Rheometer

About: Rheometer is a research topic. Over the lifetime, 5759 publications have been published within this topic receiving 125849 citations.

Rheological characterization and constitutive modeling of bread dough

Abstract: Bread dough (a flour–water system) has been rheologically characterized using a parallel-plate, an extensional, and a capillary rheometer at room temperature. Based on the linear and nonlinear viscoelastic and viscoplastic data, two constitutive equations have been applied, namely a viscoplastic Herschel–Bulkley model and a viscoelastoplastic K–BKZ model with a yield stress. For cases where time effects are unimportant, the viscoplastic Herschel–Bulkley model can be used. For cases where transient effects are important, it is more appropriate to use the K-BKZ model with the addition of a yield stress. Finally, the wall slip behavior of dough was studied in capillary flow, and an appropriate slip law was formulated. These models characterize the rheological behavior of bread dough and constitute the basic ingredients for flow simulation of dough processing, such as extrusion, calendering, and rolling.

The influence of specific mechanical energy on cornmeal viscosity measured by an on-line system during twin-screw extrusion

Abstract: The influence of specific mechanical energy (SME) on cornmeal viscosity during the twin-screw extrusion at feed moisture contents of 25 and 30% and screw speeds in the range from 100 to 500 rpm was measured. Cornmeal was extruded in a co-rotating, intermeshing twin-screw coupled to a slit die rheometer. One approach to the on-line rheological measurement is to use a slit die with the extruder. In the present work it was show that shear viscosity decreased as a function of SME. The viscosity of cornmeal at the exit die was influenced by screw speed, rate of total mass flow, mass temperature inside the extruder and SME. An increase in screw speed resulted in an increase in SME and a decrease in viscosity. A reduction in slit die height and an increase in screw speed and mass temperature led to a remarkable macromolecular degradation of the starch, as evidenced by the decrease in viscosity.

Experimental observations on the pressure-dependent polymer melt rheology of linear low density polyethylene, using a multi-pass rheometer

Abstract: We report experimental data for a linear low density grade of polyethylene at elevated temperatures using a newly designed Multi-Pass Rheometer This rheometer is capable of measuring oscillatory viscoelastic data and steady shear capillary measurements on the same test fluid within an enclosed environment Data presented in this paper show that at low pressures there is reasonable self-consistency between the Multi-Pass data and separate oscillatory data obtained by using a Rheometrics Mechanical Spectrometer and steady shear data obtained from a Rosand capillary rheometer In addition, we report experimental data on the pressure dependence for both viscoelastic and steady shear data over the range of 1–230 bar The steady shear results appear to be consistent with previously published data The apparent viscosity and the viscoelastic data both show a linear increase of about 20% over the pressure range tested

Inhomogeneous transient uniaxial extensional rheometry

Abstract: A filament stretching rheometer is used to probe the development of coil-stretch hysteresis in transient nonhomogeneous uniaxial elongation of a dilute polymer solution. Laser-Doppler velocimetry measurements are used to measure the steady centerline velocity profile in an elastic test fluid as it flows towards the throat of a 4:1:4 axisymmetric contraction/expansion over a range of Deborah numbers. The corresponding time-varying extension rate experienced by a fluid element as it flows into the contraction is then downloaded to a filament stretching rheometer in order to impose an identical inhomogeneous stretch history. Simultaneous optoelectronic measurements of the flow induced birefringence and mechanical measurements of the total tensile force in the filament allow independent determination of the evolution in the conformational anisotropy and stress. A pronounced stress-conformation hysteresis is observed with the relationship between the polymeric tensile stress and the average anisotropy in the p...