System for non-destructive inspection of structural components

Abstract

A system for non-destructive inspection of structural components comprising an ultrasonic probe having a contact face for contacting a surface of a structural component to be inspected and being adapted to emit ultrasonic energy into the structural component when the contact face abuts on a surface of the structural component, a thermal imaging camera adapted to inspect a portion of a surface of the structural component to detect region of the surface of the structural component where an increase of the temperature occurs, and a control unit connected to the ultrasonic probe and the thermal imaging camera. The contact face extends in a plane and is provided with at least two bars which are arranged in parallel and have a common separation distance from each other.

Claims

1. A system for non-destructive inspection of structural components comprising: an ultrasonic probe having a contact face configured to contact a surface of a structural component to be inspected and being adapted to emit ultrasonic energy in the form of ultrasonic waves into the structural component when the contact face abuts on a surface of the structural component, a thermal imaging camera configured to inspect a portion of a surface of the structural component to detect a region of the surface of the structural component where an increase of the temperature occurs, and a control unit connected to the ultrasonic probe and the thermal imaging camera, wherein the contact face extends in a plane and is provided with at least two bars, which bars are arranged in parallel and wherein adjacent bars of the at least two bars have a common distance therebetween, wherein the common distance between adjacent bars of the at least two bars is adjustable for matching the common distance between adjacent bars of the at least two bars to a wavelength of the ultrasonic waves emitted by the ultrasonic probe.

2. The system according to claim 1, wherein the at least two bars are formed as rectilinear bars.

3. The system according to claim 1, wherein the at least two bars each have a curved shape.

4. The system according to claim 1, wherein the at least two bars are formed as wire filaments.

5. The system according to claim 1, wherein the at least two bars have a wedge-shaped cross section perpendicular to a longitudinal direction of the bars wherein narrow edges of the wedge-shaped cross section point away from a plane defined by the contact face.

6. The system according to claim 1, wherein at least one bar comprises at least two threaded holes extending in parallel, the distance of the threaded holes being identical for each bar having said holes, and wherein at least two threaded rods are provided which extend through the threaded holes and parallel to a plane defined by the contact face.

7. The system according to claim 1, wherein the ultrasonic probe comprises a sonotrode on which the contact face is provided, and a housing receiving the sonotrode and comprising an opening with a closed rim, which rim extends in the plane defined by the contact face, so that a closed volume inside the housing is formed when the rim abuts on a surface of a component to be inspected.

8. The system according to claim 7, further comprising a vacuum source, wherein the housing comprises a suction port connected with the vacuum source.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following the present invention will be explained on the basis of preferred embodiments shown in the drawing, in which

(2) FIG. 1 shows a side view a first embodiment of a system according to the present invention,

(3) FIG. 2 shows a perspective view of the bar assembly of the system shown in FIG. 1,

(4) FIG. 3 shows a perspective view of an alternative of the bar assembly of the system shown in FIG. 1,

(5) FIG. 4 shows a side view of the alternative of the bar assembly shown in FIG. 3,

(6) FIG. 5 shows a perspective view of the ultrasonic probe with a further alternative of a bar assembly,

(7) FIG. 6 shows an enlarged view of the alternative of the bar assembly of FIG. 5,

(8) FIG. 7 shows a sectional view and a perspective view of a further alternative of the bar assembly of the ultrasonic probe of the system shown in FIG. 1,

(9) FIG. 8 shows a bottom view of a further alternative of the bar assembly of the ultrasonic probe of the system of FIG. 1,

(10) FIG. 9 shows a schematic sectional view of a second embodiment of a system for non-destructive inspection of structural components according to the present invention, and

(11) FIG. 10 shows a flow chart of the operation method for the embodiments of a system according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(12) FIG. 1 shows a first embodiment of a system 1 for non-destructive inspection of a structural component according to the present invention. The system 1 for non-destructive inspection comprises an ultrasonic probe 3, a thermal imaging camera 5 and a control unit 7.

