Research & Design Of Magnetic Memory Testing System For Welded Joints Based On Virtual Instruments

By means of advanced techniques to predict the latent flaws, an efficient and reliable testing for welds of the pipeline being built or used , is very important in the field of energy transportation for the safety of petroleum and gas pipelines, and even has a profound significance for the development of pipe engineering and the whole national economy.Magnetic Memory Testing (MMT) is one kind of advanced nondestructive testing (NDT) techniques, which is introduced in China only several years ago. MMT is also a unique way to show the prediction of hidden flaws. It's without doubt that to design efficient MMT instruments with high performance and to apply them will promote the development of MMT.According to the principle of MMT, the author develops a set of instruments for pipeline welds testing by means of virtual instruments (VI) technology. The dissertation involves the following content mainly:1. By means of the related theory of ferromagnetism, the principle of the MMT is discussed in detail.2. After the Virtual Instruments technology is studied, the hardware, software structure, the programming environment and related technology of VI are presented.3. According to PC-DAQ type for the instrument system, the hardware of the system is designed. It includes the choice of components and the circuit designs of sensor temperature compensating, amplification and filter.4. In accord with the principles of VI software development, the software structure and function modules of this testing system are carefully designed. By means of LabVIEW as the developing tool of VI, all functions of its software are implemented.5. Testing Experiment carried out with this VI system and corresponding results are introduced.At last, the author summarizes the main conclusions and proposes possible future research directions.