The Research On Dynamic Simulation And Life Prediction Of Heavy-duty Transmission Based On FEM

With the growth of our country's national economy in recent years, the heavy-duty truck plays an increasingly important role in some infrastructure industries like energy and raw materials, and also becomes the mainstream products for our country's automotive export industry. Therefore, people attach more attention to the power and reliability of heavy-duty truck. However, heavy-duty dumper mainly operates in some severe conditions like construction site and mine, and users usually have higher requirements for its transmission and load carrying system. As the key component in transmission system of heavy-duty dumper, gearbox's efficiency and reliability are closely linked with the dumper's power and safety. Since the gearbox is very complicated with many components inter-connected with each other and also works in complex conditions, the previous study on its dynamic and fatigue property usually included many simplifications or focused on certain specific components. However, it is evident that the study on the dynamic property and multi-axle fatigue life of the complete gearbox based on full elastomer model is more accurate and can acquire more information, but also with more difficulties. In this paper, the dynamic simulation is conducted for a heavy-duty dumper's gearbox, and the analysis for its dynamic stress, complete modal and dynamic response is also carried out with FE method and taking into consideration of the strength and stiffness of gears, driving shafts, bearings as well as case. Finally, the accuracy of the simulation analysis is validated through the test research on bending stress of gear tooth root, complete modal and fatigue life. This paper focuses on the research of complete gearbox's dynamic property and fatigue life with analysis and tests, and altogether includes 8 chapters:Chapter I summarizes the current status of the research on gearbox's dynamic property and fatigue life prediction in domestic and overseas. The advantages and disadvantages of applying complete gearbox's full elastomer model are presented by making comparison between different types of gearbox models; the advantages and disadvantages of applying multi-axle fatigue analysis are also explained by presenting various methods for predicting gearbox's gear life. The main study subjects, methods and purposes are put forward at the end of this chapter.Chapter II analyzes the dynamic stress of the complete gearbox. The model for the complete gearbox including gears, bearings and case is established on Software Hypermesh to display the real state of the gearbox. In the Abaqus/CAE module, the contact relation is established based on the real assembly relations, and the real load and the constrain are put on the assembly under the situation of the max export moment of the engine. The magnitude, distributing and change rule with time of the dynamic contact pressure and the bend stress on the gear in different gear condition are simulated by Abaqus/Explicit software, and the intensity of the transmission assembly is verified, the groundwork is done for the dynamic property and fatigue life prediction of the transmission assembly.Chapterâ…¢designs the test of the bending stress measure of gear tooth root. Through the all-around research of test method, equipment, measure position, signal collection and disposal, the test-bed is created using torsion machine, the bending stresses of middle axle gear tooth root are measured in different gear condition by resistance strain method, then the test results are analyzed contrastively with the dynamic simulation results in the same place. The preciseness ratio is up 75% percent, and it indicates that the FEA results are correct and credible, have engineering significance, then the method and the results can apply for dynamic performance simulation and fatigue life prediction of the transmission assembly.Chapterâ…£simulations the dynamic performance of the transmission assembly. Firstly, the quality distributing and link rigidity are reflected fully and precisely through the transmission inherent model analysis including main box, subsidiary box, clutch and shift device using Abaqus software, and all the frequencies and vibration of the gear box and axle system, then the gear tooth frequency is analyzed contrastively with the inherent model of the transmission and analyze the influence of them, under the conditions of engine idle speed, the max torque and the max power. Secondly, all kinds of vibration properties of transmission shaft and transmission in time domain are researched under the condition of different transmission speed, including the gear circle acceleration changing with time, gear shaft axle displacement changing with time, shaft circle acceleration changing with time and the box displacement changing with time in X, Y and Z direction. The vibration effect of the transmission is researched all-sided and compositively through these parameters, and analyze the changing rules providing design guidance for the transmission.Chapterâ…¤researches and designs the inherent model test of the transmission. Firstly, the test method is researched, the test project and equipment are confirmed. The Test.lab multicenter test system is used, and the random signal is loaded on the transmission using electromagnetism stimulate device. Secondly, the test data in time domain from acceleration sensors are transformed to the frequency domain. The total frequency response curve is get through the data of frequency domain, then the parameter is identified, and the frequency and vibration of the transmission inherent model is get from frequency response curve. The damp ratio of the models is get from semi power method. Finally, the test results are analyzed contrastively with the FEA results, it indicates that the results of the test and the simulation are highly consistent, the relative error is small, and the FEA result is correct, has engineering value.Chapterâ…¥predicts the fatigue life of the transmission. The max axle fatigue method is used through the result of the dynamic simulation, and the fatigue software-FEMFAT is used, the dynamic load conditions are evaluated using time domain method in one work circle that the gear runs one circle. The influence of gear fatigue life is researched including the gear material, real machining method, heat treatment, stress convergence, part size, stress grads and surface treatment, then the gear fatigue life under different gear condition is predicted using fatigue cumulate theory, the gear fatigue reasons and rules are analyzed.Chapter VII conducts fatigue reliability tests and calculation & analysis of damages for the gearbox. Based on the utilization ratio of each gear, the fatigue reliability tests under max. input torque and the validation tests for gearbox's warranty life are carried out by using propeller shaft test rig to accurately control the input torque, rotate speed and transmission oil temperature of the gearbox. Then the damage on the gears reaching warranty life is calculated by combining the results of gearbox's life prediction, to evaluate the reliability of complete gearbox.Chapter VIII is a summary chapter mainly presenting the main work and achievements as well as study direction in the future.In this paper, the in-depth and detail study on complete gearbox's dynamic property and life prediction is conducted with the methods of combining tests and analysis, which is of significance for improving our country's independent development capabilities of the gearbox, enhancing the gearbox's performance and shortening the gap with the developed countries. It also will play an important role in accelerating the development and prosperity of our country's automotive industry and other related industries, and bring enormous social and economic benefits.