| Wheel loader is a kind of Engineering Machinery used to load and transport materials, which always worked in the open mine or large-scale construction sites. The working environment is always terrible and the loader itself is very complex.So its structure components can be easily damaged. In the past, especially in the 1950s and 1960s,in our country, the design and strength check of general working device and frame depend on traditional experience and method.That is to say, we simplify the structure to analyse and design according to empirical formula of classic materials mechanics, flexibility mechanics, structural mechanics, then we check the design results with experiments, to a certain extent, this method is scientific and reliable.The advantage of empirical analysis design method lies in its simplicity. At present, this method still plays a role at a certain extent. However, this method also has obvious disadvantages, mainly as follows:1. Because of the blindness of experimental design, the optimization of the working device and frame have no Remarkable breakthroughs. Thus, the strength and stiffness of entire structure can not be solved reasonably.Besides, the design cycle is very long, which make the development of working device and frame very slowly. This make it impossible to adapt to the competition of modernization of the production of goods.2 Traditional empirical design can not give a quantitative analysis on Stress distribution and stiffness distribution of the working device and frame, which make it impossible to avoid the uneven distribution of intensity of the structure. If this, we can not achieve the purpose of optimizing the structure. This thesis will research this problem with modern design method.This thesis is mainly divided into seven chapters:1. PrefaceThis part simply described the development and prospects of china's loader industry; the direction of China's development of wheel loader; the current research situation of working device and the frame of loader and the method ,content and significance of this research.2. The basic theory of the finite element and the multi-body system dynamicIn this part, the theories of the finite element are systematically introduced; the calculating thinking and problem solving steps of the finite element method are introduced in detail; the establishment of the dynamic equation of the multi-rigid body dynamic , the establishment of the kinematics, dynamics ,static analysis equation, and analyses the flexibility bodies model methods and theories are all introduced in detail.3. Modeling and data transmissionThe drawing the 3D model of the working device and frame system with catia software, the research of the modeling method and simplification principle, the creation of the mechanical model of the overall structure, are all preparations for imposing boundaries to the 3D model in simulation. The calculation of the excitation frequency of engine in the idle state and rated speed state are compared with the natural frequency of overall structure calculated in the fifth chapter. Since the model used in ADAMS dynamic simulation and ANSYS static analysis is established by CATIA software while the data used in the transient dynamic analysis is created by dynamic simulation in the ADAMS software, a problem of data transmission is involved.So a detailed description on how to transport them is presented.4. Multi-body system dynamic modeling and simulation on working device and frame of 80 wheel loaderWith the help of interface software, import the 3D model created by CATIA software to ADAMS software to create the rigid model of the working device and frame system. In order to obtain accurate key hinge point force, the flexible bodys of some components with ANSYS were achieved; the coupling method of rigid body and flexible body was researched; the generation methods and importing to ADAMS method of the neutral paper were studied ; Finally the rigid and flexible dynamic model in ADAMS was established, and the dynamic simulation of the working process of the loader under symmetrical loading and asymmetrical loading were achieved.5. Finite element analysis on structural components of 80 wheel loaderIn this part, the model created with CATIA software to ANSYS was imported , the meshing principles and imposing boundaries methods were studied, the analogy method of connection of components and the analogy method of hydraulic cylinder was researched,, finally the finite element overall structure model of working device and frame system were established, and a static structural analysis on overall structure of working device and frame system in several typical working conditions was achieved, the weak component and the weak point on the weak component were found, the structure of the weak component was optimized and improved, and the reasonable structure was gotten. With the loading spectrum of front frame in working process which is obtained from the dynamic simulation in ADAMS, a transient dynamic analysis on the front frame which is optimized and improved was achieved, the stress time curve of the key points on the key component was gotten, the stress state of key point on the key component in the working process was known about. After a modal analysis on the overall structure of the working device and frame system, the natural frequency and natural mode of vibration of overall structure in several working condition were gotten, which will be combined with the natural frequency of the engine calculated in the third chapter to give the basis to optimize and improve the structure of the working device and frame system or vibration-control system and vibration isolation further in the future. Compared with researching single component, researching the overall structure of the working device and frame system is more reasonable than the second one.6. Strength analysis of the pinThe components of the working device and frame system are connected by the pin.In the finite element analysis of the overall structure, because of the complexity of the overall structure, the pin wasn't researched. At last, the strained condition in the loader's working process was studied and a strength analysis was achieved on the pin which is often damaged with the biggest force on the pin from dynamic simulation in the ADAMS.7. ConclusionThis paper described the research content and main conclusion of the paper and presented the research direction in the future. |
