A method for detecting longitudinal damage on the inner surface of spherical shell components by scanning with variable oblique incidence based on vector inversion

Abstract

The present invention discloses a method for detecting longitudinal defects on the inner surface of a spherical shell component using variable oblique incidence scanning based on vector inversion. The method comprises the following steps: discretization of the inner surface generatrix; determination of incident point information on the outer surface; determination of scanning trajectory point information; determination of contralateral scanning trajectory point information; and bilateral variable oblique incidence C-scan detection. Using the bilateral variable trajectory obtained in steps 3 and 4, ultrasonic water immersion scanning is performed on the thickened spherical shell component to obtain an ultrasonic C-scan image of longitudinal defects on the inner surface of the thickened spherical shell component. This method can detect longitudinal defects on the inner and near inner surfaces of thickened spherical shell components, avoiding missed detections.

Description

Technical Field

[0001] The present invention relates to the field of measurement and control technology, and in particular to a method for detecting longitudinal damage on the inner surface of a spherical shell component by scanning with variable oblique incidence based on vector inversion. Background Art

[0002] Thickened spherical shell components are ubiquitous in industries such as aerospace, weapons and ammunition, energy, and transportation. Tiny cracks created during the molding process can develop under various external loads during service, ultimately leading to failure of the entire thickened shell component. Therefore, crack detection is an essential step in component nondestructive testing and plays a crucial role in ensuring product quality and equipment operational reliability.

[0003] Ultrasonic oblique incidence is widely used in nondestructive crack testing. Thickened spherical shells have a unique shape, characterized by variable wall thickness, non-concentricity, and a hyperbolic surface. Conventional oblique incidence testing for longitudinal flaws on their inner surfaces causes ultrasonic waves to reflect and refract multiple times on the curved component's multiple surfaces, creating a complex path and making it impossible to obtain defect reflection echoes, resulting in missed detections.

[0004] In conventional oblique-incidence testing, the incident wave enters the workpiece at a certain angle within the normal cross-section of the crack, generating an end-angle reflection at the longitudinal damage on the inner surface, forming a defect echo. However, for thickened spherical shell components, the normal cross-sections of the inner and outer surfaces are not in the same plane. The refracted wave is reflected away from the longitudinal damage on the inner surface in a direction away from the incident path of the original acoustic wave, and no end-angle reflection occurs. The transducer cannot collect the defect echo, making it impossible to detect longitudinal crack defects on the inner and near-inner surfaces. Summary of the Invention

[0005] In view of this, the present invention provides a method for detecting longitudinal defects on the inner surface of a spherical shell component by scanning with variable oblique incidence based on vector inversion, which can detect longitudinal defects on the inner surface and near the inner surface of a thickened spherical shell component and avoid missed detection.

[0006] The present invention adopts the following specific technical solutions:

[0007] A method for detecting longitudinal damage on the inner surface of a spherical shell component by scanning with variable oblique incidence based on vector inversion includes the following steps:

[0008] Step 1: Discrete the inner surface busbars;

[0009] Step 2: Determine the incident point information on the outer surface: For 45° oblique incidence detection, the normal vector of any discrete point on the inner surface busbar is rotated 45° within the normal cross-section of the longitudinal injury to obtain the refracted acoustic beam vector. The expression of the refracted acoustic beam vector and the outer surface contour is solved to obtain the coordinates of the intersection point and the normal vector, i.e., the incident point information of the outer surface acoustic beam.

[0010] Step 3: Solve the scanning trajectory point information: Calculate the angle between the refracted sound beam vector obtained in step 2 and the normal vector of the incident point of the external surface sound beam, i.e., the refraction angle; calculate the incident angle according to Snell's law; in the plane formed by the refracted sound beam vector and the normal vector of the incident point of the external surface sound beam, rotate the normal vector of the incident point of the external surface sound beam at the incident angle to obtain the incident sound beam vector; calculate the coordinates of the sound beam exit point based on the coordinates of the external surface incident point, the incident sound beam vector, and the detection water distance; the exit point coordinates and the incident sound beam vector constitute the scanning trajectory point information on one side;

[0011] Step 4: Determine the position information of the contralateral scanning trajectory: Repeat steps 2 and 3 in step 2, rotating the normal vector of any discrete point on the inner surface generatrix by -45° within the normal cross-section of the longitudinal injury, to obtain the position information of the contralateral scanning trajectory;

[0012] Step 5: Bilateral variable oblique-incidence C-scan inspection: Use the bilateral variable trajectory obtained in steps 3 and 4 to perform ultrasonic water immersion scanning on the thickened spherical shell component to obtain an ultrasonic C-scan inspection image of the longitudinal damage on the inner surface of the thickened spherical shell component.

