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Microstructure evolution of 7050 aluminum forgings during surface cumulative plastic deformation

Transactions of Nonferrous Metals Society of China 2025年第1期35卷 45-59页

作者： Jian-liang HU Ze-xiong ZHANG Cheng XING Xiu-jiang WU Shi-quan HUANG Hong BO Key Laboratory of Advanced Forging&Stamping Technology and Science Ministry of EducationYanshan UniversityQinhuangdao 066004China State Key Laboratory of Precision Manufacturing for Extreme Service Performance Central South UniversityChangsha 410083China College of Mechanical Engineering Yanshan UniversityQinhuangdao 066004China Hebei Engineering Technology Research Center of Metal Precision Plastic Processing Yanshan UniversityQinhuangdao 066004China State Key Laboratory of Metastable Materials Science and Technology Yanshan UniversityQinhuangdao 066004China

To elucidate the mechanisms of regulating the microstructure uniformity in 7050 aluminum forgings through surface cumulative plastic deformation(SCPD),the microstructure under different solution treatments was investigated using metallographic observation(OM),electron backscatter diffraction(EBSD),transmission electron microscopy(TEM),and X-ray diffraction(XRD).The findings demonstrate that the most uniform microstructure in the forgings is achieved with a solution treatment at 470℃for 30 *** SCPD process generates a significant number of needle-shaped precipitates,resulting in a higher dislocation density and stored *** treatments alleviate the pinning effect of second-phase particles and facilitate static recrystallization(SRX)in forgings,leading to a reduction in grain ***,mechanical testing results demonstrate 7%−13%increase in tensile strength and more uniform elongation of the forgings in different directions.

关键词： microstructure homogeneity surface cumulative plastic deformation(SCPD) static recrystallization(SRX) dislocation density

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Research on state monitoring system of high-pressure servo motor based on SVDD and SVM

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Zhendong yu Chongji/Journal of Vibration and Shock 2025年第12期44卷 238-248页

作者： Ma, Liqiang Jiang, Anqi Jiang, Wanlu Zheng, Yunfei Wu, Fenghe Hebei Provincial Key Laboratory of Heavy Machinery Fluid Power Transmission and Control Yanshan University Qinhuangdao066004 China Key Laboratory of Advanced Forging & Stamping Technology and Science Ministry of Education Yanshan University Qinhuangdao066004 China School of Electrical Engineering Yanshan University Qinhuangdao066004 China School of Mechanical Engineering Yanshan University Qinhuangdao066004 China

In the monitoring of high-pressure servo motor, the number of normal samples far exceeds that of fault ones. Fault data are scarce and relatively difficult to collect. In addition, with the uncertain of fault occurrence, traditional monitoring methods are difficult to apply effectively. To address these issues, a state monitoring system for high-pressure servo motor was proposed based on support vector data description (SVDD) for anomaly detection and support vector machine (SVM) for fault diagnosis. Initially, time-domain (T), frequency-domain (F), and wavelet packet subband energy (W) features were extracted from raw data. These features were then fused and normalized to form a new multidimensional feature vector, TFW. Subsequently, a convolutional neural network (CNN) was employed to deeply mine the TFW, generating more expressive features, TFWCNN, which served as inputs to the SVDD and SVM models. An experimental platform for simulating high-pressure servo motor faults was constructed to collect data and validate the proposed method. The results indicate that on three dynamic datasets with different valve opening positions, the Fl scores for SVDD anomaly detection are 0. 999 1, 0. 997 8, and 0. 976 0, and for SVM fault diagnosis, the Fl scores are 0.998 8, 0.995 0, and 0. 986 7, respectively. These findings demonstrate the superior performance of the proposed method in the state monitoring of high-pressure servo motor and highlight the efficacy and accuracy of deep TFWCNN features. Furthermore, this study provides an effective technical solution for similar turbine state monitoring and diagnostic systems. © 2025 Chinese Vibration Engineering Society. All rights reserved.

