Patent Publication Number: US-2022221430-A1

Title: Ultrasonic flaw detection device and method for controlling same

Description:
TECHNICAL FIELD 
     The present invention relates to an ultrasonic flaw detection device and a method for controlling the ultrasonic flaw detection device. 
     BACKGROUND ART 
     In the related art, an ultrasonic flaw detection device that performs flaw detection by bringing an ultrasonic probe into contact with the surface of an object-to-be-inspected is known (refer to, for example, PTL 1). PTL 1discloses an ultrasonic flaw detection device in which an ultrasonic probe can be elastically and freely inclined over the entire periphery of a support rod supporting the ultrasonic probe such that a vibration generating surface of the ultrasonic probe is parallel to and in close contact with the surface of an object-to-be-inspected having a curved surface. 
     CITATION LIST 
     [PTL 1] Japanese Unexamined Patent Application Publication No. 62-56845 
     SUMMARY OF INVENTION 
     Technical Problem 
     In a case of attempting to inspect the entire region of the surface of an object-to-be-inspected with an ultrasonic probe, since at an end portion of the object-to-be-inspected, only a part of a contact surface of the ultrasonic probe with the object-to-be-inspected comes into contact with the surface of the object-to-be-inspected, it is difficult to move the probe while pressing it against the surface of the object-to-be-inspected with a desired strength. Therefore, in order to inspect an end portion region of the object-to-be-inspected, it is necessary to cause the probe to enter the end portion of the object-to-be-inspected from a position separated from the end portion of the object-to-be-inspected. 
     However, in the ultrasonic flaw detection device disclosed in PTL 1, the probe can be freely inclined with respect to the support rod supporting the probe. Therefore, when moving the probe from the position separated from the end portion of the object-to-be-inspected along a tangential direction to the surface of the object-to-be-inspected, there is a possibility that depending on an inclination angle of the probe, the probe may collide with the end portion of the object-to-be-inspected. Further, since the inclination angle of the probe is not fixed, there is a possibility that a gap may be created between the probe and the object-to-be-inspected, making the flaw detection inspection impossible. 
     The present invention has been made in view of such circumstances and has an object to provide an ultrasonic flaw detection device in which it is possible to inspect the entire region of the surface of an object-to-be-inspected including an end portion without causing a flaw detection unit to collide with the end portion of the object-to-be-inspected. 
     Solution to Problem 
     In order to solve the above problem, an ultrasonic flaw detection device according to the present invention adopts the following means. 
     According to an aspect of the present invention, there is provided an ultrasonic flaw detection device including: a flaw detection mechanism that inspects an object-to-be-inspected by transmitting and receiving ultrasonic waves; a movement mechanism that moves a position of the flaw detection mechanism with respect to the object-to-be-inspected; and a control unit that controls the flaw detection mechanism and the movement mechanism, in which the flaw detection mechanism includes a flaw detection unit having a probe that transmits and receives the ultrasonic waves and a contact part on which a contact surface that comes into contact with a surface-to-be-inspected of the object-to-be-inspected is formed, a swinging mechanism that supports the flaw detection unit so as to be swingable around a swinging axis, and a lock mechanism that switches between a swinging state where the flaw detection unit can swing around the swinging axis and a locked state where the flaw detection unit cannot swing around the swinging axis, and the control unit controls the lock mechanism and the movement mechanism so as to cause the flaw detection unit to be in the locked state in a state where a tangential direction to the contact surface and a tangential direction to the surface-to-be-inspected coincide with each other, when moving the flaw detection unit from a position separated from a first end portion of the surface-to-be-inspected to a lock release position in the vicinity of the first end portion along the tangential direction to the surface-to-be-inspected, and switch the locked state to the swinging state after the flaw detection unit has reached the lock release position. 
     According to the ultrasonic flaw detection device according to an aspect of the present invention, when moving the flaw detection unit to the lock release position along the tangential direction to the surface-to-be-inspected, a state is maintained where the tangential direction to the contact surface of the flaw detection unit and the tangential direction to the surface-to-be-inspected of the object-to-be-inspected coincide with each other. Therefore, it is possible to bring the contact surface of the flaw detection unit into contact with the surface of an end portion of the object-to-be-inspected without the contact of the flaw detection unit with the end portion of the object-to-be-inspected. Since the flaw detection unit is in the locked state, a state where the entire region of the contact surface of the flaw detection unit is in contact with the surface-to-be-inspected of the object-to-be-inspected is maintained, and thus it is possible to avoid the flaw detection inspection from becoming impossible due to the occurrence of a gap due to the non-contact between the contact surface and the surface-to-be-inspected. 
     In the ultrasonic flaw detection device according to an aspect of the present invention, a configuration may be made in which the control unit controls the lock mechanism and the movement mechanism so as to move the flaw detection unit in the swinging state from a first position separated by a first distance in a normal direction to the surface-to-be-inspected from the surface-to-be-inspected until the contact surface comes into contact with the surface-to-be-inspected, switch the swinging state to the locked state in a state where the contact surface is in contact with the surface-to-be-inspected, move the flaw detection unit to a second position separated in the tangential direction to the surface-to-be-inspected from the first end portion of the surface-to-be-inspected and separated by a second distance shorter than the first distance in the normal direction to the surface-to-be-inspected, and move the flaw detection unit in the locked state to the lock release position along the tangential direction to the surface-to-be-inspected. 
