Flow Resistance Of Materials Research Articles

In situ flow state characterization of molten resin at the inner mold in injection molding

AbstractOnline viscosity information on processing lines can reflect the material flow resistance and offer valuable guidance for manufacturing across various industries. Considering the accuracy, devices, and processes involved in injection molding, characterizing the melt's flow state during material processing poses a significant challenge. To reduce investment in viscometers, avoid influencing the components' surface aesthetics due to the installation of sensors, and make the flow state detect online in mold, this study designs a rheometric mold with cylindrical runners for identifying the in situ viscosity of molten resin during injection molding. The detection conditions of injection speed and cavity pressure variations, the entrance effect, and the viscous dissipation for Polycarbonate are analyzed under various conditions. The in situ viscosity is identified and compared with the standard cross‐WLF model. The result shows that the melt velocity and cavity pressure variations during the filling process create a stable environment for in situ rheological characterization and the detected viscosity is related to the shear rate, melt temperature, and channel dimension in injection molding. The designed mold with cylindrical runners for determining the in situ thermal‐rheological behavior of polymer is distinguished successfully and exhibits prospects for the development of low‐cost, nondestructive, and inner‐mold measurement in manufacturing applications.

Validation study of in situ sound absorption measurement

An in situ acoustic tube measurement is a non-destructive way to measure the sound absorption coefficient of a material. This method is practical for obtaining sound absorption in cases where it is not straightforward to sample specimens in applications such as automobile interiors, room walls, ceilings, or carpeted floors. However, the in-situ method's limitations lie in measurement errors due to the sound energy leakage through the open boundaries within the materials. In addition, it is not straightforward to provide a general correction factor compared to the standard in-tube method because the errors depend on various factors such as material characteristics, material flow resistance, installation conditions, pipe flange size, etc. The aim here is to provide practical guidelines for reducing in-situ error by analyzing and comparing that procedure with the standard in-tube method. Here, in-tube and in-situ methods were used to measure and they were then analyzed by creating FEM-based acoustic tube and poro-elastic material models. The effect of material flow resistivity and flange thickness were investigated and reported.

Numerical prediction of stagnant and flowing zones in a blast furnace by a novel potential flow model

Several flow zones exist in an ironmaking blast furnace, including the plug flow zone at the upper part, a stagnant zone in the central bottom and a funnel flow zone near the outlet. The prediction of the stagnant zone has remained a difficulty for years, and various approaches have been attempted in the past. In this article, a new approach based on novel potential flow model was employed to predict the profile of the stagnant zone and the plug flow and funnel flow zones. The results were verified by the experimental observations in literature. The effect of the material flow resistance in the model on the stagnant and flowing zones was investigated, and the results were also compared with the traditional potential flow model. It is demonstrated that the novel potential flow model has the advantage in predicting the stagnant and flowing zones simultaneously without a need to implement extra complicated correlations. • An approach to numerically predict deadman in blast furnace is proposed. • Deadman changes with ratio of potential flow and piping flow resistances. • Predicted results accord fairly well with reality. • Material resistance surely exists within deadman in blast furnace.

A 3D FEM-Based Numerical Analysis of the Sheet Metal Strip Flowing Through Drawbead Simulator

Drawbeads are elements of the stamping die and they are used to compensate material flow resistance around the perimeter of the drawpiece or to change the stress state in specific regions of the drawpiece. This paper presents the results of experimental and numerical analyses of tests of sheet metal flowing through a drawbead. The tests have been carried out using a special tribological simulator of the drawbead. Experimental tests to determine the coefficient of friction (COF) have been carried out for three widths of sheet metal strip and two drawbead heights. The three-dimensional (3D) elastic-plastic numerical computations were performed using the MSC. Marc program. Special attention was given to the effect of material flow through the drawbead on the distribution of the normal stress on the tool-sheet interface. The mesh sensitivity analysis based on the value of the drawing force of the specimen being pulled through the drawbead allowed an optimal mesh size to be determined. The errors between the numerically predicted values of the COF and the values experimentally determined ranged from about 0.95% to 7.1% in the cases analysed. In the case of a drawbead height of 12 mm, the numerical model overestimated the value of the COF for all specimen widths analysed. By contrast, in the case of a drawbead height of 18 mm, all experimentally determined friction coefficients are underestimated by Finite Element Method (FEM). This was explained by the different character of sheet deformation under friction and frictionless conditions. An increase in the drawbead height, with the same sheet width, increases the value of the COF.

