What is the physical meaning of principal stresses?
- AStresses that act only in the x and y directions
- BStresses that produce only shear deformation
- CNormal stresses on planes where shear stress is zeroCorrect
- DStresses that always cause failure
Solution
Concept
Physical meaning of principal stresses
Formula
NONE
Step-by-step solution
1. Principal stresses represent extreme normal stresses acting on mutually perpendicular planes. 2. On these principal planes, the shear stress values vanish completely. Answer: C
Explanation
Principal planes are specific orientations within a stressed body where the acting shear stress vanishes completely. The normal stresses acting on these zero-shear planes represent the maximum and minimum normal stresses, known as principal stresses. Thus, option C provides the correct definition of principal stresses.
Why the other options are wrong
A) Principal stresses act along principal planes where shear stress vanishes, not limited to coordinate axes. D) Principal stresses represent normal stresses on principal planes and do not inherently cause failure.
Shortcut
Principal planes are defined by having ZERO shear stress, where normal stress is maximum/minimum.
Common mistake
Assuming principal stresses are restricted to fixed x and y coordinate axes and selecting option A.
Correct answer: C) Normal stresses on planes where shear stress is zero