GB2463293A

GB2463293A - Ultrasonically inspecting a dual microstructure component

Info

Publication number: GB2463293A
Application number: GB0816437A
Authority: GB
Inventors: Robert John Mitchell; David Cameron Wright
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 2008-09-09
Filing date: 2008-09-09
Publication date: 2010-03-10
Also published as: GB0816437D0

Abstract

An apparatus for ultrasonically inspecting a rotationally symmetric dual microstructure component 12 comprises a first transducer 32 for transmitting an ultrasonic signal into the component and a second transducer for detecting the ultrasonic signal reflected from or transmitted through the component. The first and second transducers may be one and the same. Means to produce relative movement (e.g. turntable 20, carriage 26) between the component and the transducer(s) allows the whole surface of the component to be scanned. Changes in the amplitude of the detected signal from one predetermined level to another are used to determine the position, size and shape of a transition region between a fine grain microstructure region and a coarse grain microstructure region of the component. The component may be a metal or composite turbine disc, compressor disc, fan disc, integrally bladed disc, shaft, or a forging for such components.

Description

A METHOD AND APPARATUS FOR ULTRASONICALLY INSPECTING A DUAL

MICROSTRUCTURE COMPONENT

The present invention relates to a method and an apparatus for ultrasonically inspecting a dual microstructure component and in particular to a method and apparatus for ultrasonically inspecting a dual microstructure turbine disc or a dual microstructure turbine blade.

Conventionally a component is ultrasonically inspected to determine if there are one or more flaws, or defects, in the component. Conventionally a component is ultrasonically inspected at one, or more, discrete locations by transmitting an ultrasonic signal into the component and receiving a reflected, or transmitted, ultrasonic signal from the component and analysing the reflected, or transmitted, signal to determine if the amplitude of the reflected, or transmitted, signal is above a predetermined level and thus a flaw, or defect, is present or if the amplitude of the reflected, or transmitted, signal is below the predetermined level and thus a flaw, or defect, is not present. In the case of a turbine disc, or a compressor disc, the turbine disc, or compressor disc, is placed in a tank of an acoustic couplant, e.g. water, and the turbine disc, or compressor disc, is rotated about its axis and an ultrasonic probe is moved radially in incremental steps to achieve full coverage of the turbine disc, or compressor disc. The ultrasonic probe operates in a pulse echo mode to transmit ultrasound into the turbine disc, or compressor disc, and to detect reflected ultrasound. The reflected ultrasound is converted to an electric signal and electric signal levels above a predetermined threshold level are assessed to determine if there is a flaw, or defect, in the turbine disc, or compressor disc. The electric signal is converted to a signal on a flaw detector screen.

There is a requirement for gas turbine engines to have dual microstructure turbine discs or dual microstructure compressor discs. A dual microstructure turbine disc, or a dual microstructure compressor disc, is a disc in which the radially inner region of the disc comprises a fine grain microstructure, the radially outer region comprises a coarse grain microstructure and a transition region between the radially inner region and the radially outer region in which the microstructure changes from a fine grain microstructure to a coarse grain microstructure. Dual microstructure turbine discs, or compressor discs, are produced by heat treating the radially outer region of the turbine disc, or the compressor disc, differently to the radially inner region of the turbine disc, or compressor disc. In particular the radially outer region of the turbine disc, or compressor disc, may be subjected to heat treatment at a higher temperature than the radially inner region such that the radially outer region of the turbine disc, or compressor disc, has a coarse grain microstructure.

These dual microstructure turbine discs, or dual microstructure compressor discs, may be inspected conventionally, as described above, to determine if there is a flaw, or defect, present.

Dual microstructure turbine blades again have regions with fine and coarse grains.

However, it is also necessary to determine the position of the transition region, the size of the transition region and the cross-sectional shape of the transition region of the dual microstructure turbine discs or dual microstructure compressor discs or dual microstructure turbine blade.

Accordingly the present invention seeks to provide a novel method of ultrasonically inspecting a dual microstructure component to determine the position of the transition region, the size of the transition region and the cross-sectional shape of the transition region.

