During the operation and installation of offshore pipelines, high axial forces and pressures are experienced, and their effects cannot be neglected. In this article, the effect of internal flow velocity and functional...During the operation and installation of offshore pipelines, high axial forces and pressures are experienced, and their effects cannot be neglected. In this article, the effect of internal flow velocity and functional loads on vortex-induced vibration （VIV） response is investigated. On the basis of the Hamilton principle, a differential equation was derived to describe the motion of a pinned-pinned tensioned spanning pipeline conveying fluid. The VIV response was calculated according to DNV-RP-F105 under different functional loads. The results showed that functional loads influence free spanning pipeline VIV response by changing the natural frequency. Internal flow velocity was found less important for VIV response than other functional load factors, such as effective axial force, because the speed in reality is not high enough to be significant. The research may provide a reference for sensitivity studies of the effect of functional loads on allowable free span lengths.展开更多
This paper investigates the functionally graded coating bonded to an elastic strip with a crack under thermal- mechanical loading. Considering some new boundary conditions, it is assumed that the temperature drop acro...This paper investigates the functionally graded coating bonded to an elastic strip with a crack under thermal- mechanical loading. Considering some new boundary conditions, it is assumed that the temperature drop across the crack surface is the result of the thermal conductivity index which controls heat conduction through the crack region. By the Fourier transforms, the thermal-elastic mixed boundary value problems are reduced to a system of singular integral equations which can be approximately solved by applying the Chebyshev polynomials. The numerical computation methods for the temperature, the displacement field and the thermal stress intensity factors （TSIFs） are presented. The normal temperature distributions （NTD） with different parameters along the crack surface are analyzed by numerical examples. The influence of the crack position and the thermal-elastic non- homogeneous parameters on the TSIFs of modes I and 11 at the crack tip is presented. Results show that the variation of the thickness of the graded coating has a significant effect on the temperature jump across the crack surfaces when keeping the thickness of the substrate constant, and the thickness of functionally graded material （FGM） coating has a significant effect on the crack in the substrate. The results can be expected to be used for the purpose of gaining better understanding of the thermal-mechanical behavior of graded coatings.展开更多
Simulating semi-solid metal forming requires modelling semi-solid behaviour.However, such modelling is difficult because semi-solid behavior is thixotropic and depends on the liquid-solid spatial distribution within t...Simulating semi-solid metal forming requires modelling semi-solid behaviour.However, such modelling is difficult because semi-solid behavior is thixotropic and depends on the liquid-solid spatial distribution within the material.In order to better understand and model relationships between microstructure and behavior, a model based on micromechanical approaches and homogenisation techniques is presented.This model is an extension of a previous model established in a pure viscoplastic framework to account for elasticity.Indeed, experimental load-displacement signals reveal the presence of an elastic-type response in the earlier stages of deformation when semi-solids are loaded under rapid compression.This elastic feature of the behaviour is attributed to the response of the porous solid skeleton saturated by incompressible liquid.A good quantitative agreement is found between the elastic-viscoplastic predicted response and the experimental data.More precisely, the strong initial rising part of the load-displacement curve, the peak load and the subsequent fall in load are well captured.The effect of solid fraction on mechanical response is in qualitative agreement with experiments.展开更多
A new multifunctional testing device for rock fragmentation was introduced, which can conduct many experiments such as single cutting under static load, crushing under impact load, thrusting under static load and cutt...A new multifunctional testing device for rock fragmentation was introduced, which can conduct many experiments such as single cutting under static load, crushing under impact load, thrusting under static load and cutting-impact test under the dynamic and static load. The results of granite and concrete抯 experiments with polycrystalline diamond compact (PDC) flat cutters and carbide alloy cutters under different loadings show that the device has good performance, and the characteristics of broken rock under the combined loads are similar to that under the single static pressure or impact crushing the rock, and the combined loads can increase the effect of rock fragmentation obviously. The experimental methods and effects have the important meaning for studying new drill-ing tool on hard rock fragmentation.展开更多
This paper demonstrates the plane stress state and the stress free thermo-elastic deformation of FGM thick plate under thermal loading.First,the Sneddon-Lockett theorem on the plane stress state in an isotropic infini...This paper demonstrates the plane stress state and the stress free thermo-elastic deformation of FGM thick plate under thermal loading.First,the Sneddon-Lockett theorem on the plane stress state in an isotropic infinite thick plate is generalized for a case of FGM problem in which all thermo-mechanical properties are optional functions of depth co-ordinate.The proof is based on application of the Iljushin thermo-elastic potential to displacement type system of equations that reduces it to the plane stress state problem.Then an existence of the purely thermal deformation is proved in two ways:first,it is shown that the unique solution fulfils conditions of simultaneous constant temperature and linear gradation of thermal expansion coefficient,second,proof is based directly on stress type system of equations which straightforwardly reduces to compatibility equations for purely thermal deformation if only stress field is homogeneous in domain and at boundary.Finally,couple examples of application to an engineering problem are presented.展开更多
基金Supported by the National Natural Science Foundation of China (No. 50879013)China National 111 Project (No.B07019)
文摘During the operation and installation of offshore pipelines, high axial forces and pressures are experienced, and their effects cannot be neglected. In this article, the effect of internal flow velocity and functional loads on vortex-induced vibration （VIV） response is investigated. On the basis of the Hamilton principle, a differential equation was derived to describe the motion of a pinned-pinned tensioned spanning pipeline conveying fluid. The VIV response was calculated according to DNV-RP-F105 under different functional loads. The results showed that functional loads influence free spanning pipeline VIV response by changing the natural frequency. Internal flow velocity was found less important for VIV response than other functional load factors, such as effective axial force, because the speed in reality is not high enough to be significant. The research may provide a reference for sensitivity studies of the effect of functional loads on allowable free span lengths.