Grain structure evolution, grain boundary sliding and material flow resistance in friction welding of Alloy 718

Alloy 718 tubes were subjected to rotary friction welding to understand to the process fundamental and grain structure evolution during welding. The distribution of grain size, low-angle grain boundaries (LAGBs), and twin boundaries throughout the joints were quantitatively analyzed. The weld power, axial load, and weld temperature were monitored. The grain structure evolution during friction welding was clarified. The grain structure in the recrystallization zone (RXZ) of the weld was a result of competition between dynamic recrystallization and grain boundary sliding (GBS), which is controlled by the local deformation condition. The axial force during welding decreased with reducing the rotation rate from 1000rpm to 500rpm. This anomalistic phenomenon can be ascribed that a decrease in rotation rate resulted in finer grain size in the RXZ of the weld, which required lower applied force to enable GBS.

Research on the flow resistance of acoustic materials—Takes Concert Hall at Gulangyu Music School in Xiamen as an Example

Different kinds of acoustic materials are used in a concert hall design, which has different functions such as diffusing, reflecting, or absorbing. The cushion of chairs in concert halls usually uses porous sound-absorbing material, whose absorbing attributes are mainly determined by its flow resistance. In the design of Concert Hall at Gulangyu Music School in Xiamen, we measured the flow resistance of materials, trying to acquire the best sound-absorbing attributes by adjusting the flow resistance, and also tested the material samples’ absorbing coefficients in reverberation room. In a nutshell, measuring and analyzing flow resistance is an advanced method in acoustic design, which could help acousticians decide the most suitable absorbing attributes of chairs, and acquire the best sound quality.

Analysis and Simulation of Flow Field in the Ultrasonic Auto Backwash Filter

Flow field in the filter is simulated by using Computational Fluid Dynamics. At the same time, pressure and velocity field distribution in the filter are analyzed. The maximum differential pressure and filtration velocity of filter column are all decreasing with column height increasing which means that there are stagnant water zones on the top of filter column. This phenomenon not only has an effect on filtration efficiency, but also can lead cavitation erosion. So the structure of filer must be improved. The change of pressure and velocity on two sides of filtering material are caused by flow resistance of material with many holes. All theses analysis results of velocity and pressure field can be the basic theory for the design of high efficiency filter.

Application of ductile fracture criterion to manufacture of aluminium liner by drawing and ironing processes

In order to manufacture a long cylinder to be used as a seamless aluminium liner using a four‐stage deep drawing process followed by a two‐stage ironing process, finite element simulations based on the normalised Cockroft‐Latham ductile fracture criterion and experimental studies were carried out. The critical damage value indicating fracture initiation during the forming process was obtained from comparison of simulation and experimental results of tensile tests. Since the strain‐hardening of the material continuously increases during deep drawing and ironing processes, annealing of the strain‐hardened material should be done to relieve the stress and to reduce the material flow resistance. For this, finite element simulation was carried out to investigate the effect of annealing treatment on ductile fracture. The optimum taper angle of the ironing die was also investigated to minimise the damage value and to eliminate the possibility of fracture generation during ironing processes.

