Table of Content

25 November 2020, Volume 31 Issue 22

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Research on Solid Solution Forming Processes of Typical Automotive Structural Parts with 6016 Aluminum Alloy

LIU Meng, SHAN Zhongde, LI Xinya, ZANG Yong, HUANG Jianghua

2020, 31(22):  2648-2654.  DOI: 10.3969/j.issn.1004-132X.2020.22.001

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The aluminum alloy car windshield beams were taken as the research objects,and the PAM-STAMP software was used to analyze the one-step solid solution forming and step-by-step solid solution forming processes. By optimizing key processing parameters such as friction coefficient and forming temperature and carrying out the corresponding processing experiments, a processing simulation model was established. The rationalities of the forming processes were judged by using the error analysis between the experimental values and the numerical simulation ones of the wall thickness distributions on the measurement paths. The results show that after the car windshield beams using a forming way to cause cracking or deformation mutation in the middle place thinned phenomenon, along with the friction coefficient increases, the minimum thickness is fallen sharply. Compared with the one-step forming method, the step-by-step forming method is adopted, the minimum thinning rate is reduced by 4.67%, the rebound amount is reduced by 40.21%, and the temperature and friction coefficient have less influences on the minimum thickness. The mechanics property tests after aging treatment, the tensile strength is of 308 MPa, which proves that the aluminum alloy car windshield beams formed by solid solution processes are feasible.

Classification Algorithm of Casting 3D Model Based on Normal Operator and D2 Operator

SUN Xiaolong, ZHANG Zhipeng, JI Xiaoyuan, TONG Jialiang, GUAN Yaqian, ZHANG Huandong, ZHOU Jianxin

2020, 31(22):  2655-2662.  DOI: 10.3969/j.issn.1004-132X.2020.22.002

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In order to solve the problems of historical process reuse of the same casting types in casting productions, an algorithm of casting 3D model classification combining normal operator and D2 operator was proposed herein. In this method, the normal operator and D2 operator feature descriptors of the 3D models were extracted from the surface features and point feature information of the 3D models. The 3D model classification was realized by measuring the similarity between the casting feature descriptors and the basic feature descriptors of each category. The experimental results of the casting model library actually produced by companies show that the classification algorithm combining the normal operator and the D2 operator has a good feature recognition effectiveness for the common categories of castings, and solves the defects of feature insensitivity when D2 operator is used as a pre-classifier to deal with part of complex models, and may obtain classification results with higher accuracy.

Status and Development Tendency of Integrated Computational Materials Engineering in Precision Plastic Forming

ZHAN Mei, LEI Yudong, , ZHENG Zebang,

2020, 31(22):  2663-2677.  DOI: 10.3969/j.issn.1004-132X.2020.22.003

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Integrated computational materials engineering(ICME), which might quantitatively describe material preparation, processing and service processes through modeling and calculation, was an advance and effective method to realize the precision plastic forming of materials under single or integrated fields such as mechanical loading, heating, electricity, magnetism, sound field etc. In recent years, ICME was widely used by researchers in precision plastic forming. The status, progresses and development trends of ICME in multi-scale modeling of plastic forming, buckling and fracture predictions were reviewed herein. Firstly, the applications of macroscopic, mesoscopic and microscopic modelling methods on precision plastic forming were systematically reviewed in precision plastic forming. The information transmission methods were analyzed among different scale models. Based on this, progresses of the prediction methods of the two main types of defects restricting precision plastic forming, buckling and ductile fracture using ICME were discussed. The accuracy of current main instability buckling and ductile fracture models was compared. Finally, the perspectives of the applications of ICME on precision plastic forming were presented.

