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Ultrasonic testing of metallic materials has been widely used.
UPDATETIME:2016-05-28 16:33:34 CLICK:

1 from a variety of materials of composite structure subjected to thermal ablation and erosion of high temperature, high speed and high pressure, working environment is harsh, so each component has high reliability, the bonding interface of the metal shell and the metal nozzle, due to the bonding of workpiece cleaning is not clean, lining and shell with lax internal gas without adhesive drain and other reasons, prone to debonding, especially the gap type large area debonding, great harm to the reliability of products, so the adhesive quality of the adhesive interface of the nondestructive detection is also the key process of solid rocket motor production middle quality control, countries have invested a lot of manpower and resources to carry out the research of solid rocket engine zero component nondestructive testing technology, the ultrasonic testing of metal materials have been widely used, and the composite material has high anisotropy, acoustic attenuation , complex structure and other characteristics, the ultrasonic testing of composite materials and components is a weak link, according to the Japan Aerospace Technology Research "solid rocket engine ultrasonic flaw" report, they have been used for the ultrasonic multiple reflection method successfully for non metal coating layer and steel shell bonding surface were detected, after years of research, the ultrasonic longitudinal wave multiple reflection method of metal shell of the nozzle and non metal bonding interface bonding quality detection, has successfully used for batch testing of the product.

2 detection principle of ultrasonic frequencies above 20kHz elastic vibration wave, consistent with the direction of movement of the so-called longitudinal waves, the propagation direction and the particle, the bonding interface debonding injury is refers to the interface of different materials without glue and the formation of an air gap type defects, when the ultrasonic longitudinal wave vertically through the bonding of metal and nonmetal surface when, due to the different acoustic impedance of the two kinds of media products, acoustic in the interface will cause reflection and transmission, acoustic propagation path as shown in Figure 1 and figure L is the incident wave; L is the reflection wave, and t is the transmission wave. Sound waves through the products and interfaces, respectively, through the three kinds of media, namely, metal, air and non metal. In the three kinds of medium, longitudinal wave velocity respectively 59, 344 and 2200m/s; acoustic impedance points bonding interface existence debonding, quite in the ultrasonic longitudinal wave vertical incidence to metal and air interface. At this time interface acoustic reflectivity of P as the sound pressure of the incident wave, P is de bonded interface reflection wave sound for the acoustic impedance of the metal medium; Z is the acoustic impedance of the air medium.

Substituting acoustic impedance data calculation shows that, r = 1, namely, the existence of debonding of solid rocket technology, acoustic reflectivity tends to 1, transmissivity tends to 0, acoustic in almost 100% reflection. But when the bonding is good, the sound pressure of the interface is not 0, the calculation formula is as follows: R for the good bonding interface of sound pressure reflectivity; P for good bonding interface reflection wave sound pressure; Z for the acoustic impedance of the non metallic media.

The reflection wave sound pressure is calculated to be 86% of the sound pressure of the incident wave, and the sound pressure of the transmission wave is 14%.

For the amplification of ultrasonic flaw detector with good linearity, the instrument on the screen and sound pressure wave is proportional to that of any two adjacent wave height ratio is equal to the corresponding pressure ratio of two DB difference through a pulse reflection, and wave height stick area and good adhesive area is 1dB, the time when the ultrasonic wave reflection method. The vertical incident to the product, the first time the reflected sound pressure is second times the reflected sound pressure is n times the reflected pressure in P to reach the surface of the metal layer of the P sound pressure; n reflection after receiving probe pressure; R A interface (surface bonding interface for sound reflection the acoustic reflectivity attenuation coefficient); T metal parts; t metal thickness.

Easily more than 13dB after 10, namely DB off only for a given metal material and its thickness is certain, so t, t is the same, in the choice of the fixed coupling agent, R is constant, repeatedly reflected sound pressure P and R, only with the metal layer and the metal layer of the adhesive, is n n n = 10, Delta =13dB ultrasonic longitudinal wave reflection after debonding area and good bonding area of the reflection amplitude difference, reflecting on the instrument screen, debonding area than a good bonding area and higher wave amplitude, wave increased, accordingly the debonding area and good bonding area for distinguishing and evaluation of bonding quality.

Contrast test block 3.1 design and manufacture of ultrasonic flaw detection is by observing the fluorescent screen of a flaw detector echo location and amplitude characteristics evaluation was to explore the pros and cons of a quality, considering to the actual formation.

In order to avoid specimen and was to explore differences in the acoustic properties of the product, the developed No.1 test block (Figure 2) and are products of the material type, thickness, curvature, surface finish is identical and and are products of the same adhesive in the adhesive surface of the metal made with different shape and size of the debonding of the injury. Figure 2 A for round off stick (14mm for oval). Contrast test block II is a test block (Figure 3), which is cut from the test product.

Hui Rong Zhao: bonding interface of solid rocket motor nozzle ultrasonic detection of 3.2 try block detection 3.2.1 scanning speed adjust the flaw detection instrument types CTS-22, type of probe for the detection of should adjust the scanning speed according to the detection range, the instrument shows the horizontal scale of the wave on the screen time base sweep value with the actual sound path in a certain proportion of the. Is metal nozzle a 4mm thick, the Shantou ultrasonic instrument to study the production of standard depth of the test block to adjust the scanning speed, adjust the instrument panel on the level knob and the depth of the fine adjustment knob, expand the scanning range, time base sweep at the ratio of 1: 2.5, received multiple reflection echo.

