The Study Of Quantitative Analysis For Magnetic Memory Testing Signals On Metal Pipe Cracks

Pipeline transportation which can cause large losses for its leaks occupies an important position in modern industry. As stress concentration is a major reason of damage incidents, countries give non-destructive testing of the pipeline full attention. However, the traditional method is not effective. Metal Magnetic Memory (MMM) has many advantages in case of testing and monitoring the crack.This paper introduces the MMM theory, design of detection system in hardware and software, and the quantitative analysis of MMM. The hardware of testing system includes MSP430, HMC1021Z magnetoresistive sensor, and the match signal processing circuit. The software design of testing system contains the design of MCU programming, and Matlab Data processing programming. The detection system working flow is:the signal which is processed by the conditioning circuit after detected by sensor module on test board, is collected by MSP430 microcontroller, then sent to the PC through serial interface, and finally, processed by Matlab data processing program.This experiment is carried out in two steps. The first step is to detect the metal plate preferences of different types of cracks by laser beam cutting method and being eliminate residual stress by vibration method. The magnetic signal around crack is collected by the testing system, and then processed in differential and scale. The new feature is found by calculating the gradient value on both sides of zero. The second step is to verify weather this new feature is effective on different work piece through testing the pipe which has pre-cracks. New feature has great consistency in testing different work piece. Therefore, the gradient value on both sides of zero can be the new feature in MMM quantitative analysis.