| Rubber mounts are widely used in medium and heavy commercial vehicles' powertrain mount systems for their low cost and high load capacity, playing the important role of anti-vibration and position-limiter between the powertrain and chassis (body). For the work environment of medium and heavy commercial vehicle is poor, and their load are very big, premature failure of of rubber mounts often occure. The performances are cracking of rubber and rubber shedding from metal. Those seriously affect the reliability and durability of the vehicle, as well as the economic interests of users.The static and dynamic stiffness performance and life of rubber mount affected by many factors, whose mechanism is very complex, and now most of the rubber mount manufacturers adopt reversal design, that is design depend on experience. The design and development processes of top-down design are lack. The top-down design and development processes based on the static and dynamic stiffness characteristics and fatigue life of rubber mount are urgent needed. Although metal fatigue life prediction methods and theories have been developed maturely. While in terms of rubber damper design, mature method and theory are lack. Especially with respect to the fatigue life prediction of rubber damper. This dissertation take the front and rear DEUTZ powertrain mount of a heavy commercial vehicle as research object, studying the simulation of powertrain mount system vibration isolation performance and its fatigue life prediction. The content consists of seven parts:Chapter I summarizes current research status on finite element simulation and fatigue life prediction of rubber vibration isolator in domestic and overseas. Review The application and development of finite element method in the area of rubber vibration isolator as the most effective means of modern design are reviewed. The summary focused on the finite element modeling of vehicle powertrain rubber mount, static and dynamic stiffness simulation, fatigue life prediction, especially the different research methods adopted in the rubber fatigue and damage analyses.Chapterâ…¡establishes the finite element models of powertrain rubber mounts and carries through the compute. Three-dimensional geometric models is builted in CAD software. Then they are imported into finite element pre-processing software for meshing. The FE models are imported into nonlinear finite element software ABAQUS. Constitutive behavior of the rubber mount obtained by fitting test data into stain potential energy. The decreasing load capacity of rubber material due to the progressive destruction under cyclic loading is simulated by the mechanical property of mullins effect and permanent set. The static and dynamic finite element analysis of rubber mount are conducted respectively. Through comparing with the static and dynamic stiffness test data of powertrain mounts, the finite element models are verified accurate, laying a foundation for the fatigue life prediction of rubber mounts.Chapterâ…¢studies the fatigue crack initiation life of engine mounts. Taking maximum principal strain as a medium, the life of powertrain mounting components are linked to that of the standard 3D dumbbell specimen. Then the components' fatigue life under uniaxial loading are predicted. And fatigue life prediction formulae are curve fitted being indicated by load. In fact there are not only uniaxial load on the engine mounts, but impacts and vibrations in all directions. Therefore the maximum principal stress is used for the medium destruction variable of powertrain mounts' multi-axle fatigue life. The powertrain mounts' fatigue life under multiaxial loading are predicted and curve fitted expressed by the multi-axis load-fatigue life relationships. For the front mount, three-dimensional load-life fatigue diagram is made, taking the vertical and radial load as x and y value, the mount life as the z value. While for the rear mount, multi-dimensional load-life fatigue diagram is made:loads in x, y and z directions are presented by value on x, y and z axles, value of fatigue life is presented by regions of different colors. Three-dimensional fatigue life surface and the multi-dimensional cloud chart proposed here can make it effective to reveal relationships between multi-axis load and fatigue life.of powertrain mounts.Chapter IV analyzes fatigue crack growth of powertrain mounts with fracture mechanics. The failure form of front and rear DEUTZ powertrain mounts is fatigue crack growth till fracture. According to the actual failure phenomena the location and angle of cracks on mounts is determined, and the conventional fracture FE model is established with meshes converging at the crack line to simulate the failure form of mount. To analyze the mount's cracking near rubber-metal interface, the cohesive elements are made use of to simulate the complex junction layer of the rubber-metal interface, simulating the fatigue crack growth near the rubber-metal sulfide interface of engine mounts. The latest extended finite element technology is adopted to simulate the initiation and propagation of a discrete crack along an arbitrary, solution-dependent path without the requirement of remeshing in the bulk materials, meeting the needs of forecasting the appearance occasion, location and direction of cracks.Chapter V carries out the analysis with the factors that influence the performances of powertrain mounts. The stiffness and fatigue performances of rubber mounts are effected by various of complex factors. Contraposing different stages of analysis, the methods such as orthogonal design, regression curve fitting, analysis of variance and correlation analysis are combined organically to form a comprehensive analysis system of factors. Composite effects to the static and dynamic stiffness and fatigue life of engine mount costed by factors such as preload, configuration, hardness and other factors are analyzed, and a series of conclusions are obtained:hardness is of great impact for both front and rear mount, which can be adjusted easily, while its impact on the dynamic stiffness is not significant, suitable for the design of anti-fatigue performence; preload is also vnaanlbzon; the cone angle of front mount is of bigger impact, while the bottom diameter shows a lack of sensitivity; increasing the lateral size of rear mount would enhance its fatigue life and increase its vertical stiffness.The rubber vibration isolator design based on finite element simulation is still in the early stage of development, Chapter VI takes the DEUTZ powertrain rubber mounts as an research example, proposes the static and dynamic stiffness and fatigue life that DEUTZ powertrain rubber mounts should possess.Chapterâ…¦conducts experiment research on the powertrain mounts. The static and dynamic stiffness experiments, as well as fatigue bench test of powertrain mount is carried out. And the vibration transmissibility test of real vehicle powertrain rubber mounts are carried out. The experimental results demonstrate that the finite element model of engine mounts established and the analysis methods of this dissertation are veracity.Chapterâ…§is a summary of the main work and achievements, as well as the prospects of future research.
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