On-line defects detection of structural component of track crane such as crane boom, outriggers, turntable and vehicle frame, is a difficult problem of nondestructive testing (NDT). In the present study, the usefulness of acoustic emission (AE) measurements for the detection of welding crack defects in the specimen made of HG70 steel, which is widely used for manufacturing structural component of track crane, has been investigated. Firstly, three-point bending test on the standard specimen made of HG70 steel is conducted. Then the analysis of AE source location and AE source characteristics are introduced respectively. As the result, the rudimentary location analysis can be attained using the linear location method. For AE source characteristics, procedural map of amplitude, RMS or energy rate, energy accumulation map, in connection with the corresponding conditional filter means, are available analysis methods to mirror welding crack defect. We find that the maximum of the amplitude, energy rate and RMS appear approximately at the same time, and the time is the point at which energy accumulation has a remarkable jump as shown in the energy accumulation map. In the end, we deduce that the reason why there is such a sudden energy leap is because of the activities of welding crack, and the multistage energy release also because of the step by step propagation of welding crack.

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The actual road diesel emissions of heavy-duty vehicle is very high, which has been a concern around the world. In 2018, Chinese government promulgated the "China VI" regulations containing real-driving emission test requirements and limits, requiring vehicle manufacturers to effectively control vehicle emissions to meet the requirements of China VI. This article takes a heavy-duty tractor equipped with a "China VI" engine as the research object, and performs actual road emission tests after loading 10%, 25%, 50%, 75%, and 100% respectively. The results show that NOx emissions are higher at low loads and PN emissions are higher at high loads, and CO emissions are not sensitive to load changes.

Abstract. In present paper, using Acoustic Emission (AE) as a ultrasonic technique, Welding crack has been investigated on the HG70 steel used by truck crane during three-point bending test was carried out. The study shows that the activity of AE increases greatly during the welding crack initiates and propagates, and the distributing range of AE characteristic parameters can be fixed. AE signals of welding crack initiation and expansion are typical sudden signals which have a different spectrum energy distribution range with that of unstable crack propagation.

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