Research On Measurement Of Ultrasound Features And Inversion Of Elastic Constants Of Coating Materials

At present coating materials are widely used in the field of aerospace, machinery,petroleum, chemical, nuclear power, micro-devices and micro-manufacturing, whichare used to protect surface of the materials such as anti-corrosion, antifriction andanti-oxidation. Because of the coating is more and more widely used in industrialapplications, the modern industrial become increasing demands of equipmentreliability and security. The strength and failure analysis of coating is more and moreimportant, at the same time the coating mechanical properties are critical for guidingthe industrial electroplating. The elastic constant is one of the most importantmechanical properties of parameters that are needed to be evaluated. The mosteffective non-destructive testing technology is based on the ultrasound velocitymethod. TheV(f,z) analytical method is a frequency domain method, which isapplied to inverse the elastic constants of coating materials. The main contents arelisted as following:(1) Optimized the measuring system of elastic constants for the smaller specimenmaterials，since the measuring system of elastic constants needs small step, highprecision, and developed a horizontal alignment, improve the level of test-piece. Thisdevice can be used to ensure the measurement of high accuracy about the coatingmaterials. The theoretical model of theV(f,z)analytical method was discussed, andthe block of stainless steel was measured by theV(f,z)analytical method. Theexperimental result shows that this method is feasible and can be used to test thedispersion curves of the test-piece.(2) Studied principles of making coating and processing technic because ofresearching coating. A small electroplating nickel system in laboratory was set up.Optimized the process of electroplating nickel, the nickel was electroplated fordifferent matrixes, got semi-infinite coating materials and sheet coating materials.Electroplating results show that the simplified process of electroplating nickel can beused to get qualified coating materials.(3) Ultrasonic nondestructive measuring system of elastic constants for coatingmaterial was applied, the point focused PVDF transducer and line focused PVDFtransducer were used to test semi-infinite coating materials and thin-sheet coatingmaterials respectively. TheV(f,z) analytical method was used to calculate ultrasoundwave velocity of propagating in the coating materials. By changing the longitudinalwave velocity and shear wave velocity of nickel coating, and comparing thetheoretical dispersion curves with the experimentally obtained dispersion curves,inversed the elastic constants of the nickel coating. The experimental results show that the application of V(f,z) analytical methods to obtain the experimental dispersioncures, and the inversion of elastic constants of the coatings is feasible.