(13) The ultrasonic probe 3 has a substantially cylindrical casing 9 that extends along a longitudinal axis 11 having a first end surface 13 and a contact face 15, which is opposite the first end surface 13 in the direction of the longitudinal axis 11 of the ultrasonic probe 3. The surface 13 and the face 15 of the ultrasonic probe 3 are perpendicular to the longitudinal axis 11, wherein the contact face 15 is intended to contact a surface of a structural component 17 that has to be inspected. The structural component 17 is formed of a special carbon fiber reinforced plastic (CFRP) or any other material, e.g., material which can be employed to form the outer skin of an aircraft.

(14) The ultrasonic probe 3 is adapted to emit ultrasonic energy into the structural component 17 when the contact face 15 abuts on a surface of the structural component 17. In the direction of the longitudinal axis 11, the casing 9 of the ultrasonic probe 3 comprises a piezoelectric element 19 as an ultrasonic energy source and a sonotrode 21 for the generating of ultrasonic vibrations. The contact face 15 is provided on the sonotrode 21 which has a decreasing diameter in the direction of the longitudinal axis 11 of the ultrasonic probe 3.

(15) The thermal imaging camera 5 is adapted to screen a portion of a surface of the structural component 17 for the inspection of any sub-surface defect. The ultrasonic probe 3 and the thermal imaging camera 5 are coupled and electrically controlled with a control unit 7.

(16) A bar assembly 25 comprising at least two rectilinear bars is placed in the contact face 15 together with an adjusting device 27. FIG. 2 shows the bar assembly 25 in detail which comprises a first bar 29 and a second bar 31 which are arranged in parallel to each other and spaced by a distance 33. These rectilinear bars 29, 31 have wedge-shaped cross sections perpendicular to the longitudinal direction 35 of the bars 29, 31 wherein the narrow edges 37, 39 of the wedge-shaped cross sections point away from the plane defined by the contact 15 (see FIG. 1). These edges 37, 39 face and abut on the structural component 17 during use of the system 1 for non-destructive inspection of structural components 17.

(17) The adjusting device 27 further comprises a first and a second threaded rod 43, 45. The first bar 29 comprises first and second threaded holes 47, 49, and the second bar 31 comprises a first and a second through hole 47, 49, which extend in parallel and perpendicular to the longitudinal direction 35 of the two bars 29, 31. Further, the distance 51 between the first and the second threaded holes 47, 49 and the through holes 47, 49 in the longitudinal direction 35 of the two bars 29, 31 is identical for each bar 29, 31, so that the threaded rods 43, 45 can extend through the through holes 47, 49 and can be threaded into the threaded holes 47, 49 of the first bar 29. The distance 33 between the adjacent bars 29, 31 is consequently adjustable with this adjusting device 27 by rotating the threaded rods 43, 45.

(18) FIG. 3 depicts an alternative assembly 25 including an adjusting device 27 that differs from the first bar assembly 25 in comprising an additional third bar 53. The rectilinear third bar 53 has the same dimensions as the first and second bars 29, 31 and is arranged in parallel to the first and second bar 29, 31, wherein it also has a wedge-shaped cross section perpendicular to the longitudinal direction 35 of the bars 29, 31. The three bars 29, 31, 53 are aligned with the same unitary or common distance 33. In this case, the third bar 53 is also provided with first and second threaded holes 47, 49. However, these threaded holes 47, 49 have a left-hand thread whereas the threaded holes 47, 49 in the first bar 29 have a right-hand thread. Correspondingly, the threaded rods 43, 45 of this bar assembly 25 have right-hand threads in the region of the first bar 29 and a left-hand thread in the region of the third bar 53. Thus, rotation of the threaded rods 43, 45 results in an opposite movement of the first and third bars, 29, 53 wherein the respective distance between the respective bars 29, 31, 53 remains common, i.e., the distance between the first and the second bars 29, 31 is the same as the distance between the second bar 31 and the third bar 53.

