Investigation of mode-I fracture behavior by essential work of fracture during the single-point incremental forming process

Abstract

A promising technique for manufacturing low-thickness workpieces with complicated geometries is Incremental Sheet Forming (ISF). Due to its dieless process, ISF is a proper candidate for the production of workpieces at low rates or prototypes of the samples. The mechanical properties of the workpieces produced by ISF are a critical factor in determining their potential applications. Pyramid-shaped samples made of cold rolled steel (DC01) were produced using the single point incremental forming (SPIF) process in this study. To examine how the forming process affects mechanical properties, specimens were obtained from both raw and deformed surfaces. Subsequently, the specimens underwent tensile and fracture tests. The fracture toughness of the specimens was assessed using the essential work of fracture (EWF) technique. Through the use of incremental forming process, the tensile tests revealed a considerable improvement in both ultimate and yield tensile strength, with increases of 33.72% and 90.02%, respectively. However, the forming process led to a reduction of 86.64% in formability compared to the raw specimens. Fracture tests performed on the deformed specimens demonstrated a noteworthy reduction of 59.12% in the amount of energy needed for the initiation of crack growth, compared to the raw specimens. Additionally, we examined how the properties of deformed specimens are affected by the initial rolling direction of the sheets in this study. The study revealed that the mechanical properties and fracture characteristics of the material varied significantly along the transverse direction. The study utilized scanning electron microscopy (SEM) to analyze the fracture mechanisms and found that ductile fracture was the dominant mode of failure. The raw specimens demonstrated more ductile fractured surfaces, which corresponded to higher values of essential work of fracture (EWF).