| The elastic constants and characteristics of wave propagation are importantcharacterization of material’s mechanical property, so, research on testing differenttypes of materials’ elastic constants and characteristics of wave propagation issignificant. For the past few years, measurement of material’s elastic constants andwave velocity using ultrasonic microscope technology has become a hot spot. Themain purpose of this thesis is to test different materials’ elastic constants andcharacteristics of wave propagation. Designing and manufacturing a special ultrasonictransducer independently, setting up a hardware platform based on measuringtechnique of ultrasonic microscope, designing a software system based on virtualinstrument technology, measuring a few types of materials’ wave velocity anddetermining elastic constants some of them using the wave velocity, researching onrelation between hydrogen concentration and wave velocity fundamentally. All are thefoundation of using ultrasonic microscope technology to test material’s performancedegradation caused by hydrogen. The main contents are listed as following:(1) Domestic and international research profile about ultrasonic microscopetechnology, measuring elastic constant technology and measuring hydrogenconcentration technology are analyzed. Theories of measuring surface wave velocityand dispersion curves are derived in detail.(2) Hardware system of ultrasonic microscope is set up, and the function of eachpart is optimized, speed and precision of the hardware system are improved. So thehardware system can meet the requirement of using V(f, z) method to test material’swave velocity. A special ultrasonic line-focus PVDF transducer is designed andmanufactured. Selecting of piezoelectric element, manufacturing of back material andrequirements of production technology are optimized, the frequency band is raised. Sothe transducer can meet the requirement of broadband in ultrasonic microscopetechnology.(3) Special software is designed to control the hardware system. The z axis ofmovement platform can scan precisely in small distance, and the chassis of movementplatform can revolve in small angle. Echo signal is acquired and displayed in real time,waveform is preprocessed effectively, and mass of waveform data is stored quickly.Data is on-line processed and wave velocity is calculated. So software system cancontrol hardware system to test wave velocity and material’s elastic constants automatically.(4) A few types of materials’ wave velocity are tested experimentally, and someof the materials’ elastic constants are determined by curve fitting. The experimentvalue and theory value are compared, and the results are agreed well. So the ultrasonicmicroscope measurement system can meet the requirement of practical application.Surface wave velocity of hydrogen permeation specimen is tested experimentally, andsurface wave velocity affected by hydrogen concentration is analyzed, laying afoundation for testing material’s mechanical property degradation caused byhydrogen. |
