Effects Of The Partial Heating Roll Forming Process On HSS And UHSS Profiles

High-and ultra-high-strength steel products are crucial in the automotive and construction industries,but are becoming of much broader significance in the pursuit of excellent structural performances and attractive appearances in almost all branches of engineering.One of the most predominant methods employed to produce various cross-sectional sections and profiles from high-strength steels is by using a cold roll forming process.This manufacturing method is characterized by the gradual bending process at which the desired sections are achieved by feeding a flat sheet of material to successive pairs of rotating rolls.However,due to their limited ductility and demand for large forming tool loads,high-strength steels are challenging to be roll-formed.Consequently,a deficiency such as a shape deviation(springback phenomenon)is observed on the final product.Furthermore,high-strength materials,especially during a roll forming with a tight bend radius,are prone to develop cracks that may grow slowly under quite modest stresses.As a result of the great demands on roll-formed high-strength steel products,manufacturing industries must develop a new and innovative roll-forming method to overcome the challenges of roll-forming high-strength steel profiles and sections with more complex features at a high standard of quality that satisfies end-product users.Partial heating roll forming is a recently proposed method that can be employed efficiently to manufacture high-strength steel sections and profiles with the advantages of greatly enhancing the material's formability and producing highly accurate product geometry.The prominent characteristic of the partial heating roll forming process is to increase the formability of the sheet by partially applying high-intensity heat on the outer surface of the bend areas of the strip/sheet immediately prior to the forming station that large plastic deformations are anticipated.Moreover,the partial heating forming method can reduce the manufacturing process-induced residual stresses,which is one of the primary concerns on roll-formed products.Thus,it is beneficial as it helps ease deformation and reduces forming defects.Despite these clear advantages,the partial heating roll forming technique is currently only utilized in minimal industrial applications.One reason is that the significance of the partial heating roll forming method to overcome the challenges of forming high-strength steel is not yet well understood.Hence,to advance this technology and improve the quality of the products,particularly those made from high-strength steels,more investigations about the effects of the partial heating roll forming method on the quality of roll-formed high-and ultra high-strength steel profiles and sections is needed.The main objective of this thesis is to investigate the effects of the partial heating roll forming process on residual stresses,springback,and ductile fracture during roll forming of high-and ultra high-strength steel profiles and sections.The study begins by comprehensively reviewing available numerical and experimental studies of the roll forming process and challenges of roll forming high strength steels.Subsequently,the finite element software LS-DYNA was utilized to predict effective plastic strain and stress developments and associated residual stresses induced during the partial heating roll forming method.After that,investigations on the effects of the partial heating roll forming method on the springback of U-Channel and predictions of ductile fracture during roll forming hat-channel from DP980 high strength steel have been conducted.Moreover,residual stresses,springback,and ductile fracture comparisons are performed between the cold partial heating roll forming methods.This thesis results provide complete information on stress and strain distributions and residual stress stresses and give a better report on the springback and ductile fracture during the partial heating roll forming process.The results provide better insight into manufacturing high-quality sections and profiles from high-strength steel.It is evident,manufacturing defect-free products will,in turn;undoubtedly lead the roll-forming industry to technological advancements in the manufacturing sector.