1: The concept of stress state
1:
The components are not all damaged along the cross-section under the basic deformation of tension, torsion and bending. In order to analyze various failure phenomena and establish the strength conditions of combined deformation, the stress on each different inclined section must also be studied.
The collection of stresses on surfaces in different directions through a point is called the stress state at this point.
The calculation of the stress state must indicate: which surface and which point
2: Concept of point of stress
The formula can be consolidated again: 
3: The concept of stress surface
Stress on a uniaxially stretched oblique section
4: Main unit body, principal stress, principal plane
Two: plane stress state analysis
1: Stress on the inclined section
Capable students can deduce, if you don't want to, just remember the conclusion! ! ! ! ! ! ! ! ! !
example:
Stress extreme
discuss
