Papers by Keyword: Rheology

Abstract: Viscosity and rheological investigation are preliminary investigation to identify the mixture behaviour. The investigation found that SD mixtures behave like pseudoplastic behaviour and this showed that the mixture is the right solution to be a paint mixture. Scratch hatch is a conventional method to measure the adhesion of dried coating. SD15, SD10 and SD5 were showed the smooth edges of the cut. However, nanoscratch test is a high technology method measure the minimum depth of penetration on SD40 followed by SD25, SD15 and SD5. This showed that the SD40 is the hardest coating film. As for all adhesion performance, SD15 becoming the best coating film with medium standard evaluation.

Abstract: In the framework of the model of large elastic-plastic deformations, the flow of the material in a spherical matrix at varying loads is examined. Simulation is carried out under the condition of steady elastic-plastic boundary. In order to find an exact solution the assumption of an ideal smoothness of the walls and incompressibility of the material is accepted.

Abstract: The rheological viscous flow model of deformable, irreversibly compressible, porous body based on mechanics of continua, and creep theory of crystalline materials, is used to describe quantitatively the sintering of powder materials with pressure in isothermal and nonisothermal conditions. Densification of the porous body occurs under action of Laplace pressure, generated by surface tension, and applied pressure. The densification kinetics of porous metals and crystalline compounds in initial and intermediate stages of sintering with static external pressure represent nonlinear steady-state creep controlled by a climb dislocation mechanism in solid matrix forming porous material. Activation energies of this mechanism are consistent with the bulk diffusion. A diffusional creep controls the pressure sintering kinetics in a later stage. The rheological models of deformable viscoelastic bodies and the associated dynamic strain theory for viscoelastic irreversibly compressible bodies, based on the energy conservation law, enable a quantitative description of their densification under dynamic loading. At the same time it is taking into account the internal energy of deformable body. The solutions of dynamic systems involve the mechanical interaction of compacting machine with this body. The simulation of impact sintering of porous metals shows that the viscosity of the matrix, that forms the porous body, and the activation energy of viscous deformation dramatically decrease with increasing initial impact velocity. This promotes the compaction of the material to practically nonporous state and enhances its mechanical properties.

Abstract: MIM technique is described in which allows for the production of highly porous metallic foams with porosity levels up to 90%. It makes use of the pressure built up by the decomposition of a foaming agent which is incorporated in a foamable precursor copper material obtained by powder compaction. A suitable behaviors feedstock that refers to its rheological is one of the key factors to ensure the successful of MIM technique and to predict failure, whether due to the binder component and compositions, powder loading or unsuitable process parameters. Potassium carbonate and polyethylene is added and were mixed homogeneously to form a copper feedstock. The rheological results in term of shear rate, shear stress, viscosity, melting rate and softening temperature which related to pseduoplastic behaviors have been conducted using a capillary rheometer (CFT-500D, Shimadzu) at various temperature and loads. The result has indicated that the viscosity of the feedstock is decreased with increasing shear rate thus proved the feedstock to be pseudoplastic.

Abstract: The advantageous influence of two different polycarboxylate and melamine superplasticizers is studied in relation to the properties of blended mortar plaster made with recycled polymers (polyamide powder and polyurethane foam). The characteristics of the test specimens are defined and tested in both a fresh and a hardened state. The influence of the additives on the microstructure of the lightweight mortar plaster is defined through an analysis of the compatibility of the interface zone of the materials using Fast Scanning Electron Microscopy (FSEM).Our results show that the addition of additives influences the properties of the mortar plaster, enhances its mechanical properties, and increases its adherence with ceramic materials. These results confirm that superplasticizers (depending on the type and dosage) enhance both the properties of the mortar plasters produced with recycled polymers and the rheological properties of the mortars that include polyamide waste.

Abstract: This article presents results of research aimed at identifying the phenomenon of stress relaxation in compressed concrete elements. The study used a special test stand, designed and constructed by Dr.Eng. Krzysztof Kaminski which allows permanent strain of cylindrical concrete sample by adjusting force. Cylindrical samples with a diameter of 15 cm and 10.5 cm and a height of 30 cm for the study were used. The samples were made of different classes of concrete. There was also defined the influence of applied tensile stress and the age of the sample on the relaxation phenomenon. The expected result of the research was to obtain relaxation curves of concrete samples with different compressive strength and age. Relaxation of concrete is important for the analysis of bending elements sections, which behavior during the operational phase of the concrete can significantly deviate from the assumed one, causing other than triangular or parabolic distribution of compressive stresses.

