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Salvatore Pasta - One of the best experts on this subject based on the ideXlab platform.
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Finite-element simulation of residual stress induced by split-sleeve cold-Expansion Process of holes
Journal of Materials Processing Technology, 2008Co-Authors: Vincenzo Nigrelli, Salvatore PastaAbstract:A three-dimensional finite-element simulation was conducted for a split-sleeve cold-Expansion Process in order to determine the residual stress field around an expanded hole. The commercial FEA software DEFORM-3D™, a Lagrangian implicit code designed for metal forming Processes, was used to model the cold-Expansion Process of a fastener hole. The results show a through-thickness residual stress field in good agreement with the analytical solution developed by Guo. Moreover, the simulation has highlighted the effect of the split sleeve and the plate thickness on the residual stress field. © 2007 Elsevier B.V. All rights reserved
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Finite-element simulation of residual stress induced by split-sleeve cold-Expansion Process of holes
Journal of Materials Processing Technology, 2007Co-Authors: Vincenzo Nigrelli, Salvatore PastaAbstract:A three-dimensional finite-element simulation was conducted for a split-sleeve cold-Expansion Process in order to determine the residual stress field around an expanded hole. The commercial FEA software DEFORM-3D™, a Lagrangian implicit code designed for metal forming Processes, was used to model the cold-Expansion Process of a fastener hole. The results show a through-thickness residual stress field in good agreement with the analytical solution developed by Guo. Moreover, the simulation has highlighted the effect of the split sleeve and the plate thickness on the residual stress field.
Tasneem Pervez - One of the best experts on this subject based on the ideXlab platform.
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microstructure evolution of ultra fine grain low carbon steel tubular undergoing radial Expansion Process
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2016Co-Authors: Omar S Alabri, Tasneem Pervez, Majid Almaharbi, Rashid KhanAbstract:Abstract Tubular Expansion is a cold metal forming Process where diameteral change is achieved by propagating a conical mandrel through the tubular either by mechanical pull or hydraulic push. Cold metal forming alters post-Expansion mechanical and microstructural properties of tubular material, which may lead to premature failure during operation. In order to prevent tubular from failure, its post-Expansion material and mechanical properties must be investigated thoroughly. Initial grains morphology, distribution of phases, and subsequent variation in material and mechanical properties due to Expansion Process of low-carbon LSX-80 steel tubular are investigated in the current study. The observed microstructure is typical of high strength steels with a mixture of carbon-poor and carbon-rich regions. A noticeable volume fraction of martensite phase was also observed. Presence of smaller grains in the material is a clear indication of the application of grain refinement mechanism to improve strength and toughness. Microhardness and Charpy impact tests were done on unexpanded and expanded sections of tubular in order to determine their mechanical properties. In addition, fractographic analysis was accomplished and obtained results showed that the morphology of the fractured surface was nearly alike at the macroscopic scale throughout the range of Expansion ratios considered in this study. However, at the fine microscopic scale, the fractured surface was mostly ductile at low Expansion ratio, while it was mainly brittle at large Expansion ratio. Hence, an Expansion ratio in the vicinity of 15% is highly recommended for the current tubular material in order to have adequate safe margin for down-hole application. An alternative material has to be selected and/or developed in order to realize the goal of achieving higher Expansion ratio (≥30%) while preserving the tubular structural integrity after Expansion.
