Research On The Modeling And Analysis Of A Kind Of Interface Element Method And Its Application On The Design Of Equipment

The interface element(IE) is the finite elements within a certain range of the contact interface between two kinds of continuous structures, or finite/discrete elements between continuous structure and discrete media. The interface element method(IEM) is a numerical simulation method of researching the interaction and the equivalent transition of node property between elements within IE region. This paper puts forward the IEM to simulate and analyze the interaction and the equivalent transition of node property on the interactive interface between continuous mechanical structures and between continuous mechanical structure and discrete media in the working process of mechanical equipment. This research work can be reflected in the following five aspects:First, for a discrete particle assembly should being generated quickly in the preprocessing stage of IEM, an algorithm by considering geometric and physical factors is put forward, this algorithm constructs the moving model of particle packing by making best use of the geometrical and physical properties of discrete element. It can quickly generate circular particle assembly in2D region and sphere particle assembly in3D region. The time to create the granular particles set is linear with the particle number and this process is completed in a comparatively short time with high-density particles set.Second, a IE model on the direct contact interface of the finite/discrete element is proposed for simulating and computing the interaction between continuous structure and discrete media. According to the geometrical touch type between finite and discrete element, the interaction force between discrete element and finite element patch is calculated with linear elastic model. Then the contact force is equivalent to the finite element nodes and the force and displacement on the nodes can be computed, so the force and the change of displacement of discrete media can be visualized ideally, and it is the same case with the force and the strain of continuous structure.Third, aiming at the analysis of stress and strain of discrete media composed of a great number of particles acted by mechanical structure, a IE model is proposed in the overlap region presented by finite and discrete element in one kind of media, The region acted by mechanical structure directly and its near region is presented by discrete element, the far region by finite element with hexahedron, and the regions of these two kind of elements have an overlapping level on their interface. In the overlapping region, first, with the particle-in-cell method, the mass of the discrete particle which lies in the finite element and the force acting on the particle are equivalent to the nodes of the finite elements. Then the velocity and acceleration of the node of the finite element is obtained. Last, the velocity and acceleration are isoparametric interpolated to the discrete element, so the strain and stress on the position of discrete particle can also be obtained. At the same time, the force and strain of the whole region can be solved with the boundary condition of the force of the finite element in the overlapping region.Fourth, in order to solve the problem that the node property can’t transit smoothly on the interface of two or many contact heterogeneous meshes with non-matching nodes, the model and the analysis method of interface element between heterogeneous finite element meshes is put forward, the shape functions of the nodes and the non-matching nodes of2-D heterogeneous quadrilateral element are constructed, the smooth connection of the attributes at the contact face for heterogeneous quadrilateral element is realized, and the method is extended to the analysis of the interface element between the quadrilateral mesh and the triangular mesh. In the meanwhile, the method for the smooth connection of the nodal attributes of the heterogeneous hexahedron elements in3D is studied. For the proposed method, its correctness is verified by one example of heterogeneous interface mesh, and it is applied to the contact analysis of the gears.Fifth, a primary-secondary-mesh method is put forward which focuses on how to integrate the properties of the multiple physical fields on heterogeneous finite element meshes. That is, one of the heterogeneous meshes is taken as primary mesh and the other the secondary one. The properties of the secondary mesh are equivalent to that of the primary mesh by the inverse isoparametric mapping method, thus, all the different fields on different meshes are integrated and visualized on the primary mesh. This method has already been used to integrate and visualize the stress field and the temperature field on the cutters and cutter head of the shield machine, the strongest effect aera of multi-physical fields is got, and some advice on the structural design of the cutters and the cutter head is given by the finite element analysis.