摘要:

AbstractMeans of improving the deep drawability of thermoplastic sheets were explored by introducing temperature gradients in the deforming material during deep drawing of initially flat sheets. The specific experimental procedure consisted of either limiting the heating to the flange section of the deforming sheet or exposing the entire material to higher temperatures. At the same time, the initial blank size and the clamping force at the flange section were varied systematically. Both polypropylene and polypropylene with 40 percent calcium carbonate in the form of sheet were tested up to 130°C. It is demonstrated that the draw‐ability increases markedly with increasing temperature gradient between the flange and punch sections. The results of measured strain distribution in the deformed part indicate that the magnitude of temperature difference between the flange and punch sections determines the relative amount of deep drawing and stretching in the wall of the formed part, which in turn dictates the drawability of the materi

ISSN:0032-3888    

DOI:10.1002/pen.760280702

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractThis paper presents the development of the boundary element equations for the compression molding process of isothermal Newtonian fluids. It shows the numerical implementation of the boundary element equations and presents a simple method of carrying out the domain integral present in the governing equations. The results and accuracy of a boundary element simulation are discussed, and the numerical results compared to experimental values.

ISSN:0032-3888    

DOI:10.1002/pen.760280703

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractThe paper describes two different computational approaches for simulating the effects due to temperature variations and therein the associated thermally induced stresses and warpage with emphasis on computer aided engineering applications to ‘plastic’ components. One approach is the conventional finite element approach, and the other is termed as the transfinite element approach. The development of unified thermal/stress formulations for each of the aforementioned approaches is described for applications to injection molded plastic parts. Results of both computational formulations are in excellent agreement for predicting the thermal response and unified thermal/stress response and agree qualitatively with previous studies. For this study, it is found that the transfinite element formulations are computationally more efficient although the conventional formulations can still be effectively used. Both formulations are capable of serving as powerful computational tools to help part designers to predict the thermal/stress responses accurately and effectively. The unified concepts and approaches offer potential for extension to more complex geometries and for combined heat transfer and stress probl

ISSN:0032-3888    

DOI:10.1002/pen.760280704

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractA method for estimating the polymer melt extrudate temperature fluctuation in the single screw extrusion process is proposed. Predictions of the melt temperature fluctuation is feasible if the extrusion process parameters are known. The method is superior to these in the literature because it incorporates effects of the melting process on the temperature fluctuation. The method has been verified experimentally.

ISSN:0032-3888    

DOI:10.1002/pen.760280705

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractThe radial flow of a chemically reactive fluid between two parallel circular disks during the process of Reactive Injection Molding (RIM) has been simulated in a decelerative, non‐isothermal, transient flow environment. The effects of key operating and system parameters (feed temperature, volumetric flow rate, reaction rate, and cavity thickness) on velocity, conversion, and temperature profiles which occur in this decelerative flow environment were determined. A catalyzed, unfilled polyurethane RIM system was modeled by a linear step polymerization scheme using average literature values for the reaction rate, and thermodynamic and constitutive parameters. The numerical solution was achieved using the method of lines and upwind approximations of the spatial derivatives. The geometry studied (two parallel, center gated circular disks) models flow patterns in commercial RIM processes more realistically than the rectangular flow between two parallel surfaces (studied by previous workers) in which the average velocity is constant along the length of the mold. This simulation predicts the accumulation of high polymer near the entrance to the mold and near the outer edge of the cavity in fast reactive systems. The accumulation of material near the gate results in viscous heat generation and a maximum in temperature in the region immediately downstream from the restrictio

ISSN:0032-3888    

DOI:10.1002/pen.760280706

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractA numerical method has been developed for simulating fully developed multilayer shear flows of non‐Newtonian fluids with arbitrary viscosity functions. Poiseuille and combined Poiseuille/Couette flows in both slits arid annuli may be modeled. The method employs a finite difference system where grid points lie on streamlines and move to their correct positions as the solution procedure converges. Interfaces are easily handled as particular stream lines with the equation of motion replaced by a boundary condition. The method is stable for high interface viscosity ratios and readily handles a large number of layers. Many authors have employed power law models to model multi‐layer non‐Newtonian flows. We find that the power law is sufficient to predict pressure gradients and interface positions in most cases, but gives unrealistically flat velocity profiles, even when truncated at finite viscosity. Results are presented for the Carreau fluid and for the rubber‐like liquid with shear thinning via Wagner's strain fun

ISSN:0032-3888    

DOI:10.1002/pen.760280707

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractAn investigation was undertaken to study the extrusion behavior of composite systems. A compound made up of approximately 50 percent ceramic particulates by volume dispersed in a high molecular weight thermoplastic polymer was characterized by measuring the shear viscosity on an Instron capillary viscometer. The experimental data indicated that the ceramic composite exhibited an apparent yield stress. As a result, an expression that was previously shown to provide flexibility for describing a yield stress at low rates of deformation could explain the viscosity of the ceramic composite. The expression was then applied to the flow analysis of both a “rod” and a “slit” die in an extrusion process, and the derived equations adequately correlated experimental volumetric flow rate us. Pressure drop data obtained on a laboratory e

ISSN:0032-3888    

DOI:10.1002/pen.760280708

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractMost of the commercially available computation programs for injection molding use restrictive assumptions which lead to simple mechanical and thermal equations. These computations are generally sufficient to predict the flow distribution in the mold but the pressure and temperature distributions are not precise. Our aim was first to model very accurately the filling stage of several molds of elementary geometries. For this purpose, a two‐dimensional model has been built which solves at each time step the finite difference forms of the continuity, momentum, and energy equations. A refined grid is used near the mold walls to take into account the great temperature gradients. These models have been validated by comparing the pressure field with experimental measurements. The precision of the model is better than 15 percent for several mold geometries and several injection conditions. In a second step, molds of complex geometries have been analyzed by assembling elementary geometries. The flow distribution at the branching between several geometries has been studied with special attention. These computations have been compared with short shots and pressure measurements in a four rectangular cavities tool and in a box shaped cavity tool. Experimental and theoretical results are in good agreemen

ISSN:0032-3888    

DOI:10.1002/pen.760280709

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractAn analysis of a drawing plate test for easily monitoring the low‐pressure frictional characteristics of powders is presented. The test is performed by measuring the force required to withdraw a plate from a cylindrical bed of dry powder. The characteristics of the drawing force profile are analyzed using Janssen's classical differential element approach to relate the product μKof powders as a function of packing of powder medium, where μ is the coefficient of friction of the powders against the solid drawing plate, andKis Janssen's constant, an anisotropic pressure distribution factor of a powder bed. The packing arrangement, expressed as the external void fraction, due to tapping, significantly alters the μKvalue and the effective sustaining strength of a powder bed. Experimental results on spherical glass beads having mono‐ and bimodal size distributions, and on three different poly (vinyl chloride) (PVC) powders are discussed. A spherical, high bulk density PVC powder has the combination of low μKand high, bulk density desirable for rigid powder compounding appli

ISSN:0032-3888    

DOI:10.1002/pen.760280710

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractA computer simulation model was established to analyze the reaction injection molding process of nylon 6. A numerical calculation was carried out to predict the temperature, conversion, and crystallinity profile within a disc type mold. The effects of the feed temperature, wall temperature, and overall reaction constant on the eject time were discussed for searching the optimum processing conditions.

ISSN:0032-3888    

DOI:10.1002/pen.760280711

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY