A method for detecting defects in a rail based on a phased array ultrasound

Abstract

The application discloses a steel rail defect detection method based on a phased array ultrasonic device, which comprises the following steps: a 128-element phased array ultrasonic probe is used as a probe for detecting a steel rail, the probe is installed on a mechanical arm capable of moving along the longitudinal direction of the steel rail, the elements of the phased array ultrasonic probe are divided into five groups, the first group comprises elements No. 1-50 and is used for scanning damage at the right upper side of the rail head, the second group comprises elements No. 51-60 and is used for scanning damage near the right rail jaw of the steel rail, the third group comprises elements No. 61-68 and is used for scanning damage at the middle part of the rail head, the rail waist and the middle part of the rail bottom, the fourth group comprises elements No. 69-78 and is used for scanning damage near the left rail jaw of the steel rail, and the fifth group comprises elements No. 79-128 and is used for scanning damage at the left upper side of the rail head; and the wave form in the rail is a transverse wave. The steel rail damage in several key areas is detected by using multiple beams excited by the phased array probe simultaneously, and high-precision and high-efficiency nondestructive detection of the steel rail can be realized.

Description

Technical Field

[0001] This invention belongs to the field of ultrasonic nondestructive testing technology for rails, specifically relating to a method for detecting rail defects based on phased array ultrasound. Background Technology

[0002] As the carrier of trains, rails operate under complex and harsh conditions for extended periods, making them prone to internal defects. If we divide the rail into three parts—rail head, rail web, and rail base—typical defects include: horizontal cracks at the rail head, longitudinal cracks at the rail head, progressive transverse cracks at the rail head, and oblique cracks at the rail web and rail base. Failures or malfunctions in these areas can cause incalculable loss of life and property.

[0003] Ultrasonic nondestructive testing (NDT) has become an important method for rail inspection due to its advantages of high safety, high reliability, strong adaptability, and rich characteristic parameters. In the early days, inspectors mostly used conventional ultrasonic probes and A-mode ultrasound with pulse-echo method for rail flaw detection. However, this method was not intuitive, required a high level of operator skill, and was prone to missed or false detections. Furthermore, it required multiple probes with complex mechanical structures on the outside of the track to ensure comprehensive coverage of the entire track cross-section. Phased array ultrasound can overcome these shortcomings. By setting delay rules, the probe can focus and deflect the sound beam, allowing a single probe to detect defects at multiple angles. It offers significant advantages in scanning range, beam reachability, and sensitivity. However, the method of using phased array ultrasonic probes to emit beams in different directions requires sequential emission of each beam, resulting in a low imaging rate. How to improve the rail scanning rate while maintaining a simplified inspection structure and high inspection quality is a critical problem that urgently needs to be solved. Summary of the Invention

[0004] To address the issues of missed and false detections caused by conventional ultrasonic probes and the low imaging rate of traditional phased array scanning methods in the background art, this invention provides a rail defect detection method based on phased array ultrasound. By using multiple focused beams simultaneously excited by a phased array probe, damage in several key areas within the rail can be detected, achieving high-precision and high-efficiency non-destructive testing of rails.

[0005] The present invention adopts the following technical solution:

[0006] This invention provides a method for detecting rail defects based on phased array ultrasound, which includes the following steps:

[0007] Step 1: Install the 128-element ultrasonic phased array probe for testing at the end of the six-degree-of-freedom robotic arm; place the rail to be tested in the water tank;

[0008] Step 2: Adjust the position and posture of the robotic arm so that the array elements of the ultrasonic phased array probe are arranged along the width of the rail, the vertical height of the probe center to the rail surface is 128mm, and the perpendicular bisector of the array element forms an angle of 24.2° with the rail surface.

[0009] Step 3: Operate the robotic arm to move the probe to one end of the rail. During the movement, constantly observe the relative position of the probe and the rail until the probe moves to the initial detection position.

[0010] Step 4: Divide the array elements of the phased array ultrasonic probe into five groups, set the transmission and reception delay rules for the array elements within each group, and have the five groups of array elements simultaneously transmit focused beams in five directions according to the delay rules of their respective internal array elements to detect damage in different areas within the sample rail; during the detection, ensure that there is a water layer between the rail and the probe as a coupling layer.

[0011] Step 5: Manipulate the robotic arm so that the end of the robotic arm drives the probe to move at a constant speed in a straight line along the length of the rail. While moving, the probe performs rail defect detection until the probe extends beyond the other end of the rail in the vertical direction.

