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Noncontact Imaging Technique Calculates Strain during Electric Resistance Welding
As described in Materials World (July 2009), an online, noncontact, digital imaging technique to calculate local strain during electric resistance welding (ERW) metal pipe forming has been developed at the University of Alberta, Canada. Researchers hope to produce pipes with uniform properties by understanding the strain history around the circumference and correlating it to mechanical properties. “Reverse plastic deformation can result in reduction in yield strength (softening—due to the Bauschinger effect) at discrete locations around the circumference,” explains Barry Wiskel of the University of Alberta. “By understanding the relation between mill setup and ‘softening,’ corrective action can be taken.”
The technique involves mounting a digital camera and calibration target inside the ERW forming process. An image is taken of the pipe’s interior, and a reflective strip is attached to its wall to enhance...