Research On Simulation Analysis Methods Of Auto-body Panel Forming Defects

With the development of economy and technology, people’s needs and demands of the vehicle are increasing continously. Environmental protection, economic benefits, and high efficiency has become the main pursuit of vehicle development. Since stamping parts occupy a large proportion in automotive parts, the development cycle of auto body panels has a strong influence on the development cycle of vehicle. In the early development of stamping tools, a large number of repeated feasibility analysis consumes a lot of development time, mainly due to the large size, thin material, complex shape, and multi stamping variables, which brings about difficulties to the formability control, a lot of trial and error in practical engineering is required, as well as rich engineering experience.Under the above background, in order to reduce costs and improve efficiency of development, six kinds of forming defects (including rupture, edge split, wrinkling, shape change, low stretch, and surface soft) of auto-body panels have been investigated in this paper, based on the Universal Formability Technology (UFT).Firstly, the generation mechanisms of six kinds of forming defects were summarized, and the UFT was introduced systematically. Secondly, the key methods of simulation analysis for stamping defects were introduced in detail, including analysis of deformation zone, evaluation of the formability, analysis of strain, adjustment of metal flow, and interference analysis method for adjusting metal flow. Among them, deformation zone analysis aims to get the states of stress by mastering the geometric features of defect regions; in evaluation of formability, to assess the severity of forming defects accurately, multi stamping variables are considered to calculate formability indexes, such as size of deformation zone, characteristic of strain path, bending process module, the work properties of defect regions (inner or outer panel, surface level, whether assembly area or welding area, etc.), and so on, in addition, as a reference, application of engineering practice also be considered; strain analysis is used to understand stress states in forming process, to find the cause of defects, by analyzing plane strain path, equivalent strain path, and strain distribution on reference curve; metal flow adjustment and interference analysis mainly serve for elimination of defects, by providing reference direction and amount of the metal flow adjustment, and assisting for adjustment plans of process, and controlling the material flow during forming process. Thirdly, with the help of finite element software development platform COMX, the above simulation analysis methods are realized by a simulation analysis system KMAS|SFT for stamping defects, the system contains six models for six kinds of defects, auxiliary analysis tool, experiment database, expert experience database for reuse, and optimization of process parameters for improving the efficiency of simulation analysis. Lastly, some typical forming defects of auto-body panels were analyzed by using KMAS|SFT, such as rupture and wrinling on a fender, split on edge of an auto-body side outer, warpage of a roof, etc., and the results show that the methodology is effective and feasible, which can improve the simulation analysis efficiency of stamping defects.