[0012] As a preferred embodiment of the present invention, the waveform emitted by the ultrasonic probe is a longitudinal wave, and only a transverse wave exists after entering the rail.

[0013] As a preferred embodiment of the present invention, the rail is placed in the center of a water tank that can fully accommodate the rail. The water tank has an opening at the top, and water needs to be added before testing until the water level is more than 140mm below the upper surface of the rail.

[0014] As a preferred embodiment of the present invention, the array elements of the 128-element ultrasonic phased array probe are numbered sequentially from left to right as 1-128, and divided into five groups. The first group includes array elements 1-50, the second group includes array elements 51-60, the third group includes array elements 61-68, the fourth group includes array elements 69-78, and the fifth group includes array elements 79-128.

[0015] The ultrasonic waves emitted by the five array elements are used to detect damage in different areas of the sample rail. The first array element scans for damage at the upper right corner of the rail head, the second array element scans for damage near the right rail jaw, the third array element scans for damage in the middle of the rail head, the fourth array element scans for damage near the left rail jaw, and the fifth array element scans for damage at the upper left corner of the rail head.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] (1) Each array element adopts the focusing law to focus the beam near the defect, which can make the echo signal of each defect the strongest, so as to ensure good detection accuracy and detection signal-to-noise ratio, thereby detecting small defects that cannot be detected by traditional rail inspection methods.

[0018] (2) Each array element transmits and receives beams simultaneously, ensuring that when the probe and the rail are in a certain relative position, only one transmission and reception are needed to detect the entire cross section, thus ensuring a high detection rate. Compared with general phased array ultrasonic rail detection methods, the efficiency is increased by five times.

[0019] (3) Using one ultrasonic phased array probe to replace multiple ultrasonic single probes in traditional testing can replace the probe frame of ten single probes in traditional rail testing equipment with the probe frame of two phased array probes, making the overall flaw detection equipment smaller and the mechanical structure such as the probe frame more streamlined. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall scheme of the present invention;

[0021] Figure 2 This is a schematic diagram of the beam propagation paths of the first and fifth array elements of the present invention;

[0022] Figure 3 This is a schematic diagram of the beam propagation paths of the second and fourth array elements of the present invention;

[0023] Figure 4 A schematic diagram of the beam propagation path of the third array element in this invention. Detailed Implementation

[0024] The feasibility of implementing the present invention and the specific details of the technical solution will be further explained below with reference to the accompanying drawings and specific embodiments.

[0025] This invention relates to a method for detecting defects in rails, applicable to defect detection of rail samples before they leave the factory. Before testing, a water layer must be ensured between the rail sample and the probe as a coupling layer. Therefore, the rail sample is first placed in the center of a water tank that can completely contain the rail. The water tank has an opening at the top, and water must be added until the water level is more than 140mm below the upper surface of the rail sample before testing.

[0026] like Figure 1 , Figure 2 As shown, before testing, it is necessary to ensure that the phased array ultrasonic probe and the test track are in a specific relative pose. The method is as follows:

[0027] Step 1: Install the 128-element ultrasonic phased array probe for testing at the end of a robotic arm that can move at a constant speed in a straight line along the length of the rail being tested.

[0028] Step 2: Adjust the position and posture of the robotic arm so that the 128 elements of the ultrasonic phased array probe are arranged along the width of the rail, the center of the probe is 128mm above the rail surface, and the perpendicular bisector of the array element forms a 24.2° angle with the rail surface.

[0029] Step 3: Manipulate the robotic arm to move the probe to one end of the sample rail. During the movement, the relative position of the probe and the sample rail must be observed at all times until the probe moves to the initial detection position. Since the ultrasonic phased array probe of the present invention is installed at an angle to the surface of the rail, the initial detection position needs to be at least 50mm away from the front end face of the sample rail, preferably 50-100mm away from the front end face of the sample rail.

[0030] After completing the above operations, the probe can be activated, and the scanning process can begin in conjunction with the uniform linear motion of the robotic arm's end effector, as follows:

[0031] Step 4: Divide the array elements of the phased array ultrasonic probe into five groups, set the transmission and reception delay rules for the array elements within each group, and have the five groups of array elements simultaneously transmit focused beams in five directions according to the delay rules of their respective internal array elements to detect damage in different areas within the sample rail; during the detection, ensure that there is a water layer between the rail and the probe as a coupling layer.

[0032] Step 5: Manipulate the robotic arm so that its end effector drives the probe to move at a constant speed in a straight line along the length of the test track until the probe extends vertically beyond the other end of the test track. During this process, the probe continuously transmits and receives ultrasonic waves.