Accordingly the present invention provides a method of ultrasonically inspecting a dual microstructure component, the dual microstructure component comprising a first region having a fine grain microstructure, a second region having a coarse grain microstructure and a third region between the first region and the second region, the method comprising transmitting an ultrasonic signal from a first transducer into a dual microstructure component, detecting the reflected, or transmitted, ultrasonic signal by a second ultrasonic transducer, producing relative movement between the dual microstructure component and the first and second transducers to scan the whole of a surface of the rotationally symmetrical component and analysing the reflected, or transmitted, ultrasonic signal to determine where the amplitude of the reflected, or transmitted, ultrasonic signal changes from a first predetermined level to a second predetermined level, the second predetermined level is greater than the first predetermined level, the first predetermined level corresponding to the first region of the dual microstructure component, the second predetermined level corresponding to the second region of the dual microstructure, the change from the first predetermined level to the second predetermined level corresponding to the third region of the dual microstructure and providing the position, shape and size of the third region of the dual microstructure component.

Preferably the dual microstructure component has rotational symmetry, producing relative rotation between the rotationally symmetrical component and the first and second transducers, producing relative radial motion between the rotationally symmetrical component and the first and second transducers.

Preferably the method comprises rotating the component about its axis of symmetry.

Preferably the method comprises moving the first and second transducers radially relative to the component.

Preferably the first transducer is the second transducer.

Preferably the component is a turbine disc, a turbine disc forging, a compressor disc, a compressor disc forging, a fan disc, a fan disc forging, an integrally bladed disc, an integrally bladed disc forging or a shaft.

Preferably the component comprises a metal, a metal matrix composite or an in-situ composite.

Preferably the method comprises immersing the component in an acoustic coupling liquid.

Preferably the first transducer is a piezoceramic transducer, an electromagnetic acoustic transducer or a transducer comprising a laser.

Preferably the method comprises producing relative rotation at a constant speed. Preferably the method comprises producing relative rotation at a constant speed between 3 rpm and 30 rpm and more preferably the method comprises producing relative rotation at a constant speed between 20 rpm and 30 rpm.

Preferably the method comprises storing and analysing all the detected ultrasonic signals.

Preferably the method comprises providing a permanent record of the ultrasonic inspection in terms of the response level, position, shape and size of the third region of the dual microstructure component.

The present invention also provides an apparatus for ultrasonically inspecting a dual microstructure component, the dual microstructure component comprising a first region having a fine grain microstructure, a second region having a coarse grain microstructure and a third region between the first region and the second region, the apparatus comprising a first ultrasonic transducer for transmitting an ultrasonic signal into a dual microstructure component, a second ultrasonic transducer for detecting the reflected, or transmitted, ultrasonic signal, means to produce relative movement between the dual microstructure component and the first and second transducers to scan the whole of a surface of the rotationally symmetrical component and means to analyse the reflected, or transmitted, ultrasonic signal to determine where the amplitude of the reflected, or transmitted, ultrasonic signal changes from a first predetermined level to a second predetermined level, the second predetermined level is greater than the first predetermined level, the first predetermined level corresponding to the first region of the dual microstructure component, the second predetermined level corresponding to the second region of the dual microstructure, the change from the first predetermined level to the second predetermined level corresponding to the third region of the dual microstructure and means to provide the position, shape and size of the third region of the dual microstructure component.

Preferably the dual microstructure component has rotational symmetry, means to produce relative rotation between the rotationally symmetrical component and the first and second transducers, means to produce relative radial motion between the rotationally symmetrical component and the first and second transducers Preferably the means to produce relative rotation comprises means to rotate the component about its axis of symmetry.

Preferably the means to produce relative radial motion comprises means to move the first and second transducers radially relative to the component.

Preferably the first transducer is the second transducer.

Preferably the apparatus comprises a tank containing an acoustic coupling liquid, the component is immersed in the acoustic coupling liquid.

Preferably the apparatus comprises means to store and analyse all the detected ultrasonic signals.

