GOALI/Collaborative Research: Improving Incremental Sheet Forming by Ultrasonically Enhanced Material Deformation

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This Grant Opportunity for Academic Liaison with Industry (GOALI) award supports research that contributes to the understanding of ultrasonically-enhanced incremental sheet forming with funding from the Advanced Manufacturing Program in the Civil, Mechanical, and Manufacturing Innovation Division and from the Metals and Metallic Nanostructures Program in the Division of Materials Research. Despite the rapid development of ultra-high strength materials, their readiness to use is limited by limitations in the associated manufacturing processes, especially in the field of sheet metal forming. One promising solution is to temporarily soften the material during the forming process, which can be achieved with the assistance of ultrasonic energy. However, the underlying principles of this softening phenomenon remain elusive. Another benefit of applying ultrasonic energy is improved tribological behavior. Among forming technologies, incremental sheet forming is advantageous in rapid prototyping based on its universal tooling and high flexibility, which meet the increasingly competitive market demands of product updates and customization. However, achieving high geometric accuracy and surface finish quality are challenging. In this aspect, both the ultrasonic softening and modified friction can be harnessed as a unique process and property enhancement solution. The fundamental research of ultrasonic effects on material behavior facilitates effective incorporation of ultrasonic energy into incremental sheet forming, which greatly benefits sheet metal applications in industries such as aerospace, automotive and biomedical. Students involved in the project gain multidisciplinary knowledge and research experiences in materials, mechanical engineering and manufacturing. Students, particularly women and underrepresented minorities, have the opportunity to interact with GOALI partner Boeing engineers.This project aims to advance the fundamental knowledge of ultrasonic softening mechanisms on material deformation behavior. The research is to effectively utilize ultrasonic energy to enhance the incremental sheet forming (ISF) process based on both its bulk softening and modified surface tribological behavior. First, an innovative ultrasonically assisted (UA) micro-tensile testbed, equipped with an in situ high speed optical microscope imaging system, is developed. This enables digital image correlation analysis on the transient inter and intragranular strain field within the ultrasonic vibration cycle. Post mortem multiscale microstructure characterizations are then performed. A dislocation density-based crystal plasticity constitutive material model is developed to reveal the physical principles that are beyond experimental observations. Second, the UA-ISF process is comprehensively studied, in which relationships between the reduced forming force, increased forming accuracy, improved surface finish and the ISF and ultrasonic parameters are established. Finally, a coupled acousto-mechanical process model for UA-ISF is developed, which incorporates the ultrasonically affected material constitutive model developed in the first task. With experimental validations, this model would be utilized to optimize UA-ISF in forming parts with complex free-form geometries.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.