Research On The Relationship Between Damage And Acoustic Emission Characteristics Of The Crane-used Q235B Plate

The metal components in crane can conduct plastic deformation,crack propagation and even fatigue fracture under the long-term alternate loads,which will cause severe accidents.Therefore,it is of great significance to monitor and evaluate the operating state of the components in crane.Considering the active defect sensitivity and the wide detection coverage,the acoustic emission detection technology is usually adopted to detect and evaluate the running state of crane components.In this paper,meso-damage model is utilized to carry out the simulation and build the relationship between the acoustic emission characteristics and the damage of the commonly used material Q235B in crane.Besides,a more convenient and accurate theoretical basis is provided with for the application of acoustic detection technology in crane state monitoring.The main work of this paper is summarized as follows:(1)The mechanical parameters of Q235B are obtained by experiment.And the GTN tensile mechanical model of Q235B is established in ABAQUS/EXPLICIT through the explicit integral algorithm based on micro-mechanics theory.In addition,the parameters of micropores are studied and optimized to verify and improve the accuracy of the GTN model.(2)On the basis of analyzing the main reasons of the acoustic emission noise formation,the traditional wavelet threshold noise reduction,whose threshold function and threshold are refined and defects are overcome,is applied in the process of the acoustic emission signal in order to improve signal-to-noise ratio.And the optimized algorithm is implemented to eliminate noise interference and improve the accuracy of the extracted acoustic emission characteristics.(3)The changing situations of the stress,stress triaxiality,equivalent plastic strain and pore volume fraction during Q235B stretching's four stages(i.e.elasticity,yield,strengthening and fracture)are analyzed by selecting the void growth ratio as the damage mechanics parameter.To achieve the relationship between the acoustic emission parameters and the damage feature quantity,the changing condition of acoustic emission energy counting is analyzed simultaneously.And the relationship between the damage and the acoustic emission energy count is established.