How do you define yield stress and plastic strain for plastic materials?

Yield stress. In the process of material tension or compression, when the stress reaches a certain value, the stress increases slightly, but the strain increases sharply, which is called yield, and the normal stress when the material yields is the yield stress of the material.

Plastic strain: any object will be deformed under the action of external force, when the deformation does not exceed a certain limit, after the external force is withdrawn, the deformation energy will disappear, this deformation is called elastic deformation. If the external force is large, when its action stops, the deformation caused by it does not disappear completely, but there is a residual deformation, which is called plastic deformation.

Plastic strain

Introduction

Plastic processing is a processing method that uses the plasticity of the material to make the material plastically deformed under the action of external force to prepare a product with a certain shape and structural properties. External force is the external cause of plastic processing, which can be divided into two categories: surface force and volume force. The surface force is the force acting on the surface of the workpiece, which is divided into concentrated load and distributed load, which is generally provided by the processing equipment and mold.

Volumetric force is the force acting on each particle of the workpiece, such as gravity, magnetism, and inertia.

Wait a minute. In general machining, the role of volumetric forces is much smaller than that of surface forces, so they are often ignored.

But in acceleration.

In larger cases, the volume force cannot be ignored. For example, in the hammer die forging, the inertia force on the workpiece is upward, which is conducive to the filling of the material in the upper die, so the cavity with complex shape is often set in the upper die.

The input in structural>nonlinear>inelastic>rate independent>isotropic hardening plasticity >mises plasticity > is only the stress-strain change in the plastic phase of the material, and the stress-strain change in the elastic stage is not the structural>nonlinear >elastic.

In general, you should enter the elastic parameter of the material first, and the menu path is (which may not be accurate):

main menu > preprocessor > material props > material models > structural > elastic >

If you enter the plasticity parameter directly (such as the menu you gave), ANSYS will ask you to enter the elastic properties first.

The magnitude of the bending normal stress is not affected by the modulus of elasticity of the material.

Stress is not affected by the modulus of elasticity, only deformation is affected by the modulus of elasticity. The magnitude of the bending stress is directly proportional to the bending moment and inversely proportional to the modulus of the member section. The cross-sectional modulus of the member is a shape constant, so the bending stress is independent of the elastic modulus of the material.

The bending deformation is inversely proportional to the product of the modulus of elasticity of the material and the moment of inertia of the cross-section.

Derivation of bending normal stress:The bending normal stress formula is derived in the case of pure bending. When the beam is subjected to transverse force, in the cross-section, there is generally both a bending moment and a shear force, and this bending is called transverse force bending.

Due to the presence of shear force, there will be shear stress in the cross-section and thus there will be shear strain = g. Since the shear stress varies along the beam section height, the shear strain along the beam section height is also non-uniform.

There will be an impact. The modulus of elasticity is the stress required for a material to produce a unit of elastic deformation under the action of an external force. It is an indicator of the material's ability to resist elastic deformation, which is equivalent to the stiffness in ordinary springs.

In the elastic deformation stage of the material, its stress and strain are directly proportional. The larger the elastic modulus value, the greater the bending normal stress that causes a certain elastic deformation of the material, that is, the greater the stiffness of the material, that is, the smaller the elastic deformation occurs under a certain stress.

Application Points:Bending stress refers to the change component of normal stress along the thickness, which can be linear or nonlinear. The maximum value occurs at the surface of the wall thickness, and the maximum value is generally used for strength verification during design. After the surface of the wall thickness reaches the yield limit, the bearing capacity can still be improved, but the surface stress does not increase, and the yield layer expands from the surface to the middle.

Therefore, in the pressure vessel, the bending stress is less harmful than the film stress of the same value.

The yield strain and yield strength of plastic tensile are not the same! Hello, I am glad to answer for you<> the yield strain and yield strength of the pro-plastic tensile are not the same tensile strength, and the yield strength is different: 1. The strength is different:

The yield strength corresponds to the yield point, which refers to the point at which the metal undergoes plastic deformation, and the corresponding strength becomes the yield strength. Tensile strength refers to the ability of the material to resist external forces, and the strength of the general tensile test when it is broken. 2. The deformation ability is different

Yield strength reflects the ability of a material to resist deformation; Tensile strength reflects a material's ability to resist tensile failure. 3. Different degrees: when the steel yields to a certain extent, due to the rearrangement of the internal grains, its ability to resist deformation is increased again, although the deformation develops rapidly, it can only increase with the increase of stress until the stress reaches the maximum.

1. Yield stress is the stress at the yield point on the stress-strain curve. The yield strength, as an index of the resistance of the material, that is, the yield limit, is the critical stress value of the material yield, which is called the yield point or yield strength and yield limit. The ultimate stress of a plastic material is the yield limit or yield strength, and the ultimate stress of a brittle material is the strength limit or tensile strength.

2. The yield strength corresponds to the yield point, which refers to the point where the metal is plastically deformed, and the corresponding strength becomes the yield strength. Allowable stress refers to the use of yield stress divided by a safety factor for the use of mechanical parts for safety purposes. Tensile strength refers to the ability of the material to resist external forces, and the strength when it is broken during a general tensile test.

3. The conversion relationship is: yield stress excitation early = yield strength safety travel coefficient, I hope mine can help you <>

Do you have any other questions?