     According to the ultrasonic flaw detection device of this configuration, by moving the flaw detection unit in the swinging state from the first position to bring the contact surface into contact with the surface-to-be-inspected and switching it to the locked state in that state, it is possible to create a state where the tangential direction to the contact surface of the flaw detection unit coincides with the tangential direction to the surface-to-be-inspected of the object-to-be-inspected, and maintain the state. Further, by moving the flaw detection unit from the second position closer to the surface-to-be-inspected than the first position to the lock release position, it is possible to avoid the flaw detection unit from colliding with the end portion of the object-to-be-inspected. 
     In the ultrasonic flaw detection device according to an aspect of the present invention, the control unit may control the lock mechanism and the movement mechanism so as to move the flaw detection unit along the surface-to-be-inspected while maintaining a state where the contact surface is in contact with the surface-to-be-inspected, after the flaw detection unit reaches the lock release position and the locked state is switched to the swinging state. 
     By moving the flaw detection unit in the swinging state along the surface-to-be-inspected while maintaining a state where the contact surface is in contact with the surface-to-be-inspected, it is possible to perform the flaw detection while adjusting the contact surface to an appropriate angle along the shape of the surface-to-be-inspected. 
     In the ultrasonic flaw detection device according to an aspect of the present invention, the control unit may control the lock mechanism and the movement mechanism so as to switch the swinging state to the locked state in response to arrival of the flaw detection unit in the swinging state at a lock start position in the vicinity of a second end portion of the surface-to-be-inspected, and move the flaw detection unit in the locked state to a third position separated in the tangential direction to the surface-to-be-inspected from the second end portion along the tangential direction to the surface-to-be-inspected. 
     If the flaw detection unit is in the swinging state when performing the flaw detection on the end portion of the surface-to-be-inspected, there is a possibility that the flaw detection unit may swing when the flaw detection unit passes through the end portion. In this case, a gap is formed between the contact surface of the flaw detection unit and the surface-to-be-inspected, so that a state is created where the flaw detection of an end portion region of the surface-to-be-inspected is not performed. Therefore, in the ultrasonic flaw detection device according to an aspect of the present invention, the flaw detection unit is moved to the third position after switching from the swinging state to the locked state. In this way, it is possible to avoid a state where the flaw detection of the end portion region of the surface-to-be-inspected is not performed. 
     In the ultrasonic flaw detection device according to an aspect of the present invention, the swinging mechanism may be a mechanism that swings the flaw detection unit around a pair of swinging axes orthogonal to each other, and the lock mechanism may be a mechanism that switches between a swinging state where the flaw detection unit can swing around the pair of swinging axes and a locked state where the flaw detection unit cannot swing around the pair of swinging axes. 
     Since the swinging mechanism swings the flaw detection unit around the pair of swinging axes, even in a case where the surface-to-be-inspected of the object-to-be-inspected has a three-dimensional curved surface shape having curvatures in a plurality of directions, it is possible to swing the flaw detection unit such that the tangential direction to the surface-to-be-inspected of the object-to-be-inspected and the tangential direction to the contact surface coincide with each other. Further, since the lock mechanism can create a locked state of making it impossible to swing around the pair of swinging axes, it is possible to fix the contact surface of the flaw detection unit at an appropriate swinging angle according to the three-dimensional curved surface shape. 
     In the ultrasonic flaw detection device according to an aspect of the present invention, the flaw detection unit may be a local water immersion type flaw detection unit having a contact medium holding part for filling a space between the probe and the surface-to-be-inspected with a contact medium. By adopting the local water immersion type flaw detection unit, it is possible to perform the flaw detection of the object-to-be-inspected without using a large-scale facility for immersing the object-to-be-inspected in water. 
     In the ultrasonic flaw detection device according to an aspect of the present invention, the flaw detection unit may be a water immersion type flaw detection unit that transmits and receives ultrasonic waves in a state where the surface-to-be-inspected of the object-to-be-inspected immersed in water is in contact with the contact surface. By adopting the water immersion type flaw detection unit, it is possible to reliably maintain a state where water is filled between the probe and the surface of the object-to-be-inspected, and improve the accuracy of the flaw detection. 
     According to another aspect of the present invention, there is provided a method for controlling an ultrasonic flaw detection device that includes a flaw detection unit having a probe that transmits and receives ultrasonic waves and a contact surface that comes into contact with a surface-to-be-inspected of an object-to-be-inspected, a swinging mechanism that supports the flaw detection unit so as to be swingable around a swinging axis, and a lock mechanism that switches between a swinging state where the flaw detection unit can swing around the swinging axis and a locked state where the flaw detection unit cannot swing around the swinging axis, the method including: a first control step of causing the flaw detection unit to be in the locked state in a state where a tangential direction to the contact surface and a tangential direction to the surface-to-be-inspected coincide with each other; a second control step of moving the flaw detection unit in the locked state along the tangential direction to the surface-to-be-inspected from a position separated from a first end portion of the surface-to-be-inspected to a lock release position in the vicinity of the first end portion; a third control step of switching the locked state to the swinging state after the flaw detection unit has reached the lock release position; and a fourth control step of moving the flaw detection unit along the surface-to-be-inspected while maintaining a state where the contact surface is in contact with the surface-to-be-inspected. 
