Standard Depth of Penetration (4)

Question 1

What is the Standard Depth of Penetration?

Answer 1

The depth at which the EC strength has dropped to 37% of the total strength at the material surface..

Question 2

% at 2 Standard Depths:

Answer 2

15%

Question 3

Standard Depth of Penetration decreases how many times without an associated loss in EC strength?

Answer 3

x5 any inspections beyond 5 standard depth are rendered invalid.

Question 4

Loss in EC strength from increasing material depth is due to what?

Answer 4

• material conductivity
• material permeability
• selected frequency

highly conductive and low permeable materials will cause EC to concentrate more at the surface (skin effect)

Question 5

EC inspection sensitivity will always be the highest at the _____.

Answer 5

at the surface of a material, and will decrease with depth.

Question 6

Symbol for Standard Depth of Penetration:

Answer 6

Delta δ

Question 7

Formula for Standard Depth of Penetration

Answer 7

δ = 50 √p/fu

δ  = standard depth of penetration
p = resistivity (uΩ/cm)
f = frequency (Hz)
u = permeability