Two-parameter Power Law Model Research Articles

Creep Model of Natural Fiber Reinforced Polymer Composite

The flexural performance, 24 h creep-24 h recovery of the Populus alba wood fiber reinforced high-density polyethylene composites prepared by forming mat-compression molding method is investigated. Two-parameter power law model, Findley’s power law model and Burgers model are used to describe the 24 h creep curve of wood fiber reinforced polymer composite. Through model testing and parameter testing, and comparing the sum squared error of three models found that four elements Burgers model is successfully simulated with the creep resistance performances of resulted wood fiber reinforced polymer composites, and the two-parameter power law model is the worst. In summary, the four elements Burgers model is suitable for describing the creep performances of wood fiber reinforced polymer composites and predicting the safety and stability during application.

Modeling and analysis of the creep behavior of jute/green epoxy composites incorporated with chemically treated pulverized nano/micro jute fibers

This paper reports the creep behavior of alkali treated jute/green epoxy composites incorporated with various loadings (1, 5 and 10wt%) of chemically treated pulverized jute fibers (PJF) at different environment temperatures. Composites were prepared by hand layup method and compression molding technique. The creep and dynamic mechanical tests were performed in three-point bending mode by dynamic mechanical analyzer (DMA). The incorporation of PJF is found to significantly improve the creep resistance and strain rate of composites. Three creep models i.e. Burger’s model, Findley’s power law model and a simpler two-parameter power law model were used to model the creep behavior in this study. The time temperature superposition principle (TTSP) was applied to predict the long-term creep performance. The Findley’s power law model was found to be satisfactory in predicting the long-term creep behavior. Dynamic mechanical thermal analysis (DMTA) results revealed the increase in storage modulus, glass transition temperature and reduction in the tangent delta peak height of composites with higher loading of PJF.

Creep behavior of bagasse fiber reinforced polymer composites

The creep behavior of bagasse-based composites with virgin and recycled polyvinyl chloride (B/PVC) and high density polyethylene (B/HDPE) as well as a commercial wood and HDPE composite decking material was investigated. The instantaneous deformation and creep rate of all composites at the same loading level increased at higher temperatures. At a constant load level, B/PVC composites had better creep resistance than B/HDPE systems at low temperatures. However, B/PVC composites showed greater temperature-dependence. Several creep models (i.e., Burgers model, Findley’s power law model, and a simpler two-parameter power law model) were used to fit the measured creep data. Time–temperature superposition (TTS) was attempted for long-term creep prediction. The four-element Burgers model and the two-parameter power law model fitted creep curves of the composites well. The TTS principle more accurately predicted the creep response of the PVC composites compared to the HDPE composites.

Determining the velocity of a non-newtonian medium flowing past spherical particles

The general hydrodynamic approach is used to formulate and solve the problem of determining the velocity field and pressure of a non-Newtonian medium flowing past a spherical particle. The rheological properties of the non-Newtonian medium are described in terms of a two-parameter power-law model. Expressions are obtained for the velocity of a sphere (in particular, a bubble) relative to the flow of the non-Newtonian liquid in different hydrodynamic pattern. The effects of rheological parameters on the flow velocity and on the limiting sizes of bubbles what retain spherical form, are analyzed.

A Granulometry-Based Selection Methodology for Separation of Traffic-Generated Particles in Urban Highway Snowmelt Runoff

