A method for measuring sound velocity based on ultrasonic water immersion penetration method

Abstract

The present invention relates to a sound velocity measurement method based on ultrasonic water immersion penetration method. A sound velocity measurement method based on ultrasonic water immersion penetration method adopts ultrasonic water immersion penetration method; first, the transmission time of the first transmission wave of the water layer between the transmitting probe and the receiving probe is measured; then, the comparison specimen and the test specimen to be tested are placed in the water layer in turn, and the transmission time of the first transmission wave of the comparison specimen and the test specimen to be tested is measured; finally, the interference of the system error is eliminated through the intermediate detection of the comparison specimen, and then the sound velocity correction result of the test specimen to be tested is obtained, and the result is more reliable.

Description

Technical Field

[0001] The invention relates to a sound velocity measurement method based on an ultrasonic water immersion penetration method. Background Art

[0002] The ultrasonic speed depends on the type of sound wave, material properties, temperature, etc. When the test surface of the test piece is infinitely large relative to the sound wave diffusion area, and the sound wave type and temperature remain unchanged as fixed conditions, the speed of ultrasonic waves depends only on the material properties, and the ultrasonic speed is an important acoustic parameter reflecting the relevant properties of the material.

[0003] The ultrasonic transmitting probe transmits pulse waves or continuous waves into the test piece to be tested. The method of detecting the performance or defects of the test piece based on the transmitted waves received by the receiving probe is called the penetration method. This method uses a transmitting and receiving probe, which are placed on both sides of the test piece. When the ultrasonic wave penetrates into the test piece, if the test piece is uniform, intact and has no defects, the amplitude of the transmitted wave received by the receiving probe is high and stable; if there are defects of a certain size in the test piece or there are drastic changes in the material, the amplitude of the transmitted wave received by the receiving probe will be significantly reduced or even disappear due to the defects blocking part of the transmitted wave sound energy or the sound energy attenuation caused by the material change. The detection principle of the penetration method is as follows: Figure 1 , T represents the original wave, and P represents the transmitted wave.

[0004] Existing sound speed calculation models:

[0005] The water immersion penetration method is used to measure the sound velocity of the test piece. The propagation speed of the ultrasonic wave in the test piece is calculated based on the time it takes for the transmitted wave to propagate from the transmitting probe to the receiving probe, and then based on the sound path:

[0006]

[0007] Where: t represents the transmission time of the transmitted wave; Δt represents the system error, including the time error caused by the system measurement circuit and coupling layer; S represents the propagation path of the ultrasonic wave.

[0008] Problems:

[0009] Based on the above formula, there is a systematic error in the sound velocity measurement of the same test piece, which causes the time corresponding to the maximum peak of the single transmission waveform signal detected by the detection system to be too long and the sound velocity to be too small. Therefore, eliminating the interference of systematic errors is a key issue that must be considered.

[0010] Therefore, based on the penetration detection principle, this paper adopts an immersion ultrasonic acoustic parameter measurement method to measure the sound velocity of the test piece. Summary of the invention

[0011] The invention provides a sound velocity measurement method based on ultrasonic water immersion penetration method.

[0012] The technical solution of the invention is:

[0013] A sound velocity measurement method based on ultrasonic water immersion penetration method adopts ultrasonic water immersion penetration method; first, the transmission time of the first transmission wave of the water layer between the transmitting probe and the receiving probe is measured; then, the comparison file and the test piece to be tested are placed in the water layer in turn, and the transmission time of the first transmission wave of the comparison file and the test piece to be tested is measured; finally, the interference of the system error is eliminated through the intermediate detection of the comparison test piece, and then the sound velocity correction result of the test piece to be tested is obtained.

[0014] A sound velocity measurement method based on ultrasonic water immersion penetration method, using ultrasonic water immersion penetration method, the specific operation process of the sound velocity measurement method is:

[0015] Step 1: Use the ultrasonic water immersion method to place the transmitting probe T and the receiving probe R in the water layer, adjust the distance between the transmitting probe T and the receiving probe R, so that the transmitting probe T is between the far field area and the sound beam non-diffusion area, and detect the transmission time of the first transmission wave in the water layer between the transmitting probe T and the receiving probe R. Then:

[0016]

[0017] Where: t0 represents the transmission time of the primary transmission wave in the water layer between the transmitting probe T and the receiving probe R, unit is us;

[0018] d0 represents the thickness of the water layer between the transmitting probe T and the receiving probe R, in mm;

[0019] c0 represents the speed of sound in water, in km / s;

[0020] Δt represents the system error, unit is us;

[0021] Step 2: Place the test piece i in turn; calculate the transmission time of the first transmission wave of the test piece i;

[0022] i=1 means the test piece is a comparison piece; i=2 means the test piece is a test piece to be tested;

[0023] Without changing the distance between the transmitting probe T and the receiving probe R, the transmission time of the first transmission wave of the test piece i is

[0024]

[0025] Where: t i It represents the transmission time of the first transmission wave of the test piece i, in us;

[0026] d i Indicates the thickness of the test piece i, in mm;

[0027] c i Indicates the longitudinal wave speed of the test piece i, in km / s;

[0028] Step 3: Calculate the sound velocity correction result of the test piece

[0029] Considering that the water immersion coupling condition is relatively stable, the system parameters remain unchanged during multiple tests, and the water layer height between the transmitting probe T and the receiving probe R is not easy to obtain accurately, Δt and d0 are eliminated, and the sound velocity correction result of the test piece to be tested is:

[0030]

[0031] Where: c2 represents the sound velocity correction result of the test piece to be tested, unit: km / s;

[0032] c1 represents the longitudinal wave speed of the comparison specimen, in km / s;

[0033] d2 represents the thickness of the test piece to be tested, in mm;

[0034] d1 represents the thickness of the comparison specimen, in mm;

[0035] t1 represents the transmission time of the first transmission wave of the comparison specimen, unit is us;

[0036] t2 represents the transmission time of the first transmission wave of the test piece to be tested, in us.