     According to the method for controlling an ultrasonic flaw detection device according to an aspect of the present invention, when moving the flaw detection unit to the lock release position along the tangential direction to the surface-to-be-inspected, a state is maintained where the tangential direction to the contact surface of the flaw detection unit and the tangential direction to the surface-to-be-inspected of the object-to-be-inspected coincide with each other. Therefore, it is possible to bring the contact surface of the flaw detection unit into contact with the surface of an end portion of the object-to-be-inspected without the contact of the flaw detection unit with the end portion of the object-to-be-inspected. Since the flaw detection unit is in the locked state, a state where the entire region of the contact surface of the flaw detection unit is in contact with the surface of the object-to-be-inspected is maintained, and thus it is possible to avoid the flaw detection inspection from becoming impossible due to the occurrence of a gap due to the non-contact between the contact surface and the surface of the object-to-be-inspected. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to provide an ultrasonic flaw detection device in which it is possible to inspect the entire region of the surface of the object-to-be-inspected including an end portion without causing the flaw detection unit to collide with the end portion of the object-to-be-inspected. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side view showing an ultrasonic flaw detection system according to an embodiment of the present invention. 
         FIG. 2  is a plan view of the ultrasonic flaw detection system shown in  FIG. 1 , as viewed from above. 
         FIG. 3  is a side view of a flaw detection head shown in  FIG. 1 , as viewed in an X direction. 
         FIG. 4  is a side view of the flaw detection head shown in  FIG. 1 , as viewed in the X direction. 
         FIG. 5  is a side view of the flaw detection head shown in  FIG. 1 , as viewed in the X direction. 
         FIG. 6  is a block diagram showing a control configuration of the ultrasonic flaw detection system. 
         FIG. 7  is a diagram showing an example of a movement locus of the flaw detection head that moves due to flaw detection processing of a composite material. 
         FIG. 8  is a flowchart showing composite material flaw detection processing that is executed by a control unit. 
         FIG. 9  is a flowchart showing the composite material flaw detection processing that is executed by the control unit. 
         FIG. 10  is a side view showing a flaw detection unit in a state where it has moved to a first position. 
         FIG. 11  is a side view showing the flaw detection unit in a state where it has moved to a lock release position. 
         FIG. 12  is a side view showing the flaw detection unit in a state where it has moved to a second position. 
         FIG. 13  is a side view showing the flaw detection unit in a state where it has reached the lock release position. 
         FIG. 14  is a side view showing the flaw detection unit in a state where it has reached a lock start position. 
         FIG. 15  is a side view showing the flaw detection unit in a state where it has reached a third position. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an ultrasonic flaw detection system  1  according to an embodiment of the present invention will be described with reference to the drawings.  FIG. 1  is a side view showing the ultrasonic flaw detection system  1  according to an embodiment of the present invention. FIG.  2  is a plan view of the ultrasonic flaw detection system  1  shown in  FIG. 1 , as viewed from above. 
     As shown in  FIGS. 1 and 2 , the ultrasonic flaw detection system  1  of the present embodiment includes a local water immersion type ultrasonic flaw detection device  2  and a holding device  3 . A composite material  4  is an object-to-be-inspected that is an inspection target by the ultrasonic flaw detection system  1 . The ultrasonic flaw detection device  2  includes a flaw detection head (flaw detection mechanism)  20  for inspecting (flaw detection) the composite material  4  by transmitting and receiving ultrasonic waves, and a movement mechanism  21  that supports the flaw detection head  20  and moves the position of the flaw detection head  20  with respect to the composite material  4 . 
     First, the holding device  3  will be described. The holding device  3  is a device for holding the composite material  4  at a predetermined position with respect to a floor surface  5 . As shown in  FIGS. 1 and 2 , the holding device  3  includes a first base part  32 L and a second base part  32 M, in addition to a first belt  31   a  and a second belt  31   b.    
     The first base part  32 L suspends and supports a first protrusion portion  42   a  of the composite material  4 . The first base part  32 L has a first column  32   a , a second column  32   b , a first fixing portion  33   a , and a second fixing portion  33   b . The second base part  32 M suspends and supports a second protrusion portion  42   b  of the composite material  4 . The second base part  32 M has a third column  32   c , a fourth column  32   d , a third fixing portion  33   c , and a fourth fixing portion  33   d.    
     As shown in  FIG. 2 , the first column  32   a , the second column  32   b , the third column  32   c , and the fourth column  32   d  suspend and support the composite material  4 , and are disposed around a horizontal movement mechanism such that the longitudinal direction of each column is perpendicular (vertical) to the floor surface  5 . The second column  32   b  is separated from the first column  32   a  in a positive direction of a Y axis. The third column  32   c  is separated from the first column  32   a  in a positive direction of an X axis. The fourth column  32   d  is separated from the third column  32   c  in the positive direction of the Y axis. 
     The first fixing portion  33   a  and the second fixing portion  33   b  are configured to fix two end portions of the first belt  31   a . The first fixing portion  33   a  is mounted to the first column  32   a  at a position at a height h 1  from the floor surface  5 . The second fixing portion  33   b  is mounted to the second column  32   b  at the position at the height h 1  from the floor surface  5 . On the other hand, the third fixing portion  33   c  and the fourth fixing portion  33   d  are configured to fix two end portions of the second belt  31   b . The third fixing portion  33   c  is mounted to the third column  32   c  at the position at the height h 1  from the floor surface  5 . The fourth fixing portion  33   d  is mounted to the fourth column  32   d  at the position at the height h 1  from the floor surface  5 . 
     The first belt  31   a  has a first end portion  31   a A and a second end portion  31   a B. The first end portion  31   a A is fixed to the first fixing portion  33   a . The second end portion  31   a B is fixed to the second fixing portion  33   b . The first belt  31   a  is connected to the first base part  32 L and suspends and supports the first protrusion portion  42   a . Similarly, the second belt  31   b  has a first end portion  31   b A and a second end portion  31   b B. The first end portion  31   b A is fixed to the third fixing portion  33   c . The second end portion  31   b B is fixed to the fourth fixing portion  33 d. The second belt  31   b  is connected to the second base part  32 M and suspends and supports the second protrusion portion  42   b.    
