Chapter 12
Origin and Development of Plasticity
Theory
12.1 Primary Definitions 1
As said above (p. 10), the difference in distance between different particles of a body
before and after loading characterizes permanent deformation. Experiments show
that a property to acquire permanent deformations is observed in specific conditions
in all real solid bodies. In many cases, permanent deformations are almost as high
as elastic ones or even exceed them.
The studies have shown that for some bodies (steel, non-ferrous metals, their
alloys, etc.), permanent deformations are accompanied by a residual change in body
volume. We will call them plastic deformations. For elastic bodies (cast irons, soils,
rocks, etc .), a residual change in the volume is observed. In this case, one always
separates that part of permanent deformation that is not related to the change in
body volume. Let us call this part of permanent deformation purely plastic or simply
plastic deformation. The difference between full non-elastic deformation and purely
plastic deformation is called softening deformation. Let us call negative softening
deformation as compaction.
Experiments found that this component of non-elastic deformation accompanied
plastic deformation in some conditions. In what follows, we will use the term “complex deformation” to denote such solid body deformation when it contains all three
previously defined types of deformation, e.g. plastic and softening deformation.
1 This chapter can be omitted during first reading.
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
V. Molotnikov, A. Molotnikova, Theory of Elasticity and Plasticity,
https://doi.org/10.1007/978-3-030-66622-4_12
145
Origin and Development of Plasticity
Theory
12.1 Primary Definitions 1
As said above (p. 10), the difference in distance between different particles of a body
before and after loading characterizes permanent deformation. Experiments show
that a property to acquire permanent deformations is observed in specific conditions
in all real solid bodies. In many cases, permanent deformations are almost as high
as elastic ones or even exceed them.
The studies have shown that for some bodies (steel, non-ferrous metals, their
alloys, etc.), permanent deformations are accompanied by a residual change in body
volume. We will call them plastic deformations. For elastic bodies (cast irons, soils,
rocks, etc .), a residual change in the volume is observed. In this case, one always
separates that part of permanent deformation that is not related to the change in
body volume. Let us call this part of permanent deformation purely plastic or simply
plastic deformation. The difference between full non-elastic deformation and purely
plastic deformation is called softening deformation. Let us call negative softening
deformation as compaction.
Experiments found that this component of non-elastic deformation accompanied
plastic deformation in some conditions. In what follows, we will use the term “complex deformation” to denote such solid body deformation when it contains all three
previously defined types of deformation, e.g. plastic and softening deformation.
1 This chapter can be omitted during first reading.
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
V. Molotnikov, A. Molotnikova, Theory of Elasticity and Plasticity,
https://doi.org/10.1007/978-3-030-66622-4_12
145