Preferably the apparatus comprises means to provide a permanent record of the ultrasonic inspection in terms of the response level, position, shape and size of the third region of the dual microstructure component.

The present invention will be more fully described by way of example with reference to the accompanying drawings in which:-Figure 1 is a side view of an apparatus for ultrasonically inspecting a rotationally symmetrical dual microstructure component according to the present invention.

Figure 2 is a plan view of the apparatus for ultrasonically inspecting a dual microstructure component shown in figure 1.

Figure 3 is a schematic section through a half of the rotationally symmetrical dual microstructure component showing the ultrasonic transducer at three positions relative to the dual microstructure component.

Figure 4 shows the ultrasonic signal received when the ultrasonic probe is at position (1) in figure 3.

Figure 5 shows the ultrasonic signal received when the ultrasonic probe is at position (2) in figure 3.

Figure 6 shows the ultrasonic signal received when the ultrasonic probe is at position (3) in figure 3.

Figure 7 shows an ultrasonic B scan in a radial-axial plane of the dual microstructure component of figure 1.

An apparatus 10, as shown in figures 1 and 2, for ultrasonically inspecting a rotationally symmetrical dual microstructure component 12 comprises a tank 14 containing a liquid 16 and a frame 18. A rotatable turntable 20 and means 24 are provided to rotate the turntable 20. The means 24 to rotate the turntable 20 is preferably a motor directly driving the turntable, but alternatively the means to rotate the turntable 20 may be a motor indirectly driving the turntable via a belt, or a chain. The rotationally symmetrical dual microstructure component 12 is immersed in the liquid 16 in the tank 14 and is positioned on the turntable 20 such that the axis of rotational symmetry P of the dual microstructure component 12 coincides with the axis of rotation R of the turntable 20.

The frame 18 is provided with a carriage 26, which is movable along first and second tracks 28 and 29 on the frame 18 and means 30 and 31 are provided to move the carriage 26 along the tracks 28 and 29. The tracks 28 and 29 are arranged perpendicularly to enable movement in a Y-axis and an X-axis respectively. The carriage 26 carries an ultrasonic transducer 32 on a member 33 and means 35 are provided to move the member 33 towards or away from the turntable 20 and dual microstructure component 12 in a direction perpendicularly to the tracks 28 and 29 in a Z-axis. The member 33 may also be rotated. The means to move the carriage 26 and to move the member 33 may be motors or hydraulic, pneumatic or electric pistons and cylinders etc. The ultrasonic transducer 32 transmits and receives ultrasonic signals and the ultrasonic transducer is electrically connected to an ultrasonic signal pulser and receiver 34 by an electric cable 36 and is electrically connected to an ultrasonic signal analyser and display 38 by the ultrasonic signal pulser and receiver 34 and electric cables 36 and 40. The ultrasonic signal analyser and display 38 comprises a computer e.g. a personal computer. The ultrasonic transducer 32 may also have A and B normalising axes. The ultrasonic pulser and receiver 34, sometimes called an ultrasonic flaw detector, comprises a very high gain amplifier and a timing trigger. There is also a controller 42 electrically connected to the motor 24 via a cable 44, electrically connected to the motor 31 via a cable 46, electrically connected to the motor 30 via a cable 48 and electrically connected to the motor 35 via a cable 50 to provide signals to move the carriage 26 and the member 33.

In operation the controller 42 sends signals to the motor 24 such that the turntable 20 is rotated about its axis of rotation for one complete revolution while the carriage 26 and transducer 32 are at a first radial position of the dual microstructure component 12. During the rotation of the turntable 20 the ultrasonic transducer 32 is supplied with ultrasonic signals from the ultrasonic signal pulser and receiver 34 and the ultrasonic transducer 32 injects ultrasonic signals through the liquid 16 and into the dual microstructure component 12. The ultrasonic transducer 32 detects reflected ultrasonic signals from the dual microstructure component 12 and supplies ultrasonic signals to the ultrasonic signal analyser 38 via the ultrasonic signal pulser and receiver 34. The ultrasonic signal analyser 38 stores the ultrasonic signals.