Research Progresses on Coupling Multi-scale Simulation of Deformation and Microstructure Evolution of Titanium Alloy in Hot Forming Processes

LIU Zhiqiang, ZHAO Jie, WANG Kehuan, WU Yong, LYU Liangxing, LIU Gang, YUAN Shijian,

2020, 31(22):  2678-2690,2698.  DOI: 10.3969/j.issn.1004-132X.2020.22.004

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Firstly, the research progresses in finite element simulation of titanium alloy high temperature deformation crystal plasticity were discussed, the applications of crystal plasticity model in the microscopic nonuniform deformation behaviors and microstructure evolution of titanium alloy were analyzed. Then the development of unified viscoplastic constitutive models was discussed around the requirements of the coupling simulation of deformations and microstructure evolution of titanium alloy in hot forming processes. And some application examples of titanium alloy hot forming were introduced. The coupling effects among the flow stress and microstructure parameters such as dynamic recovery, dynamic recrystallization, phase transformation and damage were included in the unified viscoplastic constitutive models. The simulations with unified viscoplastic constitutive models provide an effective method for the shape and microstructure predictions of titanium alloy components during hot forming. Finally, the problems of multi-scale simulation of hot forming for titanium alloy were analyzed, and the future development trends were prospected.

Simulation of Deformation Behaviors and Laws of Steel Pipes in Rolling Processes of Retained Mandrel Pipe Mills

ZHANG Dazhi, GUAN Mingsheng, ZHANG Qingdong, WANG Aiguo, ZHOU Xinliang

2020, 31(22):  2691-2698.  DOI: 10.3969/j.issn.1004-132X.2020.22.005

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A steel pipe continuous rolling process simulation model of a 180 mm retained mandrel pipe mill was established. The model was simulated to show the distributions of stress, strain and displacement on the cross-sections of steel pipes and the evolutions of wall thicknesses and diameters during the rolling processes of retained mandrel pipe mills. This model was designed to reveal the rolling pressure distributions, variations of the total rolling forces, the effects of temperature and the friction coefficient in the rolling zones on wall thicknesses and rolling forces. The wall thickness and diameter data of the steel pipes were extracted from the simulation results by cubic spline interpolation method. The finite element model was validated by the measured rolling force and wall thickness data of the industrial productions of the target units. It is found by simulation that during the continuous rolling processes, the steel pipes firstly reduced the diameter in the longitudinal direction, and then the wall thickness deformations occurred. In the lateral direction, the metal mainly flows from the top areas to the open areas. The contact pressures of the first three mill stands mainly concentrate on the top areas with large amount of deformations, which is the main deformation mill stand. The contact pressures of the fourth and fifth mill stands are the largest in the side areas with small amount of deformations, which mainly plays the role of finishing and rounding. With the rolling temperature increases, the wall thickness of steel pipes increases and the rolling forces decrease. With the friction coefficient between the mandrel and the steel pipe increases, the wall thickness decreases and the rolling force decreases. The simulation results support the key structural design of the rolling mills, the determination of rolling process parameters and the optimization of process parameters in engineering commissioning.

Optimization of RHCM Mould Electric Heating Systems for Constrainted Heating Pipe Layout

LIU Feng, , LI Jiquan, PENG Xiang, JIANG Shaofei

2020, 31(22):  2699-2707.  DOI: 10.3969/j.issn.1004-132X.2020.22.006

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Under the constraints of given heating pipe layout and the maximum allowable energy consumption, aiming to achieve rapid and uniform heating of the RHCM mould cavity surfaces, with the heat flux density of the single heating rod as the design variable, a method combining the finite element simulation, response surface design and multi-objective particle swarm optimization(MOPSO) technology was proposed to optimize the RHCM mould electric heating systems. After optimization, the maximum temperature difference of the mould cavity surfaces and the energy consumption of the heating systems are reduced by 63.4% and 9% respectively. The surface quality of flat plastic parts molded was compared with that under the conventional injection molding and RHCM processes respectively. The results show that the product surface roughness Ra may be reduced from 320 nm to 118 nm, and the surface defects such as weld marks and shrink marks also may be effectively suppressed by RHCM processes. It is also found that the product surface roughness has a negative correlation with the temperature of the cavity surfaces at the same location, indicating that the optimized cavity surface temperature distribution is more conducive to improve the product surface quality.

