When inspecting a thin sheet with ultrasonic waves directed normally to the surface, which observation is used to assess the sheet?

When inspecting a thin sheet with ultrasonic waves directed normally to the surface, which observation is used to assess the sheet?

• A. All front surface reflections
• B. The multiple reflection pattern
• C. The amplitude of the front surface reflection
• D. None of the above

Answer: (B)

When a ultrasonic pulse is sent normal to a thin sheet, energy reflects from both the front and back surfaces and bounces inside the material. This creates a train of echoes—the multiple reflection pattern. The timing between these internal echoes directly relates to twice the sheet thickness divided by the wave velocity, so measuring that spacing lets you determine thickness and check for uniformity across the sheet. The front surface reflection amplitude alone doesn’t reveal thickness or internal integrity, and focusing only on that single reflection misses the information carried by the echoes bouncing inside. Therefore, the multiple reflection pattern is what you use to assess a thin sheet.

When a ultrasonic pulse is sent normal to a thin sheet, energy reflects from both the front and back surfaces and bounces inside the material. This creates a train of echoes—the multiple reflection pattern. The timing between these internal echoes directly relates to twice the sheet thickness divided by the wave velocity, so measuring that spacing lets you determine thickness and check for uniformity across the sheet. The front surface reflection amplitude alone doesn’t reveal thickness or internal integrity, and focusing only on that single reflection misses the information carried by the echoes bouncing inside. Therefore, the multiple reflection pattern is what you use to assess a thin sheet.