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substructure evolution in two phases based constitutive model for hot deformation of TC18 inα+βphase region

Chinese Journal of Aeronautics 2023年第4期36卷 573-588页

作者： Lian LI Jixiong LIU Ning DING Miaoquan LI School of Materials Science and Engineering Northwestern Polytechnical UniversityXi’anShaanxi 710072China BAOTI Group Co. LtdXi’an 721014China

Theα+βdual phase titanium alloys are key structural materials in aviation and aero-space industries,and the complicated flow behavior of these titanium alloys during hot deformation requires to establish a constitutive model incorporating physical mechanism for optimizing process-ing parameters and designing forming *** work aims to establish a constitutive model incor-porating physical mechanism for hot deformation of TC18 inα+βphase ***,the flow behavior and microstructure evolution for hot deformation of TC18 inα+βphase region are *** TC18 shows significant strain hardening rate and negative strain hardening exponent around and after peak flow stress,*** peak flow stress,Dynamic Recovery(DRV)mechanism dominates the evolution of a and b phases according to the results of substructure ***,the internal state variables method is applied to establish a constitutive model incor-porating physical mechanism for hot deformation of dual phase titanium *** variation of dislocation density during the hot deformation of titanium alloys is modeled by considering the accumulation of dislocation due to the impediment to dislocation movement by substructure obsta-cles and the annihilation of dislocation due to the dynamic restoration *** interaction between dislocations,the subgrain boundaries and the grain/phase boundaries obstruct the disloca-tion movement in the a phase,and the first two obstructs the dislocation movement in the b phase during the hot deformation of *** dislocation annihilation process in theαandβphases dur-ing the hot deformation of TC18 is dominated by ***,the substructure evolution in the two phases based constitutive model for hot deformation of TC18 inα+βphase region is *** model is well applied to predict the flow stress and quantitively analyze the role of DRV effect in the evolution ofαandβphases during the hot deformation of TC18.

关键词： Constitutive model Dynamic recovery Hot deformation substructure TC18

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substructure isolation and damage identification using free responses

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Science China(Technological Sciences) 2014年第9期57卷 1698-1706页

作者： HOU JiLin JANKOWSKI Lukasz OU JinPing School of Civil Engineering Dalian University of Technology Smart-Tech Centre Institute of Fundamental Technological Research Polish Academy of Sciences School of Civil Engineering Harbin Institute of Technology

Structural health monitoring （SHM） has become a hot and intensively researched field in civil engineering. Thereinto, damage identification play an important role in maintaining structural integrity and safety. Many effective methods have been proposed for damage identification. However, accurate global identification of large real-world structures is not easy due to their com- plex and often unknown boundary conditions, nonlinear components, insensitivity of glohal response to localized damages, etc. Furthermore, global identification often requires lots of sensors and involves large number of unknowns. This is costly, rarely feasible in practice, and usually yields severely ill-conditioned identification problems. Substructuring approach is a possible solution： substructuring methods can focus on local small substructures; they need only a few sensors placed on the substruc- ture and yield smaller and numerically much more feasible identification problems. This paper proposed an improved sub- structure method using local free response for substructure damage identification. The virtual supports are constructed by Sub- structure Isolation Method （SIM） using the linear combination of the substructural responses. The influence of the global errors is isolated by adding the virtual supports on the main degree of freedoms （DOFs） of the substructure. Through the correlation analysis, the substructural modes are selected and used for damage identification of the substructure. A plain model of cable stayed bridge is used for the verification of the proposed method.

关键词： structural health monitoring (SHM) damage identification substructure cable stayed bridge free response

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Seismic wave input method for three-dimensional soil-structure dynamic interaction analysis based on the substructure of artificial boundaries

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Earthquake Engineering and Engineering Vibration 2019年第4期18卷 747-758页

作者： Liu Jingbo Tan Hui Bao Xin Wang Dongyang Li Shutao Department of Civil Engineering Tsinghua University

The method of inputting the seismic wave determines the accuracy of the simulation of soil-structure dynamic interaction. The wave method is a commonly used approach for seismic wave input, which converts the incident wave into equivalent loads on the cutoff boundaries. The wave method has high precision, but the implementation is complicated, especially for three-dimensional models. By deducing another form of equivalent input seismic loads in the fi nite element model, a new seismic wave input method is proposed. In the new method, by imposing the displacements of the free wave fi eld on the nodes of the substructure composed of elements that contain artifi cial boundaries, the equivalent input seismic loads are obtained through dynamic analysis of the substructure. Subsequently, the equivalent input seismic loads are imposed on the artifi cial boundary nodes to complete the seismic wave input and perform seismic analysis of the soil-structure dynamic interaction model. Compared with the wave method, the new method is simplifi ed by avoiding the complex processes of calculating the equivalent input seismic loads. The validity of the new method is verifi ed by the dynamic analysis numerical examples of the homogeneous and layered half space under vertical and oblique incident seismic waves.

