Just a decade ago Rheometrics introduced the Mechanical Spectrometer.1 Sophisticated rheological measurements are now common in most large academic, industrial and government laboratories. These measurements are being made over an ever widening range of materials and test conditions. Rheologists are now beginning to push present instruments to their design limitations. One example is measurements at ultra-low shear rate. It is extremely valuable for molecular characterization to obtain limiting viscosity and normal stress coefficients for polymer melts. This often requires shear rates below 0.01 s-1. At the opposite extreme, ver fast transient measurements are needed for determination of short relaxation times and for identifying the rubbery plateau. Furthermore, not only shear but tensile deformations are required for many applications. To deal with the range of materials encountered in many laboratories much wider ranges in stress detection are required: from water-like fluids to rigid solids.
KeywordsShear Rate Relaxation Modulus Sinusoidal Oscillation Digital Control System Transient Shear
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