The experimental results obtained, and numerous studies have led to indication of general laws, valid at the plastic deformation of metals and alloys, laws valid and applicable in the design of any technological process of making the plastic deformation of parts.
These laws are: the law of plastic deformations coexistence with the elastic deformations during plastic deformation; law of constant volume, the law of minimum resistance , the law of the emergence and balancing of internal tensions and the law of similarity.
The law of plastic deformations coexistence with the elastic deformations during plastic deformation
Experimentally it was found that plastic deformation of metallic materials is always accompanied by an elastic deformation and plastic deformation begins only after exceeding a size limit of elastic deformation. This law can be explained very well on the stress-strain diagram which is seen as the total deflection εt is composed of an elastic deformation εe and a plastic strain εp and is given by:
εe + εt = εp.
Law of constant volume
In the case of minimum loss of material by burning technology (the case of hot plastic deformation) or material jamming with interior hollows,it can be considered that material volume remains constant in any stage of deformation, thus:
V0 = V1 = V2 =... Vi =...= Vn.
The law of minimum resistance
The move of any point of material, with respect to the deformed body, located on a surface perpendicular to the direction of deformation forces, is where the perimeter is greater than the smallest distance of section.Because the point is perpendicular to the perimeter section, means that between the various ways of moving, points will choose the one where encountered resistance is minimal.
The law of the emergence and balancing of internal tensions and the law of similarity
During plastic deformation, within the material, there are tensions that are opposing to deformation (using the action and reaction principle) and that tend to balance each other.
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