Andrey M. Ilinich

Trimming of Advanced High Strength Steels

Modern product design and manufacturing often utilizes a wide variety of materials. Where once low carbon steel predominated, a variety of different materials such as aluminum alloys and advanced high-strength steels (AHSS) are now being utilized. Although such alternative materials may provide a variety of benefits in manufacturing and design, these same materials may present difficulties when subjected to manufacturing processes originally designed for low carbon steel. One such manufacturing area where difficulties may arise is in trimming operations. A defect that may arise directly in the trimming operation are burrs. Burrs decrease the quality and accuracy of stamped parts and cause splits in stretch flanging and hemming. Current standards limit the production of burrs through accurate alignment of the upper and lower edges of the trim knives. The clearance between the shearing edges should be less than 10% of the material thickness. For automotive exterior sheet, this requires a gap less than 0.06mm. Unfortunately, tolerances often exceed the capabilities of many trim dies resulting in the production of burrs. To satisfy the current standards of quality and to meet customer satisfaction, stamped parts frequently need an additional deburring operation, which is often accomplished as a metal-finish operation and conducted manually. The objective of the research described in this paper was to study the mechanisms of burr generation and the impact on AHSS formability in stretch flanging. Results on both the conventional trimming process and a recently developed robust trimming process, which has the potential to expand tolerances of trim die alignment, will be discussed.Copyright

Development of a New Technology for Trimming of Dual Phase Steels

This paper describes the development and investigation of a new technology for trimming of dual phase steels and provides a comparison with other trimming processes. This technology utilizes an elastic support of the offal, sharp upper trim knife and angled lower trim knife. Such a configuration allows for a high quality trimmed surface with little or no burr and without slivers over a wide range of cutting clearances.

Measurement of fracture stress for 6000-series extruded aluminum alloy tube using multiaxial tube expansion testing method

A servo-controlled tension-internal pressure testing machine with an optical 3D digital image correlation system (DIC) is used to measure the multiaxial deformation behavior of an extruded aluminum alloy tube for a strain range from initial yield to fracture. The outer diameter of the test sample is 50.8 mm and wall thickness 2.8 mm. Nine linear stress paths are applied to the specimens: σɸ (axial true stress component) : σθ (circumferential true stress component) = 1:0, 4:1, 2:1, 4:3, 1:1, 3:4, 1:2, 1:4, and 0:1. The equivalent strain rate is approximately 5 × 10-4 s-1 constant. The forming limit curve (FLC) and forming limit stress curve (FLSC) are also measured. Moreover, the average true stress components inside a localized necking area are determined for each specimen from the thickness strain data for the localized necking area and the geometry of the fracture surface.A servo-controlled tension-internal pressure testing machine with an optical 3D digital image correlation system (DIC) is used to measure the multiaxial deformation behavior of an extruded aluminum alloy tube for a strain range from initial yield to fracture. The outer diameter of the test sample is 50.8 mm and wall thickness 2.8 mm. Nine linear stress paths are applied to the specimens: σɸ (axial true stress component) : σθ (circumferential true stress component) = 1:0, 4:1, 2:1, 4:3, 1:1, 3:4, 1:2, 1:4, and 0:1. The equivalent strain rate is approximately 5 × 10-4 s-1 constant. The forming limit curve (FLC) and forming limit stress curve (FLSC) are also measured. Moreover, the average true stress components inside a localized necking area are determined for each specimen from the thickness strain data for the localized necking area and the geometry of the fracture surface.