Location

Snowmass Village, CO

Start Date

1-1-1995 12:00 AM

Description

Transmission (and retransmission) through rough surfaces degrades ultrasonic flaw detection and materials characterization. The flaw signal as well as reference signals (e.g. reflections from the front-surface or back-surface of the specimen) become difficult to interpret. In the simplest case, we make two assumptions in order to model the ultrasonic pulse-echo signal. Our first assumption is that the scatterer is large in the sense that it extends laterally for many surface correlation lengths. In this case, the signal has a small variance and is well described by its average value that will be referred to as the “specular” signal. Our second assumption is that the flaw is far from the surface, in a sense to be defined below. Given these two assumptions, the rough surface introduces a loss that is proportional to the square of the rms height, h, and the frequency, f. Further, the loss due to a double-transmission, L d , is just twice the loss due to a single-transmission, L s , i.e., L d ≈ 2 L s .

Volume

14B

Chapter

Chapter 6: Material Properties

Section

Surface Roughness

Pages

1845-1852

DOI

10.1007/978-1-4615-1987-4_236

Language

en

File Format

application/pdf

Share

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Jan 1st, 12:00 AM

Excess Scattering Induced Loss at a Rough Surface Due to Partially Coherent Double-Reflection

Snowmass Village, CO

Transmission (and retransmission) through rough surfaces degrades ultrasonic flaw detection and materials characterization. The flaw signal as well as reference signals (e.g. reflections from the front-surface or back-surface of the specimen) become difficult to interpret. In the simplest case, we make two assumptions in order to model the ultrasonic pulse-echo signal. Our first assumption is that the scatterer is large in the sense that it extends laterally for many surface correlation lengths. In this case, the signal has a small variance and is well described by its average value that will be referred to as the “specular” signal. Our second assumption is that the flaw is far from the surface, in a sense to be defined below. Given these two assumptions, the rough surface introduces a loss that is proportional to the square of the rms height, h, and the frequency, f. Further, the loss due to a double-transmission, L d , is just twice the loss due to a single-transmission, L s , i.e., L d ≈ 2 L s .