RHEA™
Software (Rheology Analysis)
User Friendly Analysis
Data Files
Verification with standard data
sets
Test methods considered
User
Friendly Analysis
The RHEA™ Software User friendly analysis RHEA™ has been
specifically developed for engineers working in rheology needing a
rapid analysis procedure. Master-curves of stiffness or compliance
information in either time or frequency domain are generated from
dynamic or creep data. For example, in the asphalt industry, the Superpave
specification and mixture design process involves the collection of
dynamic data for both binder and mixture specifications. In the plastics
industry, dynamic mechanical data is used for understanding the complex
behavior of polymers over a wide range of frequency or stiffness.
The RHEA™ software allows users to rapidly inspect the quality
of data and to develop the interrelationships with ease. RHEA™
converts dynamic mechanical data (G', G" vs. w) from the frequency
domain to the time domain, G(t) and J(t) and vice-versa. The shifted
master curves are fitted using a modified non-linear Marquadt-Levenburg
least squares optimization. This is followed by a numerical analysis
calculating the discrete relaxation and retardation spectra (Baumgaertel
and Winter, 1989). The software numerically optimizes the number of
relaxation/retardation modes used in the analysis. A maximum of 32
relaxation modes can be calculated for the data sets.
This
program has been developed as a general tool for performing rheological
analysis of a wide variety of materials that behave according to linear
visco-elastic theory.
Data
files
The RHEA™ software has been configured to read data files
generated with many test devices. For example with the Bohlin Rheometer
the data files are named using *.d?w convention. These are read by
the software and can be either Creep or Frequency Sweep data.
The user can also edit choose to add/remove single data points or
entire isotherms for analysis. The final data set is stored in a separate
file for analysis enabling the user to develop multiple data sets
for sensitivity analysis. The analysis process take only a few minutes
enabling a much greater throughput and understanding of material behavior.
Verification
with standard data sets
In the development of RHEA the software has been extensively tested
with standard data sets. A few typical examples are illustrated below.
1.
Polycarbonate
Polycarbonate Stress Relaxation; Mercier et al., JAPS 9, 447 (1965).
The data below is the G(t) isotherms which have been entered in the
standard format.
The second plot illustrates the resulting master curve with the mode
contributions (this is an option that the user chooses to display).
2.
Polystyrene
Polystyrene - the data set below shows results collected from dynamic
testing. Often data is collected in this manner, used to produce a
master curve and then transformed to
G(t).
The second
plot illustrates the resulting master curve G* and phase angle.
The final
plots shows the same data set transformed to J(t) using the spectrum
analysis.
3.
Asphalt Mixes
The plot below shows results developed from a the Superpave Shear
Tester expressed as a frequency sweep.
This program has been developed as a general tool for performing rheological
analysis of a wide variety of materials that behave according to linear
visco-elastic theory.
Test
methods considered
