1、 FORD LABORATORY TEST METHOD BO 012-05 Date Action Revisions 2001 03 27 Revised Editorial no technical change A. Cockman 1992 07 16 Printed copies are uncontrolled Page 1 of 4 Copyright 2001, Ford Global Technologies, Inc. HYSTERESIS OF FLEXIBLE AUTOMOTIVE GRADE SEATING FOAM Application This procedu
2、re is used to measure the hysteresis and/or resiliency characteristics of flexible foam padding material used for automotive seat cushions, seat backs and other applications. Scope An elastomeric foam deforms when a force is applied and recovers when a force is removed. The recovery, however, is not
3、 immediate; the deformation lags behind the applied force which gives rise to hysteresis or damping effects. These effects are important in seating foams since they affect vibration frequency and the transmissibility of forces through the foam. (Hysteresis, in a sense, is the direct opposite (or inv
4、erse) of resilience; e.g., 30 % hysteresis is equivalent to 70 % resilience.) This procedure consists of subjecting a test specimen of the foam material to a number of ILD* load (65 % identation-deflection) and unloading cycles under closely controlled conditions. The ratio of the energy absorbed to
5、 the total energy expended during the loading of the sample, obtained with the last cycle, is used to calculate the percent hysteresis (resiliency) of the material. *Reference: ASTM D 1564, Load Deflection Test, Method A Indentation Apparatus Required Electronic Testing Machine Instron Universal Tes
6、ting Equipment, Model TT-c or equivalent. Source: Instron Engineering Corporation 2500 Washington Street Canton, Massachusetts Curve Integrating Device Compensating Polar Planimeter (K the SIMPLE-COMPOUND switch to “Simple“; and the two remaining CYCLE-STOP switches both to “Cycle“. 13. Set the FULL
7、 SCALE LOAD control to the 500 kg load range. 14. Deflect the sample 80 % of the original height, twice. FORD LABORATORY TEST METHOD BO 012-05 Page 3 of 4 Copyright 2001, Ford Global Technologies, Inc. 15. Allow the sample to rest undeflected for a period of ten minutes (+ 3 0 minutes). 16. Reset LO
8、WER EXTENSION gauge to 65 % of the initial thickness of the sample. 17. Set the LOAD RANGE selector such that the load at 65 % deflection will trace a curve that utilizes more than half of the recording chart. 18. At the end of the preflex rest period noted in Step 14 above, subject the specimen to
9、five cycles of loading, to a 65 % deflection, and unloading. Record all instantaneous values of load and deflection using the Instrons recording chart. Avoid superimposing the fifth curve over any of the other tracings since the fifth cycle is used for the resiliency measurement. 19. Using the fifth
10、 recorded hysteresis curve, determine the total area in square inches under the load deflection curve (see Figure 1 attached whole cross hatched area) either by means of a suitable area planimeter or an automatic integrator. 20. Then, determine the hysteresis area between the loading and unloading (
11、recovery) curves (see Figure 1) using either an area planimeter or an automatic integrator. 21. Calculate the hysteresis of the material by using the ratio of the energy absorbed in square inches (from Step 20) to the total energy required to deflect the sample in square inches (from Step 19), expre
12、ssed as a percent by using the formula below: Energy Absorbed (Step 20) x 100 % = % Hysteresis Total Energy (Step 19) 22. Report as the Percent Hysteresis of the material. Chemicals, materials, parts, and equipment referenced in this document must be used and handled properly. Each party is responsible for determining proper use and handling in its facilities. FORD LABORATORY TEST METHOD BO 012-05 Page 4 of 4 Copyright 2001, Ford Global Technologies, Inc. HYSTERESIS OF FLEXIBLE AUTOMOTIVE GRADE SEATING FOAM Figure 1