基金The National Natural Science Foundation of China(No.10962008,51061015)Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20116401110002)
文摘This paper investigates the functionally graded coating bonded to an elastic strip with a crack under thermal- mechanical loading. Considering some new boundary conditions, it is assumed that the temperature drop across the crack surface is the result of the thermal conductivity index which controls heat conduction through the crack region. By the Fourier transforms, the thermal-elastic mixed boundary value problems are reduced to a system of singular integral equations which can be approximately solved by applying the Chebyshev polynomials. The numerical computation methods for the temperature, the displacement field and the thermal stress intensity factors （TSIFs） are presented. The normal temperature distributions （NTD） with different parameters along the crack surface are analyzed by numerical examples. The influence of the crack position and the thermal-elastic non- homogeneous parameters on the TSIFs of modes I and 11 at the crack tip is presented. Results show that the variation of the thickness of the graded coating has a significant effect on the temperature jump across the crack surfaces when keeping the thickness of the substrate constant, and the thickness of functionally graded material （FGM） coating has a significant effect on the crack in the substrate. The results can be expected to be used for the purpose of gaining better understanding of the thermal-mechanical behavior of graded coatings.
文摘Simulating semi-solid metal forming requires modelling semi-solid behaviour.However, such modelling is difficult because semi-solid behavior is thixotropic and depends on the liquid-solid spatial distribution within the material.In order to better understand and model relationships between microstructure and behavior, a model based on micromechanical approaches and homogenisation techniques is presented.This model is an extension of a previous model established in a pure viscoplastic framework to account for elasticity.Indeed, experimental load-displacement signals reveal the presence of an elastic-type response in the earlier stages of deformation when semi-solids are loaded under rapid compression.This elastic feature of the behaviour is attributed to the response of the porous solid skeleton saturated by incompressible liquid.A good quantitative agreement is found between the elastic-viscoplastic predicted response and the experimental data.More precisely, the strong initial rising part of the load-displacement curve, the peak load and the subsequent fall in load are well captured.The effect of solid fraction on mechanical response is in qualitative agreement with experiments.
文摘A new multifunctional testing device for rock fragmentation was introduced, which can conduct many experiments such as single cutting under static load, crushing under impact load, thrusting under static load and cutting-impact test under the dynamic and static load. The results of granite and concrete抯 experiments with polycrystalline diamond compact (PDC) flat cutters and carbide alloy cutters under different loadings show that the device has good performance, and the characteristics of broken rock under the combined loads are similar to that under the single static pressure or impact crushing the rock, and the combined loads can increase the effect of rock fragmentation obviously. The experimental methods and effects have the important meaning for studying new drill-ing tool on hard rock fragmentation.
文摘This paper demonstrates the plane stress state and the stress free thermo-elastic deformation of FGM thick plate under thermal loading.First,the Sneddon-Lockett theorem on the plane stress state in an isotropic infinite thick plate is generalized for a case of FGM problem in which all thermo-mechanical properties are optional functions of depth co-ordinate.The proof is based on application of the Iljushin thermo-elastic potential to displacement type system of equations that reduces it to the plane stress state problem.Then an existence of the purely thermal deformation is proved in two ways:first,it is shown that the unique solution fulfils conditions of simultaneous constant temperature and linear gradation of thermal expansion coefficient,second,proof is based directly on stress type system of equations which straightforwardly reduces to compatibility equations for purely thermal deformation if only stress field is homogeneous in domain and at boundary.Finally,couple examples of application to an engineering problem are presented.