关键词： Frequency domain analysis

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General Analytical Shakedown Solution for Structures with Kinematic Hardening Materials

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Chinese Journal of Mechanical Engineering 2016年第5期29卷 944-953页

作者： GUO Baofeng ZOU Zongyuan JIN Miao Key Laboratory of Advanced Forging & Stamping Technology and Science of Ministry of Education Yanshan University

The effect of kinematic hardening behavior on the shakedown behaviors of structure has been investigated by performing shakedown analysis for some specific problems. The results obtained only show that the shakedown limit loads of structures with kinematic hardening model are larger than or equal to those with perfectly plastic model of the same initial yield stress. To further investigate the rules governing the different shakedown behaviors of kinematic hardening structures, the extended shakedown theorem for limited kinematic hardening is applied, the shakedown condition is then proposed, and a general analytical solution for the structural shakedown limit load is thus derived. The analytical shakedown limit loads for fully reversed cyclic loading and non-fully reversed cyclic loading are then given based on the general solution. The resulting analytical solution is applied to some specific problems： a hollow specimen subjected to tension and torsion, a flanged pipe subjected to pressure and axial force and a square plate with small central hole subjected to biaxial tension. The results obtained are compared with those in literatures, they are consistent with each other. Based on the resulting general analytical solution, rules governing the general effects of kinematic hardening behavior on the shakedown behavior of structure are clearly.

关键词： elastic-plastic elastic shakedown kinematic hardening shakedown limit load general analytical solution

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Formation Mechanism of Inclusion Defects in Large Forged Pieces

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Journal of Iron and Steel Research International 2016年第6期23卷 531-538页

作者： Rong-sheng QI Miao JIN Xin-gang LIU Bao-feng GUO Key Laboratory of Advanced Forging and Stamping Technology and Science of Ministry of Education Yanshan University

Nonmetallic inclusions mixed into large forged metal objects destroy the continuity in the metal and affect the quality of the forged *** on how inclusions affect the plastic deformation of a matrix shows the significance of the formation mechanism of inclusion *** upset forging,the nonlinear finite element model was shown to be appropriate for the ingot hot-forging process by comparing the results with experiments involving plastic and hard inclusions inserted into the forged *** high-temperature stress-strain curves of MnS plastic inclusions were obtained *** results show how,during upsetting,the morphology of MnS plastic inclusions varies from spherical to ellipsoidal,until finally becoming flat in *** larger the inclusion is,the larger the degree of deformation of the inclusion is,and large inclusions enhance the risk of the final product failing to pass inspection for inclusion *** significantly concentrates in the matrix near a hard *** the hard inclusion reaches a certain size,conical fractures form on both sides of the *** pass inclusion-flaw inspection and close hole defects to the extent possible,the flat-anvil upsetting is ***,the inclusiondeformation state obtained by finite element simulation is verified experimentally.

关键词： inclusion inspection anvil spherical destroy continuity forging finally verified ingot

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Static Recrystallization Behavior of 316LN Austenitic Stainless Steel

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Journal of Iron and Steel Research International 2013年第11期20卷 67-72页

作者： JIN Miao LU Bo LIU Xin-gang GUO Huan JI Hai-peng GUO Bao-feng Key Laboratory of Advanced Forging and Stamping Technology and Science of Ministry of Education Yanshan University

The static recrystallization of 316LN austenitic stainless steel was studied by double-pass hot compression tests on a Gleeble 3500 thermomechanical simulator. The specimens were compressed at the deformation tempera- tures of 950, 1050, 1150 ℃, strain rates of 0.01, 0.1, 1 s^- 1, strains of 0.1, 0.15, 0.2, and intervals of 1-100 s. The results show that the volume fraction of static recrystallization of 316LN increases with the increase of deforma- tion temperature, strain rate, strain and interval, which indicates that static recrystallization occurs easily under the conditions of higher deformation temperature, higher strain rate and larger strain. Deformation temperature has sig- nificant influence on static recrystallization of 316LN. The volume fraction of static recrystallization could easily reach 1000% at higher deformation temperatures. By microstructure analysis, it can be concluded that the larger the volume fraction of static recrystallization, the more obvious the grain refinement. The static recrystallization activation energy of 317 882 J/mol and the exponent n of 0.46 were obtained. The static recrystallization kinetics was established. The predicted volume fraction of static recrystallization is in good agreement with the experimental results.

