CN102636576A - Measuring method for delay and leading edge of sound-transmission-wedge surface wave probe - Google Patents

Abstract

The invention discloses a measuring method for delay and leading edge of a sound-transmission-wedge surface wave probe. The measuring method is completed by the assistance of a test block, wherein the material of the test block is same as that of a sound-transmission inclined wedge, and the shape of the test block is that a circular-arc-shaped bottom surface is arranged at one end of the a cuboid. The measuring method comprises the steps of 1) connecting a surface wave probe with an ultrasonic flaw detector, then arranging the surface wave probe on the upper surface of the test block, moving the surface wave probe forwardly and backwardly, and keeping the surface wave probe to be fixed when the longitudinal waves on the ultrasonic flaw detector obtains the highest reflection waves; 2) reading the time difference t1 between the transmission waves and the received reflection on the ultrasonic flaw detector; 3) calculating the transmission time of the ultrasonic waves in the test block; 4) calculating the delay t' of the test block; 5) measuring the horizontal distance M from the front end face of the surface wave probe to the circular arc of the test block by a steel ruler; and 6) calculating the leading edge l0 of the test block. According to the measuring method, the operation is simple and convenient, the error is small, and the delay and the leading edge of the sound-transmission-wedge surface wave probe can be measured accurately.

Description

A method for measuring time delay and leading edge of sound-permeable wedge surface wave probe

technical field

The invention relates to a method for measuring the time delay and leading edge of a sound-permeable wedge surface wave probe.

Background technique

The surface wave flaw detection technology has a high sensitivity to detect surface cracks, and is widely used in the non-destructive testing of steel parts such as steam turbine blades, high-speed steel rolls, and crankshafts. At present, the sound-transmitting wedge method is commonly used to generate surface waves in steel. The probe uses a wedge similar to that of the oblique probe. When the shear wave refraction angle in the workpiece is 90°, surface waves are generated. Since the surface wave propagates along the surface of the material, in the actual inspection work, the calibration of the surface wave probe is carried out by adjusting the scanning speed. Generally, move the probe back and forth to change the L value. For example, L1=20mm, L2=40mm, etc., use the depth knob and horizontal knob, when L1=20mm, adjust the 20 position of the horizontal scale; L2=40mm, adjust the 40 position of the horizontal scale, that is, complete the 1:1 adjustment, and the incident point of the probe is directly Calculated on the leading edge of the probe (i.e. the probe tip). There is obviously a certain error in the result of calibrating the leading edge and delay of the probe by this method, which is inconsistent with the actual leading edge and delay of the probe.

Contents of the invention

The technical problem to be solved by the present invention is to provide an accurate and convenient method for measuring the time delay and leading edge of a sound-permeable wedge surface wave probe.

In order to solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for measuring the time delay and leading edge of a sound-transmitting wedge surface wave probe. To complete, the shape of the test block is that one end of a cuboid is provided with an arc-shaped bottom surface, and the steps of the method are as follows:

1) Connect the surface wave probe to the ultrasonic flaw detector, then place the surface wave probe on the upper surface of the test block, move the surface wave probe back and forth, when the longitudinal wave (the first echo after the initial wave) on the ultrasonic flaw detector is obtained When the reflected wave is the highest, keep the surface wave probe still;

2) Read the time difference t ₁ between the transmitted wave and the received reflection on the ultrasonic flaw detector;

3) Calculate the propagation time t ₀ of the ultrasonic wave in the test block according to the following formula ①:

t ₀ =S/2C _L =R/C _L ①

Among them, S is the distance that the ultrasonic wave propagates in the test block, R is the radius below the test block (2), where S is twice of R, and C _L is the sound velocity of the longitudinal wave;

4) Use the following formula ② to calculate the delay t' of the test block

t'= t ₁ - t ₀ ②   ;      

  5) Use a steel ruler to measure the horizontal distance M from the front end of the surface wave probe to the arc of the test block;

6) Calculate the leading edge l ₀ of the test block by the following formula ③

l ₀ = RM. ③.