State-of-the-art of Friction Law in Metal Forming

WANG Zhigang, YOSHIKAWA Yasuharu, DONG Wenzheng,

2020, 31(22):  2708-2714.  DOI: 10.3969/j.issn.1004-132X.2020.22.007

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In metal forming, liquid lubricants and lubrication coatings were generally employed. Based on the understanding of friction behaviors under lubricated conditions, the friction law under dry conditions was determined by experimental results in the side stretching friction tests and the high pressure friction tests with a diamond-like carbon(DLC) coated friction tool. Then the friction law of lubrication coatings was investigated. Finally, the friction law under lubricated conditions was proposed based on the friction law under dry conditions and experimental results obtained by the side stretching friction tests.

Study on Three Dimensional Simulation and Elimination Countermeasures of Melt Jetting Phenomenon in Injection Molding

HUA Shaozhen, MENG Fanjing, LIU Huabo, DING Hai

2020, 31(22):  2715-2722.  DOI: 10.3969/j.issn.1004-132X.2020.22.008

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To explore the elimination countermeasures of melt jetting phenomenon in plastic injection molding, a high resolution discrete scheme was used to track the melt front. The governing equations were discretized by finite volume method and a three dimensional algorithm was developed. Comparing to experimental results, the two modes of molding filling under jetting conditions in the cuboid cavity with 4 mm thickness and the evolution of jetting in thick cavity were successfully simulated numerically. It is found that the jet buckling presents two-dimensional folding in the cuboid cavity with small thickness and three-dimensional roiling in thick cavity. Gravity has an impact on the evolution of jetting in thick cavity. Jetting might be effectively eliminated or depressed via enlarging shear rate with changing the magnitude or the direction of velocity. Two numerical cases were performed to verify the views.

Springback Control and Compensation of Incremental Forming for Sheet Metal Parts with Open Geometric Feature

LI Ming, DAI Peipei, CHANG Zhidong, CHEN Jun,

2020, 31(22):  2723-2727.  DOI: 10.3969/j.issn.1004-132X.2020.22.009

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The incremental forming of sheet metal parts with open geometric features was realized. The optimization of processing parameters, multi pass incremental forming and trajectory compensation were proposed to improve the geometric accuracy of sheet metal parts. The intermediate configuration of multi-pass incremental forming was designed to increase the plastic deformation and reduce the geometric deviation. In order to prevent the fracture during the first pass, the forming angle of the non fixed direction was set as 75° and the sheet metal in the non fixed direction was fully formed in the second pass. The geometric deviation of sheet metal parts with open geometric features may be controlled within 0.5 mm by using two-step incremental forming method based on geometric compensation.

Data-driven Modeling and Intelligent Prediction Analysis for Hot Strip Outlet Crowns

LIU Yuanming, WANG Zhenhua, WANG Tao, LIU Wenli, XIONG Xiaoyan

2020, 31(22):  2728-2733.  DOI: 10.3969/j.issn.1004-132X.2020.22.010

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A new prediction model of strip outlet crowns was proposed based on hot rolling actual production data and intelligent algorithm. This model used differential evolution algorithm to optimize the penalty factor and kernel function width of SVM, and the optimal parameters combinations of support vector regression model were determined. The model was trained with a lot of actual production data and was used to predict the strip outlet crowns. The model structure was simple and easy to implement, and the overall performance was evaluated by mean absolute error, mean absolute percentage error, root mean square error and determination coefficient R2. The feasibility of the proposed model was verified by comparing the predicted values with the actual ones.

Intelligent Technology of Plastic Injection Molding and Its Applications

LI Yang, GUO Fei, LI Maoyuan, ZHANG Yun, LI Dequn

2020, 31(22):  2734-2744.  DOI: 10.3969/j.issn.1004-132X.2020.22.011

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The current industrial needs and technical bottlenecks of plastic injection molding, and the clarified future development trend were summarized. According to the characteristics of plastic injection molding, a scientific framework of the “intelligent manufacturing system of injection molding” was proposed, and the intelligent injection molding solutions based on sensor technology, industrial Ethernet and internet were established. Focusing on four levels, i.e. intelligent design, intelligent optimization, intelligent monitoring and manufacturing data platform, the knowledge organization and reuse, independent decision-making and optimization, process sensing and detection, cloud service and other technologies in injection molding were summarized, and the important development directions for the deep integration of plastic injection molding and new generation artificial intelligence technologies were pointed out.

