A Simultaneous Ultrasonic Inversion Method of Coating Layer Thickness, Density and P-wave Sound Velocity

Abstract

A method for simultaneous ultrasonic inversion of the thickness, density and longitudinal wave velocity of a coating belongs to the technical field of ultrasonic nondestructive testing and evaluatingof materials. An ultrasonic pulse echo detection system composed of a sample stage, a coating sample, a delay block probe, a flaw detector, a digital oscilloscope and a computer is adopted. The soundpressure reflection coefficient phase spectrum phi (f, d, rho, c) of a coating structure is derived. The correlation coefficients of the theoretical and experimental sound pressure reflection coefficient phase spectrums in the effective band of the probe are calculated, and a correlation coefficient matrix eta (d, rho, c) is obtained. The acoustic impedance of the coating is measured and used as aconstraint of the correlation coefficient matrix. The thickness d(i), density rho(i) and longitudinal wave velocity c(i) of the coating corresponding to the maximum value eta<max> (d, rho, c) in thecorrelation coefficient matrix satisfying the constraint are the thickness, density and longitudinal wave velocity of the coating required. By using the method, the problem that large measurement error is caused by the parameter fluctuation of a coating in the nondestructive testing process of the parts of the coating is solved. A novel method for simultaneous ultrasonic inversion of the thickness, density and longitudinal wave velocity of a coating is provided.

Description

technical field [0001] The invention relates to a simultaneous ultrasonic inversion method of coating layer thickness, density and longitudinal wave sound velocity, which belongs to the technical field of ultrasonic nondestructive testing. Background technique [0002] The surface coating layer refers to the use of physical and chemical methods to prepare a reinforced and protective matrix material on the surface of the material or a coating layer with special functions and a certain thickness. It is an effective measure to improve the performance of parts and endow parts with special functions. The coating layer Its performance and reliability depend on its special geometric features and physical properties, including thickness, interface roughness, sound velocity, density, elastic modulus and other parameters. For example, the thickness and density of aviation radar absorbing stealth coatings have an important impact on its absorbing and mechanical properties. Excessive co...

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Problems solved by technology

Or limited to laboratory conditions, it is difficult to apply to the field, such as Rokhlin and Lavrentyev in "An ultrasonic method for determination of elastic moduli, density attenuation and thickness of a polymer coating on a stiff plate", using the normal incidence and oblique incidence ultrasonic reflection coefficient spectrum to The thickness, density, sound velocity and other parameters of the polymer thin layer are inverted in two steps, but the experimental device contains three ultrasonic probes that need to be precisely adjusted in angle, which is difficult to use for actual engineering coating detection

Chen Jian et al. based on the ultrasonic microscope to invert the thickness, density, and transverse and longitudinal wave sound velocities of stainless steel sheets. The ultrasonic microscope system used is relatively precise and cannot be applied to the actual coating detection of parts.

At present, there is no report on the simultaneous effective and non-destructive characterization of the three parameters of the actual engineering coating layer.

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