混凝土结构超声阵列探测成像方法分析-analysis of ultrasonic array detection imaging method for concrete structures.docx

Abstract: Synthetic aperture focusing technique (SAFT) , which made a breakthrough in classical concept of ultrasonic imaging system concerning lateral resolution, can be used to detect and observe the remote object with high lateral resolution by means of actual element transducers with small aperture and low operating frequency .Smaller the element transducer aperture D is, higher the lateral resolution is. Some mutually contradictory requirements about systematic parameter design in the direct imaging technique can be solved by using this method.In this work, for satisfying the need of quick detection to the internal defects and embedded objects in concrete structures, a detect method combining linear array probes and SAFT has been presented to reach high resolution detection in concrete by ultrasonic arrays. Traditional SAFT algorithm has been improved to adapt to this new detection method according to the structural characteristics of linear array probes, where the geometrical relationship of echo sound path through reflection point is discussed in detail by different situations. Numerical simulations and ultrasonic array data fusion are conducted to form cross section figures by using the finite element software WAVE3000 and mathematical software MATLAB in the subject.In array SAFT algorithm, the scanning signals between interval transducers in array are used to increase array dimension maximum to amalgamate detecting data for higher imaging resolution compared with traditional SAFT. As frequency components of the pulse signal is rich, the grain scattering is serious in concrete material, then there will be oscillation signal at the position of echo wave height in imaging figures. This paper also presents a new method based on cross-correlation to filter oscillation signal as well better suppression effect to lateral wave magnitude.Numerical simulations have accomplished in two ways, single point reflection and the finite element simulations. Single point refl