Effects of Part Geometry on Spring-Back/Spring-Go Feature in U-Bending Process

Abstract

The U-bending process is a common sheet-metal forming process widely employed to fabricate sheet parts like channels, beams, and frames of various sizes applied in almost all industrial fields. In recent years, the precision requirements are increased on the U-bent parts. To achieve these requirements, in this study, the effects of part geometry on the spring-back/spring-go feature including work piece length, U-channel width, punch and die radii, and work piece thickness, were investigated by using the finite element method (FEM) and laboratory experiments. The FEM simulation results clearly revealed the influence of part geometry on spring-back/spring-go feature via the changes of stress distribution analyses on the bending allowance zone, the bottom of bent part, and the U-leg of bent part. Specifically, the part geometry affected on the bending characteristic on the bending allowance zone, as well as it affected on the spring-back feature. In addition, the part geometry also affected on the formation of reversed bending characteristic on the bottom and U-leg of bent parts, as well as it affected on the spring-go feature. The bending angle could be achieved by compensating these bending and reversed bending characteristics. Therefore, to meet the required bending angle, the suitable design of part geometry was strongly considered to maintain the balancing of the bending and reversed bending characteristics. The laboratory experiments were carried out to validate the accuracy of the FEM simulation results. The FEM simulation results showed good agreement with the experimental results with reference to the bending angle and bending force.

Comparison of spring-back characteristics in symmetrical and asymmetrical U-bending processes

“…The characteristics of the stress distribution analysis corresponded well with bending theory and the literature. 5,6 It was observed that the reversed bending stresses were already generated in the vertical sections in the symmetrical U-shape, whereas the reversed were not yet generated in the asymmetrical U-shape. As the bending stroke was further increased, the workpiece was further bent and made increased contact with the punch which resulted in the bending stresses being generated, as well as the reversed bending stresses, as depicted in zones A, B, and C in Fig.…”

“…These characteristics of the stress distribution analysis again corresponded well with the bending theory and the literature. 5,6 Before the unloading phase, as shown in Fig. 3(a-4), (b-4), and (c-4), the effects of the leaning towards the small angle and small tool radius sides resulted in bending stresses that were shifted towards the small angle and small tool radius sides as illustrated in Fig.…”

“…This manner of the stress distribution generated in the corner radius corresponded well with the bending theory and the literature. [4][5][6] In addition, the reversed bending stresses slightly decreased and increased in the side of the smaller and the larger tool radius, respectively. These features resulted in changes in the spring-back characteristics.…”

“…5 investigated the symmetrical closed U-bending process. The asymmetrical closed U-bending process has been rarely investigated; 6 therefore, there is little information available to design suitable bending dies. This lack of information, with regards to green manufacturing, results in an increase of energy consumption and the number of waste parts, because of the difficulty in suitable die and process designs, which are necessary to control the spring-back characteristics.…”

An Analysis of Spring-back and Spring-go on Variation of V-Dies Bending Angle Using Galvanized SGCC Steel Sheet

“…Beberapa penelitian tentang proses bending dan fenomena spring-back material pada proses metal forming telah dilakukan oleh [6] [8], [9], [10], dan [11]. Penelitian tentang fenomena pegas kembali dilakukan oleh [6] dengan menganalisis elemen struktural kendaraan dengan baja berkekuatan tinggi, penerapan material ini secara signifikan mengurangi massa kendaraan sambil mempertahankan kekuatan dan daya tahannya yang tinggi.…”