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Acta Mechanica Solida Sinica 2021年第1期34卷 79-90页

作者： Bin Chen Wen-Ping Wu Ming-Xiang Chen Department of Engineering Mechanics School of Civil EngineeringWuhan UniversityWuhan430072China State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan UniversityWuhan430072China

In this paper,the morphology and evolution of interfacial dislocation networks of(100),(110)and(111)interphases of Ni-based single-crystal superalloys are studied by molecular dynamics(MD)simulations.Three-dimensional cubic-type and sandwich-type models are chosen to explore the orientation-dependent morphology of dislocation networks,and their respective advantages and disadvantages are compared.From the simulations,it is observed that various lattice orientations and model types lead to different morphologies of dislocation networks.Based on the analysis of average atomic energy and dislocation characteristics,the(100)orientation model has a more regular dislocation network,lower energy and better stability than the(110)and(111)orientation models after MD relaxation,which are supported by previous experimental and numerical simulations.Moreover,the cubic-type model has lower energy and better stability than the sandwich-type model.This will be helpful for choosing a more appropriate and reasonable model for simulating the interfacial dislocation networks of Ni-based single-crystal superalloys.

关键词： Ni-based single-crystal superalloys Molecular dynamics simulation orientation Interfacial dislocation networks

orientation and strain rate dependent tensile behavior of single crystal titanium nanowires by molecular dynamics simulations

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Journal of Materials Science & Technology 2018年第5期34卷 864-877页

作者： Le Chang Chang-Yu Zhou Hong-Xi Liu Jian Li Xiao-Hua He School of Mechanical and Power Engineering Nanjing Tech University Nanjing 211816 China School of Mechanical Engineering Jiangsu University of Science and Technology Zhenjiang 212000 China

Molecular dynamics simulation was employed to study the tensile behavior of single crystal titanium nanowires（NWs）with[112^-0],[1^-100] and[0001]orientations at different strain rates from 10^8s^-1 to 10^11s^-1.When strain rates are above 10^10s^-1,the state transformation from HCP structure to amorphous state leads to super plasticity of Ti NWs,which is similar to FCC NWs.When strain rates are below 10^10s^-1,deformation mechanisms of Ti NWs show strong dependence on orientation.For [112^-0] orientated NW.{101^-1} compression twins（CTs）and the frequently activated transformation between CTs and deformation faults lead to higher plasticity than the other two orientated NWs.Besides,tensile deformation process along [112^-0] orientation is insensitive to strain rate.For [1^-100] orientated NW,prismaticslip is the main deformation mode at 10^8s^-1.As the strain rate increases,more types of dislocations are activated during plastic deformation process.For[0001]orientated NW,{101^-2} extension twinning is the main deformation mechanism,inducing the yield stress of [0001] orientated NW,which has the highest strain rate sensitivity.The number of initial nucleated twins increases while the saturation twin volume fraction decreases nonlinearly with increasing strain rate.

关键词： Molecular dynamics Single crystal titanium nanowires Strain rate orientation Plastic deformation mechanisms

orientation dependence of deformation twinning in Cu single crystals

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Journal of Materials Science & Technology 2018年第8期34卷 1364-1370页

作者： S.S.Cai X.W.Li N.R.Tao Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Department of Materials Physics and Chemistry School of Materials Science and Engineeringand Key LaboratoryforAnisotropy and Texture of Materials(Ministry of Education)Northeastern UniversityShenyang 110819China

Cu single crystals were subjected to dynamic compression plastic deformation to investigate orientation- dependent twinning. The experimental results showed that twinning is closely related to the ratio of the maximum Schmid factor for twinning partial （mt） to the maximum Schmid factor for perfect dislocation （ms）, i.e., mT/ms, rather than roT. The twin volume fraction VT increases with the rot/ms value and the most favorable orientation for twinning has the maximum roT/ms value （1.15）. The relationships of roT/ms with both effective stacking fault energy γeff and threshold stress for twinning TT were established for under- standing orientation-dependent twinning. Further insights into the orientation-dependent twinning and guidance for developing bulk high density nanotwinned materials are provided.

