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[August 2000]
Advanced Rheology Data Analysis Software
Bohlin Instruments new RHEA(tm) software is described as a user friendly analysis package that has been specifically developed for rheologists who require rapid and easy to use viscoelastic analysis procedures.
RHEA(tm) includes a time temperature superposition (TTS) package with automatic shifting routines. Master-curves of stiffness or compliance information in either the time or frequency domains can be easily generated from dynamic or transient data types produced at different isotherms, says Bohlin.
The shift factors can be related using the Williams-Landel Ferry (WLF) equations. The TTS package has several applications. For example, in the plastics industry, dynamic mechanical data is used for understanding the complex behaviour of polymers over a wide range of frequency or stiffness. Typically, a master curve can be generated covering many orders of magnitude in the frequency or time domain than would be possible using the rheometer's experimental operating range.
Additionally, RHEA(tm) converts dynamic mechanical data from the frequency domain to the time domain, and vice versa. The shifted master curves are fitted using a modified non-linear Marquadt-Levenburg least squares optimisation route. This is followed by a numerical analysis calculating the discrete relaxation and retardation spectra (Baumgrtel and Winter, 1989).
The software then numerically optimises the number of relaxation/retardation modes used in the analysis, thereby generating a discrete spectrum of relaxation or retardation times. A maximum of 32 relaxation modes can be calculated for the data sets.
Website: www.bohlin.co.uk
ENDS