Applied Rheology: Publications

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Kamalesh Prasad
Rheology for Chemists - An Introduction (Jim W Goodwin, Roy W Hughes)

Appl. Rheol. 16:2 (2006) 69

Cite this publication as follows:
Prasad K: Rheology for Chemists - An Introduction (Jim W Goodwin, Roy W Hughes), Appl. Rheol. 16 (2006) 69.

Youwen Liu, Bo Li, Qihong Fang
Interaction Between a Screw Dislocation and a Piezoelectric Circular Inhomogeneity with Interfacial Cracks in Viscoelastic Matrix

Appl. Rheol. 16:2 (2006) 102-109

This paper attempts to investigate the problem for the interaction between a screw dislocation and a piezoelectric circular inhomogeneity with interface cracks in viscoelastic matrix. Utilizing the Laplace transform method, we find that the viscoelastic problem is first reduced to an associated elastic one. After solving the associated elastic problem through complex function method, the solution of viscoelastic problem is obtained by using the inverse Laplace transformation. The viscoelasticity of material is modeled by the combination of spring and dashpot. Particularly, the boundary value problem for standard linear solid model is solved analytically. The analytical results show that the force acting on the dislocation depends on the piezoelectric properties of inhomogeneity and interfacial crack, and the magnitude of the force evolves toward a constant value as time elapses. However, the viscoelasticity of material cannot alter the equilibrium position of the dislocation. Results presented in this paper are in agreement with the previous solution as special cases.

Cite this publication as follows:
Liu Y, Li B, Fang Q: Interaction Between a Screw Dislocation and a Piezoelectric Circular Inhomogeneity with Interfacial Cracks in Viscoelastic Matrix, Appl. Rheol. 16 (2006) 102.

Choon K. Chai, Swe Chong Ang
An Evaluation of Dilution Rheology for the Characterization of Long Chain Branching of Polyethylenes

Appl. Rheol. 16:2 (2006) 90-101

The purpose of this paper was to re-evaluate the novel rheological method of Crosby et al. [J. Rheol. 46 (2002) 401] to characterise long chain branching (LCB) in polyethylenes (PE) using the rheology of concentrated solutions. The feasibility of this dilution method centred on knowing the class of branched material and the molecular tube theory-based technique for the determination of two topological parameters (n, bU), where n is the number of entanglements between branch points while bU is the probability of meeting a branch point when tracing along the molecule from a random monomer against the direction of polymerisation. This paper proposes new possible approaches to calculate the two topological parameters (n, bU) set for metallocene polyethylenes (mPE), and their ambiguity discussed, as the results are dependent on the approach taken, though the previous authors mentioned only one. In addition, their approach requires an input value of LCB/1000C obtained from the standard analytical solution (SEC-V or SEC-LALLS) methods, hence, until now, without proper demonstration of the potential advantage of the dilution rheology method for LCB characterisation, as the main premise of their published article was to characterise the degree of LCB via rheological measurements without recourse to other methods of LCB characterisation.

Cite this publication as follows:
Chai CK, Ang SC: An Evaluation of Dilution Rheology for the Characterization of Long Chain Branching of Polyethylenes, Appl. Rheol. 16 (2006) 90.

Cirillo Atzeni, Ulrico Sanna, Nannina Spanu
A Rheological Fuzzy Model for Lime Plasticity and Mortar Consistency

Appl. Rheol. 16:2 (2006) 80-89

This paper is concerned with a fuzzy model developed for describing the rheological properties of lime pastes and mortars. We have identified the physical parameters on which the flow properties of these materials depend, and whose complex interrelationships make it difficult to model the phenomena using a traditional approach. The basic notions of fuzzy modelling are described, a technique which enables different kinds of variables and other knowledge elements to be handled in a formal context that can be easily computerized. Applying the Fuzzy Approximation Theorem we can develop a model irrespective of whether the correlation functions are expressed in explicit analytical form or not. The definitions of the fuzzy sets for the different variables are provided which, together with IF/THEN rules comprise the knowledge base of the model. The model is then applied to determine the plasticity of lime pastes and consistency of lime-based mortars using ordinary fuzzy inference mechanisms.

Cite this publication as follows:
Atzeni C, Sanna U, Spanu N: A Rheological Fuzzy Model for Lime Plasticity and Mortar Consistency, Appl. Rheol. 16 (2006) 80.

Montgomery T. Shaw, Zhizhong Z. Liu
Single-point Determination of Nonlinear Rheological Data from Parallel-Plate Torsional Flow

Appl. Rheol. 16:2 (2006) 70-79

Of the torsional drag-flow experiments, the hands-down winner for simplicity and ease of use is that using parallel- plate fixtures. This geometry is highly flexible, allowing custom modification of plate size and material, and is easily adaptable for optical use and the application of electric fields. However, its nonuniform flow is a major encumbrance for measuring nonlinear response. In 1987, Cross and Kaye offered a simple and clever solution for this problem, which essentially states that one assumes the sample is Newtonian, but the shear rate assigned to the observed ''Newtonian'' viscosity is 3/4ths of the rim shear rate . This shift factor arises from the use of Gaussian integration over radius of the nonlinear stress profile. Recent re-examination of the Cross-Kaye rule indicates that there may be a more accurate rule of thumb with the shift factor being 0.8 instead of 0.75 (4/5 instead of 3/4). However, for complex materials, the real question is how much useful information is covered up by this approach vs. the traditional differentiation of the integral to account for the stress profile. We have attempted to answer this question using a selection of nonlinear measurements on an AB block copolymer solution that is rheologically complex.

Cite this publication as follows:
Shaw MT, Liu ZZ: Single-point Determination of Nonlinear Rheological Data from Parallel-Plate Torsional Flow, Appl. Rheol. 16 (2006) 70.

Piotr Ratajczak
Third International Conference on Engineering Rheology ICER 2005

Appl. Rheol. 16:2 (2006) 110

Cite this publication as follows:
Ratajczak P: Third International Conference on Engineering Rheology ICER 2005, Appl. Rheol. 16 (2006) 110.


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