关键词： soil-structure dynamic interaction seismic wave input wave method equivalent input seismic loads substructure of artifi cial boundaries

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Damage detection test of a substructure model of the National Swimming Center

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Science China(Technological Sciences) 2008年第7期51卷 940-948页

作者： QIAN JiaRu JI XiaoDong ZHANG WeiJing XU LongHe FU XueYi GU Lei Key Laboratory for Structural Engineering&Vibration of Education Ministry Department of Civil EngineeringTsinghua UniversityBeijing 100084China China State Construction International Design Consultant Co.LTD. Beijing 100029China

In order to detect the damage locations of complex spatial structures, a sensor region-based damage detection approach was developed based on the damage locating vectors method. A normalized damage locating index was introduced to identify the damage regions. An experiment on damage detection of a substructure model of the National Swimming Center 'Water Cube' was carried out. Two damage patterns were involved in the experiment. The test model was excited by using hammer impacts. Acceleration responses of the undamaged and damaged structure model were measured. Modal parameters were identified from the acceleration responses by utilizing the eigensystem realization algorithm (ERA). By using the developed sensor region-based method, the damage regions of the substructure model were located. The results show that the proposed method is able to effec- tively locate the damage regions.

关键词： structure vibration damage detection sensor region substructure model of the National Swimming Center experiment

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Effect of substructure on the Thermoelectric Power of aβ-Quenched ZrCrFe Alloy

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Rare Metals 1993年第2期12卷 110-116页

作者： DerekO.Northwood 孙喜臣 Engineering Materials Group Deptof Mechanical EngineeringUniversity of WindsorWindsorOntarioCanada N9B3P4

β-quenching a Zr-1.15 wt％Cr-0.10 wt％Fe alloy produces a martensitic or a Widmanst(a|¨)tten transforma- tion morphology,or a mixture of the two,depending on the cooling *** the Widmanst(a|¨)tten structure,or the mixed martensitic-Widmanst(a|¨)itten structure,a grain boundary phase is observed at most prior-β grain boundaries.X-ray line broadening analysis and the thermoelectric power(TEP)measurements of these quenched samples show that not only the solubility of alloying elements in α-Zr matrix,but also substructure (microstrain,crystallite size and dislocation density)have an effect on ***,TEP measurements are very well suited for following the structural transformations taking place in Zr alloys during fabrication.

关键词： ZrCrFe alloy substructure Heat treatment Thermoelectric power

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Revealing substructure in clock-rolled Ta aided with triple focused ion beam

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Rare Metals 2017年第4期36卷 284-288页

作者： Shi-Feng Liu Xiao-Bo Hao Chao Deng Hai-Yang Fan Qing Liu College of Materials Science and Engineering Chongqing UniversityChongqing 400044China

Clock rolling was developed to make defor- mation microstructure homogenize in high-purity Ta. The substructure of deformed Ta was revealed by electron back-scatter diffraction （EBSD） technique aided with triple focused ion beam （FIB）. The results indicate that the triple FIB method can produce a mirror surface required by EBSD analysis. The clock rolling works well for the homogenization of deformed microstructure. Particularly, the local stored energy in { 111 } orientated grains is largely reduced by clock rolling, whereas it is enhanced in {100} orientated grains because of the occurrence of grain subdivision.

关键词： Deformation substructure Strain pathchange Dislocation boundary Focused ion beam

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Dynamic substructure model for multiple impact responses of micro/nano piezoelectric precision drive system

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Science China(Technological Sciences) 2009年第3期52卷 622-633页

作者： SHEN YuNian YIN XiaoChun Department of Mechanics and Engineering Science Nanjing University of Science and TechnologyNanjing 210094China

A dynamic substructure technique which considers the electromechanical coupling effect of the PZT and the inertial effect of flexible components is presented to study the multiple impact dynamic be- havior of micro/nano piezoelectric impact drive systems. It can investigate the step-like motion of ob- ject body and the multiple impacts behaviors reasonably by the comparison of the experimental data and the numerical solution of the spring-mass model. It is expected to have higher accuracy in the numerical simulations of the motion and the responses, especially to high frequency pulse voltage excitations. The present dynamic substructure technique has firstly studied reasonably the propaga- tions of piezoelectric-induced transient waves and impact-induced transient waves. It is helpful to the failure analysis and the design of piezoelectric stack and flexible components. The present dynamic substructure technique can be applied to the transient dynamics optimization design and the precision control of the micro/nano piezoelectric impact drive systems.

