Imeko Technical Committee 15
2nd Youth Symposium on Experimental Solid Mechanics
May, 7-10 2003 Milano Marittima (Ravenna), Italy
EXPERIMENTAL MESUREMENTS OF THE DYNAMIC PROPERTIES OF VISCOELASTIC
MATERIALS AND SYSTEMS
Andrea Magalini, David Vetturi
Dipartimento di Ingegneria Meccanica, Università degli Studi di Brescia
via Branze 38, 25123 Brescia, Italy
INTRODUCTION
Rubber-to-metal devices Standard elastomer test pieces
This contribution deals with the experimental
characterisation of the dynamic behaviour of rubber to
metal visco-elastic systems. An innovative methodology, Engine
using an electro-dynamic shaker and a measurement support
chain based on ICP accelerometers and thermocouples,
has been designed to investigate and measure the
dynamic interesting quantities on standard geometry
rubber test pieces and also on complex rubber to metal Adaptive
Vibrations-damping device for journal
vibration damping devices used for automotive Elastomer cylindrical standard
Mc-Pherson suspensions boxes
applications (such as engine mountings, adaptive specimens and fixture
journal boxes, elastic hinges, etc.). components for axial tests
MATERIALS
Dynamic quantities have to be considered as complex numbers. So stiffness is a Master curves
complex value and also the Young’s and the shear modulus are complex values.
Elastomeric materials have typical properties of: The real part takes into account effects of elasticity, while the imaginary one relates Coming from
to dissipative effects.
DMTA analysis
• Viscoelasticity
Static stress-
• Non linearity strain curves
Stress
Their Young’s modulus E and shear modulus G depend are non linear
from: and they Temperature
describe Those curves show the
• Frequency hysteresis dependence of the
complex Young’s
• Temperature cycles. Curves Modulus E (=E’+jE’’)
change with Strain
from frequency and
• Static pre-strain (pre-load) temperature. temperature
EXPERIMENTATION
THE MEASUREMENT CHAIN
Accelerations are
measured by ICP
accelerometers.
Temperatures are
measured by
standard industrial
thermocouples.
Temperature
PC &Controller
Acceleration functions sent
measurement ADC
as input signal for the
vibrating board are
Acceleration DAC sinusoidal sweeps
Data
measurement (typically in ranges going
from about 30 Hz to about
Drive signal 500 Hz, depending from the
analysed system). By the
Shaker Power drive controller those functions
are defined giving amplitude
Test Design
Test are conducted on values for each frequency
an elctro-dynamic PowerAmplifier tested in the sweeps.
shaker.
FIXTURES