HEXAHEDRAL ELEMENT REFINEMENT FOR THE PREDICTION- CORRECTION ALE FEM SIMULATION OF 3D BULKINGFORMING PROCESS

Based on the characteristics of 3D bulk forming process, the arbitrary Lagrangian-Eulerian (ALE) formulation-based FEM is studied, and a prediction-correction ALE-based FEM is proposed which integrates the advantages of precisely predicting the boundary configuration of the deformed material, and of efficiently avoiding hexahedron remeshing processes. The key idea of the prediction-correction ALE FEM is elaborated in detail. Accordingly, the strategy of mesh quality control, one of the key enabling techniques for the 3D bulk forming process numerical simulation by the prediction-correction ALE FEM is carefully investigated, and the algorithm for hexahedral element refinement is formulated based on the mesh distortion energy.

Finite Element Simulation of Flexible Roll Forming with Supplemented Material Data and the Experimental Verification

Flexible roll forming is a promising manufacturing method for the production of variable cross section products. Considering the large plastic strain in this forming process which is much larger than that of uniform deformation phase of uniaxial tensile test, the widely adopted method of simulating the forming processes with non-supplemented material data from uniaxial tensile test will certainly lead to large error. To reduce this error, the material data is supplemented based on three constitutive models. Then a finite element model of a six passes flexible roll forming process is established based on the supplemented material data and the original material data from the uniaxial tensile test. The flexible roll forming experiment of a B pillar reinforcing plate is carried out to verify the proposed method. Final cross section shapes of the experimental and the simulated results are compared. It is shown that the simulation calculated with supplemented material data based on Swift model agrees well with the experimental results, while the simulation based on original material data could not predict the actual deformation accurately. The results indicate that this material supplement method is reliable and indispensible, and the simulation model can well reflect the real metal forming process. Detailed analysis of the distribution and history of plastic strain at different positions are performed. A new material data supplement method is proposed to tackle the problem which is ignored in other roll forming simulations, and thus the forming process simulation accuracy can be greatly improved.

AB057.Diagnostic information for the recognition of 3D forms in humans

Background:The perception of visual forms is crucial for effective interactions with our environment and for the recognition of visual objects.Thus,to determine the codes underlying this function is a fundamental theoretical objective in the study of the visual forms perception.The vast majority of research in the field is based on a hypothetico-deductive approach.Thus,we first begin by formulating a theory,then we make predictions and finally we conduct experimental tests.After decades of application of this approach,the field remains far from having a consensus as to the traits underlying the representation of visual form.Our goal is to determine,without theoretical a priori or any bias whatsoever,the information underlying the discrimination and recognition of 3D visual forms in normal human adults.Methods:To this end,the adaptive bubble technique developed by Wang et al.[2011]is applied on six 3D synthetic objects under varying views from one test to another.This technique is based on the presentation of stimuli that are partially revealed through Gaussian windows,the location of which is random and the number of which is established in such a way as to maintain an established performance criterion.Gradually,the experimental program uses participants’performance to determine the stimulus regions that participants use to recognize objects.The synthetic objects used in this study are unfamiliar and were generated from a program produced at C.Edward Connor’s lab,Johns Hopkins University School of Medicine.Results:The results were integrated across participants to establish regions of presented stimuli that determine the observers’ability to recognize them-i.e.,diagnostic attributes.The results will be reported in graphical form with a Z scores mapping that will be superimposed on silhouettes of the objects presented during the experiment.This mapping makes it possible to quantify the importance of the different regions on the visible surface of an object for its recognition by the participants.Conclusions:The diagnostic attributes that have been identified are the best described in terms of surface fragments.Some of these fragments are located on or near the outer edge of the stimulus while others are relatively distant.The overlap is minimal between the effective attributes for the different points of view of the same object.This suggests that the traits underlying the recognition of objects are specific to the point of view.In other words,they do not generalize through the points of view.

An approach to form the dome shape by 3D laser forming

Application of a thermal source in non-contact forming of sheet metal is known for some time. Replacement of this thermal source with a laser beam promises the much greater controllability of the process. To date, research focuses on dealing with rectangular plates, and only a few studies are presented for axis-symmetric geometries like circular plates. This study presents the work to get the dish or bowl shape by an initially flat circular plate. Two different scanning strategies circular and radial are attempted to get the desired dish shape. Following the unexpected distortion throughout the plate, a second series of experiments are conducted on a wide range of specimen geometries. An interesting phenomenon is observed. It is suggested that homogeneous dissemination of heat along with combined form of both of the scanning strategies, could have more potential to form dome shape.