Whole-Period Springback Issue in Metal Forming: Phenomena, Mechanisms, Modeling and Control

Due to increasing demand for intelligent and high-precision manufacturing of metal parts, springback is attracting overwhelming attention in the industrial and academic fields, since it causes vital problems such as increased geometry tolerances in forming accuracy, variabilities in subsequent processing, final assembly and service performance. Springback is the “closing work” in the forming of parts so that it becomes the paradise for almost all the factors throughout the whole period of metal forming to show off their abilities, such as the materials properties, tribological behaviors, processing parameters, deformation history, storage duration of parts, etc. Hence, springback is one of the most challenging issues in high-end manufacturing, and it is vital to understand the springback defects better and achieve more effective control over them. This talk will first introduce the fundamental phenomena and definitions of springback defects in the whole period of metal forming, viz., the transient springback during forming/unloading process and the time-dependent springback during the storage/transportation and service of the parts. Then, the mechanical phenomena of materials upon forming, unloading and post-unloading, such as Bauschinger effect, nonlinear elastic unloading behaviors, time-dependent behaviors as well as their physical mechanisms will be described and discussed. On this basis, some multi-scale constitutive models for description of the above-mentioned rate-independent and rate-dependent mechanical behaviors will be introduced for improving the prediction capability of the whole-period springback. To achieve for the accurate control of springback, the springback minimizing methods and several developed compensation strategies for a typical metal forming process – tube bending will be introduced. Finally, some trends and challenging relating to the big-data-driven prediction/control, real-time and in-process detection and control will be discussed to promote the accurate, robust and intelligent prediction and control of springback in metal forming.