Question

The shear stress required to move a dislocation through a crystal lattice is called:

• A. Critical resolved shear stress
• B. Flow stress
• C. Hoop stress
• D. Peierls stress

Hint:

Slip starts when resolved shear stress reaches CRSS.

Answer 1

The Correct Option is A

Concept: Plastic deformation in crystals occurs due to dislocation motion along slip systems. The minimum shear stress required to initiate slip is called: \[ \text{Critical Resolved Shear Stress (CRSS)} \]

Step 1: Resolved shear stress concept.
When a load is applied: \[ \tau = \sigma \cos\phi \cos\lambda \] Slip begins when: \[ \tau = \tau_c \]

Step 2: Physical meaning.
CRSS is:
• minimum stress required for dislocation motion
• depends on crystal structure and temperature

Step 3: Check options.

• Flow stress → general plastic stress
• Hoop stress → pressure vessel stress
• Peierls stress → lattice resistance (specific case) CRSS is the general governing parameter. Final Answer: \[ \boxed{\text{Critical resolved shear stress}} \]