Incremental Sheet Forming (ISF) is emerging as one of the popular dieless forming processes for the small-sized batch production of sheet metal components. However, the parts formed by the ISF process suffer from poor surface finish, geometric inaccuracy, and non-uniform thinning, which leads to poor part characteristics. Hammering, on the other hand, plays an important role in relieving residual stresses, and thus enhances the material properties through a change in grain structure. A few studies based on shot peening, one of the types of hammering operation, revealed that shot peening can produce nanostructure surfaces with different characteristics. This paper introduces a novel process, named the Incremental Sheet Hammering (ISH) process, i.e., integration of incremental sheet forming (ISF) process and hammering to improve the efficacy of the ISF process. Controlled hammering in the ISF process causes an alternating motion at the tool-sheet interface in the local deformation zone. This motion leads to enhanced material flow and subsequent improvement in the surface finish. Typical toolpath strategies are incorporated to impart the tool movement. The mechanics of the process is further explored through explicit-dynamic numerical models and experimental investigations on 1 mm thick AA1050 sheets. The varying wall angle truncated cone (VWATC) and constant wall angle truncated cone (CWATC) test geometries are identified to compare the ISF and ISH processes. The results indicate that the formability is improved in terms of wall angle, forming depth and forming limits. Further, ISF and ISH processes are compared based on the numerical and experimental results. The indicative statistical analysis is performed which shows that the ISH process would lead to an overall 10.99% improvement in the quality of the parts primarily in the surface finish and forming forces.
Origami is to transform a flat square sheet of paper into a finished sculpture through folding and sculpting techniques. It is widely used in many fields such as traditional art, furniture design, solar panels and medical devices. To address the problems of complex configuration of origami, uneasy folding, and the difficult process of establishing origami model, this paper proposes a digital origami representation and design optimization method with DAG (Directed Acyclic Graph) model and directional plane. Firstly, the DAG model is constructed, whose nodes and branches represent the paper states and folding behaviors respectively. Secondly, the constraint relations are defined and established between the point-line-surface geometric elements and the folding behaviors, making it feasible to conform to the paper folding process. Lastly, combined with DAG model, the folding design process, including similar folding, reasonable folding and fewer folding operations, can be optimized to improve the computational efficiency. The method provides a digital theory for origami and is validated and tested by the software Unity3d.
The demand for product customization and flexible manufacturing techniques is growing day by day to meet the rapid changes in customer requirements. The current review presents the developments in the domains of incremental sheet forming (ISF) and deformation machining (DM) strategies to obtain thin monolithic geometries. The study focuses on the literature on room temperature single point incremental forming that can be applied to the DM. Thin structural parts are challenging to produce by machining, because they have inadequate static and dynamic stiffness and low thermal stability. Significant research work on the evolution of diverse theories that emerged to address the fundamental mechanisms of ISF and DM processes has been reported in the literature. This paper presents an outline of the significant process and response parameters, experimental strategies, deformation mechanics and fracture behavior, toolpath generation techniques, and processes' applications. The paper reports the motivation, research directions, existing gaps, and expansion in the domains of DM processes. The paper also outlines the evolution of incremental forming for deformation machining in the context of future critical applications in the domains of biomedical, aerospace, and automotive engineering.
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