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Jianhui Li

Other affiliations: Huawei
Bio: Jianhui Li is an academic researcher from Huazhong University of Science and Technology. The author has contributed to research in topics: Finite element method & Shell (structure). The author has an hindex of 5, co-authored 7 publications receiving 57 citations. Previous affiliations of Jianhui Li include Huawei.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the effect of molding conditions on shrinkage and warpage was analyzed through a combination of experimental and numerical methods, and it was shown that packing pressure affects shrinkage most while packing time is the dominant factor in determining warpage.
Abstract: A challenging task in injection molding industry is to minimize shrinkage and warpage (S&W) through optimal setting of molding conditions. In determining the relationship between molding conditions and product dimension, most existing literature considered S&W as a whole entity or focused on only one of them. The intention of this study was to distinguish these two terms, and perform a thorough analysis on the effect of operative conditions on S&W during injection molding process through a combination of experimental and numerical methods. Six process parameters with five levels were examined on a box-shaped product, and the single factor analysis of variance (ANOVA) was adopted in identifying the significance of each variable in the experiment. Results indicated that the effect of processing conditions on shrinkage is different from that on warpage. Specifically, packing pressure affects shrinkage most while packing time is the dominant factor in determining warpage. The reaction of shrinkage to packing pressure is monotonic, whereas the plot of warpage shows a U-shaped variation. A differential treatment of S&W can therefore help to enhance product quality. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

23 citations

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TL;DR: In this article, a practical model of cavity filling in gas-assisted injection molding (GAIM) based on the surface mode has been presented, according to the flow field at the gas front, gas penetration thickness was induced by solving the theoretical equations governing the behavior of the gas penetration through the matching asymptotic expansion method.

12 citations

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TL;DR: In this article, a 3-node flat triangular shell element is developed by combination of a membrane component and a plate bending component, which exhibits excellent all-around properties, such as free of aspect ratio locking, passing the patch test, free of shear locking, good convergence and high suitability for thin to moderately thick plates.
Abstract: The formulation, implementation and testing of simple, efficient and robust shell finite elements have challenged investigators over the past four decades. A new 3-node flat triangular shell element is developed by combination of a membrane component and a plate bending component. The ANDES-based membrane component includes rotational degrees of freedom, and the refined nonconforming element method-based bending component involves a transverse shear correction. Numerical examples are carried out for benchmark tests. The results show that compared with some popular shell elements, the present one is simple but exhibits excellent all-around properties (for both membrane-and bending-dominated situations), such as free of aspect ratio locking, passing the patch test, free of shear locking, good convergence and high suitability for thin to moderately thick plates. The developed element has already been adopted in a warpage simulation package for injection molding. Copyright © 2011 John Wiley & Sons, Ltd.

10 citations

Journal ArticleDOI
TL;DR: In this article, a surface model-based warpage simulation is presented, in which the part is represented as a perfect bonding of two half-thickness plates with their reference surfaces at the outer boundary of the part.
Abstract: The mid-plane model for warpage simulation of injection-molded parts requires a mid-plane mesh whose transformation is considerably time consuming. To overcome this drawback, a surface model-based warpage simulation is presented, in which the part is represented as a perfect bonding of two half-thickness plates with their reference surfaces at the outer boundary of the part. The plates over the surface mesh are modeled as flat shell elements, and a new triangular flat shell element is developed which combines an Assumed Natural DEviatoric Strain (ANDES) based membrane component and a Refined Nonconforming Element Method (RNEM) based bending component. The bonding is accomplished by multipoint constraints and a Lagrange multiplier based elimination method is proposed for constraint application. The results show that compared with some popular shell elements, ANSYS, Moldflow and the experiments, the presented model exhibits a high performance in computation accuracy. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

9 citations

Journal ArticleDOI
TL;DR: In this article, a hybrid control-volume finite element/finite difference method (CV/FEM/FDM) similar to conventional injection molding simulation is employed to solve the gas penetration interface within the gas channel by applying the matching asymptotic expansion method.
Abstract: Present gas-assisted injection molding simulations are all based on either a midplane model or a 3D model, in which second modeling is unavoidable for a midplane model, and a 3D simulation needs a full-scale three-dimensional discretization of parts leading to unsustainable computing time and unstable numerical analysis. In this paper, surface model based modeling and numerical simulation of gas-assisted injection molding are proposed. By taking the influence of gas penetration on melt flow as boundary conditions of the melt-filling region, a hybrid control-volume finite element/finite-difference method (CV/FEM/FDM) similar to conventional injection molding simulation is employed. The gas penetration interface within the gas channel is solved by applying the matching asymptotic expansion method, which educes an analytical model of the gas penetration thickness ratio. A technology of generating gas-channel mesh semiautomatically is put forward, which combines selecting the path of gas channel manually and calculating the parameters of gas nodes automatically. The second modeling is thus avoided. The proposed model and simulation are verified by comparing with the experiment.

5 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, a review of the factors affecting shrinkage of molded parts in injection molding is presented, which is organized according to molding scale and by considering four branches of influence: material behaviors, processing parameters, mold and specimen design.
Abstract: Purpose: This paper reviews the factors affecting shrinkage of molded parts in injection molding. Methods: A selective screening of the papers published in the last 10 years was adopted. The review was organized according to molding scale (macro or micro) and by considering four branches of influence: material behaviors, processing parameters, mold, and specimen design. Results: Within the interval of confidence, at the macroscale, critical processing parameters were the temperatures, the packing parameters, cooling time, and injection speed; temperatures and packing parameters resulted critical factors at the microscale as well. Concerning the design aspects, the runner size and the ribs affect shrinkage at the macro and microscale, respectively. The analysis of the literature review has shown an absence of statistical approach for determining the material influences, a lack of information on shrinkage occur in powder-molded parts and the absence of data in specimen with dimensions below 10 µ. Conclusion...

105 citations

Journal ArticleDOI
TL;DR: Wang et al. as discussed by the authors investigated and further solved the sink mark and warpage of the molded parts in RHCM to solve the problem of sink mark, a new “bench form” structure for the screw stud on the product coupling with a lifter structure of the injection mold was proposed The external gas assisted packing was also proposed to reduce the sink marking in Rapid Heat Cycle Molding (RHCM).

68 citations

Journal ArticleDOI
TL;DR: In this paper, a gas-assisted injection molding method was applied to rice husk-filled polypropylene eco-composites polymers in different compositions, and different stages of injection pressure and delays of gas pressure were applied to improve the flow characteristics.

37 citations

Journal ArticleDOI
Chang Min Shin1, Byung Chai Lee1
TL;DR: In this paper, a three-node triangular flat shell element based on the assumed natural deviatoric strain (ANDES) formulation is proposed to improve the performance of the 18DOF triangular shell element.

36 citations

Journal ArticleDOI
TL;DR: In this paper, a multistage experimentation approach for modeling and optimization of the shrinkage and warpage of injection molding parts is proposed, which has moderate experimental size while analyzing all important interactions.
Abstract: This article suggests a multistage experimentation approach for modeling and optimization of the shrinkage and warpage of injection molding parts. This methodology has moderate experimental size while analyzing all important interactions. Phase 1 is Tag..

34 citations