ASTM D522-93a pdf free.Standard Test Methods for Mandrel Bend Test of Attached Organic Coatings.
With the operating lever of the apparatus in a horizontalposition，slip the test specimen between the mandrel and thedrawbar with the finish side towards the drawbar. Rigidlyclamp the specimen in a vertical position adjacent to themandrel by placing the long edge behind the clamping bar insuch a manner that the panel is always set up to the narrow endof the mandrel.Slip two sheets of No. 1 brown kraft wrappingpaper，substrate 30,thoroughly lubricated on each side withtalc,between the specimen and the drawbar and hold inposition only by the pressure of the drawbar against the paper.8.2 Move the lever through about 180° at uniform velocityto bend the specimen approximately 135.If the purpose of thetest is to measure elongation,the bend should be 15 s. Todetermine crack resistance under more simulated use condi-tions, the bend time should be about 1 s unless an alternativetime is agreed upon between the producer and the user.Examine the bent surface of the specimen immediatelywith the unaided eye for cracking.Having determined andsuitably marked the end of the crack farthest from the smallend of the mandrel, which shall be considered as the end point,bring the drawbar to the starting position and remove the panelfrom the mandrel. Measure the distance from the farthest endof the crack to the small end of the mandrel.This distance isused to compute the elongation. The mandrel diameter atwhich cracking ceased is taken as the resistance to crackingvalue.
When required， determine the elongation of the finishfrom the plotted curve in Fig. 2.This curve represents therelationship between the percent elongation and the diameter ofthe conical mandrel for a 1.0 mil coating thickness. Therelation between the distance along the conical mandrel and thecorresponding diameter has also been plotted on this curve.Adjust the percent elongation value obtained from Fig.2 for coating thickness by adding the correction obtained fromFig.3.ASTM D522 pdf download.