Meng Fanjiang

MICROSTRUCTURE NEAR SCRATCH ON ALLOY 690TT AND STRESS CORROSION INDUCED BY SCRATCHING

The microstructure and stress corrosion cracking(SCC) behavior of scratched zone on alloy 690TT were studied by using microhardness,TEM,EBSD-OIM and immersion experiment in caustic solution.It was found that a deformed hardening layer with a dimension range of 100μm was produced near the scratch.TEM and EBSD-OIM observations showed that the grains at shallow surface of scratch groove were refined to nano-size.SCC tests for scratched alloy 690TT were performed in caustic solution at high temperature with or without addition of lead oxides.The results showed that SCC cracks initiated and propagated at scratch banks and scratch grooves.Grain boundaries, twin boundaries deformed and microcracks produced during scratching process arc preferential sites for SCC.The oxide films formed on scratch groove were loosed by lead.The SCC crack length increased with increase of lead content.Scratched alloy 690TT is susceptible to SCC.

Inhibition of electromagnetic interference in control system based on DSP of high-power TEA CO 2 laser

The strong electromagnetic interference (EMI) generated in high-power TEA CO2 laser system mainly comes from main discharge circuit, pulse spark switch and power supply. Such strong EMI causes great damage and interference to the control system based on DSP. In this paper, we present the interference sources and their distribution and propose the methods of anti-interference. Measures for hardware design include weakening transient ground potential difference by using equipotential lines between devices, using signal isolation interface to inhibit the transient ground potential interference, and rational layout, shielding and filtering to the control system. And methods for software design include range-limited filter, self-diagnosis and self-repair for the critical data and anti-interference during abnormal reset. The EMI has been inhibited effectively by the anti-interference method proposed above. The result shows that: the software anti-interference method is as important as the hardware anti-interference method for the control system in a complex environment of strong EMI.