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Geometric Conversion Approach for the numerical evaluation of Hypersin gular and Nearly Hypersingular Boundary Integrals over Curved Surface Boundary Elements

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Journal of Shanghai University(English Edition) 2002年第2期6卷 101-110页

作者：马杭 Department of Mechanics College of Sciences Shanghai University Shanghai China

With the aid of the properties of the hypersingular kernels, a geometric conversion approach was presented in this paper. The conversion leads to a general approach for the accurate and reliable numerical evaluation of the hypersingular surface boundary integrals encountered in a variety of applications with boundary element method. Based on the conversion, the hypersingularity in the boundary integrals could be lowered by one order, resulting in the simplification of the computer code. Moreover, an integral transformation was introduced to damp out the nearly singular behavior of the kernels by the distance function defined in the local polar coordinate system for the nearly hypersingular case. The approach is simple to use, which can be inserted readily to computer code, thus getting rid of the dull routine deduction of formulae before the numerical implementations, as the expressions of these kernels are in general complicated. The numerical examples were given in three dimensional elasticity, verifying the effectiveness of the proposed approach, which makes it possible to observe numerically the behavior of the boundary integral values with hypersingular kernels across the boundary.

关键词： boundary element method numerical evaluation hypersingular boundary integral nearly hypersingular boundary integral geometric conversion.

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numerical evaluations on the effects of thermal properties on the thermo-mechanical behaviour of a phase change concrete energy pile

Energy and Built Environment

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Energy and Built Environment 2023年第1期4卷 1-12页

作者： Weibo Yang Binbin Yang Feng Wang Naidong Jing College of Electrical Energy and Power EngineeringYangzhou UniversityChina Hengtong Construction Group Co.Ltd YangzhouJiangsuChina Jiangsu Tongya Housing Industrialization Technology Co.Ltd YangzhouJiangsuChina

Energy pile is a kind of economic and efficient geothermal utilization technology that the ground heat exchanger(GHE)used in ground source heat pump(GSHP)is embedded into building pile foundation to realize heat ex-change with surrounding soil.Adding phase change material(PCM)into the energy pile can not only reduce the temperature variation and thermal deformation range of energy pile,but also improve its energy storage and heat transfer performance.In this work,phase change concrete energy pile(PCCEP)is proposed by using PCM as a part of backfill material of energy pile.A three-dimensional numerical model is developed to find the influences of thermal properties of PCCEP on its thermo-mechanical behaviour.According to the model,the in-fluences of thermal conductivity,phase change latent heat(PCLE)and phase change temperature(PCT)on the thermal performance and mechanical characteristics of PCCEP are numerically investigated.It can be seen that for improving heat transfer performance of PCCEP,the thermal conductivity should be increased,but from the perspective of reducing change of pile displacement,axial force and side friction resistance,the thermal conduc-tivity should be reduced.Under heat release mode,lower PCT and larger PCLE contribute to the improvement of thermal performance of PCCEP,and accordingly the rise range of pile temperature,pile displacement change and pile thermal stress can all be reduced.The experimental validation on the model shows that the simulation values of pile wall middle temperature(PWMT)and pile top displacement are agreed well with the corresponding experimental results,the real-time relative error of PWMT and pile top displacement are respectively within 5.1 and 12%.

关键词： GSHP Energy pile Phase change concrete Thermo-mechanical behaviour numerical evaluation

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Reinforcement Effect evaluation on Dynamic Characteristics of an Arch Bridge Based on Vehicle-Bridge Coupled Vibration Analysis

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Computer Modeling in Engineering & Sciences 2022年第5期131卷 1041-1061页

作者： Yanbin Tan Xingwen He Lei Shi Shi Zheng Zhe Zhang Xinshan Wang National&Local Joint Engineering Laboratory of Bridge and Tunnel Technology Dalian University of TechnologyDalian116023China Design Institute of Civil Engineering&Architecture of Dalian University of Technology Co. Ltd.Dalian116023China Faculty of Infrastructure Engineering Dalian University of TechnologyDalian116023China