关键词： orientation Twinning Cu Single crystal

An orientation-dependent creep life evaluation method for nickel-based single crystal superalloys

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Chinese Journal of Aeronautics 2022年第1期35卷 238-249页

作者： Duoqi SHI Tianxiao SUI Zhenlei LI Xiaoguang YANG School of Energy and Power Engineering Beihang UniversityBeijing WO 191China

This paper aims to propose a creep life evaluation method considering the effect of crystallographic orientation.First,the maximum Schmid factor of{111}〈112〉and the corresponding lattice rotation angle were introduced to form an“orientation factor”.Then the equivalent stress was calculated by multiplying this factor and the nominal stress.Latterly,the Larson-Miller Parameter(LMP)method was adopted as the rupture life evaluation criteria,in which the input variable was the equivalent stress instead of the nominal stress.All the predictions showed high accuracy when the proposed method was applied to Mar-M247,SC7-14,CMSX-2,Alloy454,CMSX-4 and DD6.Finally,the applicable temperature ranges of the orientation-dependent method(using equivalent stress)and the traditional LMP method(using nominal stress)were discussed.The results show that only the orientation-Dependent(OD)method is reliable at intermediate temperatures(760–850°C)because the orientation has significant effect on the stress rupture life,while the influence of orientation is considerably reduced at high temperatures.Both methods provide precise predictions in this situation,and the LMP method should be favored since it is much easier to implement.

关键词： Creep life Lattice rotation orientation Schmid factor Single crystal superalloys

A new multiple-factor clustering method considering both box fractal dimension and orientation of joints

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第2期14卷 366-376页

作者： Tiexin Liu Annan Jiang Jianhui Deng Jun Zheng Zhenghu Zhang Department of Civil Engineering Dalian Maritime UniversityDalian116026China State Key Laboratory of Hydraulics and Mountain River Engineering College of Water Resource&HydropowerSichuan UniversityChengdu610065China Department of Civil Engineering Zhejiang UniversityHangzhou310058China State Key Laboratory of the Coastal and Offshore Engineering School of Civil EngineeringDalian University of TechnologyDalian116024China

The paper proposes a new multiple-factor clustering method(NMFCM)with consideration of both box fractal dimension(BFD)and orientation of joints.This method assumes that the BFDs of different clusters were uneven,and clustering was performed by redistributing the joints near the boundaries of clusters on a polar map to maximize an index for estimating the difference of the BFD(DBFD).Three main aspects were studied to develop the NMFCM.First,procedures of the NMFCM and reasonableness of assumptions were illustrated.Second,main factors affecting the NMFCM were investigated by numerical simulations with disk joint models.Finally,two different sections of a rock slope were studied to verify the practicability of the NMFCM.The results demonstrated that:(1)The NMFCM was practical and could effectively alleviate the problem of hard boundary during clustering;(2)The DBFD tended to increase after the improvement of clustering accuracy;(3)The improvement degree of the NMFCM clustering accuracy was mainly influenced by three parameters,namely,the number of clusters,number of redistributed joints,and total number of joints;and(4)The accuracy rate of clustering could be effectively improved by the NMFCM.

关键词： Joint clustering Box fractal dimension(BFD) orientation Hard boundary

The effect of horizontal elements and building orientation on PM_(2.5)concentration in classrooms

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Frontiers of Architectural Research 2023年第4期12卷 775-787页

作者： Nachawit Tikul Apiruk Hokpunna Panphat Chawana Faculty of Architecture and Environmental Design Maejo UniversityChiang Mai 50290Thailand Faculty of Engineering Chiang Mai UniversityChiang Mai 50290Thailand Chiang Mai Primary Education Service Area Office 2 Office of the Basic Education CommissionChiang Mai 50290Thailand

This study aimed to evaluate the effect of horizontal elements and building orientation on indoor particulate matter with a diameter of less than 2.5 mm(PM_(2.5))concentration and airflow.We added horizontal elements to the envelope of a standard Thai school building using computational fluid dynamics for testing the dispersion and concentration of PM_(2.5)in classrooms under the PM_(2.5)crisis condition in Chiang Mai Province.The results showed that the building orientation and the addition of horizontal elements to the front wall of the school building had different effects on the concentration of PM_(2.5)and airflow within the classroom in eight directions.Classrooms in standard school buildings facing NE and SW directions had the highest indoor PM_(2.5)concentrations,and those facing NW and SW had the least compared to all directions.Adding horizontal elements on the front wall of the standard school building was found to reduce the PM_(2.5)concentration in the classrooms of the building facing the N,NE,E,and SE directions.Increasing the horizontal element width from 1 m to 2 m reduced the PM_(2.5)concentration in classrooms of the N-and SE-facing buildings but had little effect in the classrooms of the NE-and E-facing buildings.This study will provide insight into the optimization of air quality in school buildings,informing the decision-making for adding horizontal elements and controlling their widths.

