Investigation of Spring Back in Air Bending of Electrogalvanized CR4 Steel

Objectives: To analyze the effects of galvanizing thickness and punch speed on spring back of CR4 steel. Methods: Galvanizing is done by electro-deposition method using an alkaline cyanide-free zinc plating system and different thickness of deposition was achieved by changing the time. Galvanizing thickness was measured by coating thickness gauge. Experiments were conducted on a universal testing machine, using various combinations of punch travel, punch speed, and sheet orientation, using the same tooling and size of the specimen. An approach to change one parameter at a time was applied. Measurement of angles was done with the help of graphics and optical profile projector. Spring back was analyzed graphically. Findings: It was observed that spring back increases with the increase of punch travel and punch speed both. With the increase of galvanizing thickness increase of spring back was observed. Application/ Improvements: These results will be useful for design engineers and manufacturing engineers since the use of galvanized steel sheets has increased and the methods of initial bent angle and galvanizing used is as per industry's current practice.