Abstract
Pulse-echo laser ultrasonic propagation imaging is a nondestructive testing technique developed for composite materials and aluminum alloys used in aerospace. Although this method has been in usage for a considerable time, information of the detectable depth and the relationship between ultrasonic frequencies and the acoustic properties of metals is not readily available. Therefore, we investigate the A-scan and C-scan ultrasonic testing data of aluminum alloy, hot rolled steel, stainless steel, and copper alloy, which are used in aircraft bodies, frameworks, and gas pipelines. Experiments are performed with the pulse-width and excitation laser power fixed at 32 ns and approximately 4 W, respectively. The metal specimens include 24 artificial cylindrical defects with a diameter of 5 mm, located at depths of 1–12 mm on the front surface. The A-scan and C-scan data obtained at room temperature indicate the detectable depth for metals via the pulse-echo laser ultrasonic propagation imaging technique.
Highlights
IntroductionComposite materials, such as glass fiber reinforced plastics (GFRPs), carbon fiber reinforced plastics (CFRPs), and honeycomb composite sandwich structures, are extensively used in aerospace and other industries
This study examines the results of the laser FF PE UPI inspection of copper alloy, hot rolled steel, stainless steel, and aluminum alloy specimens
The copper alloy, hot rolled steel, stainless steel, and aluminum alloy plates were measured in a single scan
Summary
Composite materials, such as glass fiber reinforced plastics (GFRPs), carbon fiber reinforced plastics (CFRPs), and honeycomb composite sandwich structures, are extensively used in aerospace and other industries. Suitable ultrasonic testing techniques have been investigated for detecting the defects in composite materials [1,2,3]. If delamination or other defects are present in GFRP, CFRP, or honeycomb composite sandwich structures, the strength of the material can be critically degraded. The greater the difference in the speed of sound between the media across the interface, the greater the reflection. Since delaminated spaces can be regarded as air or vacuum, the intensity of the reflected ultrasound wave is strong, and the delaminated area can be detected
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