关键词： static recrystallization austenitic stainless steel hot deformation

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Calibration of discrete element parameters and FEM-DEM coupling analysis for solid granules medium deep drawing forming

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Powder technology 2025年 463卷

作者： Haiwei Shi Changcai Zhao Bing Du Guoyi Shen Hengkai Ren Key Laboratory of Advanced Forging & Stamping Technology and Science (YanShan University) Ministry of Education of China Qinhuangdao 066004 China

To analyze the internal interactions of solid granules medium (SGM) and their interactions with sheet metal during the SGM deep drawing forming process, the discrete element method (DEM) is used for the SGM, and the finite element method (FEM) is employed for the sheet metal. A new FEM-DEM coupling method is developed based on the force conservation principle. To address the issues of circularity and deformation under high pressure present in the SGM, the rolling resistance linear (RRL) model is applied. A high-precision inversion method utilizing the back propagation neural network-particle swarm optimization (BP-PSO) algorithm is proposed to enhance the efficiency of DEM parameter calibration. The SGM deep drawing forming process is conducted and compared with the simulation results of the FEM-DEM coupling model, which confirms the accuracy of the coupling model. This model analyzes force transmission and flow of the granules, efficiently visualizing interactions during the forming process.

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Flow Stress Behaviors and Microstructure Evolution of 300M High Strength Steel under Isothermal Compression

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Journal of Iron and Steel Research International 2014年第12期21卷 1116-1123页

作者： Rong-sheng QI Bao-feng GUO Xin-gang LIU Miao JIN Key Laboratory of Advanced Forging & Stamping Technology and Science(Yanshan University) Ministry of Education of China

The compressive deformation behaviors of 300M high strength steel were investigated over a wide range of temperatures （850- 1200 C） and strain rates （0. 001- 10 s^- 1 ） on a Gleeble-3800 thermo-mechanical simulator. The measured flow stress was modified by the corrections of the friction and the temperature compensations, which nicely reflect negative effects of the friction and temperature on the flow stress. The corrected stress-strain curves were the dynamic recrystallization type on the conditions of higher deformation temperature and lower strain rate. Flow stress increases with the increase of strain rate at the same deformation temperature and strain. By contrast, flow stress decreases with the increase of temperature at the same strain rate and strain. Dependence of the peak stress on temperature and strain rate for 300M steel is described by means of the conventional hyperbolic sine equation. By re gression analysis, the activation energy （Q） in the whole range of deformation temperature is determined to be 367. 562 kJ/mol. The effects of the temperature and the strain rate on mierostructural evolution are obvious. With the increase of the deformation temperature and the decrease of the strain rate, the original austenite grain sizes of 300M steel increase. At the same time, the corrected flow stress curves more accurately determine the evolution of the microstrueture.

关键词： 300M high strength steel flow stress curve correction microstructural evolution

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Hot Granules Medium pressure forming Process of AA7075 Conical Parts

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Chinese Journal of Mechanical Engineering 2015年第3期28卷 580-591页

作者： DONG Guojiang ZHAO Changcai PENG Yaxin LI Ying College of Vehicles and Energy Yanshan University Key Laboratory of Advanced Forging & Stamping Technology and Science of Ministry of Education Yanshan University