(19) In FIG. 4 the bar assembly 25 of FIG. 3 is shown mounted on the piezoelectric element 19 and the sonotrode 21. Further, in this figure it is shown that a drive motor 55 and a gearbox 57 are mounted on the combination of the piezoelectric element 19 and the sonotrode 21, wherein the output of the gearbox 57 is connected with the threaded rods 43, 45 so that the latter are rotationally driven by the drive motor 55. Since the threaded rods 43, 45 have a right-hand thread in the region of the first bar 29 and a left-hand thread in the region of the third bar 53, rotation of the threaded rods 43, 45 results either in an expansion of the distance 33 between the bars 29, 31, 53 or the distances 33 contract. The drive motor 55 is connected with the control unit 7 so that the control unit may send corresponding control signals to the drive motor 55 so as to adjust the distance 33 between the bars 29, 31, 53.

(20) In FIGS. 5 and 6 a further alternative of a bar assembly 25 is shown. In FIG. 5 the assembly 25 is depicted mounted on the sonotrode 21 of the ultrasonic probe 3, whereas FIG. 6 shows the bar assembly 25 only. In this case, the bar assembly 25 comprises a first, a second, a third and a fourth rectilinear bar 29, 31, 53, 59 which are arranged in parallel having a unitary distance 33 between adjacent bars. As in case of the afore-mentioned bar assemblies, 25, 25, the bars 29, 31, 53, 59 have a wedge-shaped cross section perpendicular to their longitudinal distance.

(21) Piezo elements 61 are arranged between adjacent bars 29, 31, 53, 59. These contacts 63 are connected with the control unit 7 via lines 65, so that also in this case the control unit may adjust the distance 33 between the bars 29, 31, 53, 59.

(22) FIG. 7 shows a further alternative bar assembly 25 that differs from the afore-mentioned assemblies 25, 25, 25 in the shape of the cross section perpendicular to the longitudinal direction 35 of the first and the second bars 29, 31. The bars 29, 31 of the third exemplary embodiment of the adjusting device 27 are formed as wire filaments with a circular cross section perpendicular to their longitudinal direction 35. Moreover, also in this assembly 25 threaded rods 43, 45 are employed to adjust the distance 33 between the bars 29, 31.

(23) In further embodiments (not shown) the cross section of the bars 29, 31 may also have a rectangular, elliptic or hyperbolic shape.

(24) In FIG. 8 a bottom view of a further alternative bar assembly 25 is shown. In this assembly 25 first, second and third bars 29, 31, 53 are provided, and different from the afore-mentioned assemblies the bars 29, 31, 53 have a curved shape and are arranged in parallel, i.e., the distance measure perpendicular to tangents along the bars 29, 31, 53 is unitary. In particular, the shape of the bars 29, 31, 53 is such that they are segments of a circle having a common center 67. In such an arrangement, when the ultrasonic probe 3 is activated the generated waves 69 are focused into the center 67, so that a large portion of the energy introduced by the ultrasonic probe 3 is transferred to this point. If a defect 71 is located near the center 67 of the segments of a circle describing the shape of the bars 29, 31, 53, heat will be generated in a very efficient manner in the region of this defect 71.

(25) FIG. 9 shows a second embodiment of a system 1 for non-destructive inspection of structural components 17. In this embodiment, the ultrasonic probe 3 comprises a housing 73 in which the piezoelectric element 19 and the sonotrode 21 together with the bar assembly 25 and the adjusting device 27 are received. The bar assembly 25 is identical to the assembly shown in FIG. 3 and comprises three wedge-shaped bars 29, 31, 53. The housing 73 has a cylindrical cross section with a closed top end 75 and a bottom opening 77 opposite the top end 75 with respect to the longitudinal axis 11. The bottom opening 77 is surrounded by an annular closed rim 79 formed of elastic rubber material, the rim 79 extending in the plane 81 of the contact face 15 and being adapted to abut on a surface of a component 17 to be inspected. When this is the case, the housing 73 and the component 17 delimit a closed volume in which the sonotrode 21 is received.

