(i) Radiographic Testing

A non-destructive testing method that uses penetrating radiation (X-rays or gamma rays) to detect internal flaws in materials. The radiation passes through the material, and variations in its intensity are recorded on a X-ray film. Darker areas on the image correspond to denser regions (defects) within the material. X-ray radiography is better suited for smaller defects, while gamma radiography can penetrate thicker materials and detect larger flaws.

Advantages:

• Highly sensitive to internal discontinuities
• Relatively less time-consuming
• Produces permanent records.

Disadvantages:

• Involves radiation hazards, requiring specialized training and safety precautions
• Necessitates skilled operators
• High initial equipment cost.

(ii) Ultrasonic Testing

Employs high-frequency sound waves (ultrasonic) to detect internal and sometimes surface flaws. The ultrasonic waves are transmitted into the material, and any reflections caused by discontinuities are detected and measured. Methods include pulse-echo (single transducer sends and receives waves) and through-transmission (separate transducers transmit and receive).

Pulse-echo method:

Transmission method:

Advantages:

• Effective at detecting deep-seated flaws
• Determines flaw depth, size, and location
• Portable and relatively easy-to-use equipment
• Good accuracy and reliability.

Disadvantages:

• Sub-surface discontinuities near the surface may be difficult to detect
• Challenging to examine irregularly shaped or rough components
• Requires skilled interpretation of the results.