The internal stresses of cold plastic deformation are divided into 3 according to the range of actio

The mechanical properties of plastic materials and brittle materials are very different in tension and compression, as follows:

Stretch. Plastic deformation will occur during the tensile process, and the tensile stress will gradually increase, and after reaching the ultimate strength, it will begin to shrink and eventually break. Fragile materials, on the other hand, break quickly during the tensile process, and the tensile stress-strain curve is linear.

The cross-section of the plastic material will undergo obvious shrinkage deformation, and there will be a significant difference in length before and after stretching. However, the cross-sectional deformation of brittle materials is small, and the length change is not obvious.

The fracture of the plastic material is dimple-like and has obvious toughness. The fracture of brittle material presents a flat surface and lacks toughness.

Compress. During the compression process of plastic materials, due to the existence of multiple microscopic strength directions inside, shrinkage deformation in different directions will occur, and the compressive stress-strain curve will show an obvious plateau region until local failure. The brittle material presents a linear stress-strain curve during compression, and the compressive stress quickly reaches the ultimate strength and then causes failure.

The compressive failure mode of plastic materials shows a short columnar shape, showing a certain toughness. However, the compressive failure mode of brittle materials is flat or block-like, lacking toughness.

In summary, the mechanical properties of plastic materials and brittle materials are very different in tension and compression, and the application occasions are also different. Plastic materials are usually used in occasions that require good toughness and plasticity, such as metal materials, plastics, etc.; Embrittle materials are usually used in applications that require high hardness and wear resistance, such as ceramics, cemented carbide, etc.

Answer] :d 2021 2020 2019 textbook p39

The tensile yield strength refers to the stress of the steel when it begins to produce plastic deformation under the use of external forces.

Summary. There are generally two basic forms of stress-strain curves for plastic materials: smooth curves with a decreasing curve after the yield point and curves with quasi-linear segments.

There are generally two basic forms of stress-strain curves for plastic materials: smooth curves with a decreasing curve after the yield point and curves with quasi-linear segments.

Can you tell us more about that?

There are two basic forms of stress-strain curves of plastic materials: one is a curve with a degradation section, that is, after the rigid stage reaches the maximum value, the strain gradually increases, but the stress shows a downward trend; The other is that there is no descending equilibrium stage, that is, the stress and the strain in the rigid stage correspond to the linear growth, but the subsequent increase of the strain makes the stress gradually increase to the maximum value and maintain stability. In the stress-strain curves of plastic materials, there are usually some phenomena of uneven orientation distribution, such as the yield point is not obvious, the staircase-shaped stress-strain curve, etc., which are all irregular forms of stress-slip strain curves, which need to be analyzed in combination with the specific characteristics of the material.

Summary. There are two basic forms of stress-strain curves for plastic materials: unimodal curves and bimodal curves.

There are two basic forms of stress-strain curves for plastic materials: unimodal curves and bimodal curves.

Excuse me, but please go into more detail?

There are two main forms of stress-strain curves for plastic materials, one is unimodal and the other is bimodal. The characteristic of the unimodal stress-strain curve is that in the process of gradual increase of strain, the stress first increases linearly, and after reaching the limit, the stress begins to decrease rapidly, while the strain still continues to increase, indicating that the material has undergone plastic deformation at this time. The bimodal field shielding stress-strain curve refers to the situation where the stress of the material will suddenly drop when it is formed, and then rise again, and this kind of early loss curve usually occurs under certain conditions, such as high temperature, low strain rate, and large deformation.

Summary. Hello, there are two basic forms of stress-strain curves for plastic materials: unimodal and bimodal.

The stress-strain curve of the unimodal type shows that the strain increases linearly with increasing stress during the tensile phase before the maximum stress point. When the stress reaches its maximum strength, the strain begins to increase no longer linearly, but begins to deform plastically, and the rate of strain increase gradually slows down. At this point, the stress reaches its maximum, known as the yield point, and the material begins to enter the yield phase.

During the yield period, the material can undergo plastic deformation within a certain range, at which point the stress decreases, a process called a flow process. As the stress continues to increase and the material reaches its ultimate strength, the rate of strain increase rapidly and eventually leads to the rupture of the material.

Hello, there are two basic forms of stress-strain liquid laughter curves for plastic materials: unimodal and bimodal. The stress-strain curve of the unimodal pattern shows that the strain increases linearly with the increase of the leased or buried stress during the tensile phase before the maximum stress point.

When the stress reaches its maximum strength, the strain begins to increase no longer linearly, but begins to deform plastically, and the rate of strain increase gradually slows down. At this point, the stress reaches its maximum, known as the yield point, and the material begins to enter the yield phase. During the yield period, the material can undergo plastic deformation in the range of one trillion meters, at which point the stress decreases, a process called the flow process.

As the stress continues to increase and the material reaches its ultimate strength, the rate of strain increase rapidly and eventually leads to the rupture of the material.

Can you elaborate on that a little bit more?

The stress-strain curves of the bimodal type show that the material enters a weakening zone first, during which the material strain increases, but the stress increase rate gradually slows down. After that, the material enters a strengthening zone, during which the rate of strain increase of the material begins to accelerate and reaches a peak, and as the stress continues to increase, the rate of strain increase begins to decrease, at which point the material enters the rheological zone. When the final material reaches its ultimate strength, the rate of strain increases rapidly, eventually leading to rupture.

The stress-strain relationship during plastic deformation is called the constitutive guanqing finch system, and the mathematical expression of this relation.

It is called the constitutive equation, also known as the physical equation, and is used to solve the plastic forming problem.

The stress-strain relationship during plastic deformation has the following characteristics:

1) The relationship between stress and strain is nonlinear;

2) Plastic deformation is irreversible and irreversible;

3) The plastic deformation can be considered as the volume is constant, the strain ball tensor is zero, and the Poisson's ratio.

v=；4) The total strain spindle and the stress spindle generally do not coincide.

When simple loading is taken (only loading can be carried out during the loading process, and the stress components should be increased according to a certain praise ratio), there is the following relationship between the principal stress and the principal strain at each moment of plastic deformation

In the formula, the ratio c is called the proportionality constant, and under certain deformation conditions, it is only related to the properties and deformation degree of the material, but not to the stress state of the object. In short, the material is certain, the degree of deformation is certain, and c is a fixed value. c. One-way tensile test can be used.

Find. If the average stress is m, the above equation can also be expressed as.

The above-mentioned physical equation for plastic deformation is called the total strain theory, which is used to study the small deformation problem under the condition of simple loading in Gyeongjeong-jeong. But for plastic bending forming in Africa.

For the problem of large deformation of simple loading, as long as the direction of the spindle does not change too much and the spindle order is basically unchanged, the above relationship can also be used to calculate.