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Products > Product properties > DMA Dynamic Mechanical Analysis
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Dynamic Mechanical Analysis (DMA)
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In dynamic mechanical analysis, the specimen
under study is subjected to sinusoidal mechanical loading which
changes over time as a function of the temperature. This causes
the specimen to deform with the same period. What is measured here
is the amplitude of the force, the amplitude of the deformation
and the phase shift Δ φ between the force signal and the
deformation signal. The result obtained from
dynamic mechanical analysis is the complex module of the specimen.
A condition for this is that the specimen must not, under any
circumstances, be loaded outside the linear-elastic range (Hooke’s
range). A distinction is drawn between three
fundamentally different types of behavior in the specimen:
| > | purely elastic specimens react without any delay to the
force that is applied to them, with a phase angle φ = 0. They
undergo loss-free oscillation |
| > | purely viscous specimens attain their maximum
deformation when the force passes through the zero point. In
this case, the phase angle is therefore φ = π / 2 (90°). They
convert the excitation energy into heat in its entirety |
| > | viscoelastic materials are characterized by the fact
that the deformation of the specimen follows the force acting
upon the specimen with a certain time lag. For a phase angle of
Δ φ, the following then applies: 0 < φ < π / 2.
The bigger the phase angle, the greater the damping of the
oscillation will be |
DMA can be used to determine:
| > | material properties (such as moduli and the loss factor
tan (δ)) |
| > | temperatures that characterize the viscoelastic behavior |
| > | damping |
| > | the glass transition temperature, in particular – DMA
is the most sensitive method for this |
| > | the frequency-dependent mechanical behavior of
materials |
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