Page 23 - 4749

a)

b)

Figure 1.12

Physical hypothesis (hypothesis of no pressing fibers) is as
follows. If you think that the core consists of longitudinal fibers
(rod of infinitely small cross-section), then in the deformation of
the rod these fibers do not press one another and under normal
stresses they may only undergo linear stretching or compression.
Geometric hypotheses (Bernoulli’s hypotheses) are as follows:
- cross sections that were flat before the deformation remain
flat during the deformation (fig.1.12, a);
- cross sections that are normal to the axis of the rod before
the deformation remain orthogonal to the axis during the
deformation (fig.1.12, b).

Questions for self-assessment

1. Give the definition of deformation.
2. What deformation is defined as elastic and plastic?
3. What do you mean under the terms: strength, rigidity and
resistance?
4. Which basic tasks do the science of strength of materials study?
23