Working ability of mechanical parts
Various mechanical and engineering structures are composed of a number of components. These components work to bear the role of the force, in order to ensure that the components in the working conditions and the use of life during the normal work, to meet the following requirements:
1. Have enough strength
It is a prerequisite for the normal operation of the component to ensure that the component does not occur under the external force, so the strength of the component is the ability to resist the damage under the action of external forces.
2. Have enough stiffness
The deformation caused by the member under the external force should be within the allowable limit. The capacity of the member to resist deformation under the action of external force, that is, the stiffness of the member.
3. Have enough stability
Some slender members (or thin-walled members) in the axial pressure to reach a certain value, will lose the original balance of the form and the loss of work ability, this phenomenon is known as instability. Stability refers to the ability of the component to maintain the balance of the original form.
The strength, stiffness and stability of the components are related to the mechanical properties of the materials used, and the mechanical properties of the materials must be determined by experiments. In addition, some practical engineering problems can not be solved by theoretical analysis, which must depend on the experimental methods.
The actual engineering structure in many load-bearing components such as bridges, automobile transmission shaft, the beam and column, the length of the size is far greater than the cross-sectional dimensions, this kind of component in the study of mechanics of materials, often referred to as a bar, all the centroid of cross section of the rod connecting line, called the axis for the bar, if the axis is a straight line, it is called straight rod; axis curve is called curved bar. Rod shape and size of all cross section are the same as with rod; different called variable cross-section bar. The mechanics of materials research uniform bar.
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