Plasticity strain method: The measurable strain limit of a general resistance strain gauge is 8,000 to 20,000 mm (ie. For small plastic strains such as less than 2%, ordinary foil strain gauges are sufficient.

For cases where plastic strain greater than 2% needs to be measured, a special large strain strain gauge is used.

There are a variety of specifications of Huaichun products abroad, which can measure % and 20% plastic strain respectively. There are also large strain strain gauges used for % strain measurement in China.

Definition. Stress occurs in engineering materials. When the stress is less, an elastic strain will be generated, i.e., the coincidence stress is proportional to the strain.

Relations (Hooke's Law of Argumentation.

, and this strain disappears with it when the stress disappears. When the stress increases to a certain value, the stress is no longer proportional to the strain, and after the stress disappears, it will leave a permanent deformation in the Ming Dynasty, which is called plastic strain.

The formula for the relationship between stress and strain: f=k·x or f=k·δx, stress is the cause of strain, and strain is the result of stress. When an object is deformed due to external factors (force, humidity, temperature field changes, etc.), an internal force is generated between the various parts of the object to resist the action of this external factor, and the object is restored from the deformed position to the pre-deformed position.

The internal forces per unit area at a certain point of the cross-section under investigation are called stresses. Those perpendicular to the same cross-section are called normal stresses or normal stresses, and those tangent to the same cross-section are called shear stresses or shear stresses.

Stress will increase with the increase of external force, for a certain material, the increase of stress is limited, beyond this limit, the material will be destroyed. The limit of stress that can be reached for a material is called the ultimate stress of that material. The ultimate stress value is determined by mechanical tests of the material.

The measured ultimate stress is appropriately reduced to specify the maximum stress value of the material that can work safely, which is the allowable stress. For a material to be safe to use, the stress in it should be lower than its limit stress during use, otherwise the material will break during use. In most cases, the internal forces are not uniformly distributed, and usually the "failure" or "failure" often starts from the maximum concentration of internal forces, so it is necessary to distinguish and define the concept of stress.

The relationship between strength and plasticity is as follows

Strength refers to the ability of metal materials to resist plastic seepage deformation and fracture under static load. Plasticity refers to the ability of metal materials to produce plastic deformation under static load without causing damage. The criterion of strength and plasticity of metal materials can be determined by tensile tests.

Generally, the yield strength of steel is between 200-1000MPa. The higher the strength, the more the metal material can withstand higher loads when working. When the load is constant, the use of high-strength materials can reduce the size of components or parts, thereby reducing their own weight.

What is the engineering significance of strength and plasticity:

Strength is a mechanical index that reflects the bearing capacity of the material, which generally refers to the bearing capacity of the material when it does not undergo plastic deformation, or the bearing capacity when it does not break and break; In engineering, the stress on the part is below the yield strength, and the part will not be plastically deformed during use; Under the tensile strength of the part, the part will not break and damage during use.

Plasticity characterizes the ability of a material to be permanently deformed before it breaks. Only better materials can be deformed. The material with good plasticity is not easy to brittle, and the safety is better when applied.

Impact toughness reflects the resistance of metal materials to external shock loads. <>

Qinqin is happy to answer for you: What is the yield stage of plastic materialsAnswer: Qinqin plastic materials Yield stage (the increase of strain is greater than the increase of stress, and the plastic Zheng Shenqi deformation begins, and the lower limit of stress is shouted as the yield point) Yield strength is the yield limit of metal materials when the yield phenomenon occurs, that is, the stress that resists trace plastic deformation.

For metal materials without obvious yielding phenomenon, the stress value of residual deformation is used as its yield limit, which is called conditional yield limit or yield strength. An external force greater than the yield strength will cause the part to fail permanently and cannot be recovered. For example, the yield limit of mild steel is 207MPa, when the external force greater than this limit acts, the parts will produce permanent deformation, less than this, the parts will return to their original appearance.

1 For materials with obvious yield phenomena, the yield strength is the stress (yield value) at the yield point. 2 For materials where the yield phenomenon is not obvious, the stress when the ultimate deviation of the linear relationship with stress-strain reaches a specified value (usually the original gauge distance). It is usually used as an evaluation index for the mechanical properties of solid materials, and is the practical use limit of materials.

Because after the stress exceeds the yield limit of the material, the necking will occur, and the strain will increase, so that the material will be damaged and cannot be used normally. When the stress exceeds the elastic limit, the deformation increases rapidly after entering the yield stage, and at this time, in addition to the elastic deformation, part of the plastic deformation is also generated. When the stress reaches point b, the plastic strain increases sharply, and the stress fluctuates slightly, a phenomenon called yield.

The maximum and minimum stresses at this stage are called the upper and lower yield points, respectively. Since the value of the lower yield point is relatively stable, it is used as an indicator of the resistance of the material, which is called the yield point or yield strength (rel or.

For plastic materials, the greater the strength of similar materials, the worse their plasticity, but there is no obvious law, and there are many exceptions.

For brittle materials, it is generally only under certain special conditions that they exhibit a certain plasticity. Therefore, it does not make much sense to study the relationship between the two.

These are just general rules. In the case of metal materials, it is sometimes possible to improve both strength and plasticity by means of technical means such as grain refinement.