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structural behavior of solid expandable tubular undergoes radial Expansion Process analytical numerical and experimental approaches
International Journal of Solids and Structures, 2013Co-Authors: Omar S Alabri, Tasneem PervezAbstract:Abstract Today’s structures have to meet increasingly rigorous requirements during operation. The economic and human costs of failure during service impose a great responsibility on organizations and individuals who develop new products as well as those who select/integrate products in a final engineering design. A crucial aspect for successful product development and/or inclusion is the careful selection of the best material(s), derived from an informed awareness of the capabilities and opportunities afforded by all candidate materials, together with a design that takes full benefit of those competencies. Thick-wall tubular is an example where all these issues are playing a major role in deciding their industrial applications. Given for their desirable features of high strength and geometrical shape, they are widely used in aerospace, marine, military, automotive, oil and gas, and many other fields. This paper focuses on developing analytical solution to investigate the structural response of thick-wall tubulars undergo plastic deformation due to expanding them using a rigid mandrel of conical shape. Volume incompressible condition together with the Levy–Mises flow rule were used to develop the equations which relate the Expansion ratio of the tubular to the length and thickness variations. Besides, Tresca’s yield criterion was used to include the plastic behavior of the tubular material. Further to this, a numerical model of the tubular Expansion Process was also developed using the commercial finite element software ABAQUS. Experiments of tubular Expansion have been conducted using a full-scale test-rig in the Engineering Research Laboratory at Sultan Qaboos University to validate the analytical and numerical solutions. The developed analytical and numerical models are capable of predicting the stress field in the Expansion zone, the force required for Expansion, as well as the length and thickness variations induced in the tubular due to the Expansion Process. Comparison between analytical, experimental, and simulation results showed that a good agreement has been attained for various parameters.
Omar S Alabri - One of the best experts on this subject based on the ideXlab platform.
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microstructure evolution of ultra fine grain low carbon steel tubular undergoing radial Expansion Process
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2016Co-Authors: Omar S Alabri, Tasneem Pervez, Majid Almaharbi, Rashid KhanAbstract:Abstract Tubular Expansion is a cold metal forming Process where diameteral change is achieved by propagating a conical mandrel through the tubular either by mechanical pull or hydraulic push. Cold metal forming alters post-Expansion mechanical and microstructural properties of tubular material, which may lead to premature failure during operation. In order to prevent tubular from failure, its post-Expansion material and mechanical properties must be investigated thoroughly. Initial grains morphology, distribution of phases, and subsequent variation in material and mechanical properties due to Expansion Process of low-carbon LSX-80 steel tubular are investigated in the current study. The observed microstructure is typical of high strength steels with a mixture of carbon-poor and carbon-rich regions. A noticeable volume fraction of martensite phase was also observed. Presence of smaller grains in the material is a clear indication of the application of grain refinement mechanism to improve strength and toughness. Microhardness and Charpy impact tests were done on unexpanded and expanded sections of tubular in order to determine their mechanical properties. In addition, fractographic analysis was accomplished and obtained results showed that the morphology of the fractured surface was nearly alike at the macroscopic scale throughout the range of Expansion ratios considered in this study. However, at the fine microscopic scale, the fractured surface was mostly ductile at low Expansion ratio, while it was mainly brittle at large Expansion ratio. Hence, an Expansion ratio in the vicinity of 15% is highly recommended for the current tubular material in order to have adequate safe margin for down-hole application. An alternative material has to be selected and/or developed in order to realize the goal of achieving higher Expansion ratio (≥30%) while preserving the tubular structural integrity after Expansion.
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structural behavior of solid expandable tubular undergoes radial Expansion Process analytical numerical and experimental approaches
International Journal of Solids and Structures, 2013Co-Authors: Omar S Alabri, Tasneem PervezAbstract:Abstract Today’s structures have to meet increasingly rigorous requirements during operation. The economic and human costs of failure during service impose a great responsibility on organizations and individuals who develop new products as well as those who select/integrate products in a final engineering design. A crucial aspect for successful product development and/or inclusion is the careful selection of the best material(s), derived from an informed awareness of the capabilities and opportunities afforded by all candidate materials, together with a design that takes full benefit of those competencies. Thick-wall tubular is an example where all these issues are playing a major role in deciding their industrial applications. Given for their desirable features of high strength and geometrical shape, they are widely used in aerospace, marine, military, automotive, oil and gas, and many other fields. This paper focuses on developing analytical solution to investigate the structural response of thick-wall tubulars undergo plastic deformation due to expanding them using a rigid mandrel of conical shape. Volume incompressible condition together with the Levy–Mises flow rule were used to develop the equations which relate the Expansion ratio of the tubular to the length and thickness variations. Besides, Tresca’s yield criterion was used to include the plastic behavior of the tubular material. Further to this, a numerical model of the tubular Expansion Process was also developed using the commercial finite element software ABAQUS. Experiments of tubular Expansion have been conducted using a full-scale test-rig in the Engineering Research Laboratory at Sultan Qaboos University to validate the analytical and numerical solutions. The developed analytical and numerical models are capable of predicting the stress field in the Expansion zone, the force required for Expansion, as well as the length and thickness variations induced in the tubular due to the Expansion Process. Comparison between analytical, experimental, and simulation results showed that a good agreement has been attained for various parameters.
