Analysis Based On The Elastic Contact Of Bolted Structure Of Frame

Bolted structure connection is an important form of the metal joint, it can connect components closely, this paper especially analyzes the structure of the mechanical properties of bolts and bolts connecting structure on mechanical properties, to explore a CAE modeling structured methods of bolt connection.the traditional method of modeling the structure will be simplified into cylindrical beam elements, beam elements of the radius are same as the radius of actual bolts, the ends of the beam elements and steel panels are connected by rigid elements, rigid unit connections generally take to screw in the center of the circle bar on the center line, and is used to simulate the bolt connections between the relative positions without considering other factors such as elastic contact and bolt preload, In this paper, we take the bolt preload and elastic contact into account, bolt preload generates during the tensile deformation of the bolts, Preload compresses different panels to play the role of connection, if the preload makes too much, the force of the bolt to withstand will be relatively large, the use of life is difficult to be protected, if the preload is too small, the pressure between the components surface is not enough to prevent the two part to slip, the connection is poor, so the size of preload have certain requirements. the panels to be joint are the surface and the surface contact, the structure is connected by interaction between the panels caused by bolt preload, squeeze pressure between the surfaces generates the main source of friction. Accurate calculation take the preload and elastic contact into account, the gap between adjacent nodes elements are simulated by elastic contact between the surfaces.Since the study of bolt connection structure of the CAE method need to repeatedly adjust the model, the frame with Bolt is complex structure, the adjustment of the model increases the difficulty and time. In this paper we built a typical structure of the small model to study the elastic contact analysis based on bolted connections, we explore the performance of the bolted region through a small model, in this way we can reduce workload and increase research efficiency. Investigation bolted structure in three typical load cases such as tensile, bending, shear stress under conditions, to fully research the structure mechanical properties. to compare with original model method of bolt connection structure, elastic contact modeling method is reasonable, so we can find a more accurate method of modeling. To analysis Local model structure on the fatigue life, we analysis elastic contact based on structural modeling of bolted connections in durability performance, stress in an analysis of the results need to be imported to calculate the fatigue life of bolted model structures.so we get the stress information of bolted structure model, and create the S-N curve of the material. Then add the load curve to the time history serious to get the stress information of the elements, then we statistic the time history in rain-fall cycle to calculate the fatigue life of the structures. Compare the different between new and old structural modeling method in the fatigue life analysis, and to study the fatigue characteristics of bolted structures.Firstly, regardless of bolt force and the contacts between the plates, then we create the finite element model of frame structure, two typical conditions are taken into account in the analysis of strength, that is bending load case and reverse load case, Frame bending condition is to investigate the driving road in the rugged road, the load is born by the structure of the main bending deformation, so called bending conditions. To meet the requirements of comfort the frame must have a certain frame bending stiffness, so that the hard stiffness can reduce the vibration in the road, it makes the vehicle more stable. Reverse the condition is used to study the frame of a wheel in the potholes of the road obstacle vacant, we create three constraints, force is loaded on the center of the vacant wheel, scale factor is added on the load to ensure the reliability. Compare the elastic contact model with general model to explore a more precise analysis of the frame structure. Make a rapid assessment of Bolted frame structure on the fatigue life, taking the linear superposition of stress events on the risk of fatigue life under a comprehensive analysis of the durability of the frame structure and effective method.The frame structure with elastic contact modeling relatively large the amount of work, it needs to be adjusted to create a neat gap elements, through copying and translating the elements of contact surface to align the grid nodes. Study without considering the elastic contact to change the cross-section beam element radius to enhance the carrying capacity of bolt structure, so that after the adjustment bolt connecting plate of the stress distribution in cross-section becomes similar to the model with the elastic contact. To reduce the workload of elastic contact analysis we make bolt structure into modules, the bolted super elements structure are created between the elastic contact surfaces.beam elements are applicated to simulate the steel tube, shell elements are used to simulate the contact areas, thus greatly reducing the size of the model, through the super-unit the beam in the form of the frame unit and shell elements combine to reduce both the size of the model, but also an important part of the calculation to ensure accuracy. Combining the beam and shell elements with the super element, both to reduce the size of the model and increase the Efficiency.Through the research of the simplified model, we increase the precise of the analysis and reduce the workload, through efficient CAE analysis method to help the designers to increase the performance of the product in order to achieve the purpose of concurrent engineering.