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Formation of edge crack in 1.4%Si Non-oriented Electrical Steel during Hot Rolling

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Journal of Iron and Steel Research(International) 2014年第2期21卷 269-274页

作者： Ai-hua CHEN Hai-rong GUO Hua-long LI Toshihiko EMI Institute of Research of Iron and Steel Shasteel

Microstructure evolution, dynamic recrystallization, high temperature oxidation and hot ductility of 1.4 % Si non-oriented electrical steel sheets were investigated to reduce edge cracking. The causes of cracking were found to be coarse as-cast microstructure, grain boundary oxidation in reheating furnace, lack of dynamic recrystallization during hot rolling and increase of temperature, resulting in reduced hot ductility in strip edge region. Countermeas- ures against the edge crack are proposed accordingly. Lowering reheating temperature and reducing holding time re- duced oxidation and decarburization. Hot charging temperature was increased to decrease reheating temperature. And using an edger can refine microstructure in strip edge region. Finally, edge heater can be added to increase edge re- gion formability by inducing dynamic reerystallization and ductility by increasing temperature.

关键词： edge crack non-oriented electrical steel hot rolling

PARAMETER AND INTERACTION STUDY OF edge crack PROBLEM USING MESHFREE METHOD

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International Journal of Modeling, Simulation, and Scientific Computing 2012年第4期3卷 58-76页

作者： KAMAL SHARMA VIVEK BHASIN I.V.SINGH B.K.MISHRA K.K.VAZE Reactor Safety Division BARC TrombayMumbaiMaharastraIndia MIED IIT RoorkeeRoorkeeUttarakhandIndia

In this work,element free Galerkin method(EFGM)has been used to obtain the solution of edge crack problem under mechanical loads as it provides a versatile technique to model static as well as moving crack problems without any requirement of remeshing.At first,some techniques are presented for enriching the EFG approximations near the crack tip such as extrinsic and intrinsic enrichment.Extrinsic enrichment involves the addition of solution form to the trial function,whereas the EFG basis is expanded to include few terms from crack tip solution in intrinsic enrichment.Apart from enrichment techniques,four basic techniques of smoothing meshless approximations near nonconvex boundaries are also presented such as diffraction,transparency,see through and wedge model.These techniques are then used for the parameteric analysis of an edge crack problem under mode-1 loading and results obtained using different approaches are compared with each other as well as with exact solution.Among these techniques,the extrinsic PU enrichment technique was found to be more accurate as compared to other approaches.Extrinsic PU enrichment technique has also been used for the analysis of a shear edge crack problem.In all these techniques,the value of mode-1 stress intensity factor and mode-2 stress intensity factor has been evaluated by interaction integral approach.Effect of crack orientation is also studied for different cases.

关键词： EFGM edge crack enrichment techniques meshfree.

Comparison of edge cracking and tensile cracking in in-situ deformation at 150℃of Mg-2Zn-1.5Mn alloy sheet

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Journal of Materials Science & Technology 2022年第17期112卷 24-35页

作者： Qiang Liu Jiangfeng Song Yuanding Huang Bin Jiang Biquan Xiao Fusheng Pan National Engineering Research Center for Magnesium Alloys Chongqing UniversityChongqing 400044China MagIC-Magnesium innovation Centre Helmholtz-Zentrum GeesthachtMax-Planck-Str.121502 GeesthachtGermany

The Mg-2Zn-1.5Mn alloy(ZM21)sheets were hot-rolled in a single pass at 150℃with different reductions through on-line heating rolling.Microstructures and edge cracking behavior of the rolled sheets were investigated.The in-situ tensile tests at 150℃were also carried out,the crack initiation and propagation were compared with the edge cracking behavior of ZM21 sheets prepared by on-line heating rolling.The results reveal that the edge cracks are most likely to originate in the rolling direction and normal direction(RD-ND)plane due to the secondary tensile stress along RD.edge cracking becomes more severe with an increasing reduction.The edge cracks mainly initiate and propagate in the fine recrystallized grain areas and the junction of recrystallized grains and sub-grains with hard orientation.The in-situ tensile test indicates that micro-cracks mainly initiate at the triple junction of grain boundaries where grains have hard orientation with low basal Schmid factor(SF).Meanwhile,those cracks are more likely to propagate along the grain boundaries with maximum difference in basal Schmid factor.Besides,the crack initiation and propagation during the in-situ tensile deformation at 150℃are found not to be associated with the recrystallization.