Lijun Wang - One of the best experts on this subject based on the ideXlab platform.
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Study of Post-Arc Sheath Expansion Process with a Two-Dimensional Particle-in-Cell Model
2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV), 2018Co-Authors: Yongpeng Mo, Junliang Li, Lijun WangAbstract:The dissipation of residual plasma after current zero is very important during the post-arc dielectric recovery Process, which has caused a lot of concern in the past a few decades. The electrons and ions of residual plasma separate from each other under the effect of a transient recovery voltage and then a post-arc sheath forms in front of the post-arc cathode. In order to study the radial motion of residual plasma during the post-arc sheath Expansion Process, a 2-D cylindrical particle-in-cell (PIC) model based on the VSim code is developed. Firstly, the influence of boundary condition setting on the post-arc sheath Expansion Process is studied. Then the radial motion of residual plasma and the development of post-arc sheath are analyzed.
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Numerical simulation of the initial Expansion Process of cathode spots in high-current triggered vacuum arc
2016 IEEE International Conference on Plasma Science (ICOPS), 2016Co-Authors: Cong Wang, Zongqian Shi, Shenli Jia, Lijun WangAbstract:The cathode spot (CS), as an intense source of inter-electrode arc plasma, plays a predominant role in maintaining the burning of vacuum arc, especially with an inactive anode. Consequently, the dynamics of CSs have a significant influence on the characteristics of the vacuum arc. Many experimental investigations have been devoted to better understanding of the motion of CSs, especially the initial Expansion Process of cathodes spots in high-current triggered vacuum arc. It has been indicated that the motion characteristic of cathode spots is greatly influenced by external axial magnetic field (AMF). In this work, a method is established to simulate the initial Expansion Process of CSs in high-current triggered vacuum arc, based on the proposed stepwise model of the motion of a single CS1. In this method, every new CS can be ignited in any direction around the old one with certain probability, which is connected with the magnetic field around the position of the old CS. With this approach, the initial Expansion Processes of CSs in free-burning and AMF-stabilized high-current triggered vacuum arc are simulated numerically with CSs initially uniformly distributed on a ring. The self-generated transverse magnetic field at the position of every CS is calculated by commercial software ANSYS with the current distribution in contact plate taken into account2. Simulation results agree well with relevant experiment results. Simulation results show that CSs expand faster without external AMF than that under AMF, and external AMF has significant influence on the distribution of CSs on the cathode surface, e.g., more and more CSs appear inside the ring when external AMF is present. Furthermore, the results also indicate that the expanding ring structure of CSs is unstable, and AMF can accelerate the breaking of the ring.
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Experimental Investigation on the Initial Expansion Process in a Drawn Vacuum Arc and the Influence of Axial Magnetic Field
IEEE Transactions on Plasma Science, 2012Co-Authors: Xiaochuan Song, Zongqian Shi, Shenli Jia, Zhonghao Qian, Chang Liu, Lijun WangAbstract:The initial Expansion Process in a drawn vacuum arc and the influence of axial magnetic field (AMF) were investigated experimentally in a demountable vacuum chamber. Arc characteristics were investigated with the aid of a high-speed digital camera with an exposure time of 2 μs . In a drawn vacuum arc, the arc sequence begins with the bridge column arc formed after the rupture of the molten metal bridge. This column evolves into the transition mode, which consisted of a central column with few or no cathode spots (CSs) outside the column, and then into the fully diffuse mode. Experimental results indicated that in transition mode arc, the Expansion Process could be characterized by the appearance of CSs outside the central column, and could be classified into two patterns, “slow” Expansion and “quick” Expansion according to the characteristics of the formation and motion of new CSs (conducting channels) outside the central column of arc. The influence of AMF and its distribution on the Expansion Process was also investigated. Investigation results indicated that AMF had two contrary effects, i.e., inhibiting effect and prompting effect, on the initial Expansion stage of drawn vacuum arc. Furthermore, saddle-shaped AMF could encourage the arc transition into diffuse mode more effectively than bell-shaped AMF.