[0013] Furthermore, the inner surface generatrix discretization in step 1 is specifically as follows: the inner surface generatrix is ​​obtained according to the three-dimensional model of the thickened spherical shell component, and is discretized at equal intervals to obtain information of each discrete point of the inner surface generatrix.

[0014] Furthermore, the discrete point information includes coordinates and normal vectors.

[0015] Furthermore, in step five, an ultrasonic scanning system is used to perform ultrasonic water immersion scanning on the thickened spherical shell component.

[0016] Beneficial effects:

[0017] Different from conventional oblique incident scanning, which discretizes the outer surface busbars and ensures that the outer surface incident angle is fixed, the detection method of the present invention is aimed at the inner surface longitudinal damage in three-dimensional thickened spherical shell components. Starting from the discrete points of the inner surface busbars, the refracted sound beam and the incident sound beam are obtained by vector inversion, thereby obtaining a variable scanning trajectory. The incident points of the variable oblique incident detection on the outer surface of the spherical shell component are not on the same busbar, and the incident angles of each incident point are different. By discretizing the inner surface busbars and ensuring that the incident angle of the refracted sound beam on the inner surface is fixed, it is ensured that the refracted sound beam forms an end-angle reflection on the normal cross-section of the inner surface longitudinal damage, so that the defect echo returns along the original sound beam path, ensuring that the transducer can receive the defect echo, and realizing the detection of longitudinal damage defects on the inner surface and near the inner surface of the thickened spherical shell component. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a flow chart of the method for detecting longitudinal damage on the inner surface of a spherical shell component according to the present invention by scanning with variable oblique incidence;

[0019] Figure 2 It is a cross-sectional view of a spherical shell component with variable wall thickness;

[0020] Figure 3 Schematic diagram for solving incident point information on the outer surface of a spherical shell component with variable wall thickness;

[0021] Figure 4 Schematic diagram of solving scanning trajectory point information of variable wall thickness spherical shell components;

[0022] Figure 5 Schematic diagram of the double-sided variable scanning trajectory of a spherical shell component with variable wall thickness;

[0023] Figure 6 Ultrasonic C-scan image of a spherical shell component with variable wall thickness. DETAILED DESCRIPTION

[0024] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0025] The present invention provides a method for detecting longitudinal damage on the inner surface of a spherical shell component by scanning with variable oblique incidence based on vector inversion. Figure 1 As shown, the detection method includes the following steps:

[0026] Step 1 S10, discretizing the inner surface generatrix, specifically: obtaining the inner surface generatrix according to the three-dimensional model of the thickened spherical shell component, and discretizing it at equal intervals to obtain information on each discrete point of the inner surface generatrix; the discrete point information includes the coordinates and normal vectors of each discrete point;

[0027] Step 2 S20, solving the incident point information on the outer surface: For 45° transverse wound oblique incidence detection, the normal vector of any discrete point on the inner surface generatrix is ​​rotated 45° within the normal cross section of the longitudinal wound to obtain the refracted acoustic beam vector. The expression of the refracted acoustic beam vector and the outer surface contour is solved to obtain the coordinates of the intersection point and the normal vector, i.e., the incident point information of the outer surface acoustic beam;

[0028] Step 3 S30, solving the scanning trajectory point information: the angle between the refracted sound beam vector obtained in step 2 and the normal vector of the incident point of the external surface sound beam is calculated, i.e., the refraction angle; the incident angle is calculated according to Snell's law; within the plane formed by the refracted sound beam vector and the normal vector of the incident point of the external surface sound beam, the normal vector of the incident point of the external surface sound beam is rotated at the incident angle to obtain the incident sound beam vector; the coordinates of the sound beam exit point are calculated based on the coordinates of the external surface incident point, the incident sound beam vector, and the detection water distance; the exit point coordinates and the incident sound beam vector constitute the scanning trajectory point information on one side;

[0029] Step 4 (S40) is used to determine the position information of the contralateral scanning trajectory. In step 2, the normal vector of any discrete point on the inner surface generatrix is ​​rotated by -45° within the normal cross-section of the longitudinal injury, and steps 2 and 3 are repeated to determine the position information of the contralateral scanning trajectory. That is, in step 2 (S20), the rotation of 45° within the normal cross-section of the longitudinal injury is changed to a rotation of 45° in the opposite direction, and steps 2 and 3 are repeated to determine the position information of the scanning trajectory on the other side.

