Micromechanisms of deformation and fracture in shearing aluminum alloy sheet

A systematic experimental investigation is presented on trimming of aluminum alloy autobody sheets. The variations of cut surface quality and burr height are related to the cutting parameters of clearance, blade sharpness and cutting angle. It was discovered that, contrary to conventional wisdom requiring the blade to travel perpendicularly to the sheet (0°-“cutting angle”), at appropriate cutting angles the surface quality becomes insensitive to the blade sharpness, and almost zero burrs are produced for large clearances and extremely dull blades. The findings suggest that the robustness of current shearing practices for aluminum sheets can potentially be greatly improved, requiring much less frequent tool-sharpening and less restrictions on clearance control. A counter-intuitive phenomenon was revealed. At certain cutting angles and intermediate clearances, instead of burr heights and cut surface roughnesses monotonically increasing with decreases in the blade sharpness as expected, they first increased and then surprisingly decreased. Instability conditions exist at which cut surface quality and burr height are extremely sensitive to the cutting parameters.