The Characteristics Analysis Of Focused Sound Field Of TRL Phased Array Probes

Combining the pseudo focusing of traditional TRL probe and dynamical focusing of phased array probe, TRL (Transmit Receive Longitudinal Wave) phased array probe shows flexible beam control and good focusing ability. However the correct operation is difficult to maintain with its complex structure, while the set up of its focal laws will affect the efficient examine area and quantitative accuracy. The technique of sound field calculation and analysis provides an efficient method to find probe’s sound field characteristics, and for analyzing testing sensitivity, lateral resolution, optimization of probe design, it is significant to study TRL probe’s sound field.Being aware of the particularity of TRL phased array probe structure, and by simulating and experimenting of several related types of probe sound fields, the TRL phased array probe’s sound field characteristic was finally found after comparing analysis and tested by experiments. The main content of this thesis covers:(1) The basic theory of TRL phased array probe was illuminated, its structure, beam control principle and sound field basic theory were discussed. Regular analysis method was introduced, matrix TRL probe (element number of8×4, bore diameter of28mm X16mm) with center frequency of1.5MHz was selected, sound field characteristic research project was designed.(2) The sound fields of regular rectangle probe, TRL probe, two dimensional rectangle array probe and TRL phased array probe were simulated using CIVA. Sound field experiment was conducted on carbon steel samples with Φ3mm, depth from5mm to120mm SDH, and verified the accuracy of simulation results.(3) Probes’sound fields of four types were compared and focused sound field characteristics of TRL phased array probe were summarized. Results are:①There is no obvious near surface dead zone for TRL phased array probe, but the studied probe can’t examine defects in depth of9.35mm efficiently as the structure limitation, when using a wedge, the dead zone can almost wiped off;②Compared with2D PA probe, the optimum sensitivity zone of TRL probe is deeper;③While the beam diverges slowly, the probe’s resolution maintains good in depth direction;④The depth focusing ability is optimal and energy of the focused beam is more concentrated. (4) The ultrasonic examination on forged austenitic stainless steel with thick of66.5mm was taken using2D PA probe and TRL PA probe. The results indicate:①TRL PA probe with focal depth15mm and refraction angle50°can effectively detect side-drilled holes with depth of10mm;②With refraction angle50°and focal depth of30、50and70mm, the2D PA probe can only have a good image to the side-drilled hole with the depth of30mm, while the TRL PA probe can good images to all the side-drilled holes;③When detecting the side-drilled hole with the depth of30、50and70mm, the2D PA probe has an average signal-to-noise ratio about19dB; while the TRL PA probe has an average signal-to-noise ratio more than30dB.