(26) The top end 75 of the housing 73 supports the piezoelectric element 19 and the sonotrode 21 of the ultrasonic probe 3. Further, the top end 75 is provided with a suction port 83, which is connected with a vacuum source 85. In this embodiment the vacuum source 85 employs a venture nozzle so that the vacuum nozzle is supplied with compressed air via a conduit 87.

(27) However, it is also conceivable that the housing 73 is fixed on a flat surface of the component 17 to be inspected in a manner similar to a cup suction assembly as it is used in glass holders so that no supply of compressed air is required.

(28) Thus, the ultrasonic probe 3 can be fixed to the surface of a component 17 to be inspected by evacuating the closed inner volume of the housing 55 by means of the vacuum source 67 or other means.

(29) The above described embodiments of a system 1 for non-destructive inspection of structural components according to the invention operate as follows.

(30) At the beginning, the distance 33 between the at least two bars 29, 31, 53, 59 of the respective bar assembly 25, 25, 25, 25, 25 is adjusted to agree with the wavelength of the ultrasonic waves 69 to be generated within the structural component 17. This is achieved with the method depicted by the flow chart of FIG. 10.

(31) Firstly, the frequency with which the sonotrode 21 and hence the bars 29, 31, 53, 59 vibrate, the thickness of the component 17 to be inspected, the selected Lamb Wave Mode to be excited and properties such as the sound velocity are input into the control unit 7 (first step 91).

(32) In the second step 93 the resulting Lamb Wave group velocity is retrieved from a table or function stored in the control unit 7. Based on this velocity the control unit 7 calculates in the third step 95 the wavelength of the waves 69 generated in the component 17. Finally, in a fourth step 97 the control unit 7 calculates a control signal, e.g., for the drive motor 55 or the piezo elements 61, so as to adjust the distance 33 between adjacent bars 29, 31, 53, 59 to the wavelength.

(33) The ultrasonic probe 3 is placed onto a surface of the component 17 to inspected with the contact face 15 pointing towards the component 17, wherein in case of the second embodiment the probe 3 is fixed on the component 17 due to the vacuum generated inside the housing 73.

(34) When the ultrasonic probe 3 is pressed against the surface of the component 17, the bars 29, 31, 53, 59 abut thereon, and when the piezoelectric element 19 is operated with the correct frequency, ultrasonic waves 69 are generated within the component 17, wherein these waves 69 propagate along a direction perpendicular to the longitudinal direction 35 of the bars 29, 31, 53. Thus, by choosing the angular position of the longitudinal direction 35 of the bars 29, 31, 53, the direction can be adjusted along which the waves 69 are focused. When there are any defects 71 in those regions which are intersected by the direction of the waves 69, heat will be generated which will be detected by the thermal imaging camera 5.

(35) In case of the fifth alternative of a bar assembly 25, the waves 69 are focused into a spot, namely the center 67 of segments of a circle along which the bars 29, 31, 53 extend, and if a defect is located in the region of this center 67, it will be excited so that heat is effectively generated.

(36) Thus, with the system according to the present invention the energy introduced by the ultrasonic probe 3 is focused along a predetermined direction or into a spot and not distributed in an isotropic manner which in turn reduces the energy which needs to be introduced when a component is to be inspected along a certain direction. This reduces the overall stress induced in the component during inspection at the point where the ultrasonic probe 3 is fixed on the component 17.

(37) With the above described embodiments a point source of the ultrasonic energy generated by the ultrasonic probe 3 is transformed into a line source due to the at least two parallel bars 29, 31, 53, 59 in the plane of the contact face 15. This reduces the total ultrasonic energy which has to be introduced to inspect a component along a given direction.

(38) While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms comprise or comprising do not exclude other elements or steps, the terms a or one do not exclude a plural number, and the term or means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.