关键词： PM_(2.5) Horizontal element orientation Classroom Computational fluid dynamics

orientation variation along growth direction of millimeter free-standing CVD diamond thinned by mechanical grinding

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International Journal of Minerals,Metallurgy and Materials 2014年第8期21卷 839-844页

作者： Xing-kai Wen Jun-jun Wei Jin-long Liu Jian-chao Guo Liang-xian Chen Cheng-ming Li Institute of Advanced Materials and Technology University of Science and Technology Beijing

A free-standing diamond film with millimeter thickness prepared by DC arc plasma jet was thinned successively by mechanical grinding. The orientation and quality of the diamond films with different thicknesses were characterized by X-ray diffraction and Raman spectroscopy, respectively. The results show a random grain-orientatinn distribution during the initial growth stage. As the film thickness increases, the preferred orientation of the diamond film changes from （111） to （220）, due to the competitive growth mechanism. Twinning generated during the nucleation stage appears to stabilize the preferential growth along the 〈110〉 direction. The interplanar spacing of the （220） plane is enlarged as the film thickness increases, which is caused by the increase of non-diamond-phase carbon and impurities under the cyclic gas. In addition, the quality of the diamond film is barely degraded during the growth process. Furthermore, the peak shift demonstrates a significant inhomogeneity of stress along the film growth direction, which results from competitive growth.

关键词： diamond films chemical vapor deposition grinding orientation growth mechanisms quality

Tuning crystal orientation and charge transport of quasi-2D perovskites via halogen-substituted benzylammonium for efficient solar cells

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Journal of Energy Chemistry 2022年第3期31卷 205-209,I0007页

作者： Guiqiang Cheng Jian Wang Rong Yang Cheng Li Hao Zhang Nana Wang Renzhi Li Jianpu Wang Wei Huang Key Laboratory of Flexible Electronics(KLOFE)&Institute of Advanced Materials(IAM) Nanjing Tech University(NanjingTech)Nanjing 211816JiangsuChina Frontiers Science Center for Flexible Electronics Xi’an Institute of Flexible Electronics(IFE)Xi’an Institute of Biomedical Materials and EngineeringNorthwestern Polytechnical University(NPU)Xi’an 710072ShaanxiChina School of Electronic Science and Engineering Xiamen UniversityXiamen 361005FujianChina

Quasi-two-dimensional(quasi-2D)perovskites with high stability usually suffers from poor device efficiency.Chemical tuning of the spacer cations has been an effective strategy to achieve efficient and stable quasi-2D perovskite solar cells.Here,we demonstrate that 3-halogon-substituted benzylammonium iodide(3X-BAI,X=F,Cl,Br,I)can significantly affect the orientation of low-dimensional perovskites and charge transport from perovskite to hole extraction layer,as well as device performance.With 3Br-BAI,we achieve the highest device efficiency of 13.21%for quasi-2D perovskites with a nominal n=3 average composition.Our work provides a facile approach to regulate vertical crystal orientation and charge transport via tuning the molecular structure of organic spacer toward high performance quasi-2D perovskite solar cells.

关键词： Perovskites Solar cells Quasi-two dimensional orientation Charge transport

Can building orientation perturb micro-climatic conditions inside classrooms located in hot-humid climatic condition?

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Energy and Built Environment

Energy and Built Environment 2022年第4期3卷 467-477页

作者： Shanmugga Rani A Kannamma D Department of Architecture National Institute of TechnologyTiruchirappalliTamil Nadu 620015India

Thermal comfort inside classrooms located in an institutional building is examined as a function of air tempera-ture,relative humidity and wind velocity.The effect of east-west orientation on the thermal comfort inside the classrooms located in different floor levels is understood based on field experiments and validated using compu-tational fluid dynamics simulations.The air temperature inside the classrooms shows an increasing trend with the floor level.Air temperature and relative humidity inside the classrooms reveal an inverse relationship as a function of east-west orientation with different floor level.As time progresses,the air temperature inside class-rooms located on the eastern side of the building is apparently higher than rooms situated on the western side of the building,both field experiments and simulation acknowledge the same.Appropriate reasons have been proposed behind the discussed phenomenon using computational fluid dynamics simulation.

关键词： Air temperature Relative humidity Wind velocity orientation Thermal comfort Computational fluid dynamics

orientation of KRb molecules in a switched electrostatic field

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Chinese Physics B 2013年第5期22卷 290-294页

作者：黄云霞徐淑武杨晓华 School of Science Nantong University State Key Laboratory of Precision Spectroscopy East China Normal University

We theoretically investigate the orientation of the cold KRb molecules induced in a switched electrostatic field by numerically solving the full time-dependent Schr6dinger equation. The results show that the periodic field-free molecular orientation can be realized for the KRb molecules by rapidly switching off the electrostatic field. Meanwhile, by varying the switching times of the electrostatic field, the adiabatic and nonadiabatic interactions of the molecules with the applied field can be realized. Moreover, the influences of the electrostatic field strength and the rotational temperature to the degree of the molecular orientation are studied. The investigations show that increasing the electrostatic field will increase the degree of the molecular orientation, both in the constant-field regime and in the field-free regime, while the increasing of the rotational temperature of the cold molecules will greatly decrease the degree of the molecular orientation.

关键词： orientation KRb molecule electrostatic field