[0030] Step 5 S50, bilateral variable oblique incidence C-scan inspection: using the bilateral variable trajectory obtained in steps 3 and 4, an ultrasonic scanning system is used to perform ultrasonic water immersion scanning on the thickened spherical shell component to obtain an ultrasonic C-scan inspection image of the longitudinal damage on the inner surface of the thickened spherical shell component.

[0031] Different from conventional oblique incident scanning, which discretizes the outer surface busbars and ensures that the outer surface incident angle is fixed, the detection method of the present invention is aimed at the inner surface longitudinal damage in three-dimensional thickened spherical shell components. Starting from the discrete points of the inner surface busbars, the refracted sound beam and the incident sound beam are obtained by vector inversion, thereby obtaining a variable scanning trajectory. The incident points of the variable oblique incident detection on the outer surface of the spherical shell component are not on the same busbar, and the incident angles of each incident point are different. By discretizing the inner surface busbars and ensuring that the incident angle of the refracted sound beam on the inner surface is fixed, it is ensured that the refracted sound beam forms an end-angle reflection on the normal cross-section of the inner surface longitudinal damage, so that the defect echo returns along the original sound beam path, ensuring that the transducer can receive the defect echo, and realizing the detection of longitudinal damage defects on the inner surface and near the inner surface of the thickened spherical shell component.

[0032] Below Figure 2 The variable wall thickness hemispherical shell specimen shown is a model, which illustrates the specific process of the variable wall thickness spherical shell component inner surface longitudinal damage detection method with variable oblique incidence scanning:

[0033] Step 1: Discrete inner surface busbars

[0034] The Cartesian coordinate system is established with the center point O of the bottom surface of the sample, and the length of each straight line segment or arc segment on the inner surface generatrix AB of the radial section of the sample is recorded as l i , take the spacing d as 1mm to discretize the contour line AB at equal intervals, and use the ratio parameter n for each straight line segment and arc length segment during discretization i =d / l i To control, take any point L(X L ,Y L ,Z L ), calculate the normal vector LC of the point on the radial section, that is, n1(a1, b1, c1), point C is the intersection of LC and the outer surface contour; and calculate the radial section normal vector n2(a2, b2, c2).

[0035] Step 2: Solving the incident point information on the outer surface

[0036] like Figure 3 As shown, the normal vector n1 of any point on AB on the radial section and the normal vector n2 of the radial section are cross-producted to obtain the normal vector n3(a3, b3, c3) of the refraction plane α. The point normal expression α(x, y, z) of the refraction plane α is obtained by the following formula (1):

[0037]

[0038] Adopting 45° transverse oblique incidence detection, the vector n1 is rotated 45° around point L in the plane to obtain the refracted acoustic beam vector LD, namely n4(a4, b4, c4), as shown in the following equations (2) and (3):

[0039] n4=n1R (2);

[0040]

[0041] Combine the refracted sound beam vector LD and the analytical expression of the outer surface A(x,y,z) to obtain the intersection point D(X D ,Y D ,Z D ), as shown in the following formula (4); calculate the normal vector n5(a5, b5, c5) of the incident point D of the sound beam on the outer surface, that is, the coordinates of point D and the normal vector of the outer surface at this point constitute the incident point position information of the outer surface;

[0042]

[0043] Step 3: Scan the trajectory point information to solve

[0044] like Figure 4 As shown, the angle between the refracted sound beam n4 and the normal vector n5 is obtained by the following formula (5), which is recorded as the refraction angle θ R ; Then calculate the angle of incidence θ according to Snell's law I , as shown in the following formula (6), where c1 represents the sound speed in water and c2 represents the sound speed of the test piece material;

[0045]

[0046]

[0047] The cross product of vectors n4 and n5 gives the normal vector n6(a6, b6, c6) of the incident plane β. The point normal expression β(x, y, z) of the incident plane β is obtained from the following equation (7):

[0048]