To numerically evaluate the reinforcement effect on dynamic characteristics of a concrete-filled steel tube arch bridge with vibration problems,a 12-degree-of-freedom sprung-mass dynamic vehicle model and a 3D finite element bridge model were established.Then,the coupled equations of vehicle-bridge interaction were derived and a computer program was developed using the FORTRAN language.This program can accurately simulate vehicle-bridge coupled vibration considering the bumping effect and road surface irregularity during motion of the vehicle.The simulated results were compared with those of relevant literatures to verify the correctness of the self-developed program.Then,three reinforcement schemes for the bridge(Addition of longitudinal beams,Reinforcement of bridge decks,and Replacement of suspenders)were proposed and numerically simulated,and the vibration reduction effects of the three schemes were evaluated based on the numerical results to find effective ones.It is confirmed that the reinforcement scheme of Addition of longitudinal beams shows the most significant vibration reduction effect.It is recommended in the engineering practice that the combination of the reinforcement schemes of Addition of longitudinal beams and Replacement of bridge deck can be used to solve the excessive vibration problem.

关键词： Arch bridge vehicle-bridge coupled vibration reinforcement numerical evaluation

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Investigation of straightforward impedance eduction method on single-degree-of-freedom acoustic liners

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Chinese Journal of Aeronautics 2018年第12期31卷 2221-2233页

作者： Xianghai QIU Bo XIN Long WU Yang MENG Xiaodong JING Fluid and Acoustic Engineering Laboratory School of Energy and Power Engineering Beihang University

In order to address the current aircraft noise problem, the knowledge of impedance of acoustic liners subjected to high-intensity sound and grazing flow is of crucial importance to the design of high-efficiency acoustic nacelles. To this end, the present study is twofold. Firstly, the StraightForward impedance eduction Method(SFM) is evaluated by the strategy that the impedance of a liner specimen is firstly experimentally educed on a flow duct using the SFM, and then its accuracy is checked by comparing the numerical prediction with the measured wall sound pressure of the flow duct. Secondly, the effects of grazing flow and high-intensity sound on the impedance behavior of two single-layer liners are investigated based on comparisons between educed impedance and predictions by three impedance models. The performance of the SFM is validated by showing that the educed impedance leads to excellent agreement between the simulation and the measured wall sound pressure for different grazing flow Mach numbers and Sound Pressure Levels(SPLs) and over a frequency range from 3000 Hz down to 500 Hz. The grazing flow effect generally has the tendency that the acoustic resistance exhibits a slight decrease before it increases linearly with an increase in Mach,predicted successfully by the sound-vortex interaction theoretical model and the Kooi semi-empirical impedance model. However, the Goodrich semi-empirical impedance model gives only a simple linear relation of acoustic resistance starting from Mach zero. Additionally, when the SPL increases from 110 to 140 d B in the present investigation, the acoustic resistance exhibits a significant increase at all frequencies in the absence of flow; however, the resistance decreases slightly under a grazing flow of Mach 0.117. It indicates that the SPL effect can be greatly inhibited when flow is present,and the grazing flow effect can be reduced partly as well at a relatively high SPL.

关键词： Acoustic liner Experimental validation Grazing flow effect High sound intensity effect Impedance eduction numerical evaluation Straightforward impedance eduction method

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A NEW CYCLIC J-INTEGRAL FOR LOW-CYCLE FATIGUE CRACK GROWTH

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Applied Mathematics and Mechanics(English Edition) 2006年第2期27卷 149-160页

作者：胡宏玖郭兴明李培宁谢禹钧李洁 Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai 200072 P. R. China College of Mechanical Engineering East China University of Science and Technology Shanghai 200237 P. R. China

The constitutive equation under the low-cycle fatigue （LCF） was discussed, and a two-dimensional （2-D） model for simulating fatigue crack extension was put forward in order to propose a new cyclic J-integral. The definition, primary characteristics, physical interpretations and numerical evaluation of the new parameter were investigated in detail. Moreover, the new cyclic J-integral for LCF behaviors was validated by the compact tension （CT） specimens. Results show that the calculated values of the new parameter can correlate well with LCF crack growth rate, during constant-amplitude loading. In addition, the phenomenon of fatigue retardation was explained through the viewpoint of energy based on the concept of the new parameter.

关键词： cyclic J-integral low-cycle fatigue constitutive equation numerical evaluation fatigue retardation

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