Question

Dye penetrant test is based on the principle of

• A. polarized sound waves in liquid.
• B. magnetic domain.
• C. absorption of X-rays.
• D. capillary action.

Hint:

For NDT methods, remember the key principle: Dye Penetrant \(\rightarrow\) Capillary Action; Magnetic Particle \(\rightarrow\) Magnetic Fields; Ultrasonic \(\rightarrow\) Sound Waves; Radiography \(\rightarrow\) X-rays/Gamma rays.

Answer 1

The Correct Option is D

Step 1: Understanding Dye Penetrant Testing (DPT):
Dye penetrant testing is a non-destructive testing (NDT) technique used to detect surface-breaking defects such as cracks, porosity, and laps in materials.
Step 2: Principle of Operation:
The test uses a liquid penetrant with low viscosity and high wettability. When applied to the surface, the liquid penetrant enters small surface cracks and discontinuities without any external force.
Step 3: Role of Capillary Action:
The penetration of the liquid into narrow defects occurs due to capillary action, which is the ability of a liquid to flow into small spaces because of surface tension and adhesive forces. Later, a developer draws the penetrant back to the surface, making the defects visible.
Final Conclusion:
Thus, dye penetrant testing is fundamentally based on the principle of capillary action.