Huamin Zhou

Numerical Filling Simulation of Injection Molding Based on 3D Finite Element Model

The traditional numerical simulation of injection molding is the 2.5D technique based on the Hele-Shaw approximation, which cannot predict the filling of thick or nonuniform-thickness parts and some flow behaviors such as the fountain flow. A three-dimensional (3D) finite element model is presented to perform more accurate simulations of a fully 3D flow. The model employs an equal-order velocity-pressure interpolation method. The relation between velocity and pressure is obtained from the discretized momentum equations in order to derive the pressure equation. A 3D control volume scheme is introduced to track the flow front. The validity of the model has been tested by case studies and experimental verification.

Numerical simulation of temperature history during the picture tube panel‐forming process

Purpose – This paper aims to develop an integrated cooling simulation for the temperature history of the panel during the forming process.Design/methodology/approach – A local one‐dimensional transient analysis in the thickness direction is adopted for the panel part, which employs finite‐difference method. And a three‐dimensional, boundary element method is used for the numerical implementation of the heat transfer analysis in the mold region, which is considered as three‐dimensional conduction. The Renormalization‐Group turbulence model is applied for the jet impinging cooling. The part and mold analyses are coupled so as to match the temperature and heat flux on the glass‐mold interface.Findings – The paper provides mathematical model and numerical strategy adapted to the problem, with experimental verification that shows a good agreement.Practical implications – Cooling design in the forming operation of picture tube panel is of great importance because it significantly affects the part quality associ...

Fast Prediction of Injection Pressure and Minimal Front Temperature for Injection Moulding

Abstract Fast prediction of injection pressure and minimal front temperature can usually be used to optimize the process parameters for injection moulding. In this paper, a fast strip analysis (FSA) model was presented on the basis of a geometric approximation method, which simplifies an original part to a rectangular edge-gated strip. The dimensions of the rectangular strip were calculated through the original parts geometric mesh by using graph theory. Subsequently, a finite difference method was employed to simulate a non-isothermal and unidirectional flow in the strip. Numerical examples show that although FSA model is an approximation method, its results are approximately identical to that of detailed CAE software, while the running time of the proposed model is several magnitudes less than that of CAE software.

Data driven injection molding process monitoring using sparse auto encoder technique

Injection molding process monitoring is quite essential for the stabilization of product quality. One of the most important things is to identify the character of injection batch process. In this study, sparse auto encoder technique is applied to extract features from the raw trajectories of system pressure and screw position. Subsequently, the process condition is identified by performing a classification on the features, in comparison with the raw trajectories data, and the principal components. The mean reconstruction error and the classification accuracy are selected to evaluate the representation capability of the extracted features. The experimental results show that the sparse auto encoder is an effective method of extracting features from the injection processing batch data, indicating that it is useful in injection molding process monitoring.

An efficient parallel algebraic multigrid method for 3D injection moulding simulation based on finite volume method

Elapsed time is always one of the most important performance measures for polymer injection moulding simulation. Solving pressure correction equations is the most time-consuming part in the mould filling simulation using finite volume method with SIMPLE-like algorithms. Algebraic multigrid (AMG) is one of the most promising methods for this type of elliptic equations. It, thus, has better performance by contrast with some common one-level iterative methods, especially for large problems. And it is also suitable for parallel computing. However, AMG is not easy to be applied due to its complex theory and poor generality for the large range of computational fluid dynamics applications. This paper gives a robust and efficient parallel AMG solver, A1-pAMG, for 3D mould filling simulation of injection moulding. Numerical experiments demonstrate that, A1-pAMG has better parallel performance than the classical AMG, and also has algorithmic scalability in the context of 3D unstructured problems.

An efficient preconditioned Krylov subspace method for large-scale finite element equations with MPC using Lagrange multiplier method

Purpose – The purpose of this paper is to propose an efficient iterative method for large-scale finite element equations of bad numerical stability arising from deformation analysis with multi-point constraint using Lagrange multiplier method. Design/methodology/approach – In this paper, taking warpage analysis of polymer injection molding based on surface model as an example, the performance of several popular Krylov subspace methods, including conjugate gradient, BiCGSTAB and generalized minimal residual (GMRES), with diffident Incomplete LU (ILU)-type preconditions is investigated and compared. For controlling memory usage, GMRES(m) is also considered. And the ordering technique, commonly used in the direct method, is introduced into the presented iterative method to improve the preconditioner. Findings – It is found that the proposed preconditioned GMRES method is robust and effective for solving problems considered in this paper, and approximate minimum degree (AMD) ordering is most beneficial for th...

A combined reordering procedure for preconditioned GMRES applied to solving equations using Lagrange multiplier method

Purpose – The purpose of this paper is to propose a combined reordering scheme with a wide range of application, called Reversed Cuthill-McKee-approximate minimum degree (RCM-AMD), to improve a preconditioned general minimal residual method for solving equations using Lagrange multiplier method, and facilitates the choice of the reordering for the iterative method. Design/methodology/approach – To reordering the coefficient matrix before a preconditioned iterative method will greatly impact its convergence behavior, but the effect is very problem-dependent, even performs very differently when different preconditionings applied for an identical problem or the scale of the problem varies. The proposed reordering scheme is designed based on the features of two popular ordering schemes, RCM and AMD, and benefits from each of them. Findings – Via numerical experiments for the cases of various scales and difficulties, the effects of RCM-AMD on the preconditioner and the convergence are investigated and the comp...

Structure, injection molding process and fracture behavior of composite plastics

Abstract High strength and toughness are of importance for composite plastics used as mechanical structure parts. How to provide general and engineering plastics with high performances is one of the critical challenges in advanced manufacturing. In the past decade, the phase dispersion, interfacial interaction, injection molding simulation and fracture behaviors of composite plastics were investigated systematically in our research group in order to simultaneously reinforce and toughen polymer matrix. Here, we review the progress and advances which have been made in the above items.

Dimensional precision simulation of the formed picture tube panel

In the forming process of picture tube panel, the accumulated residual stresses cause the formed part to shrink, and the thermal and mechanical loads cause the mold blocks to deform. These two factors result in large deviations on the dimensions of the formed panel, which are both modeled and simulated in this paper. For residual stresses analysis, a thermo-rheologically simple viscoelastic material model is introduced to consider the stresses relaxation effect and to describe the mechanical behavior according to the temperature change. The shrinkage of formed parts induced by the residual stresses is calculated based on the theory of shells, represented as an assembly of flat elements formed by combining the constant strain and the discrete Kirchhoff triangular elements. A thermoelastic model is presented to predict the deformation of the mold blocks during pressing, which is based on the steady mold temperature field and thermoelastic boundary element method. The integrated simulation results suggest the amounts that the mold cavity should be machined by, and have been verified by comparing the dimensional precision of the panels produced by the mold considering a uniform part shrinkage and mold expansion or the mold considering the predicted ununiform part shrinkage and mold deformation.