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This paper mainly discusses the tower models in lightning overvoltage calculation, especially analysis the lossless and lossy models. Build the muti-wave impedance model of the most commonly used towers, which are portal tower, glass tower, cat head tower and strain tower in accordance with the reality. The simulation shows that muti-wave impedance model has a higher lightning overvoltage than simple model under the same condition. This is because the simple model ignores the influence of resistance and inductance, so the more accurate the model is, the more effective the protection will be.

The fatigue failure of the piston pin hole is considered as a key factor affecting the service life of engines. In this work, the piston pin hole profile was designed as tapered shape following a power law. By combining finite element analysis and hydraulic pulsating fatigue tests, the pin hole profile was optimized. It has been found that the maximum contact pressure on the pin hole surface was reduced by 16,7% with appropriate increasing the radius enlarging rate of the piston pin hole, the maximum tensile stress of the piston pin seat was reduced by 13,1%, and the piston pin seat fatigue safety factor was increased by 41,4%, the piston pin hole fatigue safety factor was increased by 15,9%. The piston pin hole's hydraulic pulsating fatigue test results were found to be consistent with the FEA results. It could be concluded that appropriate increasing the radius enlarging rate of the pin hole could significantly weaken the fatigue wear of the pin hole, further improving its fatigue resistance.

Gear flank twist has a significant effect on the load-carrying capacity. However, most prediction models of gear flank twist can't be applicable for gears with profile modification. A new method for predicting gear flank twist for the generating grinding process is developed in this paper, taking into consideration the effect of lead modifications, profile modifications and position errors of CNC machine tools on gear flank twist. And the influences of four gear parameters on gear flank twist were studied using orthogonal experiments, which proves that the change of module has the greatest effect on gear flank twist. And the maximal profile modification value has minimal effect on gear flank twist. The experimental results proved that the model can accurately predict the gear flank twist. Besides, this paper described an gear parameters optimization study to reduce gear flank twist based on nine well-planned orthogonal experiments.