249
Mechanical Properties
11
11.1
General Considerations
In 1987 Gleiter and coworkers [1] published a paper on plastic deformation of CaF 2
at room temperature. This paper was the starting point for the huge scientific
interest on nanomaterials. In the meantime, bulk nanomaterials and their
mechanical properties are no longer at the center of the scientific interest as the
thermodynamic stability of these materials is quite limited. However, the mechanical properties of nanocomposites filled with one- or two-dimensional nanoparticles
are getting increasingly important, from both the scientific and commercial
aspects. Additionally, a new type of material with extremely small grain size,
materials produced by severe plastic deformation moved in the center of interest
[2]. However, because of their relatively large grain size, in general, more than
100 nm, these materials, with excellent new properties, will not be discussed
within this book.
The mechanical properties of bulk materials, independent of their grain size,
are characterized by the stress–strain diagram. Such a stress–strain diagram,
which is typical, for example, for metals is depicted in Figure 11.1.
The stress–strain diagram depicted in Figure 11.1 is typical for tension experiments with metallic specimen. The graph is characterized by the regions where
the specimen is deformed elastically or plastically, separated by the yield stress.
Further parameters characterizing the specimen are the ultimate strength and the
rupture strain. The strain ε, as used in Figure 11.1 is defined as
ε =
∆l
l
,
(11.1)
where l is the length of the specimen and Δl the elongation of the specimen during
the experiment. The stress σ is defined as
σ =
P
A
.
(11.2)
The quantity P stands for the force and A for the cross-sectional area of the specimen. Generally, it is difficult to determine the yield stress exactly; therefore, the
Nanoparticles – Nanocomposites – Nanomaterials: An Introduction for Beginners, First Edition. Dieter Vollath.
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA. Published 2013 by Wiley-VCH Verlag GmbH & Co. KGaA.
Mechanical Properties
11
11.1
General Considerations
In 1987 Gleiter and coworkers [1] published a paper on plastic deformation of CaF 2
at room temperature. This paper was the starting point for the huge scientific
interest on nanomaterials. In the meantime, bulk nanomaterials and their
mechanical properties are no longer at the center of the scientific interest as the
thermodynamic stability of these materials is quite limited. However, the mechanical properties of nanocomposites filled with one- or two-dimensional nanoparticles
are getting increasingly important, from both the scientific and commercial
aspects. Additionally, a new type of material with extremely small grain size,
materials produced by severe plastic deformation moved in the center of interest
[2]. However, because of their relatively large grain size, in general, more than
100 nm, these materials, with excellent new properties, will not be discussed
within this book.
The mechanical properties of bulk materials, independent of their grain size,
are characterized by the stress–strain diagram. Such a stress–strain diagram,
which is typical, for example, for metals is depicted in Figure 11.1.
The stress–strain diagram depicted in Figure 11.1 is typical for tension experiments with metallic specimen. The graph is characterized by the regions where
the specimen is deformed elastically or plastically, separated by the yield stress.
Further parameters characterizing the specimen are the ultimate strength and the
rupture strain. The strain ε, as used in Figure 11.1 is defined as
ε =
∆l
l
,
(11.1)
where l is the length of the specimen and Δl the elongation of the specimen during
the experiment. The stress σ is defined as
σ =
P
A
.
(11.2)
The quantity P stands for the force and A for the cross-sectional area of the specimen. Generally, it is difficult to determine the yield stress exactly; therefore, the
Nanoparticles – Nanocomposites – Nanomaterials: An Introduction for Beginners, First Edition. Dieter Vollath.
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA. Published 2013 by Wiley-VCH Verlag GmbH & Co. KGaA.