Applied Mechanics and Materials Vols. 239-240

Abstract: Insulator contamination threatens grid safety. And insulator pollution detection can prevent accident occurrence. An invented insulator pollution detector based on microwave radiation is introduced in the paper. The result of testing on-site high-voltage insulator pollution with the detector compared with ESDD and NSDD. And the comparison results indicate the insulator pollution detector can test high-voltage insulator pollution.

Abstract: In the design and production process of car’s electronic equipment, the SE of the shield is reduced greatly for the existence of aperture.There is a modeling analysis to the aperture leakage EMI problems and derived a numerical calculation formula of the SE influenced by aperture leakage based on the slot antenna theory, also put forward the way to increase the SE of the shield by using Matlab software to simulate the SE of the shield with three regular apertures in different interference frequency. The simulation results have universal utility and which can provide data support for the design and layout of car’s internal circuits and devices.

Abstract: This paper describes the setup of a complex voltage ratio measurement system for the audio frequency range. A wideband two-channel digitizer and a differential analogue channel switching front-end are used as the heart of the system. The complex error, frequency response characteristics and short term stability of the system are tested in this paper. The errors range from 1×10^-7 at 50 Hz to 10×10^-6 at 200 kHz in ratio 1:1 test with 6 V input voltages. And errors are below ±8×10^-7 and ±0.06 μrad in ratio 1:1 test with a 4V power line (50 Hz) input voltage over 64 hours. The test results and comparisons between with and without channel exchange mode confirm the remarkable improvement regarding the suppression of the static mismatch errors of the digitizer and show the usefulness of the system at 50 Hz too.

Abstract: The SE of the shield is reduced greatly for the existence of aperture in the electronic equipment design process. The shielding characteristic of slot apertures and pore array are analyzed with the method of FDTD, and also put forward the way to increase the SE of the shield. The metallic box of some electronic equipment has been redesigned by applying the conclusion. Practice shows that FDTD method is a fast and efficient method for an aperture question, and the analysis conclusion can be helpful to the electromagnetic shielding design of the metallic box with apertures.

Abstract: Neutron energy spectrum has a high correlation with all kinds of nuclear processes in nuclear reactor. Neutron energy spectrums of the TMSR in some conditions were simulated using MCNP5.The distributions of thermal neutrons, epithermal and resonance neutrons, and fast neutrons in axial and radial were simulated, respectively. The simulation results indicate that thermal neutrons have a high ratio and control rods inserting the nuclear reactor have a serious effect on neutron distribution. The study of neutron energy spectrum is theoretical basis for measurement in the TMSR.

Abstract: Most of pipeline-inspection techniques above ground can only locate the damages of the pipeline anticorrosive coating and give no information regarding the metal loss defects. Based on the detection and analysis of the AC magnetic field around the pipeline, this paper presents an alternative technique, which is able to detect and distinguish the metal loss defects. It turns out that the inspection based on lock-in amplification technique has a higher magnetic induction resolution of 10e-10T. And the analysis of frequency spectrum on magnetic field can be applied to recognize the metal loss defects on buried pipelines effectively.

Abstract: Electromagnetic induction angle displacement sensor processing error seriously affected the measurement accuracy, the system using multi-position probes method to eliminate harmonic errors. According to the electromagnetic induction angle sensor error characteristics, the 32 antipodal sensors are analyzed theoretically, 64 multiple harmonics are isolated，and the influence of periodicity multiple harmonic error have been removed by multi-position probes method. The error correction method eliminated systematic error of manufacturing processes. The electromagnetic induction angle sensor precision reach expected targets of 2′.

Abstract: This paper studies the numerical calculation method of mutual inductance between two superconducting pancake coils. And the calculation results are proved through experiment. Use this calculation method, the isoline map of two superconducting pancake coils’ coupling coefficient with the different spatial distributions is calculated. Then the designer can rapidly design the spatial distribution of superconducting pancake coils according to the coupling coefficient they needs. Specially, there is a curve of coupling coefficient equals 0 in the isoline ma. For the occasions which want to eliminate the mutual inductance between two superconducting pancake coils, this curve can provide a good guidance for design a compact layout and reduce the volume. Finally, the 0 value curve is tested under the guidance of calculation result. Through this experiment, the correctness and engineering guidance of isoline map is verified.

Abstract: Over the last two decades, the electromagnetic radiation is becoming the fourth public pollution in addition to the noise, water and air pollution. Here, we had studied the structure and the electromagnetic properties of machine-knitted fabric coated with silver by means of microscopy and shielding effectiveness in the open space. The silver-plated polyester fabric showed a different shielding effectiveness of electromagnetic wave in the open space compared with enclosed space. The value of SE had closed relation with transmitting and receiving distance except the theory factor. When the frequency dropped below 900 MHz, the value SE usually became negative.

Abstract: In this work, Split Hopkinson Pressure Bar (SHPB) was employed to test the material properties dynamic forming. The stress-strain curves and dynamic yield strengths under variable strain rates were obtained. Constitutive equation of 3A21 aluminium alloy was formulated by Johnson-Cook model and then, it was applied to simulate the forming behavior of 3A21 aluminum alloy tube under dynamic state by software Ansys/ls-dyna. The results show that, for magnetic pulse forming process, the simulating results well corresponded with those of experiments that demonstrate the constitutive equation established present good accuracy.