Traffic activities generate a wide gradation of anthropogenic particulate matter that is entrained in highway snow and snowmelt. Granulometric-based analyses of this particulate mattercan provide guidance for selection and design for snowmelt solid/liquid separation processes. This study presents a granulometry-based analysis of snow melt particles from 10 highway shoulder sites in urban Cincinnati (State of Ohio, U.S.A.) generated from a 46 cm, 48 hr snowfall with a highwayshoulder residence time of 102 hr. Each site was exposed totraffic and maintenance activities (plowing and de-icing saltsonly). Despite variations in gradations and particle indices, measured lnv-Nt (number-volume mean size-particle counts) values for all sites were closely modeled using a two-parameter power law model. The model exponent, β, ranged from 2.22 to 2.64 indicating that a significant fractionof surface area is associated with the coarser gradation of particles. Modeled results support previous experimental data indicating the predominance of surface area and heavy metal mass is associatedwith the coarser fraction of particles. Results indicated a statistically significant difference in densities for coarse (2.86 gm cm-3) and fine particles (2.75 gm cm-3) (P < 10-11).A methodology is presented in the form of a process selection diagram to evaluate mechanisms of particle separation. It was determined that sedimentation could remove 90% of particles, bymass, within 2 hr for a typical roadway drainage design. The influence of particle specific gravity on sedimentation efficiency is illustrated for a range of specific gravities from 1.1 to 4.0. Although the very high concentrations of particulate matter in highway snow melt do not make it amenableto straining or direct filtration, such processes may be feasible as a secondary treatment for snowmelt or storm water effluent discharges to receiving waters.

Foam flow phenomena in sudden expansions and contractions

A sudden change in flow area induces complex transient processes in foams, which increase in significance with increasing flowrate. The effects are a function of the method of foam generation and, hence, depend on the initial foam structure. In vertical upflow at a sudden expansion or contraction, a substantial fraction of the liquid in the foam drains back upstream. This leads to a greatly reduced liquid holdup downstream and a recirculating flow regime upstream. For the area ratios of the fittings investigated, the extent of liquid holdup reduction was less pronounced in the case of a sudden contraction. At low gas rates, a plug flow regime usually existed on either side of the fitting; however, with an increase in gas throughput the presence of the fitting led to the establishment of a recirculating flow regime upstream. At sufficiently high flowrates complete breakdown of foam structure occurred resulting in the onset of a `flooding' regime downstream. Foam rheology was successfully described by a two-parameter power-law model, and the friction factor for foam flow could be described by a simple explicit relationship.

Rheological properties of plain yogurt during coagulation process: impact of fat content and preheat treatment of milk

A study of the effect of fat content and preheat treatment of milk has shown their respective effects on the rheological behavior of curd during the coagulation process of plain yogurt. Increase in fat content leads to an increase in viscosity. The highest viscosity was manifested by milk heated at 137°C while the lowest value was exhibited by milk heated at 65°C. The process viscosity curves for three different stages are described by mathematical relationships. Finally, a two-parameter power law model was used to describe the flow behavior of the yogurt during coagulation.

Pressure Drop of the Polymer Melt Flow in a Pipe

Rheological properties of polymer melts are often described with a linear model, the two-parameter power-law model in industrial applications, while the real polymer melts behave more or less nonlinearly, particularly in the low shear rate regions. In a lot of real flows, such as the simple pipe flow, there is even a zero shear rate region. Therefore, the adequacy of this linear approximation has to be examined. In this paper, the polymer melt flow in a pipe is studied using the nonlinear three-parameter Powell model. Numerical results are presented in several graphs, which can be used in engineering calculations. A comparison with the test data has been given. The restrictions of using the power-law model and the impact in handling the experimental data are discussed.

A Power Law Fatigue Damage Model for Fibre-Reinforced Plastic Laminates

Following an earlier comparative investigation of the tensile fatigue response, in terms of stress versus log life curves, of three epoxy-resin-based laminates of 0/90 lay-up and reinforced with carbon, glass and Kevlar-49 fibres, the authors now present a study of the accumulation of fatigue damage in terms of the residual strengths of the fatigued laminates. A stress-independent parametric relationship between normalized stress and normalized number of cycles is found to describe the behaviour of all three composites, suggesting a single major mode of fatigue damage despite the widely different mechanical characteristics of the different materials. The model is a two-parameter power law model, derived from a consideration of the appropriateness of various curve-fitting methods, and permits the incorporation of all modes of damage accumulation, from gentle ‘wear-out’ to ‘sudden death’ simply by the adjustment of this pair of power law exponents.