Vibration Severity Monitoring and Evaluation of Armored Vehicle Transmission

Vibration monitoring and vibration severity evaluation of armored vehicle transmission are realized by additional sensors. An algorithm of vibration severity in frequency domain is presented. The algorithm has powerful applicability for signal type and flexible selectivity for frequency range,and avoids the processing of signal conversion used calculus and filtering compared to the algorithm of vibration severity in time domain. An applied example is given in company with attentive proceedings and measures for improving evaluation effect.

A Grey Prediction Model on Vibration Severity Development of a Pump

The method to enhance the precis io n of a grey model GM (1, 1) for predicting the development of vibration severity of a pump is investigated. The rectifying procedures involve the structure and the parameters regarding GM(1,1). A new model based on GM(1, 1), which is GM (E,1,1), is proposed. In GM(E,1,1), the distribution of relative errors rati os between the original series and predicting series obtained by the mean of GM( 1,1) are considered in special points to set up the threshold and adjusting coef ficients to control the modified action and the rectified amount based on distri bution of the original series. The case shows that GM(E, 1, 1) is good at predic ting the vibration severity development of the pump.

Evaluation of TBM Cutterhead’s Comprehensive Performance Under Complicated Conditions

A comprehensive performance evaluation method for the tunnel boring machine(TBM)cutterhead is proposed in this paper.The evaluation system is established on strength and vibration.Based on fracture mechanics theory,fatigue strength evaluation indices are determined under critical crack length.The concept of crack regions division is proposed to evaluate fatigue strength more accurately and specifically.In addition,the velocities in three directions of critical locations are obtained with dynamics equations.Then,the root-mean-square values of velocities are taken as the vibration severity indices.Taking the cutterhead of Jilin diversion engineering as an example,the evaluations of each index are completed;then,the vibration of the TBM cutterhead is measured and compared with the theoretical calculation results.There are similar change laws between the theoretical calculation results and the testing results of the cutterhead acceleration,which proves that the method of calculation of the vibration index is effective,the reliability of the cutter saddle welding should be paid attention to when the TBM is working,and the condition of vibration severity of the TBM cutterhead meets the requirements but needs to be improved.

A Review on Grain Refinement of Aluminum Alloys:Progresses,Challenges and Prospects

Aluminum becomes the most popular nonferrous metal and is widely used in many fields such as packaging,building transportation and electrical materials due to its rich resource, light weight, good mechanical properties, suitable corrosion resistance and excellent electrical conductivity. Grain refinement, which is obtained by changing the size of grain structure by different techniques, is a preferred method to improve simultaneously the strength and plasticity of metallic materials. Therefore, grain refining of aluminum is regarded as a key technique in aluminum processing industry.Up to now, there have been a number of techniques for aluminum grain refining. All the techniques can be classified as four categories as follows： grain refining by vibration and stirring during solidification, rapid solidification, the addition of grain refiner and severe plastic deformation. Each of them has its own merits and demerits as well as applicable conditions, and there are still some arguments in the understanding of the mechanisms of these techniques. In this article, the research progresses and challenges encountered in the present techniques and the future research issues and directions are summarized.