The controller 42 sends signals to the motors 30 and/or 31 such that the carriage 26 is moved along the tracks 28 and 29 on the frame 18 and the turntable 20 is rotated about its axis of rotation for one complete revolution while the carriage 26 and transducer 32 are at a second radial position of the dual microstructure component 12. During the rotation of the turntable 20 the ultrasonic transducer 32 is supplied with ultrasonic signals from the ultrasonic signal pulser and receiver 34 and the ultrasonic transducer 32 injects ultrasonic signals through the liquid 16 and into the dual microstructure component 12. The ultrasonic transducer 32 detects reflected ultrasonic signals from the dual microstructure component 12 and supplies ultrasonic signals to the ultrasonic signal analyser 38 via the ultrasonic signal pulser and receiver 34. The ultrasonic signal analyser 38 stores the ultrasonic signals.

The carriage 26 is repeatedly moved along the tracks 28 and 29 on the frame 18 and the turntable 20 is rotated for one complete revolution so that the ultrasonic transducer 32 ultrasonically inspects all the radial positions of the dual microstructure component 12.

The turntable 20 is rotated around its axis of rotation at a constant speed of rotation of between 5 rpm and 30 rpm preferably between 20 rpm and 30 rpm.

The ultrasonic signal analyser 38 stores and analyses all the detected ultrasonic signals from the ultrasonic transducer 32.

The ultrasonic signal analyser 38 analyses the reflected, or transmitted, ultrasonic signal to determine where the amplitude of the reflected, or transmitted, signal changes from a first predetermined amplitude to a second predetermined amplitude. The second predetermined amplitude is greater than the first predetermined amplitude. The first predetermined amplitude corresponds to the first region of the dual microstructure component and the second predetermined amplitude corresponds to the second region of the dual microstructure. The change from the first predetermined amplitude to the second predetermined amplitude corresponds to the third region of the dual microstructure and the ultrasonic analyser 38 provides the position, shape and size of the third region of the dual microstructure component 12.

The ultrasonic signal analyser 38 analyses the reflected, or transmitted, ultrasonic signal to determine where the amplitude of the reflected, or transmitted, signal changes from a first predetermined amplitude to a second predetermined amplitude and where the amplitude of the reflected, or transmitted, signal changes from the second predetermined amplitude to a third predetermined amplitude. The second predetermined amplitude is greater than the first predetermined amplitude. The first predetermined amplitude corresponds to the first region of the dual microstructure component, the second predetermined amplitude corresponds to the third region of the dual microstructure component and the third predetermined amplitude corresponds to the second region of the dual microstructure component. The change from the first predetermined amplitude to the second predetermined amplitude and the change from the second predetermined amplitude to the third predetermined amplitude define the boundaries of the third region of the dual microstructure and the ultrasonic analyser 38 provides the position, shape and size of the third region of the dual microstructure component 12. There may be more than two or three different predetermined amplitudes of the detected ultrasonic signal.

Figures 4, 5 and 6 show ultrasonic A-scans at three different radial positions, (1), (2) and (3) shown in figure 3, in the dual microstructure component 12.

Referring now to figure 4, which shows an ultrasonic A-scan when the ultrasonic transducer 32 is at position (1) on the dual microstructure component 12. It is seen that there are two large amplitude ultrasonic signals at T and B, these correspond to the reflections of the ultrasonic signal from the top and bottom surfaces of the dual microstructure component 10. Between the reflected ultrasonic signals from the top surface T and the bottom surface B, the ultrasonic signal has a second predetermined amplitude A2, this corresponds to an amplitude level for a microstructure with a coarse grain size.

Referring now to figure 6, which shows an ultrasonic A-scan when the ultrasonic transducer 32 is at position (3) on the dual microstructure component 12. It is seen that there are again two large amplitude ultrasonic signals at I and B, these correspond to the reflections of the ultrasonic signal from the top and bottom surfaces of the dual microstructure component 10. Between the reflected ultrasonic signals from the top surface I and the bottom surface B, the ultrasonic signal has a first predetermined amplitude A1, this corresponds to an amplitude level for a microstructure with a fine grain size.