[0033] The waveform emitted by the ultrasonic probe is a longitudinal wave, but only a transverse wave exists after entering the test track.

[0034] The elements of the 128-element ultrasonic phased array probe are numbered sequentially (numbered 1-128 from one end to the other) and divided into five groups. The first group includes elements 1-50, the second group includes elements 51-60, the third group includes elements 61-68, the fourth group includes elements 69-78, and the fifth group includes elements 79-128.

[0035] The ultrasonic waves emitted by the five array elements are used to detect damage in different areas of the sample rail. The first array element scans for damage at the upper right corner of the rail head, the second array element scans for damage near the right rail jaw, the third array element scans for damage in the middle of the rail head, the fourth array element scans for damage near the left rail jaw, and the fifth array element scans for damage at the upper left corner of the rail head.

[0036] like Figure 2 As shown, the propagation path of the beam emitted by the first group of array elements is:

[0037] The beam emission point of the first array element is determined as its midpoint A. Based on the preset rail head upper right side deflection angle damage detection position H, the propagation speed of longitudinal waves in water and transverse waves in the rail, the law of refraction, and the law of reflection, the refraction point C of the beam on the upper surface of the rail and the reflection point F on the right rail jaw are solved. Connecting the emission point A and the incident point C, the beam propagation path AC in the water is obtained. According to the law of refraction, the beam propagates from the incident point C to the rail jaw reflection point F in the rail. According to the law of reflection, the beam then propagates from the reflection point F to the rail head upper right side deflection angle damage detection position H. Finally, the beam returns to the emission point A via the original path H.

[0038] In the above path planning, firstly, based on the φ3×15 right rail head side borehole damage defined in the GTS-60SG test block of "China Railway Transportation

[2017] No. 31", the final focal point of the first group of array elements is determined to be a point H on the damaged surface. The center of the first group of array elements is set as point A. According to Fermat's principle, when an ultrasonic wave propagates from one point to another in a medium, it always propagates along the path with the shortest time. The propagation speeds of longitudinal waves in water and transverse waves in rails are known, which are 1497 m / s and 3200 m / s respectively. Therefore, the refraction point C of the beam on the upper surface of the rail and the reflection point F on the right rail jaw can be solved, thus obtaining the propagation path of the ultrasonic beam as ACFH. The angle between AC and the ultrasonic probe plane is the emission deflection angle. Based on this angle and the characteristic that the beam is finally focused at point H, the emission delay of each element in the first group is calculated, which is the emission delay rule of the first group of array elements. In this case, array element 1 is emitted first and array element 50 is emitted last.

[0039] like Figure 3 As shown, the propagation path of the beam emitted by the second group of array elements is:

[0040] The beam emission point of the second array element is determined as its midpoint I. Based on the preset right rail jaw damage detection position N, the propagation speed of longitudinal waves in water and transverse waves in the rail, and the law of refraction, the incident point of the beam on the upper surface of the rail is determined as L. The beam propagation path IL in the water is obtained by connecting the emission point I and the incident point L. The beam propagates from the incident point L to the right rail jaw damage detection position N in the rail. Finally, the beam returns to the emission point I from N.

[0041] In the above path planning, firstly, based on the R4 right rail jaw semi-circular groove damage defined in the GTS-60SG test block of "China Railway Transportation

[2017] No. 31", the final focal point of the second group of array elements is determined to be point N on the damage, and the center of the second group of array elements is set as point I. According to Fermat's principle, when ultrasonic waves propagate from one point to another in a medium, they always propagate along the path with the shortest time. The propagation speeds of longitudinal waves in water and transverse waves in rails are known, which are 1497 m / s and 3200 m / s respectively. Therefore, the refraction point L of the beam on the upper surface of the rail can be solved, thus obtaining the propagation path of the ultrasonic beam as ILN. The angle between IL and the plane of the ultrasonic probe is the emission deflection angle. Based on this angle and the characteristic that the beam is finally focused at point N, the emission delay of each element in the second group is calculated, which is the emission delay rule of the second group of array elements. In this case, array element 51 is emitted first and array element 60 is emitted last.

[0042] like Figure 4 As shown, the propagation path of the beam emitted by the third group of array elements is:

[0043] The beam emission point of the third array element is determined as its midpoint O. Based on the preset railhead center defect detection position Q, the propagation speed of longitudinal waves in water and transverse waves in the rail, and the law of refraction, the incident point of the beam on the upper surface of the rail is determined as P. Connecting the emission point O and the incident point P, the propagation path OP of the beam in the water is obtained. According to the law of refraction, the beam propagates from the incident point P to the railhead center defect detection position Q in the rail. Finally, the beam returns to the emission point O via the original path Q.

