Efficient Prediction of Real-Time Forming Forces in Flexible Stretch Bending

Geir Ringen,Jun Ma,Torgeir Welo

doi:10.25518/esaform21.4040

Abstract

Stretch bending is commonly used in the mass production of profile-like products in many industrial sectors due to its high dimensional accuracy and process capabilities. One of the challenges of conventional stretch bending is low flexibility, however, making it difficult to meet today’s requirements for mass customization. As a countermeasure, a novel flexible rotary stretch bending process was presented (Ma and Welo, 2021), which allows the forming of complex shapes with varying curvatures and angles. However, less knowledge is known about the most fundamental force requirements during forming, which in turn limits the design and development of product and process. In this research, an analytical model is developed for accurate and efficient prediction of real-time forming forces in flexible rotary stretch bending, aiming to enhance the understanding of applied force requirements throughout the process. In this model, the entire kinematically-controlled loading (strain) history is considered to realize real-time monitoring of force. In addition, the elastic-plastic properties of profile, the profile dimensions, the tooling geometries as well as the tool-workpiece friction are comprehensively taken into account to improve the analytical accuracy of forming force predictions. As an explicit solution can be achieved, the analytical model presents high efficiency for quick prediction, which can be used in attempts to adaptively control the process. Based on finite element simulation, the analytical model is validated in the forming of aluminium rectangular, hollow profiles, showing very high accuracy and efficiency for predicting real-time forming forces of both clamp unit and bending die for forming with different pre-stretching levels.

Highlights

Stretch bending is widely used in the fabrication of lightweight profile products in many industrial sectors such as automobile, aerospace, shipbuilding, etc., owing to its high shape accuracy and process capabilities [1,2]
We present a strategy for efficient analytical prediction of real-time forming forces in flexible rotary stretch bending process, aiming to provide an effective means to know and to understand the force knowledge for improved process control
For the purpose of real-time monitoring, the developed analytical model takes the entire kinematically-controlled loading history process into account; for instance, the stretch-bending with an additional pre-stretching applied

Summary

Introduction

Stretch bending is widely used in the fabrication of lightweight profile products in many industrial sectors such as automobile, aerospace, shipbuilding, etc., owing to its high shape accuracy and process capabilities [1,2]. A new concept—flexible rotary stretch bending—was introduced for forming complex shapes including both two-dimensional (2D) and three-dimensional (3D) profile parts [1,4]. In this strategy, the increased flexibility is realized by adding rotational axes combined with a flexible tooling concept utilizing part-specific inserts to enable the manufacture of more complex part configurations with low tool costs. We present a strategy for efficient analytical prediction of real-time forming forces in flexible rotary stretch bending process, aiming to provide an effective means to know and to understand the force knowledge for improved process control. Based on finite element (FE) simulation, the accuracy of the analytical model is validated in the forming of rectangular hollow, aluminium alloy profiles for applying different pre-stretching levels

Flexible Rotary Stretch Bending Process

Analytical Modeling of Real-Time Forming Force

Model Assessment and Discussion

Conclusions and Outlook