Effective Prediction and Compensation of Springbacks for Tube Bending Using Machine Learning Approach

CHEN Guangyao, LI Heng, HE Zirui, MA Jun, LI Guangjun, FU Ying

2020, 31(22):  2745-2752.  DOI: 10.3969/j.issn.1004-132X.2020.22.012

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The machine learning algorithm modeling was adopted based on the optimized back propagation(BP) neural network and the precise prediction and efficient control method of bend springbacks was proposed. In this method, the particle swarm optimization(PSO) algorithm was improved by introducing the nonlinear inertia weight and hybrid operator of genetic algorithm, and then the BP neural network was optimized by the improved PSO algorithm, and the machine learning springback prediction and compensation model was constructed based on the improved PSO-BP neural network. Based on the springback data of different specifications, batches，and forming parameters in the actual productions, the applications of the machine learning prediction model were verified. The average relative error of the prediction results obtained by the model is as 6.3%. Compared with the traditional models, the prediction accuracy is increased by 18.5% at most, and the calculation time may be reduced from 1.5 h to 300 s. The prediction and compensation accuracy of springback and the calculation efficiency are improved significantly.

Green and Intelligent Forming Technology and Its Applications for High Strength Lightweight Materials

HUA Lin, WEI Pengfei, HU Zhili,

2020, 31(22):  2753-2762,2771.  DOI: 10.3969/j.issn.1004-132X.2020.22.013

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Research achievements and current status of high strength light material green and intelligent forming processes were reviewed. Intelligent processing design of cold stamping, intelligent tailor property of hot stamping and intelligent stamping systems and equipment were mainly introduced. Green intelligent stamping forming technology of complex components made of light and high strength materials was discussed and prospected in the aspects of applications of process design systems of cold stamping with high strength steels, post-form precision control of cold stamping with aluminum alloy, tailor properties of hot stamping with high strength steels and mechanics property control of hot stamping with aluminum alloy, which aimed to give reference for intelligent forming processes of lightweight and high strength alloy.

Hydro-mechanical Forming Process Combined with Multi-directional Local Loading for Special-shaped Exhaust Pipes

XU Yong, LI Ming, XIA Liangliang, ZHANG Shihong,

2020, 31(22):  2763-2771.  DOI: 10.3969/j.issn.1004-132X.2020.22.014

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In order to solve the manufacturing problems of the integrated exhaust pipes with special shapes in one kind of passenger car, the whole hydro-mechanical forming processes combined with multi-directional local loading of 4 series stainless steel tubes were carried out. Based on Dynaform software, the finite elements models of rotary bending and hydro-mechanical forming were established, and the evolution law of the wall thickness distribution of the tubes was monitored to optimize the forming parameters and develop experimental verification. The results show that the initial tube diameter has a significant effect on the wall thickness distribution of the hydro-mechanical formed tubes, and the initial tube diameter of 54 mm may meet the process requirements. In the longitudinal hydro-mechanical forming stages, the local loading to the tubes may be achieved by the convex ribs of the upper dies. And in the horizontal hydro-mechanical forming stages, the internal pressure of 48 MPa may avoid the occurrence of cracks, material folding and other defects. In addition, the hydro-mechanical forming combined with local loading may significantly change the stress and strain states of the tubes. The wall thickness of the tubes in the deformation zones shows an increasing trend. The maximum thinning rate of the tubes is reduced from 27.43% to 24.65%, while the maximum thinning rate of the final parts is as 28.05%. The simulation and experimental results are basically consistent and the maximum deviation is only 2.89%.