くさび型工具によるアルミニウム板の切断加工における破壊様式

抄録

Cutting of an aluminum sheet (A1100P–H12) by indentation of wedge shape punches is investigated as a process to achieve burr-free-cutting. Numerical simulations of the cutting process are done using a rigid plastic finite element code developed by the authors. The modified Cockcroft and Latham expression is used as a fracture criterion and is linked with the simulation. Stress and strain distributions at the deformation region of the sheet are calculated and compared with the fracture threshold. The effects of nose angle and radius of the wedge shape punch on the cut edge profile are discussed based on the calculated results. To confirm the results of the finite element simulations, cutting experiments are also carried out and the shape of the cut edge is observed using an optical or a scanning electron microscope. The experimental result shows that the shape of cut edge is divided into four modes depending on the wedge angle α and nose radius r of punch. When the punch of r = 0.1 mm and α = 30 degree is used a sheet is separated by cutting, while when α = 60 and 90 degree ductile fracture occurs due to the secondary tensile force induced by the wedge indentation, and when α = 120 degree brittle fracture occurs due to the excessive work hardening during compression. When the nose radius of punch is increased from 0.1 mm to 0.5 mm, the deformation of sheet material between upper and lower punches becomes compression rather than cutting. Therefore, when punches of r = 0.5 mm are used, the separated surface has a very thin flash. These experimental results can be explained well by the simulation results.