Knowledge Bank

Drawing is a near net-shape manufacturing method used to form sheet metal into complex shapes by applying holding force on sheet metal blanks while a punch draws the workpiece into or through a forming die. This method has many practical applications in industries including aerospace, automotive, and consumer goods. The material explored, commercially pure niobium, is commonly drawn to form superconducting radio frequency cavities for linear accelerators. The purpose of this research is to establish the drawing envelope of a commercially pure niobium (referred to as niobium) sheet under constant blank holding force (BHF) experimentally by adjusting the process parameters of cylindrical cup-drawing. The drawing envelope determines whether a part will be successfully drawn under specific parameters including BHF and drawing ratio. By adjusting the BHF and drawing ratio, the drawing limits can be established experimentally, which enables the determination of an optimal blank holding force to draw the tallest cup possible without failure and establishes the bounds which cause the workpiece to fail. After defining the experimental envelope, the data will be used to inform the creation of an easy to implement and relatively accurate model-based approach to deep-drawing manufacturing of commercially pure niobium for industrial applications in future work. The experiments were performed on annealed blanks of 1 mm thickness and diameter of 38 mm and 40 mm. The results demonstrate that the 38 mm blank size has a feasible drawing envelope between 232 N and 1706 N of BHF. No 40 mm cups were successfully drawn due to the draw ratio of 2.11. Future work should be done to show with better granularity the upper and lower bound of the drawing limits Additionally, this established envelope will be compared to the finite element models and analytical data from previous research done by Dr. Yannis Korkolis and Dr. Kelin Chen at the respective drawing depth to create the niobium drawing model.