Multiscale Numerical Simulations of Branched Polymer Melt Viscoelastic Flow Based on Double-Equation XPP Model

The double-equation extended Pom-Pom (DXPP) constitutive model is used to study the macro and micro thermorheological behaviors of branched polymer melt. The energy equation is deduced based on a slip tensor. The flow model is constructed based on a weakly-compressible viscoelastic flow model combined with DXPP model, energy equation, and Tait state equation. A hybrid finite element method and finite volume method (FEM/FVM) are introduced to solve the above-mentioned model. The distributions of viscoelastic stress, temperature, backbone orientation, and backbone stretch are given in 4 : 1 planar contraction viscoelastic flows. The effect of Pom-Pom molecular parameters and a slip parameter on thermorheological behaviors is discussed. The numerical results show that the backbones are oriented along the direction of fluid flow in most areas and are spin-oriented state near the wall area with stronger shear of downstream channel. And the temperature alongy=-1is little higher in entropy elastic case than one in energy elastic case. Results demonstrate good agreement with those given in the literatures.

Visualization and simulation of filling process of simultaneous co-injection molding based on level set method

Co-injection molding (CIM) is an advanced technology which was developed to meet quality requirements and to reduce the material cost. Theoretical investigations concerning it are very limited, especially for simultaneous CIM. The interactions of air, skin and core polymer melt in the process are very complex, which makes it more challenging to simulate free surface flows in the mold. Thus, this article presents a mathematical model for it. The extended Pom-Pom (XPP) model is selected to predict the viscoelastic behavior of polymer melt. The free surface is captured by the level set method. The article vividly shows the simultaneous CIM process by means of a visual numerical simulation technique. Both two-dimensional (2D) and 3D examples are presented to validate the model and illustrate its capabilities. The 3D flow behaviors of simultaneous CIM process are hard to predict numerically. To our knowledge, this is the first attempt at simulating melt flow behaviors in 3D simultaneous CIM based on the XPP constitutive equation and visual technique. The numerical results are in good agreement with the available experiment results, which establish the capability of the multiphase flow model presented in this article to simulate the flow behaviors of polymer melt in simultaneous CIM process.

Quantitative EDS analysis in the SEM applying the XPP procedure

Extensive work has been done during the last decade to develop new models able to improve the performance of data reduction procedures 1n quantitative x-ray microanalysis. Some of them are now successfully used as routine tools in microprobe work, and allow to analyze accurately light and ultra-light elements and to characterize layered specimens.In the field of analytical scanning electron microscopy (SEM) using energy dispersive spectrometers (EDS), it seems that less attention has been paid to the effective improvement of the quantitation processes. Although EDS systems have unavoidable limitations due to their lower peak-to-background ratio and poorer resolution, the authors have the feeling that the quantitative results can be significantly improved by use of more reliable models taking properly into account the specific instrumental and experimental conditions.With this aim in view, our first contribution has been to implement our recently developed XPP model and associated routines (mass absorption coefficients, efficiency of the Quantum window) into the KEVEX Delta system.