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Recovery Measurement According to IKEA Specification IOS-MAT-0076 - 20100 pages
Recovery Measurement According to IKEA® Specification IOS-MAT-0076
ERLAND E. HOFMANN
Format Messtechnik GmbH
D-76187 Karlsruhe
Germany
D. JEFFREY GROSS
Eurotech Distributors, Inc.
Northfield, Ohio 44067
USA
Viscoelastic foams show a characteristic recovery
behavior after being compressed and then released. During
the recovery process the foam gradually regains its original
shape. According to the IKEA® specification IOS-MAT-0076
the recovery time is the time needed to regain 90% of the
original thickness. Until now recovery is measured
manually by using a ruler and a stop watch. Introducing the
test device Resimat® 150 (Fig. 1), Format Messtechnik
GmbH, Karlsruhe, Germany, has created a new approach
for recovery testing according to IOS-MAT-0076.
Resimat® 150 (Fig. 1) is specially designed for cubic foam
samples with an edge length of 150 mm. During a test
cycle the foam sample is compressed vertically onto an
adjustable reference surface (Fig. 4). At a certain strain four
electro magnets clamp the pressure plate and hold it for a
pre-selected time. During compression a force gauge below
the sample measures the restoring force. Due to the
viscoelasticity of the foam the force gradually decreases.
After the hold time the magnets are switched off, which
instantly releases the compression force. The sample
recovers from its deformation and gradually regains its
original shape. An ultrasonic sensor positioned right above
the pressure plate continuously records the kinetics of the
sample. The thickness vs. time curve (Fig. 2) shows the
measured recovery giving clear insight into the dynamics of
the foam.
The distance of the reference surface and the thickness
of the unstrained foam are measured in a zero
measurement. This data is important for the applied strain.
The hold time and the recovery interval are free selectable
parameters. IKEA®’s IOS-MAT-0076 test norm for 150 mm
foam cubes specifies a strain of 75% and a hold time of 60
seconds. After compression and subsequent recovery, the
time dependant data is displayed by the software
RESIMAT. The viscoelastic appearance (Fig. 3) is the area
between the recovery curve and the original sample
thickness. It shows how long a given foam deformation
remains visible. The new measurement technology of
Resimat® 150 is easy to use and can be applied in quality
assurance testing of viscoelastic foams.
patent 10252211
- Mechanical testing of viscoelastic
foam cubes
- Force relaxation measurement
during compression
- Thickness vs. time measurement
during free recovery
- “Appearance” calculation by the
software RESIMAT
distance sensor
pressure plate
v(t)
www.format-messtechnik.com
restoring force
200
H[mm]
200
F[N]
250
160
200
thickness
150
120
restoring force
recovery time
according to
IOS-MAT-0076
100
80
comp. thickness
RECOVERY
H[mm] v[mm/s]
200 50
original thickness
40
160
viscoelastic
appearance
30
20
40
restoring force
120
80
150
10
thickness
100
recovery rate
40
comp. thickness
50
0
50
RELAXATION
0
thickness / recovery rate
RECOVERY
restoring force
RELAXATION
thickness
F[N]
250
clamp
H(t)
F(t)
0
0
30
65
60
70
75
time [s]
®
Fig. 1: Resimat 150 is designed for measuring the recovery
®
of viscoelastic foam samples according to IKEA specification
no. IOS-MAT-0076. The cubic test sample has an edge length
of 150 mm. Resimat is a brand of Format Messtechnik GmbH.
0 0
0
30
65
60
70
75
time [s]
®
Fig. 2: Graphical overlay of three Resimat 150 measurements
of different foam samples. The recovery time according to IOSMAT-0076, is the time needed to regain 90% of the original
shape after a 75% compression for 60 seconds.
Fig. 3: The restoring force shows the relaxation during the hold
time. The thickness vs. time curve shows the free recovery
after relieving the pressure. The recovery rate is the differential
of the thickness curve. The red area shows the “appearance”.
force gauge
Fig. 4: The foam sample is compressed by means of the
pressure plate. The distance sensor measures the time
dependant thickness of the sample and the force gauge (F)
reads the restoring force.