Now referring to figure 5, which shows an ultrasonic A-scan when the ultrasonic transducer 32 is at position (2) on the dual microstructure component 12. It is seen that there are again two large amplitude ultrasonic signals at I and B, these correspond to the reflections of the ultrasonic signal from the top and bottom surfaces of the dual microstructure component 10. Between the reflected ultrasonic signals from the top surface I and the bottom surface B, the ultrasonic signal has an amplitude A2 adjacent the top surface, this corresponds to an amplitude level for a microstructure with a coarse grain size, then the ultrasonic signal has an amplitude A1, this corresponds to an amplitude level for a microstructure with fine grain size, and then the ultrasonic signal has an amplitude A2, which again corresponds to an amplitude level for a microstructure with a coarse grain size. Thus there are two positions CG, in figure 5, where the microstructure of the dual microstructure component 12 has changed from a coarse microstructure to a fine microstructure or vice-versa.

The ultrasonic analyser 38 analyses the ultrasonic signals to detect where the amplitude of the ultrasonic signal changes from a first predetermined amplitude A1 to a second predetermined amplitude A2. The ultrasonic analyser 38 stores the data for the position of these three regions and also may display the data on a display 38 or chart etc. If there are other predetermined amplitudes of ultrasonic signal, if the microstructure of the third region has a different grain size then the data for the position of the three regions is stored and the data displayed on a display or chart.

Figure 7 shows an ultrasonic B-scan of the dual microstructure component 12 in a radial axial plane and shows the fine grain microstructure in the first region Fl, the coarse grain microstructure in the second region CC, and the transition from the fine grain microstructure to the coarse grain microstructure in the third region TR.

The ultrasonic signal analyser 38 may also manipulate the ultrasonic signals and displays the ultrasonic signals on the display 38. The ultrasonic signal is displayed on the display 38 as a chart of rotational position against time with ultrasonic signal amplitude displayed as a grey scale or artificial colour for each scan increment. The ultrasonic signal analyser 38 analyses the ultrasonic signals and differentiates by separation of ultrasonic signals with and without rotational symmetry, highlighting ultrasonic signals that have no rotational symmetry and have an amplitude above a third predetermined amplitude as a potential defect, such as a crack, a fissure, an inclusion or a flaw etc. The third predetermined amplitude is much larger than the first or second predetermined amplitudes. Geometric features, such as changes in changes in cross-sectional thickness, in the component have rotational symmetry. A defect, such as a crack, a fissure, an inclusion or a flaw etc, in the component however occurs at a discrete location in the component and therefore lacks rotational symmetry and is easily distinguished.

The ultrasonic signal analyser 38 detects a defect by detecting a cluster of pixels above the third predetermined amplitude. True defects possess a finite length/area whereas external interference, e.g. electrical noise, are instantaneous spikes. The ultrasonic signal analyser 38 detects a cluster of pixels above the third predetermined amplitude and containing n consecutive pixels where n > 1, where n is a fixed integer.

True defects are automatically detected and separated from background signals due to changes in cross-sectional thickness or noise, without the need for laborious manual scanning of edge features. Any indication of a defect may be manually viewed by an inspector, after the scan and this allows an inspector to operate several ultrasonic inspection systems.

Following an ultrasonic inspection of one surface of a component, the ultrasonic signal analyser 38 displays a table of all detected defect clusters, showing an ID number, e.g. component serial no, face ID and number) position and maximum ultrasonic signal amplitude. The ultrasonic signal analyser 38 allows an inspector to view the maximum A-scan ultrasonic signal for each defect cluster. The ultrasonic signal analyser 38 records the inspector decision for each defect cluster. All the detected defect clusters are assessed by an inspector and the decision recorded before the inspection process progresses to the next stage. The inspector saves the resultant A-scan and the relative positions of the ultrasonic transducer and the component. The third predetermined amplitude is greater than the second predetermined amplitude.

