Surface low/distortion is one of the most challenging surface deflections that have a great effect on the exterior appearance of automobiles.Most studies on surface distortion/deflection have focused on evaluation and visualization techniques,the research work on correction or prevention of surface low/distortion is limited,and there is no perfect surface low/distortion corrective method that can satisfy the needs of the engineering.A B-spline based geometry morphing algorithm is proposed and then a new program based on UG-NX platform is developed to modify the die face in the surface low/distortion areas.To verify this developed system,the experimental dies that can replicate the surface low/distortion phenomenon successfully is put to use.Five geometric variables are introduced to describe the basic geometry of typical depression features of automotive outer panels.The experimental dies are then designed to reflect various combinations of these geometric parameters.The stamping experiments are conducted on cold rolled grade 5(CR5) sheet steel and various static measurements,such as oil-stoning,laser scanner,etc,are performed to measure and record the surface low/distortions.Three approaches including good bearing,holds in blank and die face morphing that aim to correct low/distortions are tried out and surface low/distortions are observed in the specimen with reverse draw depth of 10 mm.The measurement results show that die morphing is a practical and effective method to correct the surface low/distortion.The correction method proposed can be used to minimize the occurrence of surface low/distortion in die manufacturing,which has certain reference significance to the correction of surface low/distortion.
The problem of quick analysis using exact geometry data was proposed by Hughes et al.and the isogeometric analysis framework was introduced as a solution.In this letter,the exact geometry concept is combined into the quasi-conforming framework and a novel method,i.e.,the exact geometry based quasi-conforming analysis is proposed.In present method the geometry is exactly described by non-uniform rational B-spline bases,while the solution space by traditional polynomial bases.Present method combines the merits of both isogeometric analysis and quasi-conforming finite element method.In this letter Euler-Bernoulli beam problem is solved as an example and the results show that the present method is effective and promising.
