检索结果-南通市图书馆

Surface nanostructure formation mechanism of 45 steel induced by supersonic fine particles pombarding

Journal of University of Science and Technology Beijing 2008年第5期15卷 561-567页

作者： Dema Ba Shining ma Changqing li Fanjun Meng Department of Remanufacture Engineering Academy of Armored Force Engineering Beijing 100072 China

By means of supersonic fine particles bombarding （SFPB）,a nanostructured surface layer up to 15 μm was fabricated on a 45 steel plate with ferrite and pearlite phases. To reveal the grain refinement mechanism of SFPB-treated 45 steel,microstructure features of various sections in the treated surface were systematically characterized by X-ray diffraction （XRD）,scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. Grain size increases with an increase of depth from the treated surface. Plastic deformation and grain refinement processes are accompanied by an increase in strain. Plastic deformation in the proeutectoid ferrite phases has precedence over the pearlite phases. Grain refinement in the ferrite phases involves： the onset of dislocation lines （Dls）,dislocation tangles （DTs） and dense dislocation walls （DDWs） in the original grains; the formation of fine lamellar and roughly equiaxed cells separated by DDWs; by dislocation annihilation and rearrangement,the transformation of DDWS into subboundaries and boundaries and the formation of submicron grains or subgrains; the successive subdivision of grains to finer and finer scale,resulting in the formation of highly misoriented nano-grains. By contrast,eutectoid cementite phase accommodated strain in a sequence as follows： onset of elongated,bended and shear deformation under deformation stress of ferrites,short and thin cementites with a width of about 20-50 nm and discontinuous length were formed. Shorter and thinner cementites were developed into ultra-fine pieces under the action of high density dislocation and strains. At the top surface,some cementites were decomposed under severe plastic deformation. Experimental evidences and analysis indicate that surface nanocrystallization of 45 steel results from dislocation activities,high strains and high strain rate are necessary for the formation of nanocrystallites.

关键词： surface nanocrystallization grain refinement mechanism microstructure 45 steel

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

FREE VIBRATION ANALYSIS OF LATTICE SANDWICH BEAMS UNDER SEVERAL TYPICAL BOUNDARY CONDITIONS

引用

Acta Mechanica Solida Sinica 2013年第5期26卷 458-467页

作者： Jia Lou Bing Wang li ma linzhi Wu Center for Composite materials and Structures Harbin Institute of Technology

Free vibration problems of lattice sandwich beams under several typical boundary conditions are investigated in the present paper. The lattice sandwich beam is transformed to an equivalent homogeneous three-layered sandwich beam. Unlike the traditional analytical model in which the rotation angles of the face sheets and the core are assumed the same, different rotation angles are considered in this paper to characterize the real response of sandwich beams. The analytical solutions of the natural frequencies for several typical boundary conditions are obtained. The effects of material properties and geometric parameters on the natural frequencies are also investigated.

关键词： vibration composites lattice materials beam analytical method

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

P^2: a robust and rotationally invariant shape descriptor with applications to mesh saliency

引用

Applied mathematics(A Journal of Chinese Universities) 2016年第1期31卷 53-67页

作者： liU Xian-yong ma li-zhuang liU li-gang School of Computer Science and Technology Shanghai Jiao Tong University

This work presents a robust and rotationally invariant shape descriptor, namely perception pronouncement （called p2）, to mathematically model the eye fixations, p2 takes two criteria - the local consideration of surface curvature and the global consideration of view- independent visibility - into account. Differing from existing works that often computed the intrinsic surface property of visibility in imaging space, a novel approach is proposed to approxi- mate the attribute in object space using Gauss map and Ray tracing. With the presented shape descriptor, mesh saliency detection, which refers to reasoning about which regions or points of a surface axe important, is more sensible, especially when 3D models fall into two categories：（1） the models possess significant interior/exterior structures; （2） the models contain regions where the contrast in visibility is high. For the models that are out of the categories, saliencies achieved by our approach are comparable to or even better than those of state-of-the-axt methods.

关键词： Human visual system mesh saliency shape descriptor bilateral filtering visibility.

