3.7 Deformation diagram (hysteresis) of the seat squabA test machine according to DIN 51220 class 1 shall be used.The test is performed on a rigid, positively engaging backing.The hysteresis characteristic values are recorded in the compression test according toDIN 53579-1; representation see Appendix A.1A zero-point setting (displacement and load) is to be made after achieving the respectivepreliminary force.3.7.1 Stamp XXI? Diameter 200 mm? Curvature radius 200 mm? Edge radius 5 mm3.7.1.1 Procedure? Test direction perpendicular to the test point? Test force acc. to drawing? Preliminary force F v = 20 N where V = 100 mm/min? Load force set cycle F s = 600 N where V = 500 mm/min? Complete unloading of the foam (-15 mm from zero point) where V = 500 mm/min? Preliminary force F v = 20 N where V = 100 mm/min? Load force hysteresis F h = 600 N where V = 100 mm/min? Unloading hysteresis where V = 100 mm/min3.7.1.2 Evaluation of the hysteresis? Indentation depth EW [mm]Stress line, where F b = 320 N? Damping characteristic value DKW [mm]Difference of unloading line F b = 320 N minus stress line F b = 320 N? Spring travel (FW) [mm]Difference of unloading line F b = 480 N minus unloading line F b = 320 N3.7.1.3 Example of the indication of a foam hardnessEW XXI at 320 N: 46 mm according to PV 3410 Section 3.7