Magnetic Particle Inspection Level 2 Practice Exam

What type of magnetic particle inspection method is commonly used for inspecting very fine cracks?

1. Dry AC

2. Wet AC

3. Dry DC

4. Wet DC

The correct answer is: Wet AC

The method of magnetic particle inspection most commonly used for detecting very fine cracks is the wet method, specifically with alternating current (AC). This approach involves suspending ferromagnetic particles in a liquid medium and using an AC magnetic field to magnetize the test object. The advantage of this method lies in the ability of the wet suspension to penetrate smaller surface discontinuities, enhancing the visibility of fine cracks. Wet AC allows for capillary action, meaning that it can easily flow into minute defects, making it particularly effective for revealing tight or very fine cracks that might not be visible with dry methods. The contrast of the particles against the background also aids in identifying surface defects. Therefore, the combination of the magnetic properties of the wet particles and the alternating current creates an effective method for detecting these smaller flaws in various materials. Other methods, while they may have different advantages, are generally less effective for this specific application.