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The 'Yield stress myth?' paper - 21 years on

Appl. Rheol.17:4 (2007) 43110 (5 pages) ►

Consideration is given to the reaction to Barnes and Walters' 4-pageThe yield stress myth?paper published 21 years ago. It has been cited approximately 180 times since then, as either a standard reference for 'yield stress' papers, or to disagree with its sentiment that yield stresses do not actually exist, but are a useful approximation. The references that cite the paper are categorized and commented on.► Cite this publication as follows:

Barnes HA: The 'Yield stress myth?' paper - 21 years on, Appl. Rheol. 17 (2007) 43110.

The Microsoft Excel Â‘SolverÂ’ tool is a very simple but powerful procedure, even in the hands of the mathematically disadvantaged. It has very good application for quickly fitting experimental flow-curve data to non-Newtonian flow models with any number of parameters, and can cope with data from a number of sources. Examples are given for a range of industrially important examples ranging from standard non-Newtonian liquids, through detergent solutions to gels, pastes, and filled polymer melts, often measured on different viscometers.► Cite this publication as follows:

Roberts GP, Barnes HA, Mackie C: Using the Microsoft Excel `solver' tool to perform non-linear curve fitting, using a range of non-Newtonian flow curves as examples, Appl. Rheol. 11 (2001) 271.

A frequent task undertaken by quality-control personnel in typical consumer-goods factories is the measurement of the viscosity of liquid products. The problem often faced in this task is how to strike the correct balance between the complete rheological characterisation of the non-Newtonian properties of the liquid of interest which requires expensive, sophisticated equipment and can be quite time-consuming and the dictates of production pressures that demand, as near as possible, an instant decision, and one usually based on a single number. Here we consider the rheological issues that arise in such a debate, which is aimed at finding what adequate characterisation would require. We will investigate the implications of liquids products being non-Newtonian for two of the most commonly encountered viscometers in factory quality laboratories, i.e. the simple dip-in rotating spindle viscometer of the Brookfield type (with its different forms and many imitations) and the more sophisticated concentriccylinder- type device typified by the Haake Rotovisco VT 550 range. Each is capable of giving a single-number answer for viscosity, but the implications of understanding this single number are different in each case, with the dip-in viscometer being in an infinite sea of liquid and the concentric-cylinder situation being narrow gap. We also investigate when the infinite sea of the dip-in viscometer is effectively infinite and when is a concentric- cylinder geometry really narrow gap? We will use the power-law model throughout our discussions.► Cite this publication as follows:

Barnes HA: An examination of the use of rotational viscometers for the quality control of non-Newtonian liquid products in factories, Appl. Rheol. 11 (2001) 89.

► Cite this publication as follows:

Barnes HA: An appreciation and critique of the suspension rheology research of, Appl. Rheol. 10 (2000) 248.Howard A. Barnes

A brief history of the yield stress

Appl. Rheol.9:6 (1999) 262-266 ►

► Cite this publication as follows:

Barnes HA: A brief history of the yield stress, Appl. Rheol. 9 (1999) 262.Howard A. Barnes

On-Line or Process Viscometry - A Review

Appl. Rheol.9:3 (1999) 102-107 ►

► Cite this publication as follows:

Barnes HA: On-Line or Process Viscometry - A Review, Appl. Rheol. 9 (1999) 102.

► Cite this publication as follows:

Barnes HA, Schimanski H, Bell D: 30 Years of Progress in Viscometers and Rheometers, Appl. Rheol. 9 (1999) 69.

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