A machine element, also known as a machine part, is the basic element that constitutes a machine, and is an inseparable single piece that composes a machine and a machine.

Mechanical parts are not only a discipline to study and design mechanical basic parts in various equipment, but also a general term for parts and components.

Mechanical parts Mechanical parts will produce different forms of deformation under the action of different external forces. The main forces and deformations are as follows:

Stretch and Compress

This type of deformation is caused by a pair of forces that are equal in size and opposite in direction, and the line of action coincides with the axis of the rod, which shows that the length of the rod is elongated or shortened. Such as the deformation of the wire rope for lifting heavy objects, the rod of the truss, the piston rod of the hydraulic cylinder, etc., all belong to the tensile or compression deformation. Rods that are subjected to tension or compression are often seen in engineering. such as tightening screws [ Figure 3-2(a)], when the nut is tightened, the compressed workpiece has a reaction force on the screw, and the screw is stretched; the screw of the jack [Figure 3-2(b)] When lifting heavy objects, it is subjected to compression. The former is elongated and deformed, the latter is shortened and deformed. The straight rod is subjected to external forces of equal magnitude and opposite direction along the axis. When the deformation of elongation or shortening occurs, it is called the axial stretching or compression of the straight rod. Only axial tension and compression of straight rods are discussed in this chapter. If the shape and force of the rod subjected to axial tension or compression are simplified, it can be simplified to the force diagram shown in Figure 3-1. In the figure, the solid line represents the shape before stress, and the dashed line represents the shape after deformation.  

Cut

Components subject to shearing are often seen in engineering. The common feature of such rods is that they are subjected to external forces of equal magnitude and opposite directions on both sides of the member, and the lines of action are very close and perpendicular to the rod axis. Under such external force, the main deformation of the rod is: with two forces The cross section m-m between the two parts is the interface, and the two parts of the component move relative to each other along this surface. This deformation form of the member is called shearing, and the section m-m is called the shearing plane, and the shearing plane is parallel to the direction of the external force. When the external force is large enough, the member will be sheared along the shear plane.