Part-mould Contact Gap Analysis And Reforming Design In Digital Inspection For Aircraft Sheet Metal Parts

With these characteristics such as complex shape, wall thickness, easy deformation, the formingaccuracy of sheet metal parts is always low. So those parts rely on detection operation to control theparts quality. The traditional analog transmission detection method for checking sheet metal parts isstill widely used in aeronautical manufacturing of china, nowadays. To improve the accuracy andefficiency in detection of sheet metal parts, digital detection method urgent need to be adopted. Thispaper puts forward a digital detection method through engineering constrained optimization to do thealignment of the measurement data and the theoretical model. Thus it is able to get the part-mouldcontact gap of sheet metal parts in natural condition. By utilizing the finite element analysis softwareto simulate the part-mould contact gap analysis under loading, this paper presents a method ofreforming simulation to those parts with big part-mould contact gap. At the same time a softwaresystem is developed and some key problems about the system are solved. The main research contentsand innovative points are summarized as following:⑴Based on Opencascade software platform and the existing algorithm of computing the closestpoint of the measurement data to the CAD model, a new method and strategy which greatly improvedthe computing speed is proposed. Some necessary preprocessing to measurement data and CADmodel is done in preparation for the follow-up work.⑵According to the characteristics of metal sheet detection, various mathematical models andsolving methods for model registration with constraints are studied, such as mould constraint,positioning constraint and datum planes constraint. The results presented verify the validity andpracticability of those algorithms.⑶On the basis of research on the theory and algorithm, sheet-metal die analysis constraintsystem is developed under Opencascade software platform. Registrations of the measured data and theCAD model with different engineering constraints are realized, and the part-mould contact gap can becomputed in the system.⑷Elastic deformation under the compressive loads is simulated on the sheet metal parts withbad rigidity in the finite element simulation software. After the deformation, the part-mould contactgap and the stress of each node are analyzed, and the reforming simulation to those unqualified partshas also been performed.