     The lengths of the first belt  31   a  and the second belt  31   b  are set to be slightly longer than the distance between the first column  32   a  and the second column  32   b  such that when the composite material  4  is disposed, the composite material  4  is suspended and supported at a position at a height h 2  from the floor surface  5 . Therefore, as shown in  FIG. 1 , the first belt  31   a  hangs down in the vicinity of the center between the first column  32   a  and the second column  32   b  when viewed from the side. Similarly, the second belt  31   b  hangs down in the vicinity of the center between the third column  32   c  and the fourth column  32   d . The height h 2  is slightly lower than the height h 1  at which each of the first fixing portion  33   a  to the fourth fixing portion  33   d  is mounted. 
     Next, the movement mechanism  21  of the ultrasonic flaw detection device  2  will be described. 
     As shown in  FIGS. 1 and 2 , the movement mechanism  21  includes a horizontal movement mechanism  21 H and a vertical movement mechanism  21 V. The horizontal movement mechanism  21 H and the vertical movement mechanism  21 V are mechanisms that move the position of the flaw detection head  20  with respect to the composite material  4  to any position below the composite material  4 . The horizontal movement mechanism  21 H is configured to move the flaw detection head  20  horizontally with respect to the floor surface  5 . The horizontal movement mechanism  21 H includes an X-axis direction movement mechanism and a Y-axis direction movement mechanism. 
     The X-axis direction movement mechanism is configured to linearly move the flaw detection head  20  in the X-axis direction. Specifically, the X-axis direction movement mechanism includes a first traveling rail  211   a  having a linear shape, a first block  212   a  that freely slides along the first traveling rail  211   a , a second traveling rail  211   b  having a linear shape, and a second block  212   b  that freely slides along the second traveling rail  211   b.    
     As shown in  FIG. 2 , the first traveling rail  211   a  and the second traveling rail  211   b  are laid on the floor surface  5  along the X-axis direction so as to be parallel to each other. The distance between the first traveling rail  211   a  and the second traveling rail  211   b  can be suitably changed in accordance with the size of the composite material  4 . The lengths of the first traveling rail  211   a  and the second traveling rail  211   b  can also be suitably changed in accordance with the size of the composite material  4 . 
     The first block  212   a  moves along the first traveling rail  211   a  from the negative direction of the X axis to the positive direction of the X axis or vice versa. The second block  212   b  moves along the second traveling rail  211   b  from the negative direction of the X axis to the positive direction of the X axis or vice versa. The first block  212   a  and the second block  212   b  simultaneously move at the same speed. 
     The Y-axis direction movement mechanism is configured to linearly move the flaw detection head  20  in the Y-axis direction. Specifically, the Y-axis direction movement mechanism includes a traverse rail  213  and a third block  214  that freely slides along the traverse rail  213 . The length of the traverse rail  213  is slightly longer than the distance between the first traveling rail  211   a  and the second traveling rail  211   b . The traverse rail  213  is disposed on both the first block  212   a  and the second block  212   b . The third block  214  moves along the traverse rail  213  from the negative direction of the Y axis to the positive direction of the Y axis or vice versa. 
     As shown in  FIG. 1 , the vertical movement mechanism  21 V is configured to linearly move the flaw detection head  20  in the vertical direction (Z-axis direction) with respect to the floor surface  5 . The vertical movement mechanism  21 V includes a vertical rail  215  having a linear shape and a fourth block  216  that freely slides along the vertical rail  215 . The vertical rail  215  is disposed on the third block  214  such that the longitudinal direction thereof is perpendicular to the floor surface  5 . The flaw detection head  20  is disposed on the fourth block  216 . The fourth block  216  moves along the vertical rail  215  from the negative direction of the Z axis to the positive direction of the Z axis or vice versa. 
     Next, the flaw detection head  20  of the ultrasonic flaw detection device  2  will be described.  FIGS. 3 to 5  are side views of the flaw detection head  20  shown in  FIG. 1 , as viewed in the X direction. As shown in  FIGS. 3 to 5 , the flaw detection head  20  has a flaw detection unit  22 , a first swinging mechanism  23 , a second swinging mechanism  24 , a first lock mechanism  25 , and a second lock mechanism  26 . 
     The flaw detection unit  22  has a probe  22   a  that transmits and receives ultrasonic waves, and a contact part (a contact medium holding part)  22   b  on which a contact surface  22   b A that comes into contact with a surface-to-be-inspected  41  of the composite material  4  is formed. A water storage tank  22   b B for storing (holding) water as a contact medium that fills the space between the probe  22   a  and the surface-to-be-inspected  41  of the composite material  4  is formed in the contact part  22   b . Water is supplied to the water storage tank  22   b B from an inflow port (not shown), so that a state where the space between the probe  22   a  and the surface-to-be-inspected  41  of the composite material  4  is filled with the water can be maintained. 
     The first swinging mechanism  23  has a main body portion  23   a  and a pair of shaft members  23   b  fixed to the main body portion  23   a  and extending along a swinging axis Y 1  parallel to the Y axis. The first swinging mechanism  23  supports the contact part  22   b  of the flaw detection unit  22  so as to be swingable around the swinging axis Y 1 . 
