Ultrasonic Non-destructive Testing Of Internal Defects Of Large Rings Used In Mechanical Engineering

With the improvement of science and technology level in China and the successive implementation of major projects,large ring parts for construction machinery have been widely used in wind power,nuclear power,mining machinery,aerospace and other engineering fields.Affected by such factors as raw material defects,billet quality,unstable surface state,complex hole shape,and fluctuation of process parameters,various manufacturing defects such as cracks,pores,crusts and inclusions are often generated on the surface and internal of large ring parts,which seriously affects the service performance and safety of related mechanical equipment.Therefore,timely,accurate and comprehensive detection of manufacturing defects was an indispensable part for the production of large-scale high-quality ring parts.The following aspects are studied for the internal defects caused by the manufacturing process of large ring parts for mechanical engineering in this thesis:(1)For the difficulty in detecting large rings used in mechanical engineering,the ultrasonic detection method and the coupling method were firstly determined,and the multi-frequency array ultrasonic detection method was proposed.Then the multivariate Gaussian sound beam model was established,and the water-immersed ultrasonic sound field distribution of different parameter probes under different water layer heights was obtained through simulation.Finally,the sound field distribution law was analyzed to determine the parameters of the probe and the water layer height between the probe and the ring.(2)In order to improve the detection efficiency and detection accuracy,the number of arrays and arrangement of multi-frequency probes were designed.The simple three-dimensional model design of multi-frequency array probes was completed in the modeling software,and then the motion trajectory of the array probes was planned.(3)In order to realize the ultrasonic automatic detection of the internal defects of large ring parts,a number of comparative test blocks were prepared,and the artificial defects on the test blocks were tested.The experimental results were compared with the sound field simulation results to verify the validity of the sound field simu-lation model,and the rationality of multi-frequency array probe design.The influencing factors of the experimental results were analyzed,and the DAC curve which was more suitable for ultrasonic automatic detection was drawn.The detection effect of the multi-frequency array probe and the accuracy of the DAC curve were verified on the large-scale water-immersed ultrasonic detection platform.(4)In order to analyze the characteristics of ultrasonic echo signals of different types of defects,the transient simulation model of water immersion ultrasonic testing was established.The validity of the simulation model was verified.And then establish a simulation model of pore defects and analyze the variation of ultrasonic detection signals.Finally,the frequency domain analysis of the ultrasonic detection signals of several artificial defects were carried out to study the variation rule of their frequency domain characteristics.The research results of this thesis will be applied to large-scale ring manufacturing enterprises and ring-use enterprises to solve the problem of ring product quality in important fields and large-scale projects,which has significant academic significance and broad application prospects.