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The Influence of Axial-Magnetic-Field Distribution on the Initial Expansion Process in Triggered Vacuum Arc
IEEE Transactions on Plasma Science, 2009Co-Authors: Zongqian Shi, Shenli Jia, Hong Dong, Zhigang Liu, Xiaochuan Song, Lijun WangAbstract:In this paper, the initial Expansion Process after trigger of vacuum arc was investigated experimentally with two typical axial-magnetic-field (AMF) distributions, i.e., bell-shaped AMF generated by traditional cup-shaped AMF electrodes and saddle-shaped AMF generated by specially designed coil-type AMF electrodes. The motion of cathode spots (CSs) in the initial Expansion Process was investigated by high-speed digital camera with exposure time of 2 mus. Experimental results indicated that CSs expanded faster under saddle-shaped AMF than under bell-shaped AMF at 5 (rms), 10, 15, and 20 kA. Furthermore, the motion of CSs slowed down between 15 and 20 kA in the case of bell-shaped AMF, whereas CSs tended to quicken up with the increase of arc current under saddle-shaped AMF. Based on the images of CSs, it was proposed that, besides direct influence of AMF on the retrograde motion of CSs, the concentration of CSs at relatively high current and strong central AMF could also inhibit the outward motion in the initial Expansion Process.
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The initial Expansion Process in triggered vacuum arc under different axial magnetic field distributions
2008 23rd International Symposium on Discharges and Electrical Insulation in Vacuum, 2008Co-Authors: Zongqian Shi, Shenli Jia, Hong Dong, Zhigang Liu, Xiaochuan Song, Lijun WangAbstract:The motion of cathode spots in the initial Expansion Process of triggered vacuum arc under bell-shaped and saddle-shaped AMF was investigated with the aid of high-speed digital camera with exposure time of 2 microseconds. Experimental results indicated that cathode spots expanded faster under saddle-shaped AMF than under bell-shaped AMF. Furthermore, the motion of cathode spots slowed down between 15 kA and 20 kA in the case of bell-shaped AMF, whereas, cathode spots tended to quicken up with the increase of arc current under saddle-shaped AMF. Based on the images of cathode spots, it was proposed that the concentration of cathode spots at relatively high current and strong central AMF could also inhibit the outward motion in the initial Expansion Process.
Vincenzo Nigrelli - One of the best experts on this subject based on the ideXlab platform.
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Finite-element simulation of residual stress induced by split-sleeve cold-Expansion Process of holes
Journal of Materials Processing Technology, 2008Co-Authors: Vincenzo Nigrelli, Salvatore PastaAbstract:A three-dimensional finite-element simulation was conducted for a split-sleeve cold-Expansion Process in order to determine the residual stress field around an expanded hole. The commercial FEA software DEFORM-3D™, a Lagrangian implicit code designed for metal forming Processes, was used to model the cold-Expansion Process of a fastener hole. The results show a through-thickness residual stress field in good agreement with the analytical solution developed by Guo. Moreover, the simulation has highlighted the effect of the split sleeve and the plate thickness on the residual stress field. © 2007 Elsevier B.V. All rights reserved
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Finite-element simulation of residual stress induced by split-sleeve cold-Expansion Process of holes
Journal of Materials Processing Technology, 2007Co-Authors: Vincenzo Nigrelli, Salvatore PastaAbstract:A three-dimensional finite-element simulation was conducted for a split-sleeve cold-Expansion Process in order to determine the residual stress field around an expanded hole. The commercial FEA software DEFORM-3D™, a Lagrangian implicit code designed for metal forming Processes, was used to model the cold-Expansion Process of a fastener hole. The results show a through-thickness residual stress field in good agreement with the analytical solution developed by Guo. Moreover, the simulation has highlighted the effect of the split sleeve and the plate thickness on the residual stress field.