Abstract: The objective of the study was to design a simulation model that approximates the real viscoelastic behavior of spinal units in stress relaxation tests. The spinal units were sampled from porcine and used in fresh condition, without frizzing or drying. The mechanical tests were conducted on Mecmesin 5i testing machine using the appropriate devices for compression tests. On the other hand, using Maxwell constitutive equation for relaxation, a Simulink model was created. At the end, the relaxation curve derived from the simulation model was draw next to experimental obtained data in order to represent the fitting.

Abstract: The influence of fibrous and solid granulated fillers on the rheological and surface properties of the polymer compositions on the basis of polyvinyl alcohol and Na-carboxymethyl cellulose is demonstrated. The polymer complexes with Na-carboxymethyl cellulose and sodium tetraborate additions and the compositions filled with polypropylene, polyethylene terephthalate and quartz sand are obtained and comparative assessment of the properties of studied polymer composites have been made. Polymer compositions with quartz sand, synthetic and plant fibrous fillers increase the effective viscosity, elasticity modulus and decrease the adhesive strength of all compositions based well on carboxymethyl cellulose and polyvinyl alcohol. The sodium tetraborate introduction promotes the formation of the composites surface with the lesser adhesive strength.

Abstract: Specific phenolic resin samples have been developed as the carbon precursor for SiC/C composites. Liquid phenolic resins suitable for fiber-infiltration in the resin transfer moulding (RTM) process are synthesized by using versatile combination of the aromatic component (phenol, naphthalen-2-ol) with various formaldehyde equivalents such as methanal, 1,3,5,7tetraazatricyclo [3.3.1.1^3,7] decane (urotropine), and 1,3,5-trioxane, under different reaction conditions. Room temperature liquid resoles (RTLR) are obtained by using an excess of the formaldehyde component over phenol (≥2) under basic conditions. Upon heating RTLR can form a crosslinked network even without addition of a hardening reagent. In addition, novolacs are synthesized under acidic conditions using a phenol/formaldehyde ratio ≥1. Nitrogen-containing resins contain nitrogen due to reaction of phenol with urotropine. Novolacs and nitrogen-containing resins are solids at room temperature and not self-curing. To infiltrate these both resins into SiC fibers in the RTM process, they are dissolved in 2furanmethanol (furfuryl alcohol FA) and urotropine which is added as curing-agent. Both, the molecular weight and the amount of the dissolved phenolic resin have an influence on the viscosity and the carbon yield after pyrolysis which is important for this application. The aim was to create different phenolic resins for the fabrication in the RTM process and to characterize the carbon after pyrolysis with respect to the structure and porosity as these are key parameters to generate a stoichiometric SiC matrix by LSI.

Abstract: Density and viscosity are two major rheological properties that determine the performance of an isopropyl laurate (IPL) ester based drilling fluid. In this study, the effect of barite particle size on the IPL drilling fluid system settling behaviour was investigated using five particle sizes namely-32, 32-45, 45-75, +75μm and the unsieved barite. Stokes’ law of separation theory was employed in the analysis. It was found that smaller barite particle sizes (<75μm) enhances the settling resistance. An ideal barite particle size of-32μm was chosen and used in the subsequent formulations to obtain optimum rheological properties by varying the amount of viscosifier used at 4.0, 10.0 and 20.0g marked as sample (a), (b) and (c). These samples were analysed for their rheology by using the conventional Fann viscometer calibrated using Bingham model. The results showed that sample (b) exhibited the most promising performance based on the plastic viscosity, yield point and gel strength rheological analyses. Moreover, IPL drilling fluid sample (b) showed improve particle suspension ability for more than 78 hours when compared to IPL drilling fluid system prepared using unsieved barite particles. The results suggested that palm oil based isopropyl laurate ester has the potential to be used as based fluid in the ester based drilling fluid system.