Experimental Study on Deep-Drawing Dies Made of Pre-Stressed UHPC

Deep drawing is a cost-efficient way of producing sheet metal parts in high production volumes. Prototypes and very small series are expensive due to the cost of steel-forming tools. Ultra-high-performance concrete (UHPC) tools offer a cheap and fast alternative to conventional steel-forming tools. However, the flexural and tensile strength of UHPC limits its use in complex loading situations occurring in the forming die during deep drawing. To overcome this challenge, we propose pre-stressing UHPC by using expansive UHPC in a mechanically restrained condition. An aluminum powder-based expansive agent can be used to induce a free volume increase in UHPC specimens. With push-out test specimens, the increase in strength was tested when restraining the free volume increase with a steel reinforcement. After 3 and 12 months, no notable pre-straining effect could be measured when restraining the expansion of UHPC. Nonetheless, in deep-drawing experiments, the die made of expansive UHPC in a restrained condition withstood a maximal load during deep drawing of 110 kN. Compared to the die made from UHPC only, the failure mode changed from complete fracture to surface degradation of the drawing radius after 15 strokes.