关键词： ZM21 Mg alloy On-line heating rolling In-situ tensile test edge crack

Effect of copper on edge cracking behavior and microstructure of rolled austenitic stainless steel plate

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Journal of Iron and Steel Research(International) 2022年第2期29卷 281-294页

作者： Guang-hui Zhao Jian Zhang Juan Li Hua-ying Li Hai-tao Liu Li-feng Ma School of Mechanical Engineering Taiyuan University of Science and TechnologyTaiyuan030024ShanxiChina Shanxi Provincial Key Laboratory of Metallurgical Device Design Theory and Technology Taiyuan030024ShanxiChina State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang110819LiaoningChina

Cu is known to affect the edge cracking characteristics of austenitic stainless steel as it causes embrittlement.The hot rolling test of four kinds of austenitic stainless steel with different copper content(0,2.42,3.60 and 4.35 wt.%)was carried out to examine the effect of hot rolling cracks on steel containing different copper contents.The evolution of crack and microstructure was analyzed using the scanning electron microscope,energy-dispersive spectrometer,electron back scattered diffraction and transmission electron microscope.Experimental results showed an upward trend in edge cracking degree when Cu content was 4.35%,and the crack extended from the edge of the steel plate to the middle by about 14 mm.Besides,severe oxidation was observed inside the crack by fractography.With the increase in copper content at 1250℃,the content of{110}brass and{112}copper textures decreased.When the content of copper was 4.35%,the decrease was most significant,and{112}copper texture content decreased to only 0.5%.Generally,the textures of 2.42%Cu and 3.60%Cu 304L steel changed little,while a large change in the texture of 4.35%Cu 304L steel was observed.To conclude,the increase in rolling temperature can prevent edge crack and its propagation effectively.

关键词： Austenitic stainless steel Copper edge crack Microstructure Ferrite

Effects of edge cracks on the thermomagnetic instabilities of type-Ⅱ superconducting thin films

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National Science Review 2023年第3期10卷 17-28页

作者： Ze Jing Institute of Extreme Mechanics and School of Aeronautics Northwestern Polytechnical University

Thermomagnetic instability is a crucial issue for the application of superconductors.Effects of edge cracks on the thermomagnetic instability of superconducting thin films are systematically investigated in this work.Dendritic flux avalanches in thin films are well reproduced through electrodynamics simulations,and relevant physical mechanisms are revealed from dissipative vortex dynamics simulations.It is found that edge cracks sharply decrease the threshold field for the thermomagnetic instability of superconducting films.Spectrum analysis shows that the time series of magnetization jumping displays scale-invariance and follows a power law with an exponent around 1.9.In a cracked film,flux jumps more frequently with lower amplitudes compared with its crack-less counterpart.As the crack extends,the threshold field decreases,the jumping frequency gets lower,while its magnitude gets larger.When the crack has extended long enough,the threshold field increases to even larger than that of the crack-less film.This counterintuitive result originates from the transition of the thermomagnetic instability triggered at the crack tip to the one triggered at the center of the crack edges,which is validated by the multifractal spectrum of magnetization jumping sequences.In addition,with the variation of crack lengths,three different modes of vortex motion are found,which explains the different flux patterns formed in the avalanche process.

