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Bend testing equipment

Our shop needs to bend test 1"x4"x.04" 4130 steel coupons with various plating on them. I would appreciate any recommendations on a bend tester to simplify this operation.

Mary Cera
Process Engineer - Oklahoma City, Oklahoma
2007

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2007

A typical requirement is "The test specimen shall be bent 180°over a mandrel of diameter 4 times the thickness (0.4 inch minimum) of the specimen."

Since 4 x 0.04" = 0.16" < 0.4", the preferred mandrel is 0.4" diameter (larger diameters lessen the rigor & value of the test).

Two mandrel devices are shown in ASTM D522, 'Standard Test Methods for Mandrel Bend Test of Attached Organic Coatings.' One is a rather standard hand-operated sheet metal bender in which one specimen end is clamped and then a pivoting plate (with handle for leverage) bends the extending specimen over the mandrel. In this device, a tapered mandrel of diameter 1/8" to 1.5" is used. The mandrel ends are clamped in place, so a straight rod of desired diameter could be substituted.

Also shown in ASTM D522 is a cylindrical mandrel test apparatus which requires bending solely by hand (fingers). Consists of 2 pentagon shaped plates, with a mandrel of a different diameter (3/8" to 1") held between at each corner. Both devices are available from Paul N. Gardner Company.

Perhaps the most suitable device would be a brake press for sheet metal of the type known as an airbrake. The specimen is placed across 2 spaced rollers between which the rounded die or mandrel is brought down. I haven't seen any small enough for lab use; perhaps someone can suggest a supplier.

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.