[0044] In the above path planning, firstly, based on the damage to the φ4 railhead center flat bottom hole defined in the GTS-60SG test block of "China Railway Transportation

[2017] No. 31", the final focal point of the third group of array elements is determined to be a point Q on the damaged end face. The center of the third group of array elements is set as point O. According to Fermat's principle, when ultrasonic waves propagate from one point to another in a medium, they always propagate along the path with the shortest time. The propagation speeds of longitudinal waves in water and transverse waves in rails are known, which are 1497 m / s and 3200 m / s respectively. Therefore, the refraction point P of the beam on the upper surface of the rail can be solved, thus obtaining the propagation path of the ultrasonic beam as OPQ. The angle between OP and the plane of the ultrasonic probe is the emission deflection angle. Based on this angle and the characteristic that the beam is finally focused at point Q, the emission delay of each element in the third group is calculated, which is the emission delay rule of the third group of array elements. In this case, array elements 61 and 68 are emitted first, while array elements 64 and 65 are emitted last.

[0045] like Figure 3 As shown, the propagation path of the beam emitted by the fourth group of array elements is:

[0046] The beam emission point of the fourth array element is determined as its midpoint J. Based on the preset left rail jaw defect detection position M, the propagation speed of longitudinal waves in water and transverse waves in the rail, and the law of refraction, the incident point of the beam on the selected upper surface of the rail is determined as K. The beam propagation path JK in the water is obtained by connecting the emission point J and the incident point K. According to the law of refraction, the beam propagates from the incident point K to the left rail jaw defect detection position M in the rail. Finally, the beam returns to the emission point J from M.

[0047] In the above path planning, firstly, based on the semi-circular groove damage on the left rail jaw of R4 defined by the GTS-60SG test block in "China Railway Transportation

[2017] No. 31", the final focal point of the fourth group of array elements is determined to be point M on the damage, and the center of the fourth group of array elements is set as point J. According to Fermat's principle, when an ultrasonic wave propagates from one point to another in a medium, it always propagates along the path with the shortest time. The propagation speeds of longitudinal waves in water and transverse waves in rails are known, which are 1497 m / s and 3200 m / s respectively. Therefore, the refraction point K of the beam on the upper surface of the rail can be solved, and the propagation path of the ultrasonic beam is obtained as JKM. The angle between JK and the plane of the ultrasonic probe is the emission deflection angle. Based on this angle and the characteristic that the beam is finally focused at point M, the emission delay of each element in the fourth group is calculated, which is the emission delay rule of the fourth group of array elements. In this case, array element 78 is emitted first and array element 69 is emitted last.

[0048] like Figure 2 As shown, the propagation path of the beam emitted by the fifth array element is:

[0049] The beam emission point of the fifth array element is determined as its midpoint B. Based on the preset defect detection position G at the upper left corner of the rail head, the propagation speed of longitudinal waves in water and transverse waves in the rail, the law of refraction, and the law of reflection, the incident point D on the selected upper surface of the rail and the rail jaw reflection point E are solved. Connecting the emission point B and the incident point D, the beam propagation path BD in the water is obtained. According to the law of refraction, the beam propagates from the incident point D to the rail jaw reflection point E in the rail. According to the law of reflection, the beam then propagates from the reflection point E to the defect detection position G at the upper left corner of the rail head. Finally, the beam returns to the emission point B via the original path from G.

[0050] In the above path planning, firstly, based on the φ3×15 left rail head side borehole damage defined in the GTS-60SG test block of "China Railway Transportation

[2017] No. 31", the final focal point of the fifth group of array elements is determined to be a point G on the damaged surface. The center of the fifth group of array elements is set as point B. According to Fermat's principle, when ultrasonic waves propagate from one point to another in a medium, they always propagate along the path with the shortest time. The propagation speeds of longitudinal waves in water and transverse waves in rails are known, which are 1497 m / s and 3200 m / s respectively. Therefore, the refraction point D of the beam on the upper surface of the rail and the reflection point E on the left rail jaw can be solved, thus obtaining the propagation path of the ultrasonic beam as BDEG. The angle between BD and the ultrasonic probe plane is the emission deflection angle. Based on this angle and the characteristic that the beam is finally focused at point G, the emission delay of each element in the fifth group is calculated, which is the emission delay rule of the fifth group of array elements. In this scenario, element 128 was launched first, while element 79 was launched last.

