Inspection of Composite Rocket Nozzle

Rocket nozzles are manufactured with composite material having good structural and heat resistance capabilities.

Because of the severe working environment of those parts, structural integrity has to be assured. Delaminations and inclusions have to be detected. Conventional ultrasound techniques are limited because of very bad ultrasonic penetration.

The use of low-frequency transducers in pulse-echo and transmit/receive configurations combined with the use of phased-array probes ensures good inspection.

A state-of-the-art mechanics with a double oblique arm and a turntable ensure reliable inspection of parts.

Rocket nozzle inspection system.

Performance and Objectives of the Inspection

• Full volume ultrasonic inspection of parts for delamination
• Detection of delamination and inclusion
• Part size:
• Height: 300 mm (0.328 in.) to 1400 mm (55.118 in.)
• Inner diameter: 100 mm (3.937 in.) to 1500 mm (59.055 in.)
• Thickness: 10 mm (0.375 in.) to 95 mm (3.74 in.)
• Material: composite
• Shape: conic
• Rotation speed: 7 r/min
• Two conventional 1-MHz probes
• One 64-element phased-array probe
• Electronics: TomoScan FOCUS LT 16:128
• Wedge with membrane
• Water recirculation system

Description of the Inspection System
The nozzle is mounted on a turntable composed of mandrels adjustable to the diameter of the nozzle.

The ultrasonic probes are mounted on the oblique vertical axis. The angle of the arm can be adjusted.

The water is recirculated through the irrigation system. The loss of water is minimal.

Parts to Inspect
Composite parts (very noisy material)

Part size
Height: 300 mm (11.811 in.) to 1400 mm (55.118 in.)
Inner diameter: 100 mm (3.937 in.) to 1500 mm (59.055 in.)
Thickness: 10 mm (0.375 in.) to 95 mm (3.74 in.)

Defects to Be Detected

• Delamination
• Inclusion
• SDH of 1 mm (0.039 in.) to 5 mm (0.196 in.) of diameter for calibration purpose

Close-up of the probe assembly (conventional probes).

Material Requirements
TomoScan FOCUS LT 16:128 ultrasonic phased-array system
 Motor drive with a joystick
TomoView software
Computer
Two 1-MHz conventional probe
One 64-element phased-array probe
Local immersion wedges with membranes
Air compressor

Close-up of the turntable.

Analysis and Reporting Using TomoView Software
All of Olympus ultrasound products, whether using phased-array, ultrasound, or EMAT technology, share the same data acquisition and analysis software. The software is PC-based and can be used on standard PCs ranging from simple laptop to powerful multiprocessor workstation.

Data Acquisition and Analysis

• Software setup and control of the acquisition system
• Easy programming of focal laws for sector, linear, and depth scans, as well as dynamic depth focusing
• Automatic volumetric settings
• Real-time display of A-scans, B-scans, C-scans, and D-scans
• Real-time display of phased-array sector scans
• Real-time display of angle-corrected top, side, and end views from either A-scan, C-scan, or peak data
• Real-time imaging with part drawing overlay
• Capability to proceed to data analysis simultaneously with data acquisition.
• Measurement cursors and time-of---flight diffraction measurement tools
• Scanner control for automated inspections
• Synthetic aperture focusing technique (SAFT)

Phased-array probe asembly with water wedge and membrane.

Cross-section of the part.

Other Aerospace Applications

Thin Welds and Friction Stir Welds
The FSW technique was developed as a method to join materials that are difficult to fusion weld, such as aluminum alloys. The quality of the weld is very high; however, the process may generate small, tight defects that are hard to detect.

The best method to inspect FSW is to use the ultrasonic phased array technique. Because of the weld shape, raster scanning is impossible; but with phased arrays, inspection of the entire weld volume is done in a single-pass scan. Phased arrays also permit lateral scanning to detect transverse defects. Inspection angle optimization maximizes the probability of detection. The increased number of zones covered by phased arrays provides accurate flaw sizing and location. High speed, accuracy, and versatility make phased arrays the choice technique for FSW inspection.

In-plant, vertical setup for 40-ft long friction stir weld inspection.