Yield Testing by Two Methods as a Practical and Convenient Analysis

Yield testing can be a practical and convenient method for QC/QA testing, as well as for R&D. This paper discusses two rotational shear methods: (1) testing a material at multiple shear rates and extrapolating the yield stress with a math model, and (2) testing the sample at one speed and finding a peak-stress reading, and the corresponding strain. These will be referred to as Methods 1 and 2, respectively. The yield stress is the stress at which a solid-like material starts to flow like a liquid. The corresponding deformation is the yield strain. The two methods provide different complementary information about the material behaviour. The multi-speed/shear rate data provide a more complete picture for process equipment designers. However, the single-speed test does provide useful data, related to the product’s end-use, in even less time than the other method.