Fundamentals of process design for dimensionally accurate roll forming of asymmetric profile geometries

The aim of the research project is to analyze basic mechanisms and relationships between unintentional deformations and profile defects during roll forming and to derive countermeasures for dimensionally accurate roll forming of asymmetric profiles.

Motivation

Roll forming is a continuous process for producing profiles from cold-rolled starting material. Profiles are mainly used in the transportation and construction industries. Weight reduction plays an important role in increasing the efficiency of means of transport. The use of asymmetrical profiles is therefore an obvious choice, as they can be designed to meet stresses and optimized for weight and can be produced efficiently in large quantities.

Figure 1: elongation and resulting twist of an asymmetrical hat profile, source: G. T. Halmos, Roll forming handbook. Taylor and Francis Group, 2006

Problem and objective

In addition to the desired transverse bending, the sheet metal also undergoes undesirable deformations due to the process, which in turn cause profile defects such as horizontal and vertical curvatures as well as twisting of the profile. These profile errors are particularly strong in the case of asymmetrical profiles. Due to the lack of fundamental knowledge regarding the relationships between deformations and profile errors in asymmetric profiles, the design of roll forming processes is iterative and thus very inefficient. Therefore, the aim of this project is to investigate mechanisms causing profile defects. Based on the knowledge gained, an analytical model for predicting twists in asymmetric profiles will be developed and countermeasures will be derived.

Procedure

Development of an analytical model:

Based on preliminary work and experimental investigations, correlations between undesired deformations and twists are analyzed and described by an analytical model.

Numerical and experimental validation of the model

Derivation and numerical investigation of countermeasures:

Selected strategies for reducing profile defects are numerically investigated and effective countermeasures are derived.

Systematic optimization of longitudinal strains by an optimization algorithm:

By coupling a finite element analysis with an optimization algorithm, the process parameters of the asymmetric roll forming process are optimized so that the occurring profile errors are minimized.

Experimental investigations with optimized parameters

Acknowledgment

The research project is funded by the German Research Foundation (Deutsche Forschungsgemeinschaft DFG).