[0037] It can be seen from the above formula that the thickness of the test piece can be accurately measured by a vernier caliper; the sound velocity of water is obtained by calculation, and the detection system measures the time, and the system error is eliminated by changing the distance between the transmitting probe T and the receiving probe R; the comparison specimen is a standard comparison specimen with small attenuation of ultrasonic energy and known sound velocity. Therefore, this method can be used to measure the ultrasonic sound velocity of the test piece to be tested, which can eliminate the interference of the original system error of the penetration method.

[0038] The technical effects of the present invention are:

[0039] The present invention adopts an ultrasonic water immersion penetration method; first, the transmission time of a primary transmission wave of a water layer between a transmitting probe and a receiving probe is measured; then, a comparison specimen and a test specimen to be tested are placed in the water layer in turn, and the transmission time of the primary transmission wave of the comparison specimen and the test specimen to be tested is measured; finally, the interference of the system error is eliminated through the intermediate detection of the comparison specimen, and then the sound velocity correction result of the test specimen to be tested is obtained, and the result is more reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the penetration detection principle.

[0041] Figure 2Schematic diagram of ultrasonic water immersion penetration detection.

[0042] Figure 3 This is a diagram showing the calculation results of the existing sound speed calculation model.

[0043] Figure 4 Graph showing the calculation results of the sound speed calculation model proposed in the present invention. DETAILED DESCRIPTION

[0044] The test piece is a plexiglass test piece with a size of 100mm×81.60mm×80mm.

[0045] 1. According to the measurement results of the existing penetration method sound speed calculation model, such as Figure 3 As shown, the sound velocity of the test piece is 2.609 km / s.

[0046] 2. The sound velocity of the test piece was 2.671km / s when the test piece was tested by reflection method.

[0047] 3. The measurement results of the sound velocity model proposed in the present invention are as follows: Figure 4 As shown in the figure, the sound velocity of the test piece is 2.694 km / s.

[0048] The comparison is as follows:

[0049] Speed ​​of sound km / s Relative error Penetration calculation model 2.609 2.3％ The calculation model after the water penetration method is revised 2.694 0.86％ Computational Model of Reflection Method 2.671

[0050] The present invention eliminates the interference of system errors by comparing the intermediate detection of the test piece, and the relative error of the sound velocity correction result is smaller than that of the measurement result of the reflection method, and the result is more reliable.

Claims

1. A method for measuring the speed of sound based on ultrasonic water immersion penetration method, characterized in that: The ultrasonic water immersion penetration method is used; first, the transmission time of the first transmission wave of the water layer between the transmitting probe and the receiving probe is measured; then, the comparison specimen and the test specimen are placed in the water layer in turn, and the transmission time of the first transmission wave of the comparison specimen and the test specimen is measured; finally, the interference of the system error is eliminated through the intermediate detection of the comparison specimen, and then the sound velocity correction result of the test specimen is obtained; The specific operation process of the sound velocity measurement method using the ultrasonic water immersion penetration method is as follows: Step 1: Use the ultrasonic water immersion method to place the transmitting probe T and the receiving probe R in the water layer, adjust the distance between the transmitting probe T and the receiving probe R, so that the transmitting probe T is between the far field area and the sound beam non-diffusion area, and detect the transmission time of the first transmission wave in the water layer between the transmitting probe T and the receiving probe R. Then: Where: t0 represents the transmission time of the primary transmission wave in the water layer between the transmitting probe T and the receiving probe R, unit is us; d0 represents the thickness of the water layer between the transmitting probe T and the receiving probe R, in mm; c0 represents the speed of sound in water, in km / s; Δt represents the system error, unit is us; Step 2: Place the test piece i in turn; calculate the transmission time of the first transmission wave of the test piece i; i=1 means the test piece is a comparison piece; i=2 means the test piece is a test piece to be tested; Without changing the distance between the transmitting probe T and the receiving probe R, the transmission time of the first transmission wave of the test piece i is Where: t i It represents the transmission time of the first transmission wave of the test piece i, in us; d i Indicates the thickness of the test piece i, in mm; c i Indicates the longitudinal wave speed of the test piece i, in km / s; Step 3: Calculate the sound velocity correction result of the test piece Considering that the system parameters remain unchanged during multiple tests under water immersion coupling conditions, and that the height of the water layer between the transmitting probe T and the receiving probe R is inconvenient to obtain, by eliminating Δt and d0, the sound velocity correction result of the test piece to be tested is: Where: c2 represents the sound velocity correction result of the test piece to be tested, unit: km / s; c1 represents the longitudinal wave speed of the comparison specimen, in km / s; d2 represents the thickness of the test piece to be tested, in mm; d1 represents the thickness of the comparison specimen, in mm; t1 represents the transmission time of the first transmission wave of the comparison specimen, unit is us; t2 represents the transmission time of the first transmission wave of the test piece to be tested, in us.

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