High strength aluminum alloy plate has a low elongation at room temperature, which leads to the forming of its components need a high temperature. Liquid or gas is used as the pressure-transfer medium in the existing flexible mould forming process, the heat resistance of the medium and pressurizing device makes the application of aluminum alloy plate thermoforming restricted. To solve this problem, the existing medium is replaced by the heat-resisting solid granules and the general pressure equipments are applied. Based on the pressure-transfer performance test of the solid granules medium, the feasibility that the assumption of the extended Drucker-Prager linear model can be used in the finite element analysis is proved. The constitutive equation, the yield function and the theoretical forming limit diagram（FLD） of AA7075 sheet are established. Through the finite element numerical simulation of hot granules medium pressure forming（HGMF） process, not only the influence laws of the process parameters, such as forming temperature, the blank-holder gap and the diameter of the slab, on sheet metal forming performance are discussed, but also the broken area of the forming process is analyzed and predicted, which are coincided with the technological test. The conical part whose half cone angle is 15° and relative height H/d0 is 0.57, is formed in one process at 250℃. The HGMF process solves the problems of loading and seal in the existing flexible mould forming process and provides a novel technology for thermoforming of light alloy plate, such as magnesium alloy, aluminium alloy and titanium alloy.

关键词： granules medium aluminum alloy sheet drawing hot forming forming limit diagram

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Research on technological parameters of pressure forming with hot granule medium on AA7075 sheet

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Journal of Central South University 2016年第4期23卷 765-777页

作者：董国疆赵长财赵建培押媛媛曹秒艳 College of Vehicles and Energy Yanshan University Key Laboratory of Advanced Forging & Stamping Technology and Science of Ministry of Education (Yanshan University)

Hot granule medium pressure forming （HGMF） process is a new process in which granule medium replaces the medium in existing flexible-die hot forming process, such as liquids, gases or viscous medium. Hot forming of light alloy sheet parts can be realized based on the properties of granule medium, such as withstanding high temperature and pressure, filling well, sealing and loading easily. In this work, the forming of AA7075 cylindrical parts by HGMF process is taken as an example to establish the constitutive relation and forming limit diagram （FLD） of AA7075 sheet which is related to temperature by hot uniaxial tensile test of sheet metal. Based on the assumption that granule medium is applied to extended Drucker-Prager linear material model, the finite element model of HGMF process is established and the effect of technological parameters, such as forming temperature, blank-holder gap and drawing ratio, on the sheet metal formability, is studied. The limit drawing ratio curve of AA7075 cylindrical parts at forming temperature of 175-300 ℃ is obtained by HGMF process test, and the limit drawing ratio reaches the maximum value of 1.71 at 250 ℃. The results of numerical simulation are consistent with the results of process test, and the forming force, distribution of wall thichness and form of instability are predicted correctly, which provides reference for the application of HGMF process.

关键词： granule medium aluminum alloy sheet drawing hot forming forming limit diagram

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High-temperature fracture behavior of MnS inclusions based on GTN model

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Journal of Iron and Steel Research International 2019年第9期26卷 941-952页

作者： Xin-gang Liu Can Wang Qing-feng Deng Bao-feng Guo Key Laboratory of Advanced Forging and Stamping Technology and Science (Yanshan University) Ministry of Education of ChinaQinhuangdao 066004HebeiChina

The influence of the MnS plastic inclusion on the accumulation of internal damage was considered, and the Gurson– Tvergaard–Needleman (GTN) model was calibrated based on the finite element inverse method and image analysis method using ABAQUS and GTN models. The modified GTN damage model was used to simulate the initiation and propagation of cracks in an as-cast 304 stainless steel with MnS inclusions at 900 C. The simulation results agreed well with the experimental results, indicating that the model can be effectively applied to examine the high-temperature fracture behavior of MnS inclusions. The simulation and high-temperature tensile test results revealed that MnS inclusions increased the number of holes initiation and the probability of hole polymerization, reduced the crack propagation resistance, accelerated the occurrence of material fracture behavior, and were closely related to the stress state at high temperatures. When the stress triaxiality was low, the plastic strain in the metal matrix was high, and the MnS plastic inclusions accelerated the polymerization of the pores, making metal fracture failure more likely. On the other hand, when the stress triaxiality was high, the stress state in the metal matrix was biased to the tensile state, the plastic strain in the metal matrix was low, and the influence of MnS plastic inclusions on the fracture behavior was not evident.

关键词： MnS inclusion GTN model Tension High-temperature fracture behavior Crack initiation Crack propagation Stress

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