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Mechanical Behavior and Failure Mechanisms of Carbon Fiber Composite Pyramidal Core Sandwich Panel after Thermal Exposure

引用

Journal of materials Science & Technology 2013年第9期29卷 846-854页

作者： Jiayi liu Zhengong Zhou linzhi Wu li ma Center for Composite materials and Structures Harbin Institute of Technology

An attempt has been made here to evaluate the effect of thermal exposure on the mechanical behavior and failure mechanisms of carbon fiber composite sandwich panel with pyramidal truss core under axial compression. Analytical formulae for the collapse strength of composite sandwich panel after thermal exposure were derived. Axial compression tests of composite laminates and sandwich panels after thermal exposure were conducted at room temperature to assess the degradation caused by the thermal exposure. Experimental results showed that the failure of sandwich panel are not only temperature dependent, but are time dependent as well. The decrease in residual compressive strength is mainly attributed to the degradation of the matrix and the degradation of fiber-matrix interface, as well as the formation of cracks and pores when specimens are exposed to high temperature. The measured failure loads obtained in the experiments showed reasonable agreement with the analytical predictions.

关键词： Composite Thermal exposure Mechanical properties Sandwich panel

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Single-Crystalline Organoiridium Complex for Gas-Triggered Chromogenic Switches and Its Applications on CO Detection and Reversible Scavenging

引用

Chinese Journal of Chemistry 2019年第8期37卷 763-768页

作者： li-Ying Sun Yuan-Yuan An li-li ma Ying-Feng Han Key Laboratory of Synthetic and Natural Functional Molecule Chemistry College of Chemistry and Materials ScienceNorthwest UniversityXi'anShaaxi 710127China State Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of MatterChinese Academy of SciencesFuzhouFujian 350002China

Summary of main observation and conclusion Nonporous molecular single crystals of coordinatively unsaturated 16-electron metallacycle are found to undergo highly selective-yet reversible-binding of CO over CH4,H2,N2,CO2,various volatile organic compounds and water,through binding of the molecule to its metal *** monoxide is taken up by black crystals and subsequently liberated from the corresponding orange CO adduct by reversible metal coordination,the structural evidence obtained from in situ X-ray *** single-crystallinity of the metallacycle is retained even after several *** material,when adsorbed on silica,shows remarkable sensitivity and selectivity for CO,allowing visual CO sensing in the solid *** metallacycle offer the possibility of serving as readily regenerable scavenger for removing trace CO from gas mixtures with N2.

关键词： Gas-Triggered Chromogenic Switches Applications CO Detection Reversible Scavenging

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Microstructure and Mechanical Properties of TWIP Steel Joints

引用

Journal of Iron and Steel Research International 2014年第8期21卷 749-756页

作者： li-li ma Ying-hui WEI li-feng HOU Bin YAN College of materials and Engineering Taiyuan University of Technology

As a new type of high manganese steel, the twinning induced plasticity （TWIP） steels have attracted a growing interest in the automotive industry due to their good performance. Thin plates of TWIP steel were welded by laser beam welding （LBW） and gas tungsten arc welding （GTAW）. The microstructure result shows that GTAW joint has obvious heat-affected zone （HAZ）, while the HAZ of LBW joint is almost invisible. The X-ray diffraction result shows that the phase compositions of both joints are austenitic and no phase transition occurs. Energy disper- sive spectrometry result shows that there is violent evaporation of Mn element in LBW joint, while the proportion of Mn element in GTAW joint is almost unchanged. Tensile tests and micro-hardness measurements were performed to take into account the mechanical properties of joints manufactured by the two different processes. The micro-hard- ness profiles of both joints present a typical saddle distribution, and the hardness of GTAW seam is lower than that of LBW seam. The failure positions of LBW joints are all located in base metal while the GTAW joints are all at the weld toe due to the softening of HAZ. By means of scanning electron microscopy, a typical ductile fracture is observed in LBW joint, while a brittle fracture with quasi-cleavage fracture characteristic is observed in GTAW joint.

关键词： TWIP steels high manganese steels LBW GTAW

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Discrete Morse Flow for Yamabe Type Heat Flows

引用

Journal of Partial Differential Equations 2023年第1期36卷 48-57页

作者： ma li ZHENG Wei School of mathematics and Physics University of Science and Technology BeijingBeijing 100083China

In this paper,we study the discrete Morse flow for either Yamabe type heat flow or nonlinear heat flow on a bounded regular domain in the whole *** show that under suitable assumptions on the initial data g one has a weak approxi-mate discrete Morse flow for the Yamabe type heat flow on any time *** phenomenon is very different from the smooth Yamabe flow,where the finite time blow up may exist.