     The second swinging mechanism  24  has a main body portion  24   a  and a pair of shaft members (not shown) fixed to the main body portion  24   a  and extending along a swinging axis X 1  parallel to the X axis. The second swinging mechanism  24  supports the main body portion  23   a  of the first swinging mechanism  23  so as to be swingable around the swinging axis X 1 . Since the first swinging mechanism  23  supports the flaw detection unit  22 , the second swinging mechanism  24  supports the contact part  22   b  of the flaw detection unit  22  through the first swinging mechanism  23  so as to be swingable around the swinging axis X 1 . 
     The first lock mechanism  25  is a mechanism that switches between a swinging state where the flaw detection unit  22  can swing around the swinging axis Y 1  and a locked state where the flaw detection unit  22  cannot swing around the swinging axis Y 1 . The first lock mechanism  25  has a disc brake  25   a  for coming into contact with the shaft member  23   b  to fix the shaft member  23   b  such that it does not rotate around the swinging axis Y 1 , a spring member  25   b  that generates a biasing force that separates the disc brake  25   a  from the shaft member  23   b , an air cylinder  25   c  that generates a biasing force that overcomes the biasing force of the spring member  25   b  by compressed air that is introduced from the outside, and a transmission mechanism  25   d  that transmits the biasing force generated by the air cylinder  25   c  to the disc brake  25   a.    
     In a case where the compressed air is not supplied from a compressed air supply source (not shown) to the air cylinder  25   c  according to a control command from a control unit  90  (described later), a state is created where the disc brake  25   a  is separated from the shaft member  23   b , as shown in  FIG. 3 . In this case, the first lock mechanism  25  supports the flaw detection unit  22  in a swinging state where the flaw detection unit  22  can swing around the swinging axis Y 1 . 
     On the other hand, in a case where the compressed air is supplied from the compressed air supply source (not shown) to the air cylinder  25   c  according to a control command from the control unit  90 , a state is created where the disc brake  25   a  is in contact with the shaft member  23   b , as shown in  FIG. 4 . In this case, the first lock mechanism  25  supports the flaw detection unit  22  in a locked state where the flaw detection unit  22  cannot swing around the swinging axis Y 1 . 
     The second lock mechanism  26  is a mechanism that switches between a swinging state where the first swinging mechanism  23  can swing around the swinging axis X 1  and a locked state where the first swinging mechanism  23  cannot swing around the swinging axis X 1 . Since the first swinging mechanism  23  supports the flaw detection unit  22 , the second lock mechanism  26  switches between a swinging state where the flaw detection unit  22  can swing around the swinging axis X 1  and a locked state where the flaw detection unit  22  cannot swing around the swinging axis X 1 . 
     The second lock mechanism  26  has the same structure as the first lock mechanism  25  and includes a disc brake (not shown) for coming into contact with a shaft member (not shown), which is fixed the main body portion  23   a  of the first swinging mechanism  23 , to fix the shaft member such that the shaft member does not rotate around the swinging axis X 1 , a spring member (not shown) that generates a biasing force that separates the disc brake from the shaft member, an air cylinder  26   c  that generates a biasing force that overcomes the biasing force of the spring member by compressed air that is introduced from the outside, and a transmission mechanism  26   d  that transmits the biasing force generated by the air cylinder  26   c  to the disc brake. 
     In a case where the compressed air is not supplied from the compressed air supply source (not shown) to the air cylinder  26   c  according to a control command from the control unit  90  (described later), a state is created where the disc brake is separated from the shaft member. In this case, the second lock mechanism  26  supports the flaw detection unit  22  in a swinging state where the flaw detection unit  22  can swing around the swinging axis X 1 . 
     On the other hand, in a case where the compressed air is supplied from the compressed air supply source (not shown) to the air cylinder  26   c  according to a control command from the control unit  90 , a state is created where the disc brake is in contact with the shaft member. In this case, the second lock mechanism  26  supports the flaw detection unit  22  in a locked state where the flaw detection unit  22  cannot swing around the swinging axis X 1 . 
       FIG. 5  shows a state where the second lock mechanism  26  causes the contact surface  22   b A of the flaw detection unit  22  to be inclined from the horizontal direction and the flaw detection unit  22  is in a locked state where it cannot swing around the swinging axes X 1 . In  FIG. 5 , an axis Z 1  is an axis parallel to the axis Z extending in the vertical direction. An axis Z 2  is an axis orthogonal to the contact surface  22   b A of the flaw detection unit  22  and passes through the swinging axis X 1 . As shown in  FIG. 5 , the axis Z 2  is inclined with respect to the axis Z 1  by an angle ex around the swinging axis X 1 . The second lock mechanism  26  allows the flaw detection unit  22  to be in the locked state in a state where the contact surface  22   b A of the flaw detection unit  22  is inclined by the angle ex with respect to the horizontal plane according to a control command from the control unit  90 . 
       FIG. 6  is a block diagram showing a control configuration of the ultrasonic flaw detection system  1  of the present embodiment. As shown in  FIG. 6 , the ultrasonic flaw detection system  1  includes the movement mechanism  21 , the flaw detection unit  22 , the first lock mechanism  25 , the second lock mechanism  26 , and the control unit  90 . The control unit  90  transmits a control command for controlling the movement mechanism  21 , the flaw detection unit  22 , the first lock mechanism  25 , and the second lock mechanism  26  to the entire system including them. 
       FIG. 7  is a diagram showing an example of a movement locus of the flaw detection head  20  that moves according to the flaw detection processing of the composite material  4  which is executed by the control unit  90  of the ultrasonic flaw detection system  1  of the present embodiment. The broken line shown in  FIG. 7  shows the movement locus of the flaw detection head  20 . As shown in  FIG. 7 , the control unit  90  moves the flaw detection head  20  from the first protrusion portion  42   a  toward the second protrusion portion  42   b  of the composite material  4  while alternately repeating the movement along the Y axis and the movement along the X axis. 