[0051] Five array elements transmit and receive simultaneously to improve the scanning rate.

[0052] This invention uses an ultrasonic phased array probe to generate an ultrasonic beam, which is then incident on the interior of the rail. Defects in the rail are detected by analyzing the echo information. The rails being tested are 43kg / m to 75kg / m type rails, and the standard specification TB / T2340-2012 "Ultrasonic Flaw Detector for Rails" is followed.

[0053] Since the distance traveled by an ultrasonic wave is proportional to its travel time, the system determines the location of the defect based on the propagation time of the ultrasonic echo in the rail. It is important to note that because the echo received by the probe travels back and forth between the defect and the transducer, the propagation distance calculated from the propagation time is twice the distance between the defect and the transducer. Therefore, half of this calculated result must be used to obtain the actual defect distance.

[0054] The monitoring gate is used to monitor damage echoes. This gate is an "advance wave alarm," meaning that an alarm is triggered when the damage signal exceeds a set threshold. If the echo is below the set threshold or outside the gate's range, no alarm is triggered. The gate range setting table for the five array elements is as follows:

[0055]

[0056] According to the measurement method in Section 7.3.5 of the Provisional Technical Regulations for Dual-Rail Ultrasonic Flaw Detectors for Rails (TJGW157-2017), the interval between ultrasonic pulse transmissions should not exceed 3 mm during testing. However, the interval between two adjacent pulse transmissions from a phased array ultrasonic probe is approximately 500 μs. This results in a maximum scanning rate of 1.2 m / s for traditional phased array scanning methods, while the maximum scanning rate of this invention is 6 m / s. Therefore, this invention can significantly improve the efficiency of phased array ultrasonic testing of rails.

