One of the first questions to consider when designing a new roll forming line is the number of forming steps required to produce a profile. The number depends on material properties, the cross-section geometry and tolerance requirements, but the tool designer also wants to minimize the number of forming steps in order to reduce the investment costs for the customer. There are several computer aided engineering systems on the market that can assist the tool designing process. These include more or less simple formulas to predict deformation during forming as well as the number of forming steps. In recent years it has also become possible to use finite element analysis for the design of roll forming processes. The objective of the work presented in this thesis was to answer the following question: How should the roll forming process be designed for complex geometries and/or high strength steels? The work approach included both literature studies as well as experimental and modelling work. The experimental part gave direct insight into the process and was also used to develop and validate models of the process. Starting with simple geometries and standard steels the work progressed to more complex profiles of variable depth and width, made of high strength steels. The results obtained are published in seven papers appended to this thesis. In the first study (see paper 1) a finite element model for investigating the roll forming of a U-profile was built. It was used to investigate the effect on longitudinal peak membrane strain and deformation length when yield strength increases, see paper 2 and 3. The simulations showed that the peak strain decreases whereas the deformation length increases when the yield strength increases. The studies described in paper 4 and 5 measured roll load, roll torque, springback and strain history during the U-profile forming process. The measurement results were used to validate the finite element model in paper 1. The results presented in paper 6 shows that the formability of stainless steel (e.g. AISI 301), that in the cold rolled condition has a large martensite fraction, can be substantially increased by heating the bending zone. The heated area will then become austenitic and ductile before the roll forming. Thanks to the phenomenon of strain induced martensite formation, the steel will regain the martensite content and its strength during the subsequent plastic straining. Finally, a new tooling concept for profiles with variable cross-sections is presented in paper 7. The overall conclusions of the present work are that today, it is possible to successfully develop profiles of complex geometries (3D roll forming) in high strength steels and that finite element simulation can be a useful tool in the design of the roll forming process.

<p>A finite element model has been developed to simulate the forming of a channel section profile with the roll forming method. The model has been optimized to experimental results with respect to strains at the edge of the sheet and spring back of the sides of the profile. Finite element models with a coarse mesh have been compared to models with a finer mesh. The models with to fine mesh become instable and a model with a rather coarse mesh was finally chosen.</p><p>Both the models with shell elements and the models with solid elements have been used in the simulations. The simulations with shell elements gave very good results both for the geometry shape and the strains at the edge of the sheet. The reaction forces at the tools found in the simulations was only half of the reaction forces fond in the experiments.</p><p>The simulations with the solid element model showed very good results for the reaction forces while the geometry shape of the sheet was really bad. The spring back was much larger in the simulations than in the experiments.</p><p>The shell element model was chosen because of the excessive spring back with the solid element model. The spring back of the sides of the sheet differs only a few percent between the simulation and the experiment results when using the shell element model. The reaction forces at the tools in the simulation are only half of the reaction forces measured in the experiments but the results from the simulations are linearly proportional to the results in the experiments. The model that finally was chosen describe both the spring back and the strains at the edge of the sheet very well. Like in the experiments there were no signs of wrinkles at the sheet in any of the simulations.</p>

A finite element model has been developed to simulate the forming of a channel section profile with the roll forming method. The model has been optimized to experimental results with respect to strains at the edge of the sheet and spring back of the sides of the profile. Finite element models with a coarse mesh have been compared to models with a finer mesh. The models with to fine mesh become instable and a model with a rather coarse mesh was finally chosen. Both the models with shell elements and the models with solid elements have been used in the simulations. The simulations with shell elements gave very good results both for the geometry shape and the strains at the edge of the sheet. The reaction forces at the tools found in the simulations was only half of the reaction forces fond in the experiments. The simulations with the solid element model showed very good results for the reaction forces while the geometry shape of the sheet was really bad. The spring back was much larger in the simulations than in the experiments. The shell element model was chosen because of the excessive spring back with the solid element model. The spring back of the sides of the sheet differs only a few percent between the simulation and the experiment results when using the shell element model. The reaction forces at the tools in the simulation are only half of the reaction forces measured in the experiments but the results from the simulations are linearly proportional to the results in the experiments. The model that finally was chosen describe both the spring back and the strains at the edge of the sheet very well. Like in the experiments there were no signs of wrinkles at the sheet in any of the simulations.

The main objective of this dissertation is an operational planning optimization with greater concentration on customers and their requirements, which are supposed to be fulfilled in time, costs and quality. The aim is an operative management analysis of production process. In terms of this analysis, deficiencies of the present condition will emerge, which should be eliminated by the solution. The analysis will be based on production system, economy of production process and product. At the deficiencies, which result from the analysis, some variants how to solve the problem will be suggested and finally, the most suitable variant will be chosen. Bending and its contemporary method of solving seems to be the most serious deficiency. Therefore, the panel bender was chosen as the most suitable solution because it is usually the most convenient compensation.