Search

Considering the current heavy mining and light digging in coal mines, limitations of the structural design of the fully mechanized excavation equipment, backward tunneling technology and other problems lead to inefficient tunneling. mining ratio is out of balance, at the same time, the comprehensive excavation equipment of the coal mine underground roadway is huge, the downhole environment is complicated, and the equipment is difficult to disassemble and assemble. It is difficult to analyze the mechanical properties of key components and cut efficiency improvement experiments under laboratory conditions. A method of active excitation assisted cutting is researched, this method is based on similarity theory, a similar model test bench with a ratio of 1:3 is established, modal experiments were performed firstly, the natural frequencies of the first six orders and the modal shapes of each order are obtained, the feasibility of the active vibration-assisted cutting experimental bench is verified, perform cutting experiments on the test bench separately with or without active excitation. With or without active excitation, the cutting contact force and cutting current change of the pick are measured. The experimental results show that during the same time period, when there is active excitation, the initial time for increasing contact force is 0.07 s earlier than when there is no excitation, longer duration, contact force is reduced by 0.12 kN compared with no excitation, after excitation, the average cutting current decreased by 1.12 A.Through the test bench based on Similarity theory, the active excitation vibration experiment and test can be carried out on the cutting arm of the road-header under limited laboratory conditions. Which provides a theoretical reference for selecting the best excitation-assisted cutting parameters. At the same time, it has opened up new ideas and new methods for the energy-saving and efficient work of the cutting machine cutting mechanism from the perspective of external excitation.

Accurate calculation of the mode shape and natural frequency of the motor stator is the basis for reducing motor noise and vibration. At present, scholars have disputes about the setting of stator core and winding material property parameters. In this paper, the modal simulation analysis and experimental test of a 2.2 kW permanent magnet brushless DC motor stator system are carried out. First, to give the stator core and the winding materials, The finite element software is used to analyze the relationship between the motor modal frequency and the parameters of the anisotropic materials. According to the modal frequency variation law, a method for correcting the parameters of the anisotropic materials based on the modal frequency is proposed. The method can complete the finite element model parameter correction of the stator. Secondly, the modal experiment is carried out by hammering method to verify the accuracy of the finite element model and determine the effectiveness of the method for correcting the equivalent material parameters. And by this method, the stator material parameters of the stator can be quickly determined. The error of this experiment and simulation is within 3%, achieving the purpose of experiment and simulation benchmarking.

The transmission shaft is a critical component of the automobile transmission system,it’s static and dynamic characteristics good or bad is directly related to the safety and NVH problems of vehicle.To solve these problems,using Abaqus software establish the finite element model of the transmission shaft assembly strength and modal analysis,and through the modal experiment verifies the correctness of the finite element simulation analysis model,point out that the reliability of the analytical method,and through the theoretical calculation verify it,results show that the strength and modal of the transmission shaft assembly are meet the requirements of the vehicle matching design,the method provides a theoretical basis for the transmission shaft static and dynamic design.