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Rheology Testing—What Is Rheology Testing

Rheology is the science of defining how materials flow and deform.

Our Anton Paar Physica MCR 301 rheometer with MR material with a magnetic field applied

Rheology is the science of defining how materials flow and deform.  Rheology mainly focuses on flow of complex liquids like cornstarch and water mixture which is referred to as shear-thickening, or a non-Newtonian fluid, since their viscosity increases as conditions change. Another example of a complex liquid is blood, which is shear-thinning, as the viscosity decreases as conditions change. Viscosity is the resistance to flow when a stress is applied on a fluid. Determining the viscosity of complex fluids is important for engineering applications that utilize non-Newtonian materials. Some examples where the rheology of a material needs to be known are: food manufacturing, plastic manufacturing, concrete development, and geophysics.

Rheometers are devices that are used to determine flow properties of fluids and soft-solids. In the case of a rotational rheometer, the material to be analyzed is placed in between a fixed structure and a rotating structure.

Different types of rheometer spindles

Although, Advanced Materials and Devices, Inc. (AMAD) can perform rheology testing using a plate-plate geometry of any non-Newtonian material, we specialize in Magnetorheological (MR) materials.

Rheometry curves for our MR fluids at different magnetic fields

MR materials are also a class of non-Newtonian materials, that change their flow properties not only with application of a stress, but a magnetic field. AMAD’s facility is equipped with a specialized rheometer that can apply a magnetic field while deforming the material. This way, engineers can determine how the stress of the material varies with application of a field. The figure below provides a typical rheometer result of an MR material, where the shear stress is shown for different magnetic fields as a function of shear strain (rotational speed). Rheology tests can also be temperature controlled to observe how the material behaves at different operating temperatures.

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