In the process of construction and service,high-grade line pipes will get defective,e.g.dents,which will change its stress and strain distribution characteristics and impact its service reliability.In this paper,a X80...In the process of construction and service,high-grade line pipes will get defective,e.g.dents,which will change its stress and strain distribution characteristics and impact its service reliability.In this paper,a X80 line pipe was taken as the research object.The distribution characteristics of the strain field in the X80 line pipe with plain dents with the change of dent depth under external load were analyzed using the finite element analysis software ABAQUS.Then,the strain distribution and microstructure characteristics in the dent zone were explored by conducting prefabrication test on physical dent.Finally,combined with the finite element simulation results,the strain distribution laws of the X80 line pipe with plain dent were discussed.And the following research results were obtained.First,under the same internal pressure,the strain distribution characteristics in the dent zone at different dent depths are similar,i.e.,the strain increases with the increase of the distance from the center of the dent,and decreases rapidly with the increase of the distance after the peak strain.Second,the strain increases with the increase of dent depth,and under the same internal pressure and dent depth,the axial strain is larger than the radial strain at the same location.Third,the greater the dent depth,the stronger the superposition effect of internal pressure and depth on the strain.Fourth,strain hardening occurs on the materials in the initial stage of the dent deformation.With the aggravation of deformation and the extension of dent radius,the strain response ability of materials increases,the grains at the bottom and side walls of the dent zone are elongated along the direction of maximum deformation,the lattice is distorted and strain hardening occurs.As a result,the dislocation density in this zone increases and the interaction occurs between dislocations,as a result,the strength of line steel is enhanced.In conclusion,the research results do well in predicting the stressestrain evolution laws in the process of dent,and provide a theoretical foundation and an experimental basis for studying the influence of mechanical damage on the service safety of pipelines.展开更多
Based on ANSYS/LS-DYNA, the dynamics analysis software, and using nonlinear dynamic finite element method, the process of a submarine pipeline impacted by dropped objects is simulated, Some conclusions are drawn： Fir...Based on ANSYS/LS-DYNA, the dynamics analysis software, and using nonlinear dynamic finite element method, the process of a submarine pipeline impacted by dropped objects is simulated, Some conclusions are drawn： First, the damage depth of suspended pipe is smaller than that of the bare pipe in case of the same fall energy, and with the increase of fall energy, the difference grows; Second, with the falling object＇s speed and mass rising, the deformation of pipeline intensifies at the impact site and the maximum vibration amplitude of submarine pipeline increases; Third, when the fall energy is equal, the smaller the contact area of falling objects and pipeline is, the greater the damage depth of pipeline becomes; Fourth, changes of seabed soil parameters （shear elastic modulus, internal friction angle, density） have less influence on the suspended pipeline＇s dent depths and maximum vibration amplitude,展开更多
This paper summarizes the authors’ experimental study on the characterization system of composite behavior to withstand impact. The content includes: (1)The dent depth is the best parameter describing the impact dama...This paper summarizes the authors’ experimental study on the characterization system of composite behavior to withstand impact. The content includes: (1)The dent depth is the best parameter describing the impact damage state. (2) There exists the knee point phenomenon for damage resistance behavior (i.e. the relationship between impact energy or contact force and dent depth) and damage tolerance behavior (i.e. the relationship between dent depth and compressive failure strain or stress) of composite laminates. (3) The physical meaning of the knee point phenomenon is that the failure mechanisms change of damaged composites to fiber breakage in the first front plies from matrix crack and delamination. Some suggestions on the characterization system of composite behavior to withstand impact were proposed.展开更多
基金supported by the National Key Research&Development Plan,“Damage Effect and Accident Investigation Technologies of the Burning Explosion of Dangerous Chemical Storage Facilities”(Grant No.2016YFC0801204).
文摘In the process of construction and service,high-grade line pipes will get defective,e.g.dents,which will change its stress and strain distribution characteristics and impact its service reliability.In this paper,a X80 line pipe was taken as the research object.The distribution characteristics of the strain field in the X80 line pipe with plain dents with the change of dent depth under external load were analyzed using the finite element analysis software ABAQUS.Then,the strain distribution and microstructure characteristics in the dent zone were explored by conducting prefabrication test on physical dent.Finally,combined with the finite element simulation results,the strain distribution laws of the X80 line pipe with plain dent were discussed.And the following research results were obtained.First,under the same internal pressure,the strain distribution characteristics in the dent zone at different dent depths are similar,i.e.,the strain increases with the increase of the distance from the center of the dent,and decreases rapidly with the increase of the distance after the peak strain.Second,the strain increases with the increase of dent depth,and under the same internal pressure and dent depth,the axial strain is larger than the radial strain at the same location.Third,the greater the dent depth,the stronger the superposition effect of internal pressure and depth on the strain.Fourth,strain hardening occurs on the materials in the initial stage of the dent deformation.With the aggravation of deformation and the extension of dent radius,the strain response ability of materials increases,the grains at the bottom and side walls of the dent zone are elongated along the direction of maximum deformation,the lattice is distorted and strain hardening occurs.As a result,the dislocation density in this zone increases and the interaction occurs between dislocations,as a result,the strength of line steel is enhanced.In conclusion,the research results do well in predicting the stressestrain evolution laws in the process of dent,and provide a theoretical foundation and an experimental basis for studying the influence of mechanical damage on the service safety of pipelines.
文摘Based on ANSYS/LS-DYNA, the dynamics analysis software, and using nonlinear dynamic finite element method, the process of a submarine pipeline impacted by dropped objects is simulated, Some conclusions are drawn： First, the damage depth of suspended pipe is smaller than that of the bare pipe in case of the same fall energy, and with the increase of fall energy, the difference grows; Second, with the falling object＇s speed and mass rising, the deformation of pipeline intensifies at the impact site and the maximum vibration amplitude of submarine pipeline increases; Third, when the fall energy is equal, the smaller the contact area of falling objects and pipeline is, the greater the damage depth of pipeline becomes; Fourth, changes of seabed soil parameters （shear elastic modulus, internal friction angle, density） have less influence on the suspended pipeline＇s dent depths and maximum vibration amplitude,
基金The financial support from the National Natural Science Foundation of China under project No.10472107 is gratefully acknowledgedThe authors also wish to acknowledge the supports from the Aeronautical Science Foundation of China under project Nos. 04B23002 and 04B52009.
文摘This paper summarizes the authors’ experimental study on the characterization system of composite behavior to withstand impact. The content includes: (1)The dent depth is the best parameter describing the impact damage state. (2) There exists the knee point phenomenon for damage resistance behavior (i.e. the relationship between impact energy or contact force and dent depth) and damage tolerance behavior (i.e. the relationship between dent depth and compressive failure strain or stress) of composite laminates. (3) The physical meaning of the knee point phenomenon is that the failure mechanisms change of damaged composites to fiber breakage in the first front plies from matrix crack and delamination. Some suggestions on the characterization system of composite behavior to withstand impact were proposed.