     The control unit  90  moves the flaw detection head  20  along the Y axis from a second position P 2  separated from a first end portion E 1  in the Y-axis direction of the composite material  4  to a third position P 3  separated from a second end portion E 2  in the Y-axis direction of the composite material  4 . Further, the control unit  90  moves the flaw detection head  20  along the Y axis from one end portion (the first protrusion portion  42   a  or the second protrusion portion  42 b) in the X-axis direction of the composite material  4  toward the other end portion (the second protrusion portion  42   b  or the first protrusion portion  42   a ) in the X-axis direction of the composite material  4 . 
     Next, the flaw detection processing of the composite material  4  which is executed by the control unit  90  of the present embodiment will be described with reference to  FIGS. 8 to 15 .  FIGS. 8 and 9  are flowcharts showing the flaw detection processing of the composite material  4  which is executed by the control unit  90 . Each processing shown in  FIGS. 8 and 9  is performed by the control unit  90  reading a control program from a storage unit (not shown) and executing the process. 
       FIG. 10  is a side view showing the flaw detection unit  22  in a state where it has moved to a first position P 1 .  FIG. 11  is a side view showing the flaw detection unit  22  in a state where it has moved to a lock release position Prl.  FIG. 12  is a side view showing the flaw detection unit  22  in a state where it has moved to the second position P 2 .  FIG. 13  is a side view showing the flaw detection unit  22  in a state where it has reached the lock release position Prl.  FIG. 14  is a side view showing the flaw detection unit  22  in a state where it has reached a lock start position Prk.  FIG. 15  is a side view showing the flaw detection unit  22  in a state where it has reached the third position P 3 . 
     In step S 801 , the control unit  90  controls the first lock mechanism  25  so as to set the first swinging mechanism  23  to be in a swinging state. The first swinging mechanism set to be in the swinging state supports the flaw detection unit  22  in a swinging state where the flaw detection unit  22  can swing around the swinging axis Y 1 . 
     In step S 802 , the control unit  90  controls the second lock mechanism  26  so as to set the second swinging mechanism  24  to be in a swinging state. The second swinging mechanism set to be in the swinging state supports the flaw detection unit  22  in a swinging state where the flaw detection unit  22  can swing around the swinging axis X 1 . 
     In step S 803 , the control unit  90  controls the movement mechanism  21  so as to move the flaw detection unit  22  to the first position P 1 . The first position P 1  is a position where the swinging axis X 1  of the flaw detection unit  22  is separated from the surface-to-be-inspected  41  by a first distance L 1  in the direction along a normal line NL 1  to the surface-to-be-inspected  41 . As shown in  FIG. 10 , in a state where the flaw detection unit  22  has moved to the first position P 1 , a tangential direction TL 1  to the contact surface  22   b A of the flaw detection unit  22  and a tangential direction TL 2  at a passing position of the normal line NL 1  to the surface-to-be-inspected  41  of the composite material  4  do not coincide with each other. 
     In step S 804 , the control unit  90  moves the flaw detection unit  22  in the swinging state vertically upward along the Z axis from the first position P 1  until the contact surface  22   b A comes into contact with the surface-to-be-inspected  41 . The position where the contact surface  22   b A of the flaw detection unit  22  comes into contact with the surface-to-be-inspected  41  coincides with the lock release position Prl (described later). As shown in  FIG. 11 , by bringing the flaw detection unit  22  in the swinging state into contact with the surface-to-be-inspected  41 , a state is created where the tangential direction TL 1  to the contact surface  22   b A and the tangential direction TL 2  to the surface-to-be-inspected  41  coincide with each other. 
     In step S 805 , the control unit  90  controls the first lock mechanism  25  so as to set the first swinging mechanism  23  to be in a locked state. The control unit  90  controls the first lock mechanism  25  to switch the swinging state to the locked state in a state where the contact surface  22   b A is in contact with the surface-to-be-inspected  41 . 
     In step S 806 , the control unit  90  controls the second lock mechanism  26  so as to set the second swinging mechanism  24  to be in a locked state. The control unit  90  controls the second lock mechanism  26  to switch the swinging state to the locked state in a state where the contact surface  22   b A is in contact with the surface-to-be-inspected  41 . As shown in  FIG. 11 , steps S 805  and S 806  described above are executed, whereby the flaw detection unit  22  enters the locked state in a state where the tangential direction TL 1  to the contact surface  22   b A and the tangential direction TL 2  to the surface-to-be-inspected  41  coincide with each other. As shown in  FIG. 11 , the angle formed by the axis Z 1  parallel to the Z axis and the normal line NL 1  is ex. 
     In step S 807 , the control unit  90  controls the movement mechanism  21  so as to move the flaw detection unit  22  to the second position P 2 . As shown in  FIG. 12 , the second position P 2  is a position where the swinging axis X 1  of the flaw detection unit  22  is separated by a predetermined distance in the tangential direction TL 2  to the surface-to-be-inspected  41  from the first end portion E 1  of the surface-to-be-inspected  41 . Further, the second position P 2  is a position separated by a second distance L 2 , which is shorter than the first distance L 1 , in the direction along the normal line NL 1  to the surface-to-be-inspected  41 . As shown in  FIG. 12 , the angle formed by the axis Z 1  parallel to the Z axis and the normal line NL 1  is maintained at ex as in  FIG. 11 . 
