Springback and Longitudinal Bow in Chain-Die Forming U and Hat Channels

Chain-die forming is an emerging sheet metal technique for manufacturing advanced high strength steel (AHSS) products. Springback and longitudinal bow are two of the major shape defects in gradual forming. In this study, the springback and longitudinal bow of AHSS in chain-die forming of hat and U profiles are investigated through experiment and finite element simulation. The disparity of springback along the longitudinal direction and disparate longitudinal bow signifies complex deformation processes of chain-die forming. Finite element simulation of the chain-die forming process gives an insight into the formation of non-uniform springback and longitudinal bow. The gradual forming process by one die block after another causes bending and reverse-bending deformation in the web area and the redundant deformation of the sheet metal, which further leads to non-uniform bending moment and accumulated stresses along the longitudinal direction. At the same time, the redundant deformation will also result in the longitudinal strain on the edge, while the downhill deformation decreases the maximum longitudinal strain at the edge and introduces the longitudinal strain on the web. The different non-uniform longitudinal strain distribution along the transversal direction causes disparate longitudinal bow behaviors for chain-die formed AHSS hat and U profiles, downward bowing and upward bowing respectively. By the established model, the disparate springback and longitudinal bow behavior can be determined, which also contribute to the process design for chain-die formed AHSS products.

Efficient Qualification Strategy of New Steel Alloys for Laser Powder Bed Fusion

The requirements regarding the materials in use are steadily increasing in the AM market. As part of a GER-CAN research project (HiPTSLAM), the development of high-performance tool steels for AM is a promising topic regarding the acceptance of LPBF technology for functionally optimized die, forming and cutting tools. Therefore, a holistic development process to efficiently qualify new materials is introduced and its advantages are shown based on a case study with a maraging tool steel. The chemical composition of the steel was particularly developed for the use in the LPBF process to achieve beneficial performance properties. In the case study, effects of the LPBF parameters are evaluated on the material properties. Based on initial microstructure analysis, a promising set of parameters is used to build samples for heat treatment studies and mechanical characterization. By means of further investigations on the process interfaces, it will be possible to optimize the interaction of the whole LPBF process chain to increase the number of qualified materials with better performance properties.

Design of Multi-Stage Roll Die Forming Process for Drum Clutch with Artificial Neural Network

The multi-stage roll die forming (RDF) process is a plastic forming process that can manufacture a transmission part with a complex shape, such as a drum clutch, by using a die set with rotational rolls. However, it is difficult to satisfy dimensional accuracy because of spring-back and unfilling. The purpose of this study is to design a multi-stage RDF process for the manufacturing of a drum clutch to improve dimensional accuracy using an artificial neural network (ANN). Finite element (FE) simulation of the multi-stage RDF process is performed to predict the dimensional accuracy according to various clearances for each stage. Moreover, the ANN is used to determine the relationship between the clearance and dimensional accuracy of the drum clutch to reduce the number of FE simulation. The results of the FE simulation and ANN are used to determine the optimal clearance for each stage of the RDF process. Finally, the drum clutch is fabricated using the determined conditions. The experimental results are in good agreement with the results of FE simulation from the aspect of outer diameter, inner diameter, thickness of outer tooth, thickness of inner tooth, and face thickness of tooth.