Question

Which of the following techniques can be used to detect an internal defect in a metal casting?

• A. Ultrasonic inspection
• B. Liquid (or dye) penetrant inspection
• C. Gamma-ray radiography
• D. X-ray radiography

Hint:

When inspecting metal castings for internal defects, ultrasonic, X-ray, and gamma-ray radiography are common techniques. Liquid penetrant inspection is better suited for detecting surface defects.

Answer 1

The Correct Option is A, C, D

Detecting internal defects in metal castings is crucial to ensure the structural integrity and performance of the casting. Various non-destructive testing (NDT) techniques are available for this purpose. Let's analyze the given options: 
Step 1: Analysis of the options 
- Option (A): "Ultrasonic inspection" - Correct: Ultrasonic inspection uses high-frequency sound waves to detect internal defects. It works by sending sound waves through the material and measuring the time taken for the waves to return. Any internal defect (such as cracks or voids) causes a reflection of these sound waves, which helps in detecting the defect. Hence, this technique is effective for detecting internal defects in metal castings. 
- Option (B): "Liquid (or dye) penetrant inspection" - Incorrect: Liquid penetrant inspection is generally used for detecting surface defects rather than internal defects. It involves applying a liquid dye or fluorescent solution to the surface of the material. It is not effective for detecting internal defects. 
- Option (C): "Gamma-ray radiography" - Correct: Gamma-ray radiography is a non-destructive testing technique that uses gamma rays to penetrate the material and produce an image of the internal structure. This technique can detect internal defects such as cracks, voids, and inclusions, making it suitable for inspecting metal castings. 
- Option (D): "X-ray radiography" - Correct: X-ray radiography is similar to gamma-ray radiography, but it uses X-rays instead of gamma rays. It is an effective method for detecting internal defects such as cracks, porosity, and voids in metal castings. It provides a detailed image of the internal structure of the material. 
Step 2: Conclusion The correct techniques for detecting internal defects in metal castings are Option A, Option C, and Option D. Ultrasonic inspection, gamma-ray radiography, and X-ray radiography are all effective methods for identifying internal flaws in the material.