     In step S 808 , the control unit  90  controls the movement mechanism  21  such that the flaw detection unit  22  starts movement from the second position P 2  to the lock release position Prl along the tangential direction TL 2  to the surface-to-be-inspected  41 . The control unit  90  controls the first lock mechanism  25  and the second lock mechanism so as to maintain the locked state until the flaw detection unit  22  moves from the second position P 2  to the lock release position Prl. 
     In step S 809 , the control unit  90  controls the flaw detection unit  22  so as to start the flaw detection of the surface-to-be-inspected  41  by transmitting and receiving ultrasonic waves in response to the arrival of the contact surface  22   b A of the flaw detection unit  22  at the surface-to-be-inspected  41 . 
     In step S 810 , the control unit  90  determines whether or not the flaw detection unit  22  has reached the lock release position Prl shown in  FIG. 13 , and in a case where it is determined that the flaw detection unit  22  has reached the lock release position Prl, the processing proceeds to step S 811 . 
     In step S 811 , the control unit  90  controls the first lock mechanism  25  so as to set the first swinging mechanism  23  to be in a swinging state. The first swinging mechanism set to be in the swinging state supports the flaw detection unit  22  in a swinging state where the flaw detection unit  22  can swing around the swinging axis Y 1 . 
     In step S 812 , the control unit  90  controls the second lock mechanism  26  so as to set the second swinging mechanism  24  to be in a swinging state. The second swinging mechanism set to be in the swinging state supports the flaw detection unit  22  in a swinging state where the flaw detection unit  22  can swing around the swinging axis X 1 . 
     The flaw detection unit  22  which has entered the swinging state in steps S 811  and S 812  moves toward the lock start position Prk along the Y axis in a state where the tangential direction TL 1  to the contact surface  22   b A coincides with the tangential direction TL 2  to the surface-to-be-inspected  41 . The control unit  90  controls the position in the Z-axis direction of the flaw detection unit  22  so as to maintain a state where the contact surface  22   b A and the surface-to-be-inspected  41  are in contact with each other. 
     In step S 813 , the control unit  90  determines whether or not the flaw detection unit  22  has reached the lock start position Prk shown in  FIG. 14 , and in a case where it is determined that the flaw detection unit  22  has reached the lock start position Prk, the processing proceeds to step S 814 . 
     In step S 814 , the control unit  90  controls the first lock mechanism  25  so as to set the first swinging mechanism  23  to be in a locked state. The control unit  90  controls the first lock mechanism  25  to switch the swinging state to the locked state in a state where the contact surface  22   b A is in contact with the surface-to-be-inspected  41 . 
     In step S 815 , the control unit  90  controls the second lock mechanism  26  so as to set the second swinging mechanism  24  to be in a locked state. The control unit  90  controls the second lock mechanism  26  to switch the swinging state to the locked state in a state where the contact surface  22   b A is in contact with the surface-to-be-inspected  41 . As shown in  FIG. 14 , steps S 814  and S 815  described above are executed, whereby the flaw detection unit  22  enters the locked state in a state where the tangential direction TL 1  to the contact surface  22   b A and the tangential direction TL 2  to the surface-to-be-inspected  41  coincide with each other. As shown in  FIG. 14 , the angle formed by the axis Z 1  parallel to the Z axis and the normal line NL 1  is ex. 
     In step S 816 , the control unit  90  controls the movement mechanism  21  such that the flaw detection unit  22  starts movement from the lock start position Prk to the third position P 3  along the tangential direction TL 2  to the surface-to-be-inspected  41 . The control unit  90  controls the first lock mechanism  25  and the second lock mechanism so as to maintain the locked state until the flaw detection unit  22  moves from the lock start position Prk to the third position P 3 . 
     The third position P 3  is a position where the swinging axis X 1  of the flaw detection unit  22  is separated by a predetermined distance in the tangential direction TL 2  to the surface-to-be-inspected  41  from the second end portion E 2  of the surface-to-be-inspected  41 . Further, the third position P 3  is a position separated by the second distance L 2  in the direction along the normal line NL 1  to the surface-to-be-inspected  41 . 
     In step S 817 , the control unit  90  controls the flaw detection unit  22  so as to end the flaw detection of the surface-to-be-inspected  41  by stopping the transmission and reception of the ultrasonic waves in response to the contact surface  22   b A of the flaw detection unit  22  being separated from the surface-to-be-inspected  41 . 
     In step S 818 , the control unit  90  determines whether the flaw detection unit  22  has reached the third position P 3  shown in  FIG. 15 , and in a case where it is determined that the flaw detection unit  22  has reached the third position P 3 , the processing proceeds to step S 819 . 
     In step S 819 , the control unit  90  controls the movement mechanism  21  so as to move the flaw detection unit  22  by a predetermined distance in the X-axis direction, and ends the processing of this flowchart. The control unit  90  repeats the processing from step S 801  to step S 819  described above, thereby performing the flaw detection processing by moving the flaw detection head  20  along the Y axis, at a plurality of positions in the X-axis direction. In this way, the control unit  90  performs the flaw detection of the entire region of the surface-to-be-inspected  41  of the composite material  4  from the first protrusion portion  42 a to the second protrusion portion  42   b  of the composite material  4 . 
     The operation and effects of the ultrasonic flaw detection system  1  of the present embodiment described above will be described. 
