Analysis Of Mechanical Characteristics And Performance On4WD Vehicle Transfer Case

With the development of4WD vehicle technology,4WD transmission, which wasfirst designed as AWD, has developed to be intellective4WD nowadays. Based on thecollected vehicle information, TOD (Torque on Demand) determines whether the vehicleskids or is steered in order to show controllable torque through the transfer case, therebyovercoming the complicated road conditions and achieving a reasonable transformationbetween2WD and4WD. Therefore, TOD is considered as the most advanced4WDtechnology.Firstly, this thesis makes a detailed introduction of the important role and workingprinciple of transfer case on4WD vehicles and its present design level; cautions indisassembling and maintenance are put forward according to the design of two-axistransfer case. In terms of an overall design, the thesis takes secondary transmissionmodel established under Romax as the subject of the study, and, based on thetransmission system established under Romax, carries out a theoretical calculation of thebearing load to get the stress of transfer case shell bearings in different driving conditions,which provides theoretical basis for the analysis of transfer case shell stress.Secondly, this thesis introduces the first to the fourth strength theories related to thefinite element, explores the relationship between the four strength theories and thecorresponding images in finite element post-processing, and summarizes the range of thefour strength theories, which is of great importance to the understanding of the finiteelement analysis results. Besides, the relationships among local geometrical mutationsand shapes, the internal force load distribution, and the failure strength, density, choiceand stress analysis of materials are also explored.Meanwhile, based on finite element analysis methods, finite element meshes aredivided in Hypermesh as processing software which pretreats finite element analysis onthe transfer case. After a satisfactory inspection of the mesh quality, it is then importedinto ANSYS/Workbench to have loading and constraints so as to carry out finite element analysis. And the finite element model is imported into Abaqus, in which loading andconstraints are carried out and the comparison of the computed stress and stain is made toverify the consistency of the finite element model analysis; when the stress and strainmeets the design requirements, the important influence of the average stress on thefatigue life which is described in the fatigue theory should be grasped, then the thesisdeals with the introduction of the nominal stress method, the fatigue life analysis of thetransfer case shell, and the analysis of the evaluation index such as the safety factor ofthe designed transfer case; since bearings serve as important components to support thetransfer case shell and make mechanical transmissions, the nonlinear finite elementanalysis of the selected bearings is made, and, on the basis of a good command of contactset principles, contact sets are made on rollers and the inner and outer rings of bearing tomake non-linear finite element analysis, so related information such as Hertz contactroller and stress and strain of the inner and outer rings is gained. Besides, it is stated thatthe design of the shell and matching of bearings comply with the design requirements.Through an accurate calculation of the bearing load on the transfer case shell and bythe application of the finite element simulation means, this thesis completes the finiteelement analysis on a complicated TOD shell early in the product design process, whichshortens the design and development time, and saves the design and development cost.From a theoretical calculation to the simulation based on the finite element method, andfrom an overall perspective, this thesis forms statics studies on the transfer case shell, andresearch approaches and technical processes of life prediction on shells, which provides astrong technical support to the design and development of the transfer case and offers anew method to predicate the fatigue life of the transfer case system.