Page 73 - 4749

.

The fourth theory has very good strength convergence with
experimental data for plastic materials.
Let also study the theory of strength of limit stress states
(Mohr’s strength theory). It is based on a logical systematization of
a number of experimental results.
According to this theory the strength criterion is the value
   ,
1 3
 

where the coefficient   t .
 

c
In other words, according to Mohr’s theory of strength the
destruction of the material in any complex stress state is reached
when the value    exceeds the allowable tensile stress that is
1 3
defined in the linear stress state.
The strength conditions by Mohr’s strength theory are:
 M        . (3.39)

eqv 1 3 t
Mohr’s theory is used in the calculation of structures with
brittle materials. It has better convergence with the experimental
data than the first and the second theories of strength, especially
for stress states in which   0 and   0 .
1 3


Obviously, for plastic materials (    )   1 and the

t c
expression (3.39) is transformed into the condition (3.35).
For very brittle materials that are practically unable to perceive
tensile stress, we can assume that   0 the formula (3.39) turns
into a strength condition in the first theory.

Questions for self-assessment

73