Roll bending is a manufacturing process in which sheet metal is continuously formed into a round shape with the help of typically three or four rotating rolls. It is used in particular for the production of thick-walled pipes and shells with large volumes, which are used in the maritime sector, in pipeline construction and in the field of renewable energies. In these areas, at the current state of the art, the process is mainly controlled manually. However, the control of the process is of great importance for its efficiency. For example, over-controlling the machine leads to over-bending of the plate and thus often to material waste, whereas under-bending requires additional rolling passes and leads to an increase in production time. To reduce the human influence on the economic efficiency of the process and to objectify the process, research is currently being carried out on the development of automation solutions for roll bending.
Automotive interior components in upper-class vehicles are often made of wood veneer sheets that are subject to a forming process [1]. Due to the anisotropy and inhomogeneity of the material caused by the development of annual rings during the growth of the tree, establishing a stable production process based on trial-and-error forming tests is time-consuming and costly [2]. Hence, numerical methods for simulating the forming process are in high demand to support the development of feasible trim part geometries. The key for reliable process simulations of wood-based materials is the consideration of the variability of material properties.
Hot forming of metal parts is characterized by forming over recrystallisation temperature [1]. For steel, press hardening is a popular production technology for creating hardened parts under hot forming conditions. In the conventional press hardening process, the blank is heated above austenitizing temperature and then transferred to the forming tool. The tools are water cooled and therefore ensure a martensitic transformation of the steel material. The most popular alloy is the boron steel 22MnB5, where a tensile strength of around 1500 MPa is reached through press hardening processes. The latest body-in-white concepts show a broad range of press hardened parts. The underlying forming methods are aiming to create purpose build components through variations of the press hardening process like tailored property processes, the use of tailor-welded or tailor-rolled blanks [2]. In the tailored property process, tailoring of the material properties is realized through the decrease of the cooling rate in a designated area of the part e.g., with a heated tool region. Due to the lower cooling rate, a softer and more ductile state is created in this area with microstructures of ferrite, pearlite and bainite. As a result, from the multiphase microstructure of tailored property parts, shape distortion is more pronounced then in conventional press hardening parts with a fully martensitic microstructure. Increased shape distortion can lead to additional rework cycles in the tool manufacturing.
Roll forming is a continuous bending operation of a long strip of metal sheet. The sheet is gradually formed through pairs of rotating rolls (called stands) until the desired cross-sectional configuration is obtained (see Fig. 1). Although roll forming is a classical method to produce constant cross-sectional profiles, it remains a complex process. Finite element analysis (FEA) can assist the designer to improve this process
Creating a virtual model of a hot plate rolling process involves many challenges. In an attempt to address these, a research project called FINBEAM (“Full Scale Integrated Workability Modelling”) was initiated by Jernkontoret and the Swedish steel industry, financed by the Swedish innovation agency, VINNOVA. The purpose was to bring research institutes, industry and software developers together to reach a common modeling ground for simulation based design of hot working processes for the steel industry in Sweden.
For most sheet metal forming simulations, shell elements that consider a reduced stress state, in particular, assuming a zero transverse normal stress 𝜎33 and neglecting the shear stress components 𝜎13 and 𝜎23 in the yield function, are used. Moreover, certain kinematic assumptions, like cross-sectional material fibers being assumed to remain straight during deformation, are typically applied. However, for some applications, like bending with small radii and thick sheets, this approach is not a workable solution to obtain accurate and reliable results, since the prerequisites that justify the aforementioned kinematic assumptions are not met anymore.
The strive for high energy efficiency through lightweight design, especially for medium- and long haul aircrafts, has significantly increased the use of carbon fiber-reinforced plastics (CFRP) in the aviation industry in recent years [1]. High specific strength, corrosion resistance and improved fatigue life are only a few advantages that qualify CFRPs as structural parts in aircrafts. However, high material, manufacturing and assembly costs are still restricting their use [2]. Highly automated manufacturing processes, which provide a high degree of mounting part integration are needed to lower the part and assembly costs. Structural frames in aircraft fuselages currently make use of a differential design and consist either of aluminum, which provides insufficient specific strength or carbon fiber-reinforced thermosets, which involve long processing times. To overcome these drawbacks, a carbon fiber-reinforced, thermoplastic frame with integrated mounting parts has been developed in order to reduce the complexity of the assembly process. The frame is manufactured in an one-shot process involving tape preform production by automated tape laying (ATL) and a subsequent thermoforming step. ATL allows near-net-shape manufacturing of preforms, which reduces scrap rates to a minimum [3]. The subsequent thermoforming step enables the production of complex 3D-parts with low cycle time [4].
Increasing resource efficiency, for example through the consistent application and further development of lightweight construction concepts, plays an important role in the development of the mobility sector. This requires a steadily increasing use of high-strength aluminum alloys in primary vehicle structures. A suitable and efficient process for joining high-strength aluminum alloys is solid self-piercing riveting (SSPR). A major advantage of this process is the elimination of time-consuming preparatory work such as pre-drilling, deburring and positioning of the components to be joined, as the rivet punches through these during the installation process. Due to the high stresses on the rivet during the installation process and the lack of knowledge on the use of ultra-high-strength aluminum alloys as the rivet material, solid self-piercing rivets (SSP-rivets) made of steel are generally used. However, against the background of recyclability, thermal expansion and corrosion protection, the use of aluminum SSP-rivets would be desirable.
A three-dimensional finite element model for the roll bending of heavy plates using a 4-roll plate bending machine