long as the maximum shear stress max reaches the ultimate shear stress of 0 in the unidirectional stress state, the material will yield failure. τmax=τ0。Axially.

The formula for stress on the tensile oblique section is 0= s 2 ( s - normal stress on the cross section) is obtained by the formula: max = 1s = ( 1- 3) 2. So the destruction condition is rewritten to 1- 3= s.

According to the third intensity theory, the strength conditions are: 1- 3 [.]

4. Shape change specific energy theory:

According to this theory, the specific energy of shape change is the main factor causing the yield failure of the material, and no matter what the stress state, as long as the shape change ratio at a point in the component reaches the limit value in the unidirectional stress state, the material will yield failure. The conditions for plastic failure to occur, so the strength conditions according to the fourth strength theory are: sqrt( 1 2+ 2 2 + 3 2- 1 2- 2 3- 3 1)<[

State(1) r3 = 1- 3 = 120-(-120) =240State(2) r3 = 1- 3 = 100-(-100) =200State(3) r3 = 1- 3 = 150-60 = 90State(4) r3 = 1- 3 = 100-0 = 240Apparently, state(1) is quite stressed, r3 is maximum.

Hello, happy to answer your questions. The theory mainly includes: the horizontal stress of the mine rock formation is generally the vertical stress 1

3～2.0x. Moreover, the horizontal stress is directional, and the maximum horizontal stress is generally 1 of the minimum horizontal stress

5～2.5 times. The stability of the roadway roof and floor plate is mainly affected by the horizontal stress, and there are three characteristics:

The roadway parallel to the maximum horizontal stress is least affected by the horizontal stress, and the stability of the roof and floor plate is the best. A roadway that intersects at an acute angle to the maximum horizontal stress. The deformation and failure of the roof is biased towards a certain gang of roadway; The roadway perpendicular to the maximum horizontal stress has the worst stability of the roof and floor plates.

When the strength of the bending and torsion combination is checked according to the third strength theory, for the solid round rod (or hollow round rod), there is a considerable stress = (1 w) (m 2 + t 2), where m is the bending moment.

t is torque, specific poke.

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Explanation of the theoretical terms of maximum horizontal stress.

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Hello, explanation of the terms of the theory of maximum horizontal stress: Australian scholar Gale (W J Gale) proposed the theory of maximum horizontal stress in the early 90s of the 20th century. The theory argues:

The horizontal stress of the mine rock formation is generally multiple of the vertical stress. Moreover, the horizontal stress is directional, and the maximum horizontal stress is generally times the minimum horizontal stress.

Solution: Since it is an equivalent circular axis (rod), the maximum shear stress occurs at the farthest point (circumference) of the maximum cross-section of the internal force (torque) from the center of the circle. The internal forces of the BC segment are: TBC=, and the internal forces of the AB segment are tab=, therefore:

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The relative torsion angle of AC is equal to the sum of the torsion angles of the AB and BC segments:

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Child, study hard, I hope it will help you.