The working principle of the present invention is: the surface wave emitted by the sound-permeable wedge probe is generated when the refraction angle of the transverse wave in the material is 90°. When the incident angle is constant, the refraction angle of the ultrasonic wave in the material is determined by the sound velocity of the ultrasonic wave in the material. Use the same material as the sound-transmitting wedge of the surface wave probe to make an arc-shaped bottom test block with a certain radius R. When the ultrasonic wave is incident on the test block, the incident angle of the longitudinal wave in the test block is the same as the sound-transmitting wedge angle, which must be less than 90°, no surface waves will be generated in the test block. When the ultrasonic wave encounters the cylindrical bottom surface, it will be emitted and received by the probe. The distance S that the ultrasonic wave propagates in the test block is twice the radius R of the test block. Since the sound velocity _CL of the longitudinal wave in the test block is known, the time _t0 for the ultrasonic wave to propagate in the test block can be calculated. The relationship between the three satisfies: t ₀ =S/2Cs=R/C _L

The time difference t ₁ between the transmitted signal and the received signal can be directly measured by the ultrasonic flaw detector, and the delay t' of the test block can be calculated, which satisfies the following formula: t'= t ₁ - t ₀

Since the test block has a cylindrical bottom surface, the front edge of the test block l ₀ , that is, the distance between the incident point of the sound wave and the front end of the probe, is the difference between the radius R of the test block and the horizontal distance M from the front end of the probe to the arc of the test block, l ₀ =RM.

The beneficial effect produced by adopting the above-mentioned technical scheme is that the measurement method is easy to operate, has small error, and can accurately measure the time delay and leading edge of the sound-permeable wedge surface wave probe.

Description of drawings

Fig. 1 is the schematic diagram of measuring method of the present invention;

Among them, 1. surface wave probe; 2. test block.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Referring to accompanying drawing 1, this measurement method is accomplished by means of a test block 2 identical in material to the sound-transmitting wedge, and the bottom end of the test block 2 is arc-shaped, and the steps of the method are as follows:

1) Connect the surface wave probe 1 to the ultrasonic flaw detector, then apply coupling agent, then place the surface wave probe 1 on the upper surface of the test block 2, move the surface wave probe 1 back and forth, when the longitudinal wave on the ultrasonic flaw detector obtains the highest reflected wave , keeping the surface wave probe 1 still;

2) Read the time difference t ₁ between the transmitted wave and the received reflection on the ultrasonic flaw detector, in seconds;

3) Calculate the time t ₀ for the ultrasonic wave to propagate in the test block 2 according to the following formula ①:

t ₀ =S/2C _L =R/C _L ①

Among them, S is the distance that the ultrasonic wave propagates in the test block 2, the unit is mm; R is the radius below the test block 2, the unit is mm, where S is twice of R, and C _L is the sound velocity of the longitudinal wave, the unit is mm/s ;

4) Use the following formula ② to calculate the delay t' of test block 2

t'= t ₁ - t ₀ ②   ;

5) Use a steel ruler to measure the horizontal distance M from the front end of the surface wave probe 1 to the arc of the test block 2, in mm;

6) Calculate the leading edge l ₀ of the test block by the following formula ③

l ₀ =RM                                 ③   .

This measurement method is very convenient. It uses an arc-shaped bottom test block with a known radius R of the same material as the sound-transmitting wedge to obtain the propagation time of the shear wave in the test block, and then use the ultrasonic flaw detector to directly measure the emission signal. The time difference t ₁ between the received signal and the probe delay is obtained by calculation. By directly measuring the horizontal distance M from the front end of the probe to the arc of the test block on the test block, the difference between M and R is the front edge of the probe.

Claims (1)

1. the measuring method in sound penetrating wedge surface wave probe time-delay and forward position; It is characterized in that: it is accomplished by means of a material test block (2) identical with the entrant sound wedge; The shape of said test block (2) is that the end at a rectangular parallelepiped is provided with the circular arc type bottom surface, and the step of said method is following:

1) surface wave probe (1) is connected with ultra-sonic defect detector; And then surface wave probe (1) is placed on test block (2) upper surface; Move forward and backward surface wave probe (1),, keep surface wave probe (1) motionless when obtaining compressional wave on the ultra-sonic defect detector during high reflection wave;

2) the mistiming t between the reflection of reading transmitted wave on the ultra-sonic defect detector and receiving ₁, unit is second;

3) 1. calculate the time t that ultrasound wave is propagated according to following formula in test block (2) ₀, unit is second:

t ₀=S/2C _L?=R/C _L ①

Wherein, S is the distance that ultrasound wave is propagated in test block (2), the Wei ㎜ of unit; R is the radius below the test block (2), unit Wei ㎜, and wherein S is 2 times of R, C _LBe longitudinal wave velocity, unit is mm/s;

4) utilize following formula 2. to calculate the delay t ' of test block (2)

t’=?t ₁-?t ₀ ② ；

5) measure surface wave probe (1) front end face to test block (2) circular arc horizontal range M with Steel Ruler, the Wei ㎜ of unit;

6) 3. calculate the forward position l of test block through following formula ₀, the Wei ㎜ of unit

l ₀=R-M ③。

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