The test results of 3.2.2 test block and the analysis of the test results are shown in Figure 4. The waveform analysis of the test results is shown in Table 1

(a) block good adhesive zone (b) A debonding area (circular) (c) B debonding area (oval) (d) C debonding area (irregular) seen from Figure 4 and table 1: a) reflected wavefront several times because there is not much difference between the height, and the ultrasonic beam not from the source began to spread, but there is not a diffusion region in the near source, not in the diffusion region, average pressure is basically unchanged, as shown in Figure 5 of the radiation field wafer is shown; b) with good bonding area, in addition there are external reflection wave, transmission wave into non metallic, non-metallic insulation nozzle compared with metal steel, loose structure, and coarse grained microstructure, its attenuation of acoustic energy is much more serious than steel, through the calculation of the 5MHz frequency, attenuation coefficient is less than 0.002dB, steel, non metal insulation layer reaches 6dB/mm, which makes good adhesive, enter the non Metal parts of the transmitted wave is repeated absorption, attenuation of energy. In the instrument shows wave screen horizontal scale within 6 squares and reflection wave envelope is a smooth arc rapid decline; c) debonding area, the incident wave is 100% reflection, reflection wave increased, in the instrument shows wave screen level moment 8 degrees format to full screen wave, than the good bonding area and in the oscilloscope screen with a horizontal scale and the amplitude increased, and with the removal of the increase of the area of glue, wave number, higher volatility, reflected wave envelope was slow down the jagged.

Area of solid rocket technology flaw detector show good adhesion area within multiple reflection wave in the oscilloscope screen level dial "6" A delamination multiple reflection wave in the oscilloscope screen level scale "6" grid at the amplitude reached more than 30%, in the "8" grid at the amplitude of delamination multiple reflection wave in the oscilloscope the horizontal scale screen "8" grid at the amplitude of up to 30%, in the "10" grid at the amplitude reached C delamination wave in the oscilloscope screen level scale "10" grid at the range was 10% to 30%3.3 test method to determine the detection sensitivity is composite component comparison test to determine the detection sensitivity by block. According to the sample test results, I try to block A debonding round) as a benchmark, the probe alignment A debonding, adjusting instrument attenuation and gain control, from the A debonding wave in the instrument oscilloscope screen level scale "8" grid at the amplitude of up to 10%, with the instrument Version of the attenuator on the surface of the attenuator as the detection sensitivity of the value of the sensitivity, the sensitivity of the adjustment is good, the fixed value of the fixed value of the db.

4.1 ultrasonic detection process 4 nozzle bonding interface is the exploration of product metal material is 30CrMnSiA, non metal materials with high silica / phenolic resin, is part of 284mm gamma probe curvature of metal parts, 4mm thick, between the metal parts and non metal insulation layer with 944 adhesive product acceptance requirements: debonding area shall not be greater than determine the total detection area of the detection sensitivity, can be on the nozzle of metal and non metal bonding interface testing, with R 14mm circular debond as a benchmark, if it is found that the multiple reflection of a location CRT screen horizontal scale instrument 8 wave in the grid at the amplitude reached more than 10%, it is judged as debonding, and determination of viscosity by area half wave height method, the principle is: after the incident sound pressure debonding 10 times one hundred percent reflection, is close to the spherical wave, can be simplified in type P as the initial pressure; D wafer diameter; wavelength lambda; s distance A for chip area.

If in the same conditions to their reflection as a new acoustic source, the debonding area equal to 100% of the area of a launch, half wave is equal to the area of a launch, the debonding and debonding of the edge to the wafer center of pressure difference is 6dB and the concrete implementation method is: the discovery of debonding, move the probe to screen the reflected pulse rate reached the highest, then up and down, left and right to move the probe, when the amplitudes of reflected the drop for the original half, the probe center line between the position is the debonding area, with 1: 1 ratio transparent tracing paper unwinding stick with planimeter calculated debonding area. Table 2 shows the test results of some nozzle bonding surface detection in a certain batch.

4.2 test results and Analysis on two actual nozzle metal and nonmetal bonding interface, using the ultrasonic longitudinal wave reflection method introduced in this paper, can be more accurate to find its internal debonding defects. Through the control of the nozzle anatomy, the debonding and debonding area are also in agreement with the test results.

In the future, after nearly one hundred products testing, it is proved that this method can be more accurate to find the internal debonding defects of the following parts: large area of A. clearance. The debonding is due to the workpiece cleaning is not clean, lining and shell with lax, workpiece deformation cause. At this time the bonding strength than a good bonding strength low reflected in the instrument display screen wave on, repeatedly reflex amplitude in the horizontal scale "10" of about 30%.

B. pore type. The debonding is caused by ultrasonic detection of glue is solid rocket motor nozzle bonding interface, layer internal gas been net and adhesive failure reason, at this time the bonding strength is lower than that of the excellent bonding strength, reflected in the instrument display screen wave on, repeatedly reflex amplitude in the horizontal scale "8" of more than 10%.

6 the end of the text using ultrasonic multiple reflection method, the use of conventional instruments and equipment, can be more accurate to find a variety of bonding interface. This method is applicable to the field detection and position detection of solid rocket motor nozzle.