| With the improving capability of acoustic emission equipment and perfecting analysis technology, AE technology had been used in oil, petrochemical, power, aerospace, aerospace, railway, transportation, coal, building, mechanical manufacturing and processing field, periodic measuring and on-line monitoring is realized. Complete evaluation of equipment integrity by means of AE source found in testing or monitoring, and ensure safe operation for equipment.Under loading effect, AE signal would generate when damage produced, analyzing characteristic of AE source and its law are a problem continuously interested to developing and studying. Lots of work had been developed home and abroad, and some results are obtained, solving some technical problems, promoting the spread and application of AE technology. In some research, existing weakness in research such as propagation characteristic of signal in waveguide, characteristic distributing of AE signal, parameter characteristic of weld defect, signal recognition and extraction of fatigue crack, need further work to solve the problem. At Present,16MnR and Q345are special equipment material proportion up to80%,so,in research, we chose16MnR and Q345to study AE signal studying work, to solve problems in testing. The main research contents and conclusion are as follows:1. Propagation characteristics of AE signal transmitting in waveguide rodSelect20steel, diameter respectively4,6,8,10,12,14,16mm,and length3.2m,break lead in different length, study system the case of breaking lead on section and circumference, conclude the characteristic parameters, wave and spectrum characteristics effect by the change of length of waveguide rod, put forward the choice of waveguide rod in AE testing; The comparison study in weld samples shows that signal propagating in waveguide rod mainly is surface propagation, and chose diameter6,4mm,length in1.5m, realized longitudinal wave separating clearly, amplitude attenuation decreased, complete the experiment successfully.2.Characteristic of AE signal of16MnR in high, low temperatureStudying tensile experiment of16MnR in-70～670℃,analyzed the rule of AE parameter changing by temperature, show that sometime yield appeared in high temperature in 16MnR,Put forward that deformation, loading and temperature can be judged by AE signal changing, enriches AE technique applying in low and high temperature performance test. In correlation study, first put correlation parameters study respectively in elastic step, yield step and strengthening step, obtained correlation in elastic step is the highest; Accumulation counts is the same with accumulation energy in characterizing damage of material in different temperature.3.AE signal characteristic of weld defect of16MnRStudying signal distributing characteristic of weld defect in tensile, obtained signal distributing rule; Using amplitude count and energy duration correlation analysis, can judge yield and crack extended signal characteristic; By analyzing distributing of AE signal, can judge the loading of material, ensure safety.Using fracture mechanical knowledge compute stress value as incomplete penetration defect fractures, comparing and verifying that the stress value in fracturing with plenty of AE signals higher than computing stress value, trying out the combination of above, provide mechanical support for AE signal evaluation, and have certain guiding significance for equipment with defect testing.4. Characteristic studying of fatigue crack signal in Q235cable tower anchorage structures of cable-stayed bridgeA large-sized model fatigue test on the anchor structure of a cable-stayed bridge tower was conducted in the laboratory, An acoustic emission instrument was used to monitor the fatigue cracks continuously in the left anchorage, studying the sensors layout, identification and extraction of fatigue signal, characteristics parameter value,and signal changing with periodic loading, and obtained successful signal of fatigue crack. By location of fatigue crack acoustie signal, ensure the time and the position of fatigue crack generating, according activity characteristics of acoustic signal, complete the evaluation, predict the failure behavior of cable tower anchorage struetures, lay a theoretical foundation for AE testing online in cable tower anchorage structures. |
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