关键词： superconducting thin film thermomagnetic instability flux jumps edge crack scaling law

Unveiling the underlying mechanism of forming edge cracks upon high strain-rate rolling of magnesium alloy

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Journal of Materials Science & Technology 2020年第15期47卷 59-65页

作者： Biwu Zhu Xiao Liu Chao Xie Jing Su Pengcheng Guo Changping Tang Wenhui Liu Key Laboratory of High Temperature Wear Resistant Materials Preparation Technology of Hunan Province Hunan University of Science and TechnologyXiangtan 411201China Faculty of Mechanical Engineering and Mechanics Ningbo UniversityNingbo 315211China Max-Planck-Institut für Eisenforschung GmbH Max-Planck-Strafie 1Dusseldorf40237Germany College of Mechanical and Electrical Engineering Central South University of Forestry and TechnologyChangsha 410004China Key Laboratory of High Temperature Wear Resistant Materials Preparation Technology of Hunan Province Hunan University of Science and TechnologyXiangtan 477207China

In the current study,high strain-rate rolling(≥10 s-1) has been successfully employed to produce Mg-3 A1-1 Zn alloy sheets to a high reduction of 82% with a fine grain structure in a single pass.The underlying mechanism of forming primary and secondary edge cracks has been investigated.It is found that dynamic recrystallization(DRX) induced by subgrains tends to blunt cracks,while twinning-induced D RX is mainly observed around sharp crack tips.The motion of emitted dislocations from blunted cracks is inhibited by the DRX grain boundaries.This,on one hand,increases local work hardening,and on the other hand,causes stress concentration alo ng grain boundaries especially in the triple junctions leading to the formation of secondary cracks.

关键词： edge crack Secondary crack High strain-rate rolling AZ31 magnesium alloy Dynamic recrystallization

WEIGHT FUNCTION FOR STRESS INTENSITY FACTORS IN ROTATING THICK-WALLED CYLINDER

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Applied Mathematics and Mechanics(English Edition) 2006年第1期27卷 29-35页

作者：陈爱军曾文骥 School of Science

The equation of stress intensity factors（SIF） of internally pressurized thick-walled cylinder was used as the reference case. SIF equation of rotating thick-walled cylinder containing a radial crack along the internal bore was presented in weight function method. The weight function formulas were worked out and can be used for all kinds of depth of cracks, rotating speed, material, size of thick-walled cylinder to calculate the stress intensity factors. The results indicated the validity and effectiveness of these formulas. Meanwhile, the rules of the stress intensity factors in rotating thick-walled cylinder with the change of crack depths and the ratio of outer radius to inner radius were studied. The studies are valuable to engineering application.

关键词： fracture mechanics weight function method rotating cylinder edge crack

FRACTURE ANALYSIS OF AN edge-crackED DIELECTRIC PLATE VIA NOVEL BOUNDARY INTEGRAL EQUATION METHOD

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FRACTURE ANALYSIS OF AN EDGE-CRACKED DIELECTRIC PLATE VIA NO...

OPTIMIZATION OF MATERIAL DISTRIBUTIONS FOR MINIMIZING THE STRESS INTENSITY FACTOR IN MULTI-PHASE FGM CIRCULAR PIPES UNDER THERMOMECHANICAL LOADING

2015全国压电和声波理论及器件技术研讨会

作者： Shi-bo WANG Ya-guang GUO Ming-hao ZHAO Cui-ying FAN School of Mechanical Engineering Zhengzhou University School of Mechanics and Engineering Science Zhengzhou University

Dielectric materials are widely used as insulating materials in electronic devices.However,cracks inside dielectric materials may cause performance degradation of the electronic devices.In this paper,the sub-region boundary element method is developed for handling the edge crack problem,in which the area in the crack cavity is treated separately.The proposed method is distinguished from any existing boundary element formulation for fracture analysis.An exact boundary condition is applied to crack faces.The whole calculation is done by using the software Mathematica.Finally,we obtain numerical results of the electric field within the crack cavity and calculate the stress and the electric displacement intensity factors.

关键词： edge crack Dielectric material Exact boundary condition Sub-region BEM Intensity factor

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OPTIMIZATION OF MATERIAL DISTRIBUTIONS FOR MINIMIZING THE ST...