The opposite surface of the component may be inspected in the same manner as above.

The ultrasonic inspection may be used with several revolutions of the ultrasonic transducer at each radial position, e.g. first pass at 9Q0, second pass at 85° and third pass at 95° relative to the surface.

The present invention is applicable to the ultrasonic inspection of turbine discs, turbine disc forgings, compressor discs, compressor disc forgings, fan discs, fan disc forgings, integrally bladed discs, e.g. discs with blades integrally formed, or machined, with the disc or discs with blades frictionally welded, diffusion bonded, e beam or laser welded to the discs, bladed disc forgings, bladed rings, e.g. rings with blades integrally formed, or machined, with the ring or rings with blades frictionally welded, diffusion bonded, e beam or laser welded to the rings or bladed ring forgings. The present invention is also applicable to the ultrasonic inspection of shafts, turbine blades, turbine vanes, compressor blade or compressor vanes.

The present invention is applicable to the ultrasonic inspection of dual microstructure metal components or metal matrix composite components or in-situ composites. The advantage of the present invention is that the shape, position and size of the transition region between the two microstructures of a dual microstructure component in radial axial planes are detectable for a rotationally symmetrical component. The present invention may be used as part of a product validation/design validation procedure and removes the need to cut up components to confirm that the grain size is as predicted in particular regions of the component, e.g. there is a dual microstructure. The present invention may be used a part of a production validation procedure to confirm that the grain size is as predicted in particular regions of the component, e.g. there is a dual microstructure and may be used for process control.

Although the present invention has been described with reference to the use of a single transducer to transmit the ultrasonic signal into the component and to detect the reflected ultrasonic signal, it may be possible to use a second transducer to detect the reflected ultrasonic signal. Although the present invention has been described with reference to detecting a reflected ultrasonic signal it may also be possible to provide a second transducer to detect an ultrasonic signal transmitted through the component.

The present invention is also applicable using other acoustic couplant methods such as water jet probes, oil or gel contact methods or remote methods such as high amplitude airborne pulse or laser generated ultrasound or electromagnetic acoustic transducers (EMATS)