[0049] In the incident plane β, the outer surface normal n5 is rotated by θ according to the following equations (8), (9) and (10): I Get the incident acoustic beam vector n7(a7,b7,c7):

[0050] n7=n5R (8);

[0051]

[0052]

[0053] Set the detection water distance t to 50, according to the outer surface incident point coordinate D (X D ,Y D ,Z D ), the incident sound beam vector n7 (a7, b7, c7) and the detection water distance t, and the coordinates of the sound beam exit point F (X F ,Y F ,Z F ), the coordinates of the emission point and the incident acoustic beam vector constitute the position information of the scanning trajectory on one side;

[0054] Step 4: Solve the information of the contralateral scanning trajectory points

[0055] like Figure 5 As shown, in step 2, the normal vector n1 of any discrete point on the inner surface generatrix is ​​rotated -45° in the refraction plane α, and steps 2 and 3 are repeated to obtain the position information of the contralateral scanning trajectory.

[0056] Step 5: Bilateral C-scan detection with variable oblique incidence

[0057] Import the scanning trajectory point information obtained in steps 3 and 4 into the trajectory generation file to obtain an executable bilateral variable ultrasonic C-scan detection trajectory point package. Through simulation verification, the dangerous factors such as singular points and interference are eliminated. The actual variable right-leaning trajectory is as follows: Figure 5 Finally, the ultrasonic scanning system was used to perform ultrasonic water immersion scanning on the variable wall thickness hemispherical shell sample, and the obtained ultrasonic C-scan image was as shown in the figure. Figure 6 shown. Figure 6 The red circles in the middle are the three pre-embedded artificial longitudinal defects obtained by scanning. The horizontal axis is the distance the probe moves relative to the sample in the circumferential direction (scanning direction), and the vertical axis is the distance the probe moves along the generatrix direction of the sample (index direction).

[0058] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for detecting longitudinal damage on the inner surface of a spherical shell component based on vector inversion and with variable oblique incidence scanning, characterized by: The following steps are involved: Step 1: Discrete the inner surface busbars; Step 2: Determine the incident point information on the outer surface: For 45° oblique incidence detection, the normal vector of any discrete point on the inner surface busbar is rotated 45° within the normal cross-section of the longitudinal injury to obtain the refracted acoustic beam vector. The expression of the refracted acoustic beam vector and the outer surface contour is solved to obtain the coordinates of the intersection point and the normal vector, i.e., the incident point information of the outer surface acoustic beam. Step 3: Solve the scanning trajectory point information: Calculate the angle between the refracted sound beam vector obtained in step 2 and the normal vector of the incident point of the external surface sound beam, i.e., the refraction angle; calculate the incident angle according to Snell's law; in the plane formed by the refracted sound beam vector and the normal vector of the incident point of the external surface sound beam, rotate the normal vector of the incident point of the external surface sound beam at the incident angle to obtain the incident sound beam vector; calculate the coordinates of the sound beam exit point based on the coordinates of the external surface incident point, the incident sound beam vector, and the detection water distance; the exit point coordinates and the incident sound beam vector constitute the scanning trajectory point information on one side; Step 4: Determine the position information of the contralateral scanning trajectory: Repeat steps 2 and 3 in step 2, rotating the normal vector of any discrete point on the inner surface generatrix by -45° within the normal cross-section of the longitudinal injury, to obtain the position information of the contralateral scanning trajectory; Step 5: Bilateral variable oblique-incidence C-scan inspection: Use the bilateral variable trajectory obtained in steps 3 and 4 to perform ultrasonic water immersion scanning on the thickened spherical shell component to obtain an ultrasonic C-scan inspection image of the longitudinal damage on the inner surface of the thickened spherical shell component.

2. The method for detecting longitudinal damage on the inner surface of a spherical shell component according to claim 1, characterized in that: The inner surface generatrix discretization in step 1 is specifically as follows: the inner surface generatrix is ​​obtained according to the three-dimensional model of the thickened spherical shell component, and is discretized at equal intervals to obtain the information of each discrete point of the inner surface generatrix.

3. The method for detecting longitudinal damage on the inner surface of a spherical shell component according to claim 2, wherein: Discrete point information includes coordinates and normal vectors.

4. The method for detecting longitudinal damage on the inner surface of a spherical shell component according to any one of claims 1 to 3, wherein: In step five, an ultrasonic scanning system is used to perform ultrasonic water immersion scanning on the thickened spherical shell component.

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