Research On Eddy-current And Metal Magnetic Memory Automatic Nondestructive Testing System Of Retired Crankshaft

Nondestructive Testing(NDT) is a vital segment in the remanufacturing of retired mechanical and electrical equipment. Most NDT used in retired crankshaft of large-size diesel engine adopt manual testing and qualitative analysis. Due to the higher requirement for the remanufacturing project quality, developing an automatic NDT system which can obtain the exact spatial position information of flaws has turned into the basic condition of doing the residual life evaluation on retired crankshaft. According to the request of the NDT and life-assessing system for parts, the project cooperated between school and enterprise, this paper focuses on the eddy current testing(ECT) and magnetic memory method(MMM) system online used in retired crankshaft remanufacturing, which go as follows:On the basis of building up the physical and equivalent circuit model of the coil and tested workpiece in ECT, a finite element model of ECT was established in ANSYS to do electromagnetic harmonic simulation. By using ANSYS postprocessor, the influence law of coil lift-off and excitation frequency on the ECT result was studied thoroughly to determine the laws of the distance between eddy current sensor and tested workpiece on the veracity of testing results. And this can offer a fundamental data support for the linkage control of the eddy current sensor and tested surface's spatial position in the NDT system.The paper researched on NDT technology based on ECT and MMM for retired crankshaft, and a general system solution integrating industrial robot and crankshaft indexing machine was put forward, building up a kinetic model of crankshaft and testing sensor correspondingly. The spatial geometrical relation between the sensor and tested surface during testing was verified by the method of off-line simulation in Robotstudio.According to the general system solution, the paper also finished the structural design of crankshaft indexing machine, electric control module, sensor clamp fixture, the upper computer software was developed to monitor the testing motion, it could be also used to read, process and manage ECT and MMM testing data. The integration of crankshaft indexing machine and industrial robot program with the upper computer software was realized. Through controlling of crankshaft indexing machine, industrial robots and ECT and MMM instrument, a continuous relative movement between the sensor and tested crankshaft was realized to attain the relevant eddy current, magnetic memory testing data and the corresponding spatial position information.This system was applied to the NDT for retired crankshaft of large-size diesel engine in the industrial field. Comparing the obtained testing data via the system and that acquired by manual testing, the reliability, stability and veracity of defect location of this system was verified. It was of great academic and engineering significance for developing the automatic nondestructive technology and system with self-owned intellectual property rights.