关键词： piezoelectric micro actuator multiple impacts dynamic substructure technique electromechanical coupling transient wave propaga- tion precision positioning

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Coupling of Peridynamics and Numerical substructure Method for Modeling Structures with Local Discontinuities

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Computer Modeling in Engineering & Sciences 2019年第9期120卷 739-757页

作者： Baoyin Sun Shaofan Li Quan Gu Jinping Ou Faculty of Infrastructure Engineering Dalian University of TechnologyDalian116024China School of Architecture and Civil Engineering Xiamen UniversityXiamen361005China Department of Civil and Environmental Engineering University of CaliforniaBerkeleyCA 94720USA

Peridynamics(PD)is a widely used theory to simulate discontinuities,but its application in real-world structural problems is somewhat limited due to the relatively *** numerical substructure method(NSM)presented by the authors and co-workers provides an efficient approach for modeling structures with local nonlinearities,which is usually restricted in problems of continuum *** this paper,an approach is presented to couple the PD theory with the NSM for modeling structures with local discontinuities,taking advantage of the powerful capability of the PD for discontinuities simulation and high computational efficiency of the *** structure is simulated using liner elastic finite element(FE)model while the local cracking regions are isolated and simulated using a PD substructure model.A force corrector calculated from the PD model is applied on the FE model to consider the effect of *** PD is integrated in the substructure model using interface elements with embedded PD *** equations of motions of both the NSM system and the PD substructure are solved using the central difference *** examples of two-dimensional(2D)concrete cantilever beams under the concentrated force are investigated to verify the proposed coupling approach.

关键词： Peridynamic numerical substructure method local discontinuities crack

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Key aspects on the behaviour of the ballast and substructure of a modern railway track:research-based practical observations in Finland

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2012年第11期13卷 825-835页

作者： Antti NURMIKOLU Department of Civil Engineering Tampere University of TechnologyTampereFinland

This paper presents an overview on the wide-ranging track structure studies at the Tampere University of Technology(TUT),Finland dealing with the key aspects of track geotechnics related to high-speed passenger traffic on ballasted *** attention is paid to ballast and sub-ballast,while also considering frost action,embankment stability,track stiffness,track geometry and transition *** a result,this paper states that understanding the ballast degradation mechanism and its consequences and assessment of its condition occupy an important role in the construction and maintenance of a smooth high-speed rail *** choices related to building the sub-ballast also have a dramatic impact on later track deformations and maintenance *** cold climate,especially where seasonal frost occurs,understanding and taking into account the frost action mechanism is *** in the maintenance and rehabilitation planning of existing tracks,high-class analyses of ground penetrating radar data and its integrated analysis with other data can yield considerable benefits.

关键词： Railway Track Ballast Sub-ballast substructure Subsoil Frost action Life cycle Ground penetrating radar

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Free-Interface Dual-Compatibility Modal Synthesis substructure Method in Large-Scale Structures

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Transactions of Tianjin University 2015年第4期21卷 347-355页

作者：彭桂瀚林伟陈尚鸿余洁歆 School of Civil Engineering Fuzhou University

Free-interface dual-compatibility modal synthesis method(compatibility of both force and displacement on interfaces)is introduced to large-scale civil engineering structure to enhance computation efficiency. The basic equations of the method are first set up, and then the mode cut-off principle and the dividing principle are proposed. MATLAB is used for simulation in different frame structures. The simulation results demonstrate the applicability of this substructure method to civil engineering structures and the correctness of the proposed mode cut-off principle. Studies are also conducted on how to divide the whole structure for better computation efficiency while maintaining better precision. It is observed that the geometry and material properties should be considered, and the synthesis results would be more precise when the inflection points of the mode shapes are taken into consideration. Furthermore, the simulation performed on a large-scale high-rise connected structure further proves the feasibility and efficiency of this modal synthesis method compared with the traditional global method. It is also concluded from the simulation results that the fewer number of DOFs in each substructure will result in better computation efficiency, but too many substructures will be time-consuming due to the tedious synthesis procedures. Moreover, the substructures with free interface will introduce errors and reduce the precision dramatically, which should be avoided.

关键词： substructure method dynamic substructure analysis free-interface dual-compatibility modal synthesismethod large-scale civil engineering structure mode cut-off principle

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