Numerical Simulation For Romote Accoustic Excitation Of Surface Cracks In Concretestructure

Concrete material is the most widely used building materials in the civil construction industry. Because concrete is a brittle material and its tensi le strength is poor, so concrete structure cracking phenomenon inevitably occur under the influence of the internal and external factors and then cracks exists. Currently most commonly used traditional methods to detect surface cracks of concrete are near structure surface(non-contact) or pre-embedded structures(contact). Due to limitations of its own characteristics of concrete structures, traditional close contact detection method exist big disadvantage, therefore, it is very necessary to study a remote distance and non-contact NDT method. This paper is based on the finite element software ANSYS, research remote-distance high directivity acoustic excitation as the excitation source, through the concrete surface particle displacement amplitude of vertical vibration to detect concrete surface cracks remote distance non-contact detection method. Including the following several aspects in detail :Study about acoustic field characteristics of circular piston transducer. Firstly, to use scientific computing software Matlab to prepare calculation program, then from two aspects(acoustic pressure and directivity) to study circular piston transducer sound pressure distribution and directivity in detail. Secondly, using finite element analysis software ANSYS to sim ulate circular piston transducers. Thirdly, to compare and analysis results between Matlab software and ANSYS software, and further explore and discuss the ANSYS software simulation accuracy and feasibility on the acoustic transducer.Based on remote-distance high directivity acoustic beam, the concrete surface crack NDT method finite element model is built and testability is analyzed. Matlab-based software, this paper explores the choice of high directivity acoustic excitation. ANSYS-based software, discussed in detail, the acoustic parametric array transducer as a method of remote excitation source and simulation procedures. Discussion focused beam focusing degree of remote distance acoustic excitation produces, and the acoustic excitation with reasonable frequency acting on concrete specimens with two constraint forms at bottom of the concrete-clamped support and simply supported, point by point scanning. By observing decreases changes in the vertical vibration displacement amplitude particle on the component surface can determine the location of the concrete surface crack, the width size and depth size. Draw a remote acoustic excitation NDT testing method can be used to detect surface cracks in concrete conclusion.According to simulation results, different surface crack width, depth, and different concrete elements size, actual ambient noise effect on detection method is studied in this paper. The results show that this detection method has a maximum depth of concrete can be measured; its value is positively correlated with the thickness of the concrete and vertical displacement of the crack tip particle amplitude is a linear relationship with the crack depth. Other factors have small effect on remote distance acoustic excitation to detect cracks in the concrete surface.