Investigation into the numerical model behaviour of Belleville washers in cold roll forming

With the steadily increase in demand for roll formed products due to their application for fields such as automotive, construction, architecture, etc., roll forming companies are challenge with rising customer demands. Companies are struggling to bring a product through from design to manufacture at improved rates, whilst achieving tighter tolerances. The roll forming process may also induce undesirable forming defects such as twist, distortion and straightness problems.Traditionally these issues would be resolved through an empirical approach which heavily relies on the designer's expertise and intuition. This approach can increase undesired development costs due to materials wasted and time delayed. Over the years, numerical simulations have been deployed to try and geometrically validate these defects and ultimately reduce the development phase of a product. The designer has the capability to virtually investigate changes in specific parameters without the risk of expensive tooling costs. The industry partner of this project, Hadley Group, Birmingham, implement Belleville washers into the roll tool configuration. The purpose of these washers is to apply pressure to the strip during roll forming in order to drive material through each forming station. They are also used to adjust the gap between the top and bottom forming rolls, since the incoming material gauge can vary by the nominal tolerance values from coil to coil. For the purpose of this paper, an investigation is carried out focusing on an individual parameter within the finite element analysis (FEA) of the cold roll forming process, i.e. the 'unknown' spring acting on the top roll during the forming process due to the implementation of Belleville washers in the pillar set up. The work explained in this paper shows the eects of the pressure applied to the forming process on the geometric attributes of the section being formed. The outcome will determine the viability of this parameter, which may ultimately require the numerical design methodology of roll formed products to be amended accordingly

Validation of a finite element model of the cold roll forming process on the basis of 3D geometric accuracy

Cold roll forming is an incremental sheet metal forming process used to supply products to numerous industries such as automotive, architecture and construction, etc. In recent years there has been an increase in the demand by customers for high value products, through the forming of high strength materials, or complex profiles. Such demands increase the challenges faced by the tooling designer to bring a successful product through from design to manufacture, on time and within specification. Finite element (FE) simulations are increasingly applied in industry due to the desired advantage of reducing design iterations by allowing the designer to investigate the effects of parameter changes, without the risk of expensive tooling costs. Some successful validation of the numerical modelling of the cold roll forming process can be found in literature, in particular when analysing the strain distribution across the material or comparing the final rolled profile geometry. However, cold roll forming is a continuous process and no one has published work on the measurement of the profile on a pass to pass basis, in particular, the three dimensional geometry of the profile. Experimental trials were carried out to obtain a 3D point cloud model of the top surface of a roll formed section. This investigation aimed to quantify how accurate FE simulation may be in relation to physical data

Industrial validation of strain in cold roll forming of UHSS

Cold roll forming is a highly productive sheet metal forming process capable of producing an exceptional range of profile geometries. Over the last few years customers have increased the demand for high value components, through the specification of complex profiles, tighter tolerances and/or use of high strength materials. In particular, there has been a high interest by the automotive industry in utilising ultra-high strength steels (UHSSs) within the roll forming process. These steels are ideal for the forming of lightweight products, which possess increased material performance when compared to traditional low strength steels. The industry’s attraction towards the roll forming process may be due to the increased deformation capabilities it can provide and due to the formability limitations of UHSS when using traditional stamping or press braking processes. This investigation aimed to determine an appropriate approach to simulating the cold roll forming process using UHSSs for future industrial applications. Currently a large volume of research can be found on the material characterisation and formability of UHSS using traditional processes. While the interest in roll forming is rapidly increasing over time, there remains a large research gap in this field. Hence, a dual phase steel (DP1000) and complex phase steel (CP1000) provided by TATA Steel were analysed using a five pass roll forming assembly to form the following two profiles: (a) V-section; and (b) flat strip with rib feature. The principal strains along the outer radius of each specimen were analysed using a GOM Argus photogrammetry system. A circle grid analysis was the method used to complete these measurements. The strain analyses were compared with corresponding strains along the surface of the finite element (FE) analysis model results. The non-linear FE simulations were carried out using COPRA® FEA RF 2017. Correlations in the results were achieved, setting a foundation for further investigations on the formability of UHSSs