Research About Ship CAE Preprocessing Based On NX

With the rapid development of computer technology,the finite element method has been applied more and more widely from the strength analysis of structural engineering to the fields of science and technology.And with the gradual improvement of numerical methods and the rapid development of computer operation,the time spent on the whole CAE system to solve the calculation is less and less.However,the data preparation and calculation results display spend more and more time,the pretreatment takes up more than 50~80% of the time during the whole analysis process.In this paper,with the design of ship structure as the object of the research,and the pre-processing module design,the key algorithm and the practical application in CAE system are systematically studied.The main contents are as follows:(1)The ship structure has the characteristics of complex surface and numerous structures.In view of this feature,this paper introduces the design and implementation of the ship CAE pre-processing based on NX platform.It mainly introduces the difference with the general ship CAE software preprocessing and innovation point,including detailed process of preprocessing module,definition of model(simplified model,polyhedral model and discrete model)and data management of module.(2)In the general CAE system,Model simplified processing is simplified by common data interface,which will import CAD model to CAE software.Then,the model is simplified by CAE tools,but the capability of CAE software modeling is relatively weak,so can only make simple processing,and the ship's structure is more complex,simplified operation can't meet the requirements of CAE software,so this paper proposers simplified model and polyhedron model.Simplified model is made by copying design model in NX B-Rep modeling environment,then carry out a series of model segmentation and simplify based on ship industry,such as finite element modeling for more tanks.First of all,it need to cut model,the vessel can be divided into multiple segment according to the flank,and then generate polyhedron model and mesh model.Polyhedral model can realize the transition between CAD model and the the mesh model,but because of the big difference between CAD and CAE,it cannot directly convert the CAD data to CAE data.Thus,the CAD model is converted into polyhedron model firstly,in a polyhedron model,we make some non-manifold geometric cleaning.and then meshing based on polyhedron model,realize the seamless integration of CAD/CAE,polyhedron model creates a correlation between the CAD model and the mesh,and modifying CAD model will automatically update the mesh.(3)The ship structure is complex,so we need to use a data structure to manage the whole ship model.Based on the NX platform,the ship pre-processing system uses a tree data structure to classify and manage the geometry of the whole model,which facilitates the operation of ship personnel.For the structure intersecting on the spatial location,we cut each other in the simplified model,store the information of matching edges,and then stitch the matching edges on the polyhedron model.(4)Finally,a 279 m bulk carrier is taken as an example to complete the transformation from the design model to the mesh model,which proves the feasibility of the scheme and the applicability of the system.