Experimental characterization, analytical and numerical investigations of metal/polymer/metal sandwich composites – Part 1: Deep drawing

Al/PP/Al laminated sheets have shown promising properties for different applications from aeronautics to construction. In this paper, an easy and fast springback prediction of Al3105/polypropylene/...

Simplified springback prediction in Al/PP/Al sandwich air bending

Analysis of the forming behaviour of in-situ drawn sandwich sheets

Dry friction under pressure variation of PACVD TiN surfaces on selected automotive sheet metals for the application in unlubricated metal forming

Rotary-draw-bending using tools with reduced geometries

Modelling and Optimization of Lightweight-Sandwich-Sheets with an Adhesive Interlayer for the Forming Process Die Bending

This study presents that finite element (FE) simulations of rotary draw bending are improved by taking into account the stiffnesses of the machine axes. The results show the influence of the axis stiffnesses of the bend die, the wiper die, the pressure die and the mandrel on the formation of wrinkles at the inner tube bend. For this purpose the axis stiffnesses are varied in FE-simulations and wrinkle evaluation factors of the final components are determined and compared. Low axis stiffnesses correspond to large axial displacements when force is applied and cause greater wrinkle formation. In addition, practical tests are carried out on the machine to measure the axis displacements and associated forces. The resulting axis stiffnesses are entered into the FE simulation. The final geometry of the bending component of the FE simulation is compared with the geometry of a component produced in a practical test. The consideration of the axis stiffness in the calculation in contrast to ideally stiff axes provides wrinkle heights that are closer to the wrinkle heights in the practical test. The knowledge gained improves the prediction of the component quality and allows the evaluation of axis displacements measured on bending machines. The overall aim of the project is to react to machine-specific axis stiffnesses in the form of process control.

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Influence of the stiffness of machine axes on the formation of wrinkles during rotary draw bending

During the bending of tubes, specific geometric deviations from the desired shape geometry occur. These deformations comprise cross-sectional deformation, wall-thinning of the outer arc and wall-thickening of the inner arc. During the bending of parts with small bend factors, geometric deviations on the inner arc in form of waves and wrinkles may arise as other typical quality criteria. A quantitative evaluation of those deviations has yet to be defined. Currently, only an instruction for measuring the height of the wrinkles at the inner arc according to DIN EN 13480-4 is known. In this standard, only the two highest wrinkles and the valley in between are included. The characteristics of the wrinkle, especially the flank angle and the rise of deformation are disregarded, although they are responsible for the failure of the bent part. Tool damages can also occur. A development of an evaluation factor to assess deformations in the bow area for bent parts is presented in this paper. In addition, it will be possible to quantify geometric deviations in the bow area. By using the newly developed evaluation factor for geometrical deformations in the bow area, the determination of the quality of the bent part should become more reproducible.

Christopher Heftrich

Papers

Modelling and Optimization of Lightweight-Sandwich-Sheets with an Adhesive Interlayer for the Forming Process Die Bending

Rotary-draw-bending using tools with reduced geometries

Influence of the stiffness of machine axes on the formation of wrinkles during rotary draw bending

A New Approach for Quantitative Evaluation of Bending Components