Papers by Keyword: Power Law

Abstract: To overcome the inlet temperature uncertainties during an in-line thermo-rheological characterization and to further apply a differential convection method for an injection molding process, a concept of device designing is proposed in this work. An analytical and numerical investigation proves that the proposed concept can provide information on the viscosity of the material via thermal measurements, despite a poorly known inlet temperature.

Abstract: A crucial problem concerned with the semi-solid forming process is the liquid segregation phenomena during shape formation, especially for rheo-casting process. Liquid segregation occurs due to the separation phenomena of the solid grain and the liquid phase. In this work, using commercial finite element software, the liquid segregation during rheo-casting process was numerically investigated by Eulerian-granular multiphase model based on the comparable results of single phase model, Eulerian-granular two-phase and three-phase model, along with Eulerian-granular DDPM three-phase model. In the study, solid grains and liquid phases were regarded as rigid material and non-Newtonian fluid at microscale, separately. This validation was experimentally proved and also compared to the proposed relationship of power law, Herschel-Bulkley model with yield stress at macroscale.

Abstract: Particulate reinforced composites show viscoelastic behavior under various loading conditions. It is important to estimate mechanical behavior when this material is used for solid fuel on rocket motor. Cracks can be generated and propagated due to high combustion pressure in the service time. These cracks expand the burning area and lead to excessive combustion. Consequently, the rocket motor can cause malfunction or the performance deteriorated. In this study, edge cracked sheet specimen was used to perform the crack propagation tests. These tests were conducted in the range of temperature from -60°C to 60°C under 2.54 and 12.7 mm/min of strain rates. Based on the results, the stress intensity factors and the crack propagation rests were calculated. The crack resistance curves show the transition that stress intensity factors increases as temperature decrease. Also, fracture surfaces were investigated by scanning electron microscope to determine the fracture behavior under various temperatures.

Abstract: The mechanical behaviour of a superplastic material is often modelled by the power law relationship between the equivalent flow stress, the equivalent strain and the equivalent strain-rate at least over a limited range of strain rates. This paper introduces an original mathematical modelling to determine the superplastic material constants m, n and K by means of experimental tests carried out using a standard forming die geometry.

Abstract: Wall Shear Stress (WSS) in the artery is one of the indicators for brain artery disease progression. WSS is proportional to the viscosity and shear rate of the flowing fluid. In this study, WSS of cerebral artery with aneurysm was predicted using Computational Fluid Dynamics (CFD). The effect of non-Newtonian properties of blood will be studied by comparing Power law model with Newtonian model. Based on the results, maximum value of WSS is 150 Pa for Newtonian model and for Power Law model is 24 Pa. Newtonian model was found overpredicted the WSS resulted from Power Law.

Abstract: The aging and shear rejuvenation behavior of a commercial printing ink have been studied experimentally using creep and oscillation modes. We observed that the printing ink has typical rheological characteristics: time-dependent, reversible and shear-thinning viscosity. Meanwhile, these properties are very strongly influenced by shear history, thus employing pre-shearing to obtain a standard test state is of vital importance. After pre-shearing, the quiescent ink undergoes structural evolution, i.e., aging, including a sol-gel (liquid-solid) transition on the early stage at room temperatures, the higher the temperature, the earlier the sol-gel transition occurs. The degree of aging and shear rejuvenation can be characterized by the waiting time after pre-shearing and the stress dependence of the power-law index. Finally, we use a time-stress superposition to obtain a universal master curve which is able to describe the aging behaviors of the printing ink. This study shows that the aging processes of printing ink for different waiting times are self similar, variation of waiting time just change the time scale and elastic modulus.

Abstract: The only grouting material used for anchoring cemented arthroplasties to contiguous bones is PMMA (Polymethyl methacrylate) bone cement. In this study the flow of bone cement through porous cancellous bone is modelled to determine the degree of penetration in total hip replacement using FIDAP simulation software. Power law viscosity model is used with constant consistency index and power law index less than 1 for pseudoplastic behaviour of Simplex P® and Zimmer bone cement. The effect of bone cement amount has been investigated under four different prosthesis insertion velocity 5, 10, 15 and 20 mm/s. The result shows that the depth of penetration increases with decreasing bone cement amount. In the case of Zimmer bone cement more penetration through cancellous bone was observed than Simplex P® bone cement.

Abstract: PMMA (Polymethyl methacrylate) bone cement is currently the only material used for anchoring cemented arthroplasties to contiguous bones. The aim of this work is to model the flow of bone cement through porous cancellous bone to study the degree of penetration in total hip replacement using FIDAP simulation software. Two different viscosity models have been used (a) power law with constant consistency index and power law index less than 1 for pseudoplastic behaviour of Simplex P® and Zimmer bone cement; (b) FORTRAN subroutine for time dependent rheopectic behaviour of CMW3 and Zimmer bone cement. For each type of bone cement the effect of prosthesis insertion velocity have been investigated under four different values 5, 10, 15 and 20 mm/s. It has been observed that the depth of penetration increases with increasing prosthesis insertion velocity. On the other hand, the maximum pressure in bone cement decreases with increasing prosthesis insertion velocity. It has been observed that there is more penetration through cancellous bone for pseudoplastic behaviour than rheopectic behaviour of bone cement.

Abstract: In industrial machine vision (MV) applications, it is a popular research direction to identify a structure mechanical part image primitive’s relationship with its background by extracting actual contour from a captured image. However, numerous nonlinear problems turn up in MV applications of measuring and inspecting mechanical parts. Those problems are brought by components of MV system including lens, cameras, lighting effect, and sheltered measured object. These nonlinear phenomena usually result in incomplete and inconsistent geometrical shape of a structure’s image primitive. Therefore, special primitive measurement theory and method are researched in the thesis, on the basis of analyzing fractal and structural features of mechanical parts. The method found that an important trait of mechanical parts image contour which can be used to reduce the impact of nonlinear phenomena and determine a closest contour of the image primitive by using different multi-scale rulers in measuring. The effect of the measurement method is proved by an example in cylindrical connectors’ inspection.

Abstract: Complex systems and complexity science to be home and abroad are believed as the 21st century scientific development frontier by numerous scientists. At present, the complex network and software engineering crossover study has just started. The research results of complex systems and complex networks provide a powerful support for exploring the structure characteristics and behavior characteristics of software systems. This paper tests scale free characteristics on NASA data empirically. More specially, this paper checks whether two of Chidamber and Kemerer metrics suite, namely, CBO and WMC follow power law or not.