[0057] The above embodiments are used to explain and illustrate the present invention, but not to limit the present invention. Any modifications and changes made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A method for detecting rail defects based on phased array ultrasound, characterized in that, Includes the following steps: Step 1: Install the 128-element ultrasonic phased array probe for testing at the end of the six-degree-of-freedom robotic arm; place the rail to be tested in the water tank; Step 2: Adjust the position and posture of the robotic arm so that the array elements of the ultrasonic phased array probe are arranged along the width of the rail, the vertical height of the probe center to the rail surface is 128mm, and the perpendicular bisector of the array element forms an angle of 24.2° with the rail surface. Step 3: Operate the robotic arm to move the probe to one end of the rail. During the movement, constantly observe the relative position of the probe and the rail until the probe moves to the initial detection position. Step 4: Number the elements of the 128-element ultrasonic phased array probe from left to right as 1-128, and divide them into five groups. The first group includes elements 1-50, the second group includes elements 51-60, the third group includes elements 61-68, the fourth group includes elements 69-78, and the fifth group includes elements 79-128. The ultrasonic waves emitted by the five array elements are used to detect damage in different areas of the sample rail. The first array element scans the damage at the upper right corner of the rail head, the second array element scans the damage near the right rail jaw, the third array element scans the damage in the middle of the rail head, the fourth array element scans the damage near the left rail jaw, and the fifth array element scans the damage at the upper left corner of the rail head. The delay rules for transmission and reception of array elements within each array element group are set, wherein the propagation path of the beam transmitted by the first array element group is: The beam emission point of the first array element is determined as its midpoint A. Based on the preset rail head upper right side deflection angle damage detection position H, the propagation speed of longitudinal waves in water and transverse waves in the rail, the law of refraction, and the law of reflection, the refraction point C of the beam on the upper surface of the rail and the reflection point F on the right rail jaw are solved. Connecting the emission point A and the incident point C, the beam propagation path AC in the water is obtained. According to the law of refraction, the beam propagates from the incident point C to the rail jaw reflection point F in the rail. According to the law of reflection, the beam then propagates from the reflection point F to the rail head upper right side deflection angle damage detection position H. Finally, the beam returns to the emission point A via the original path H. The delay rule for the first group of array elements is as follows: the angle between AC and the ultrasonic probe plane is the emission deflection angle. Based on this angle and the characteristic that the beam is finally focused at point H, the emission delay of each array element in the first group is calculated, which is the emission delay rule for the first group of array elements. Among them, array element 1 is emitted first and array element 50 is emitted last. The propagation path of the beam emitted by the second group of array elements is: The beam emission point of the second array element is determined as its midpoint I. Based on the preset right rail jaw damage detection position N, the propagation speed of longitudinal waves in water and transverse waves in the rail, and the law of refraction, the incident point L on the upper surface of the rail is determined. Connecting the emission point I and the incident point L, the propagation path IL of the beam in the water is obtained. The beam propagates from the incident point L to the right rail jaw damage detection position N in the rail. Finally, the beam returns to the emission point I from N along the original path. The delay rule for the second group of array elements is as follows: the angle between the measured IL and the ultrasonic probe plane is the emission deflection angle. Based on this angle and the characteristic that the beam is finally focused at point N, the emission delay of each array element in the second group is calculated, which is the emission delay rule for the second group of array elements. Among them, array element 51 is emitted first and array element 60 is emitted last. The propagation path of the beam emitted by the third group of array elements is: The beam emission point of the third array element is determined as its midpoint O. Based on the preset railhead center defect detection position Q, the propagation speed of longitudinal waves in water and transverse waves in the rail, and the law of refraction, the incident point of the beam on the upper surface of the rail is determined as P. Connecting the emission point O and the incident point P, the propagation path OP of the beam in water is obtained. According to the law of refraction, the beam propagates from the incident point P to the railhead center defect detection position Q in the rail. Finally, the beam returns to the emission point O via the original path Q. The delay rule for the third group of array elements is as follows: the angle between OP and the ultrasonic probe plane is the emission deflection angle. Based on this angle and the characteristic that the beam is finally focused at point Q, the emission delay of each array element in the third group is calculated, which is the emission delay rule for the third group of array elements. Among them, array elements 61 and 68 are emitted first, while array elements 64 and 65 are emitted last. The propagation path of the beam emitted by the fourth array element is: The beam emission point of the fourth array element is determined as its midpoint J. Based on the preset left rail jaw defect detection position M, the propagation speed of longitudinal waves in water and transverse waves in the rail, and the law of refraction, the incident point of the beam on the selected upper surface of the rail is determined as K. Connecting the emission point J and the incident point K, the propagation path JK of the beam in water is obtained. According to the law of refraction, the beam propagates from the incident point K to the left rail jaw defect detection position M in the rail. Finally, the beam returns to the emission point J via the original path from M. The delay rule for the fourth group of array elements is as follows: the angle between JK and the ultrasonic probe plane is the emission deflection angle. Based on this angle and the characteristic that the beam is finally focused at point M, the emission delay of each array element in the fourth group is calculated, which is the emission delay rule for the fourth group of array elements. Among them, array element 78 is emitted first and array element 69 is emitted last. The propagation path of the beam emitted by the fifth array element is as follows: The beam emission point of the fifth array element is determined as its midpoint B. Based on the preset defect detection position G at the upper left corner of the rail head, the propagation speed of longitudinal waves in water and transverse waves in the rail, the law of refraction, and the law of reflection, the incident point D on the selected upper surface of the rail and the rail jaw reflection point E are calculated. Connecting the emission point B and the incident point D, the beam propagation path BD in the water is obtained. According to the law of refraction, the beam propagates from the incident point D to the rail jaw reflection point E in the rail. According to the law of reflection, the beam then propagates from the reflection point E to the defect detection position G at the upper left corner of the rail head. Finally, the beam returns to the emission point B via the original path from G. The delay rule for the fifth group of array elements is as follows: the angle between BD and the ultrasonic probe plane is the emission deflection angle. Based on this angle and the characteristic that the beam is finally focused at point G, the emission delay of each array element in the fifth group is calculated, which is the emission delay rule for the fifth group of array elements. Among them, array element 128 is emitted first and array element 79 is emitted last. Five array elements simultaneously emit focused beams in five directions according to the delay rules of their respective internal elements to detect damage in different areas of the sample rail; during detection, a water layer is ensured between the rail and the probe as a coupling layer; Step 5: Manipulate the robotic arm so that the end of the robotic arm drives the probe to move at a constant speed in a straight line along the length of the rail. While moving, the probe performs rail defect detection until the probe extends beyond the other end of the rail in the vertical direction.

2. The rail defect detection method based on phased array ultrasound according to claim 1, characterized in that: The waveform emitted by the ultrasonic probe is a longitudinal wave, but only a transverse wave exists after it enters the rail.

3. The rail defect detection method based on phased array ultrasound according to claim 1, characterized in that: The steel rail is placed in the center of a water tank that can fully contain it. The water tank has an opening at the top. Before testing, water must be added until the water level is more than 140mm below the upper surface of the steel rail.

Images