A model relating tool torque and its associated power and specific energy to rotation and forward speeds during friction stir welding/processing

Torque ( M) is a very important quantity in the friction stir welding (FSW) process but a satisfactory model relating M to the two major FSW parameters, rotation speed ( ω) and forward speed ( v), has not been well developed. In this work, a better model of the form, M= f( ω, v), was sought. Experimentally, FSW of an aluminium alloy was conducted over a wide range of ω and v values and M was measured. An exponential decay function has been found to fit all the M versus ω data well and is meaningful for any ω value. The effect of v on M can approximately be accounted for through linearly relating the model parameters to v. The model allows for a detailed evaluation of the sensitivity of M to changes in ω and v. The model decay and the pre-exponential parameters need to be adjusted to make predictions for different aluminium alloys in the low ω range. Both the model and experimental data demonstrate a diminishing alloy effect on material flow resistance as ω increases. Furthermore, models of tool power ( P Tool ) and specific energy ( E s ) can be derived from the model for M and give predictions that are also meaningful over the entire range of ω values. Finally, the dependences of P Tool and E s on ω and v and the relationship between E s and the processing zone temperature will be discussed.

Material flow determination for radial flexible profile ring rolling

Regarding the increasing demand on annular components with complex geometries, a flexible process has been developed at the IBF to profile sleeve shaped rings. Unlike processes using grooved tools, here diverse contours can be realized on the inner surface using one “universal” tool. By extending the tool kinematics and developing an adequate forming strategy the general feasibility of the process has been shown on a bench scaled model ring rolling rig using a wax based model material. Parameters such as ring/tool geometry and roller feed strategy were detected as having an effect on material flow resistance in the rolling and transverse directions. Expressing them by geometric ratios, the material flow distribution could be determined in numerous experiments and quantified by a newly-defined extension coefficient with a certainty of 95%. This achievement enables us to predict the material flow in axial and tangential directions to manufacture complex geometries reproducibly.

The absorption of sound by anisotropic porous layers

An analytical model which describes the effect of a directional anisotropy of acoustical properties in porous sound absorbers is presented. The oblique incidence impedance of an anisotropic porous layer is derived in terms of the material's flow resistance, effective mass, and phase velocity measured in two directions. The impedance boundary condition is shown to be strongly dependent upon the absorber's transverse complex velocity, as well as on the angle of incidence. Values of the impedance and oblique incidence absorption coefficient for a layer of Fiberglas are calculated using experimental anisotropic parameter data. The random incidence sound absorption coefficient is then calculated for three boundary condition models of the Fiberglas, over frequencies ranging from 300–1200 Hz. The anisotropic model predicts absorption coefficients that agree better with reverberation chamber data than either an isotropic bulk reacting model or a locally reacting model. The absorption coefficient is shown to be insensitive to weak anisotropies.

Flow-Resistance Characteristics of Fibrous Acoustical Materials

The flow resistance of a material is highly important as a factor in determining its acoustical performance in various applications, particularly in the blankets used for soundproofing of aircraft cabins. It is desirable, therefore, to know the manner in which the flow resistance of a lightweight acoustical material varies with such physical parameters as thickness, density, size and shape of fibers, and type of construction (“felting”) of the material. From an experimental study of a large number of fibrous acoustical materials, the following empirical relation has been established for materials of high porosity (0.9 to 1.0): Flow resistance, R = KS(1+z)Tz 1r2 where K is a constant, characteristic of a particular material, S is the surface density of the blanket of material, T is the thickness, and r is the cross-sectional radius of the fibers. The type of construction of the material determines the value of x in the exponents. This value generally lies in the range from 0.3 to 1.0.

Flow-Resistance Characteristics of Fibrous Acoustical Materials

The flow-resistance of a material is highly important as a factor in determining its acoustical performance in various applications, particularly in the blankets used for sound-proofing of aircraft cabins. It is desirable, therefore, to know the manner in which the flow-resistance of a light-weight acoustical material varies with such physical parameters as thickness, density, size, and shape of fibers, and type of construction (“felting”) of the material. From an experimental study of a large number of fibrous acoustical materials, the following general empirical relation has been established: Flow-resistance, R = KS(1 + x)Tx(av)2 where K is a constant characteristic of a particular material, S is the surface density of the blanket of material, T is the thickness, and (a/v) is the ratio of surface area of the fibers to the volume of the fibers. The type of construction of the material determines the value of x in the exponents. This relation is compared with the theoretical relation derived by Fowler and Hertel for samples with randomly oriented fibers.