Is axial force internal force
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axial force refers to the internal force along the axis of the member, which is right,
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axial force is the internal force coincident with the axis of the member, which is expressed by the symbol FN. When the member is in tension, the axial force is tension, which points away from the section; When the member is compressed, the axial force is compression, which points to the section
It is generally stipulated that the pulling force is represented by a positive sign and the pressure is represented by a negative sign The unit of axial force is n or kn
the unit of axial force is n or kn< Calculation of truss axial force with node method:
two unknown forces can be obtained from a node equation, generally starting from the support node and proceeding in turn. For a node, if the member is removed and replaced by force along the member direction, it can be assumed that it is tensile force (if the force is negative, it means pressure). The equilibrium equations in X and Y directions are listed respectively (the forces are projected into the equilibrium equations in X and Y directions respectively): ∑ x = 0 ∑ y = 0. The specific form may be as follows: f1cosa + f2cosb + acosc = 0, f1sina + f2sinb + asinc = 0, where a represents the known force, F1 F2 is the unknown force. The unknown forces F1 and F2 can be obtained by solving the equations. The positive value is the tensile force and the negative value is the pressure.
Difference between internal force and stress:
1. Internal force: internal force refers to the force that causes internal interaction of components under the action of external force. Internal force is closely related to the strength, stiffness and stability of components, so it is very important to study the internal force of components
Stress: when an object is deformed e to external factors (stress, humidity, temperature field change, etc.), the internal force of the interaction between various parts of the object is generated to resist the effect of the external factors, and the object is tried to recover from the position after deformation to the position before deformation The internal force is the interaction between the parts of the same body. Stress is a vector, the component along the normal direction of the cross section is called normal stress, the component along the tangential direction is called shear stress, and the stress of a point in the body in all possible directions is called the stress state of the point When the internal force and stress appear at the same time, the internal force is generally used to represent the combined effect of the force on the member section, such as bending moment, shear force, axial force, etc., while the stress represents the force on the unit area of the member section, such as normal stress and shear stressDifference and connection between internal force and stress:
1. Difference:
Internal Force: internal force refers to the force that causes internal interaction of components under the action of external force. Internal force is closely related to the strength, stiffness and stability of components, so it is very important to study the internal force of components
stress: when an object is deformed e to external factors (stress, humidity, temperature field change, etc.), the internal force of interaction between various parts of the object is generated to resist the effect of this external factor, and the object is tried to recover from the position after deformation to the position before deformation
Connection:when the internal force and stress appear at the same time, the internal force is generally used to represent the combined effect of the force on the member section, such as bending moment, shear force, axial force, etc., while the stress represents the force on the unit area of the member section, such as normal stress and shear stress
extended data:
1. The role of internal force:
under the action of internal force, horizontal strata bend or cause fracture, which is an important reason for the formation of mountains and valleys on the earth, which is the horizontal movement of internal force; There was also the movement of ascent and descent, which changed and caused the division of the land
2. Classification of stress:
(1) normal stress and shear stress which are perpendicular to the same section are called normal stress or normal stress, and those which are tangent to the same section are called shear stress or shear stress. The stress will increase with the increase of the external force. For a certain material, the increase of stress is limited. Beyond this limit, the material will be destroyed
(2) tensile stress and compressive stress when a cylinder is compressed at both ends, the stress along its axis is compressive stress. Compressive stress is the stress that makes the object tend to compress. It is not only the compressive stress caused by the force on the object, but also any compression deformation, including the expansion of the object. In addition, if a beam is bent, whether it is caused by stress or uneven heating of the beam, and so on, the inner side of the bending will naturally bear compressive stress, and the outer side will bear tensile stress