Claims

Claims: - 1. A method of ultrasonically inspecting a dual microstructure component, the dual microstructure component comprising a first region having a fine grain microstructure, a second region having a coarse grain microstructure and a third region between the first region and the second region, the method comprising transmitting an ultrasonic signal from a first transducer into a dual microstructure component, detecting the reflected, or transmitted, ultrasonic signal by a second ultrasonic transducer, producing relative movement between the dual microstructure component and the first and second transducers to scan the whole of a surface of the rotationally symmetrical component and analysing the reflected, or transmitted, ultrasonic signal to determine where the amplitude of the reflected, or transmitted, ultrasonic signal changes from a first predetermined level to a second predetermined level, the second predetermined level is greater than the first predetermined level, the first predetermined level corresponding to the first region of the dual microstructure component, the second predetermined level corresponding to the second region of the dual microstructure, the change from the first predetermined level to the second predetermined level corresponding to the third region of the dual microstructure and providing the position, shape and size of the third region of the dual microstructure component.
2. A method as claimed ira claim 1 whereir the dual microstructure component having rotational symmetry, producing relative rotation between the rotationally symmetrical component and the first and second transducers, producing relative radial motion between the rotationally symmetrical component and the first and second transducers.
3. A method as claimed in claim 2 comprising rotating the dual microstructure component about its axis of symmetry.
4. A method as claimed in claim 2 or claim 3 comprising moving the first and second transducers radially relative to the dual microstructure component.
5. A method as claimed in any of claims 1 to 4 wherein the first transducer is the second transducer.
6. A method as claimed in any of claims 1 to 5 wherein the component is a turbine disc, a turbine disc forging, a compressor disc, a compressor disc forging, a fan disc, a fan disc forging, an integrally bladed disc, an integrally bladed disc forging or a shaft.
7. A method as claimed in any of claims 1 to 6 wherein the component comprises a metal, a metal matrix composite or an in situ-composite.
8. A method as claimed in any of claims 1 to 7 comprising immersing the component in an acoustic coupling liquid.
9. A method as claimed in any of claims 1 to 8 wherein the first transducer is a piezoceramic transducer, an electromagnetic acoustic transducer or a transducer comprising a laser.
10. A method as claimed in any of claims 2 to 4 comprising producing relative rotation at a constant speed.
11. A method as claimed in claim 10 comprising producing relative rotation at a constant speed between 3 rpm and 30 rpm.
12. A method as claimed in claim 11 comprising producing relative rotation at a constant speed between 20 rpm and 30 rpm.
13. A method as claimed in any of claims 1 to 12 comprising storing and analysing all the detected ultrasonic signals.
14. A method as claimed in any of claims 1 to 13 providing a permanent record of the ultrasonic inspection in terms of the response level, position, shape and size of the third region of the dual microstructure component.
15. An apparatus for ultrasonically inspecting a dual microstructure component, the dual microstructure component comprising a first region having a fine grain microstructure, a second region having a coarse grain microstructure and a third region between the first region and the second region, the apparatus comprising a first ultrasonic transducer for transmitting an ultrasonic signal into a dual microstructure component, a second ultrasonic transducer for detecting the reflected, or transmitted, ultrasonic signal, means to produce relative movement between the dual microstructure component and the first and second transducers to scan the whole of a surface of the rotationally symmetrical component and means to analyse the reflected, or transmitted, ultrasonic signal to determine where the amplitude of the reflected, or transmitted, ultrasonic signal changes from a first predetermined level to a second predetermined level, the second predetermined level is greater than the first predetermined level, the first predetermined level corresponding to the first region of the dual microstructure component, the second predetermined level corresponding to the second region of the dual microstructure, the change from the first predetermined level to the second predetermined level corresponding to the third region of the dual microstructure and means to provide the position, shape and size of the third region of the dual microstructure component.
16. An apparatus as claimed in claim 15 wherein the dual microstructure component having rotational symmetry, means to produce relative rotation between the rotationally symmetrical component and the first and second transducers, means to produce relative radial motion between the rotationally symmetrical component and the first and second transducers
17. An apparatus as claimed in claim 16 wherein the means to produce relative rotation comprises means to rotate the component about its axis of symmetry.
18. An apparatus as claimed in claim 16 or claim 17 wherein the means to produce relative radial motion comprises means to move the first and second transducers radially relative to the component.
19. An apparatus as claimed in any of claims 15 to 18 wherein the first transducer is the second transducer.
20. An apparatus as claimed in any of claims 15 to 19 wherein the component is a turbine disc, a turbine disc forging, a compressor disc, a compressor disc forging, a fan disc, a fan disc forging, an integrally bladed disc, an integrally bladed disc forging or a shaft.
21. An apparatus as claimed in any of claims 15 to 20 wherein the component comprises a metal, a metal matrix composite or an in-situ composite.
22. An apparatus as claimed in any of claims 15 to 21 wherein the apparatus comprises a tank containing an acoustic coupling liquid, the component is immersed in the acoustic coupling liquid.
23. An apparatus as claimed in any of claims 15 to 22 wherein the first transducer is a piezoceramic transducer, an electromagnetic acoustic transducer or a transducer comprising a laser.
24. An apparatus as claimed in any of claims 15 to 23 wherein the apparatus comprises means to store and analyse all the detected ultrasonic signals.
25. An apparatus as claimed in any of claims 15 to 24 wherein the apparatus comprises means to provide a permanent record of the ultrasonic inspection in terms of the response level, position, shape and size of the third region of the dual microstructure component.
26. An apparatus for ultrasonically inspecting a dual microstructure component substantially as hereinbefore described with reference to and as shown in figures 1 and 2 of the accompanying drawings.
27. A method of ultrasonically inspecting a dual microstructure component substantially as hereinbefore described with reference to the accompanying drawings.