Experimental and simulative investigation of crack systems during glass cutting (CrackCut)

• Applicants: Professor Dr.-Ing. Ralf Müller; Dr.-Ing. Matthias Seel; Dr.-Ing. Aris Tsakmakis
• Subject Area: Mechanics ; Applied Mechanics, Statics and Dynamics
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 552288432

The industrial cutting of flat glass is usually carried out using a cutting wheel. This is a two-stage process. In the first process step, the cutting wheel rolls over the glass surface and indents it while simultaneously a cutting force is applied. This creates a spatial crack system in the glass close to the surface (fissure). In the second process step, the fracture opening process, the glass sheet is mechanically separated along the fissure by bending. The crack system created in the first process step consists of a fragmented zone, a median crack in the thickness direction and, in part, lateral cracks that are oriented parallel to the glass surface. The above-mentioned crack characteristics are commonly known. It can be assumed that radial cracks, in particular secondary radial cracks, which are decisive for the edge strength of glass structures, additionally occur during cutting. The entire crack system, and in particular the formation and presence of secondary radial cracks and their characteristics, is not fully understood. The main objectives of the proposed research program are therefore to characterize the crack system generated during the cutting process, to identify the parameters influencing the crack system and to determine a causal relationship between the crack system and edge strength. The focus is on secondary radial cracks. The research program is based on three hypotheses. (H1) Secondary radial cracks occur during glass cutting using a cutting wheel. (H2) The characteristics (morphology and dimensions) of secondary radial cracks depend on the geometry of the indenter, the cutting force (vertical and horizontal components) and duration, as well as on the environmental conditions. (H3) The secondary radial cracks are related to the edge strength of flat glass. The hypotheses are checked by a combination of numerical simulation and experimental investigations. As part of the numerical investigations, the material behaviour of glass will first be characterized at the Institute of Steel Construction and Materials Mechanics (IfSW) and, based on this, a phase field model will be developed to describe the fracture behaviour. Subsequently, the necessary large-scale simulations will be carried out at the Institute of Mechanics (IfM). The experimental and characterization studies on crack development will be carried out at the ISMD's Glass Competence Center. A close link between experimental observations, characterization studies and numerical modelling will substantially contribute to the understanding of relevant mechanisms during the cutting process of glass and its effects on the crack system and edge strength. The results will be used in the construction and automotive industries, among others, to improve the mechanical strength of the glass.

• DFG Programme: Research Grants