     According to the ultrasonic flaw detection system  1  of the present embodiment, when moving the flaw detection unit  22  to the lock release position Prl along the tangential direction TL 2  to the surface-to-be-inspected  41 , a state is maintained where the tangential direction TL 1  to the contact surface  22   b A of the flaw detection unit  22  and the tangential direction TL 2  to the surface-to-be-inspected  41  of the composite material  4  coincides with each other. Therefore, it is possible to bring the contact surface  22   b A of the flaw detection unit  22  into contact with the surface of the first end portion E 1  of the composite material  4  without the contact of the flaw detection unit  22  with the first end portion E 1  of the composite material  4 . Since the flaw detection unit  22  is in the locked state, a state where the entire region of the contact surface  22   b A of the flaw detection unit  22  is in contact with the surface-to-be-inspected  41  of the composite material  4  is maintained, and thus it is possible to avoid the flaw detection inspection from becoming impossible due to the occurrence of a gap due to the non-contact between the contact surface  22   b A and the surface-to-be-inspected  41 . 
     Further, according to the ultrasonic flaw detection system  1  of the present embodiment, by moving the flaw detection unit  22  in the swinging state from the first position P 1  to bring the contact surface  22   b A into contact with the surface-to-be-inspected  41  and switching it to the locked state in that state, it is possible to create a state where the tangential direction TL 1  to the contact surface  22   b A of the flaw detection unit  22  coincides with the tangential direction TL 2  to the surface-to-be-inspected  41  of the composite material  4 , and maintain the state. Further, by moving the flaw detection unit  22  from the second position P 2  closer to the surface-to-be-inspected  41  than the first position P 1  to the lock release position Prl, it is possible to avoid the flaw detection unit  22  from colliding with the first end portion E 1  of the composite material  4 . 
     Further, according to the ultrasonic flaw detection system  1  of the present embodiment, by moving the flaw detection unit  22  in the swinging state along the surface-to-be-inspected  41  while maintaining a state where the contact surface  22   b A is in contact with the surface-to-be-inspected  41 , it is possible to perform the flaw detection while adjusting the contact surface  22   b A to an appropriate angle along the shape of the surface-to-be-inspected  41 . 
     If the flaw detection unit  22  is in the swinging state when performing the flaw detection on the second end portion E 2  of the surface-to-be-inspected  41 , there is a possibility that the flaw detection unit  22  may swing when the flaw detection unit  22  passes through the second end portion E 2 . In this case, a gap is formed between the contact surface  22   b A of the flaw detection unit  22  and the surface-to-be-inspected  41 , so that a state is created where the flaw detection of the end portion region of the surface-to-be-inspected  41  is not performed. Therefore, in the ultrasonic flaw detection system  1  of the present embodiment, the flaw detection unit  22  is moved to the third position P 3  after switching from the swinging state to the locked state. In this way, it is possible to avoid a state where the flaw detection of the end portion region of the surface-to-be-inspected  41  is not performed. 
     Further, according to the ultrasonic flaw detection system  1  of the present embodiment, since the first swinging mechanism  23  and the second swinging mechanism  24  swing the flaw detection unit  22  around the swinging axes X 1  and Y 1 , even in a case where the surface-to-be-inspected  41  of the composite material  4  has a three-dimensional curved surface shape having curvatures in a plurality of directions, it is possible to swing the flaw detection unit  22  such that the tangential direction TL 2  to the surface-to-be-inspected  41  of the composite material  4  and the tangential direction TL 1  to the contact surface  22   b A coincide with each other. Further, since the first lock mechanism  25  and the second lock mechanism  26  can create a locked state of making it impossible to swing around the swinging axes X 1  and Y 1 , it is possible to fix the contact surface  22   b A of the flaw detection unit  22  at an appropriate swinging angle according to the three-dimensional curved surface shape. 
     Further, according to the ultrasonic flaw detection system  1  of the present embodiment, by adopting the local water immersion type flaw detection unit  22 , it is possible to perform the flaw detection of the object-to-be-inspected without using a large-scale facility for immersing the object-to-be-inspected in water. 
     [Other Embodiments] 
     In the above description, it has been assumed that the ultrasonic flaw detection system  1  adopts the local water immersion type flaw detection unit  22 . However, other aspects is also acceptable. For example, a water immersion type ultrasonic flaw detection system adopting a water immersion type flaw detection unit is also acceptable. The water immersion type ultrasonic flaw detection system includes a flaw detection unit having a probe that transmits and receives ultrasonic waves in a state of being in contact with a surface-to-be-inspected of a water-immersed composite material (for example, a bent stringer that is used in a main wing of an aircraft). Since the periphery of the flaw detection unit of the water immersion type ultrasonic flaw detection system is filled with water, it is not necessary to provide a water storage tank for storing water as a contact medium that fills the space between the flaw detection unit and the surface-to-be-inspected of the composite material. By adopting the water immersion type flaw detection unit, it is possible to reliably maintain a state where water is filled between the probe and the surface of the object-to-be-inspected, and improve the accuracy of the flaw detection. 
     REFERENCE SIGNS LIST 
       1 : ultrasonic flaw detection system 
       2 : ultrasonic flaw detection device 
       20 : flaw detection head 
       21 : movement mechanism 
       22 : flaw detection unit 
       22   a : probe 
       22   b : contact part 
       22   b A: contact surface 
       23 : first swinging mechanism 
       24 : second swinging mechanism 
       25 : first lock mechanism 
       26 : second lock mechanism 
       31   b A: first end portion 
       31   b B: second end portion 
       41 : surface-to-be-inspected 
       90 : control unit 
     Prk: lock start position 
     Prl: lock release position 
     X 1 , Y 1 : swinging axis