The Stockbridge vibration damper is widely used in overhead transmission lines to reduce Aeolian vibration. Although a linear analytical model has been developed to interpret characteristics of the vibration damper, a much more detailed model is needed to investigate how the nonlinear factors of the structure affect its vibration characteristics. The paper presents a full-scale finite element model of the Stockbridge vibration damper, in which contact conditions are taken into account using the linear perturbation method. Relations between the contact conditions and mode frequencies were studied. It was proved that contact conditions between each two parts of the damper have significant influence on the stiffness of the whole structure. Results obtained from the numerical model compare well with those from the experiment. Finally, this numerical model was applied to investigate how the bonding material between the counterweight and steel strand cable affects the mode frequencies of the vibration damper.

Hot-stamped high strength steel parts are widely used to achieve lightweight of automobile. However, mechanical properties of formed high strength steel parts are difficult to control and predict. In order to realize field nondestructive testing of hot forming high strength steel parts, magnetic Barkhausen noise which is sensitive to microstructure of ferromagnet was used. In the paper, magnetic Barkhausen noise signals of hot-stamped high strength steel strips with different hardness were measured and analyzed. A substantial correlation was found between magnetic Barkhausen noise and hardness (in range 220∼450 HV). Then, frequency domain analysis based on autoregressive modeling was done to find out signal components which are dependent and independent to hardness of the hot-stamped high strength steel. Independent signals can be eliminated based on the frequency analysis. Accordingly, the measurement accuracy can be improved for application in industrial field

Wind tunnel tests are a commonly used method for studying wind characteristics of complex terrain; but truncation of the terrain model is usually unavoidable and affects the accuracy of the test results. For this reason, the effects of truncated and original terrain models on the simulation of wind characteristics for complex terrain were investigated by considering both nontruncated and truncated models, with the truncated model considering the applicability of two types of transition sections. The results show that the effect of topographic truncation on profiles of mean velocity and turbulence intensity is different for regions and that inclination angle profiles are extremely sensitive to the changing topographic features upwind. In those cases, the spectra of streamwise velocity were overestimated in the low-frequency range but underestimated in the high-frequency range due to topographic truncation. At the same time, the less negative value of the slope of the spectra was found at the inertial subrange. Furthermore, the normalized bandwidth was also influenced by topographic truncation, which was narrowed in windward and leeward regions and broadened in the valley region. We should note that the performance of the transition sections used in this study was quite limited and even resulted in inaccuracies in the simulation.