How to distinguish between the maximum tensile stress and the maximum compressive stress on a cross

1. Tensile stress and compressive stress exist at the same time when the material is bent.

2. If the two ends are bent downward, the lower part is the compressive stress, the bottom is the maximum compressive stress, the top is the tensile stress, and the top is the maximum tensile stress.

3. The stress of the neutral layer is zero, and the tensile stress gradually increases from the neutral layer to the upward level, and the compressive stress gradually increases from the neutral layer to the downward level.

Bending stress

It means that the change in the component of the normal stress along the thickness 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.

1. Under normal circumstances, there is both tensile stress and compressive stress when the material is bent, if it is bent downward at both ends, the following is the compressive stress, the bottom is the maximum compressive stress, the top is the tensile stress, and the top is the maximum tensile stress.

2. The external force on the material is called the external load (tensile stress), and the reaction force generated inside the material is called stress. If an object is stretched at both ends, then the stress that resists tension along its axis is tensile stress. Tensile stress is the reaction force of an object to an external force that gives the object a tendency to stretch.

3. Compressive stress refers to the stress that resists the compressive tendency of the object.

1. The method of judging tensile stress and compressive stress is as follows: the material is compressed at both ends, and the compressed object is divided into small pieces, and even if there is a tendency to resist extrusion between the small pieces, they are still extruded from each other, which is compressive stress. On the contrary, it is tensile stress.

2. The external force on the material is called the external load, and the reaction force generated inside the material is generated.

This is called stress. When an object is stretched at both ends, the stress that resists tension along the axis of the shaft is the tensile stress. Tensile stress is the reaction force of an object to an external force that gives the object a tendency to stretch. Compressive stress is the stress of the chain that resists the tendency of the object to compress.

When performing tensile testing, the magnitude of the tensile force of the cross-section and longitudinal section depends on many factors, including the physical properties of the material, the direction of the tensile force, and the magnitude of the force.

In general, if the direction of the tensile force is the same as the crystal direction of the material, the tensile force of the cross-section surface will generally be greater than that of the longitudinal section. This is because, the crystal orientation of the material is the direction of the arrangement of the atoms inside it, and if the direction of the tensile force is the same as the crystal direction, then the arrangement of the atoms inside the material will be tighter and hence the strength of the material will also be greater.

However, if the direction of the tensile force is opposite to the crystal direction of the material, the tensile force of the longitudinal section will generally be greater than that of the cross-section. This is because the crystal orientation of the material is the direction of the arrangement of atoms in the wide part of the material, and if the direction of the tensile force is opposite to the crystal direction, the arrangement of the atoms inside the material will be looser, and therefore the strength of the material will be less.

Therefore, the magnitude of the tensile force of the cross-section and the longitudinal section depends on various factors such as the physical properties of the material, the direction of the tensile force, and the magnitude of the force, and is not absolute.

The two collinear forces directed at the ends of the object are subjected to a compressive stress on the cross-section of the object, which is negative. The two ends of the object are subjected to two collinear forces facing away from it, and the tensile stress on the cross-section of the object is positive.

The external force experienced by the material is called the external load, and the reaction force generated inside the material is called stress. If an object is tensile at the end of the code, then the stress that resists tension along its axis is the tensile stress. Tensile stress is the reaction force of an object to an external force that gives the object a tendency to stretch.

To analyze whether a stress is tensile stress or compressive stress, it mainly depends on the effect of the reaction force of the force acting on the object, that is, the effect of the force exerted on the object by the outside world, which has a tendency to make the size of the object larger, and the tendency to become smaller or smaller, which is compressive stress and tensile stress.

The condition for the maximum tensile stress of the maximum moment section is equal to the maximum compressive stress is ().

a.The tensile and compressive strength of the beam material is equal.

b.The cross-sectional shape is symmetrical to the neutral axis.

c.Both of the above are met.

d.The cross-section shape is asymmetrical to the neutral axis.

Correct answer: B

The reaction force is not stress, stress is the distribution state of the internal force of the object in general, and the reaction force is just a force, which can be said to be the gap between theoretical mechanics and material mechanics.

You don't always think of strength as very real and visual, it's not that someone else punches you and calls it strength.

For example, a fat man, he is affected by the gravitational pull of the earth and the support force of the earth for him, for him the force situation is the situation you said, but whether he wants to tighten his belt, whether his belly is expanding, all this is the result of two pressures, so his belly is subjected to tensile stress, and he has to tie the belt. Also in the direction parallel to the Earth's gravity, he is subjected to compressive stress, isn't it? Is this person tying the strap ** due to compressive stress?

Without compressive stress, the belly does not expand, and there is no tensile stress in the middle.

You can first draw the axial force diagram, and then use the axial force diagram to judge, the tensile stress is positive and the compressive stress is negative.

Note: The tensile stress mentioned in the question refers to the "stress that resists compression", not the stress on the object itself, which is subjected to compressive stress, so there is no contradiction between the top and bottom.

The former is the definition of stress, and the latter is a force analysis and is not contradictory. Because the former is an idealized homogeneous material, while the latter is not, it is different at each cross-section and at each point.

9-1 Stress on the oblique section of the axial tension and compression rod.

1. Each point on the oblique section of the axial tension and compression rod has both normal stress and shear stress.

2. The calculation formula of normal stress and shear stress at each point on the oblique section of the axial tension and compression rod: The symbol stipulates that when the x-axis is turned counterclockwise to the outer normal n of the oblique section, it is positive, and vice versa. The maximum normal stress occurs in the cross-section, the maximum cut.