关键词： Discrete Morse flow Yamabe type flow critical exponent nonlinear heat flow

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Studies on Suction-Assisted Installation Behavior of Suction Caissons in Clay Under Various Undrained Shear Strengths

引用

China Ocean Engineering 2023年第6期37卷 989-999页

作者： li Da-yong HOU Xin-yu ZHANG Yu-kun ma Shi-li li Shan-shan Key Laboratory of Civil Engineering Disaster Prevention and Mitigation Shandong University of Science and TechnologyQingdao 266590China College of Pipeline and Civil Engineering China University of Petroleum(East China)Qingdao 266580China College of Civil Engineering Weifang UniversityWeifang 261061China

Suction caissons are widely used for anchoring floating platform and offshore wind *** of the suction caisson into the desired position under the combination of its self-weight and applied suction resulted from pumping out the encased water is integral to practical *** tests were carried out to investigate the suctionassisted installation of suction caissons in clay under various undrained shear *** was found that there exists a critical penetration depth *** the penetration depth is smaller than the critical value,the soil plug undrained shear strength is higher than intact clay(i.e.,clay prior to installation).However,when the penetration depth is greater than the critical penetration depth,the undrained shear strength of soil plug is lower than intact *** critical value decreases with the increasing consolidation time and undrained shear strength of *** suction-assisted installation,cracks occur around suction *** installation way has little effect on the crack *** influence range(i.e.,the maximum distance between the crack and the suction caisson edge)was found to increase with the increasing friction coefficient of interface between the suction caisson wall and soil and decreases with the increasing soil undrained shear *** addition,the drained condition of the clay during installation is dominated by the caisson aspect ratio,the undrained shear strength and the friction coefficient between the caisson wall and *** to estimate the penetration resistance and the required suction to install the suction caisson are summarized.

关键词： suction caisson suction-assisted installation model tests undrained shear strength of clay soil deformation

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Enhanced Fracture Toughness of Pressureless-sintered SiC Ceramics by Addition of Graphene

引用

Journal of materials Science & Technology 2016年第7期32卷 633-638页

作者： Qisong li Yujun Zhang Hongyu Gong Haibin Sun Wenjie li li ma Yanshuang Zhang Key Laboratory for liquid-Solid Structural Evolution & Processing of materials of Ministry of Education Shandong University School of materials and Chemical Engineering Zhongyuan University of Technology Key Laboratory of Special Functional Aggregated materials Ministry of Education Shandong University Shandong Baona New materials Co. Ltd.

To enhance the fracture toughness of pressureless-sintered SiC ceramic, graphene was introduced as an additive. The effects of graphene contents on the fracture toughness, bending strength, micro-hardness, phase compositions, and microstructure evolutions of the SiC ceramics were investigated in detail by scanning electron microscopy, energy dispersive X-ray spectroscopy, and metallographic microscopy. The fracture toughness, bending strength and micro-hardness increased initially, and then decreased with the graphene content increasing from 0 to 5.0 wt%. The highest fracture toughness of 5.65 MPa m1/2 was obtained for sample with 1.0 wt% graphene sintered at 2130 ℃ for 1 h in At, which was about 22.6% higher than that of SiC sample without graphene. In addition, the highest bending strength and microhardness of 434.14 MPa and 29.21 GPa corresponded to the SiC samples with graphene content of 0.5 wt% and 2.0 wt%, respectively.

关键词： SiCGrapheneFracture toughnessBending strengthMicro-hardness

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Two new species of Trypoxylon Latreille, 1796 from China (Hymenoptera: Crabronidae)

引用

Zoological Systematics 2024年第4期49卷 309-319页

作者： Yan Fu Qiang li li ma Department of Entomology College of Plant ProtectionYunnan Agricultural UniversityKunmingYunnan 650201PR.China

Two new species of the genus Trypoxylon,namely *** Fu&li,*** *** Fu&li,***.,are described and illustrated from Guizhou,Guangdong,Guangxi and Zhejiang Provinces,*** two species,*** Tsuneki,1956 and *** Tsuneki,1968,are... 详细信息

关键词： Crabroninae Trypoxylini taxonomy Trypoxylon China

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：