What is a Math Model and when should you use it to evaluate viscosity test data?
Various math models were empirically developed by different researchers, in order to fit trends they saw in their own data sets. The Math Model is a “best fit” line that can be used to characterize data from a specific test and has the advantage for easy data storage and comparison with similar tests by looking at slope and y-intercept. There are some simple models that provide a reasonable fit to many data sets, and have parameters that have some meaning to various practitioners – whether those people are researchers, QA/QC people, or process engineers. The modified Casson model, for example, works well for testing chocolates, among other things. The Herschel-Bulkley model is useful for materials that have a yield point and then “shear-thin” after yielding. This may be good for “gel-like” materials, for example. Brookfield’s “Analysis” module in our applications software (Rheocalc and Wingather) lists the curve-fit parameter results, along with a “Coefficient of Fit”. One could try a
