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.

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.

Used to detect surface and near-surface flaws in ferromagnetic materials (iron, steel, etc.). The material is magnetized, and finely divided ferromagnetic particles (iron powder) are applied to its surface. Flaws disrupt the magnetic field, causing the particles to accumulate at the defect locations, making them visible.

Advantages:

• Sensitive method for finding small or shallow surface and subsurface cracks
• Adaptable to various specimen shapes and sizes
• Portable and relatively easy-to-use equipment.

Disadvantages:

• Only applicable to ferromagnetic materials
• Demagnetization is necessary after testing
• Surface coatings (paint, plating) can hinder the test's effectiveness.

A method for detecting surface-breaking flaws in virtually any material. A liquid dye (penetrant) is applied to the cleaned surface, allowed to penetrate any cracks, then excess penetrant is removed. A developer is then applied, which draws the trapped penetrant out of the flaws, making them visible.

Advantages:

• Not restricted by material type (magnetic or non-magnetic)
• Simple, inexpensive, and fast.

Disadvantages:

• Only detects surface-breaking defects
• Thorough cleaning is crucial before and after testing
• Surface films or coatings can affect results.