Ultrasonic squirter systems for inspection of aerospace composites

Double click on the images above to see videos of different complex geometry systems

• Systems up to 18 metres long
• Configurations from 2 to 13 axes
• Contour following systems for complex curves with a unique range of manipulators
• Exceptional dynamic range using logarithmic receivers and remote pulser preamplifiers
• Multiple gate acquisition and display in real time
• Simultaneous through transmission and pulse echo inspection
• C scan, B scan, thickness mapping and full RF acquisition
• Multi-channel and combined immersion / squirter options

The use of composite materials for aerospace structures is increasing. Ultrasonic testing using the through transmission squirter technique remains the predominant method of inspection.

Relatively flat panels can be tested using simple 2 axis machines, but the increasing complexity of components requires more sophisticated scanners. USL can provide systems for both simple and complex applications. These combine highly rigid and accurate mechanical scanners with USL's established PC based instruments, to provide fast and effective testing of composite structures. A unique range of precision probe manipulators is available, with the type selected to suit the specific application.

Systems can operate in pulse echo mode (PE) and in through transmission (TT), either in separate scans or simultaneously. When PE and TT scans are combined, the PE scan uses a linear amplifier and the TT uses a logarithmic amplifier. This gives the optimum combination of resolution and dynamic range.

Four alternative configurations are illustrated here - the choice is dependent on the range of component shapes to be tested and also on the available floor space.

This illustrates the simplest configuration with two motorised axes, X and Y. The separation of the squirters is set manually, but this can be motorised. This is a "flat-bed" type of system, suitable for flat panels. One advantage of this system is that it can be used to test a large number of small parts simultaneously, because the parts are supported on wires stretched across the scanner. No special fixturing is needed.

This shows a "travelling gantry" system, designed for inspection of flat and single curvature components. The squirters are mounted on horizontal arms, with a single axis manipulator having a "tip" axis. One advantage of a scanner of this type is that the design can be easily adapted to suit almost any length of component - the scanning gantry is identical regardless of the scanner length.

Two pairs of squirters can be mounted on the same manipulator, in order to increase the effective scanning index and reduce the inspection time.

This is a traditional 5 axis gantry system with vertical Z axis columns. The parts are held in a two axis rotating fixture. Like the travelling gantry unit, this configuration is suitable for flat and single curvature parts. For parts having a significant curvature, the travelling gantry type is preferred, although this requires a larger floor area because of the safety zone which is needed for the horizontal manipulators.

This shows a 10 axis system with horizontally opposed squirter manipulators. This is effectively two completely independent 5 axis scanners, one on each side of the component. This type of  system is designed for contour following of dual curvature components. Sophisticated motion control is incorporated to maintain the alignment of the two squirters throughout the scanning volume. A 5 axis motorised, programmable fixture is available for fixing parts to be inspected - this leaves the floor area completely clear for the operator.

6 axis system for pulse echo inspection of conical parts. The system incorporates full contour following for components which are not roto-symmetrical. The component shape is programmed by a "teach and learn" procedure which is partly automated. The circular shape is measured ultrasonically using a time of flight mode - the operator simply has to define the position of successive rings to define the complete surface profile. The inspection generates C scans from multiple gates and the display is shown in the correct aspect ratio. True surface measurements of defect size and position can be made using cursors on the C scan image.

Typical System features

	Axis configurations from simple X-Y and X-Z units for flat panels, to 13 axes for complex shape
	Horizontal and vertical gantry types
	Custom designed, highly rigid structure
	High quality construction throughout
	Scanning speed up to 1m/sec
	Optional turntable and rotation axes
	DC servo motor drive, with rack and pinion, ballscrew or belt transmission
	High quality linear bearings (NSK type) giving long life under arduous conditions
	Precision optical encoders
	Resolution down to 5um, repeatability down to 10um (dependent on system type)
	Through transmission data using logarithmic amplifier and pulse echo data using linear amplifier in the same scan
	Precision manipulators - gimbal/gimbal, gimbal/rotate with double sealed titanium alloy housings

    Ultrasonics

	Fully integrated PC-based ultrasonics, data acquisition and motion control
	High power pulser for optimum penetration
	Remote Pulser preamplifiers for exceptional  S/N ratio
	Logarithmic receiver for wide dynamic range - instantaneous 85dB,total >100dB
	Simultaneous pulse echo (Linear amplifier) and through transmission (Log amplifier)
	High speed A-D conversion with custom DSP (digital signal processing) board for data acquisition
	Multi-channel units for more than 2 squirters
	Up to 8 independent gates per channel - amplitude, time of flight and phase monitoring
	Single and multi-channel operation
	Frequency from <0.5MHz to 35MHz

     Software

	Windows 2000 / XP software with simple operation using pull down menus
	Multi axis motion control for complex shapes, using teach and learn
	High refresh rate digital RF/A scan with simultaneous pulse echo and through transmission A scans
	Real time display of C scan images from multiple gates simultaneously
	Real time true B scan capability (from RF data)
	Full RF data acquisition and processing
	On screen measurement and analysis
	Interfaces to network and offline computers
	Scan profiles generated from CATIA data and by "teach and learn"
	Custom software for special user requirements

    Some of the software functions for motion control, imaging and processing are shown in the "Software" section.

Typical System Specification

The following specification for a through transmission system is provided for illustration only, since each system is built to meet the precise requirements of the customer and his applications, within the constraints of the budget where necessary.

Axis configuration

9 axes X, Y1, Y2, Z1, Z2, a1, b1, a2, b2