smh sharifi | Petroleum University of Technology,Iran (original) (raw)
Papers by smh sharifi
Ships and Offshore Structures
Engineering Fracture Mechanics
International Journal of Coastal and Offshore Engineering, Oct 10, 2020
International Journal of Maritime Technology, 2021
A common solution for oil and gas transportation in offshore fields is long distance pipelines. F... more A common solution for oil and gas transportation in offshore fields is long distance pipelines. Flowing of High Pressure/ High Temperature (HP/HT) fluid may cause uncontrolled buckling because of material or geometry defects. In order to reduce damages and avoid buckling in unpredictable places, the controlled buckling concept is introduced. In order to trigger buckling in predetermined location, pipeline can be placed in snaked lay configuration. In this article, it is aimed to investigate the effect of geometrical parameters, i.e., laying wavelength, laying radius and offset angle of snaked lay configuration on the displacement of offshore pipelines, axial force and bending moment in post buckling stage under HP/HT condition. Then, these results are used to evaluate the global buckling failure. This work is performed by using nonlinear finite element analysis and pipe-soil interaction of as-laid pipelines is modeled by employing spring elements. The results of investigation show that different ranges of the mentioned parameters may cause the maximum difference in displacement, bending moment and axial force about 133.6%, 155%, and 30%, respectively. Investigation of global buckling failure determine the most critical section of pipelines and it is observed that as the curved section of pipeline shrinks, the possibility of global buckling failure will increase but the effect of laying wavelength is contrary and the failure will be decreased about 8.3%.
Assistant Professor, Faculty Member of Mechanical Engineering Department, Petroleum University of... more Assistant Professor, Faculty Member of Mechanical Engineering Department, Petroleum University of Technology, Abadan, Iran; sharifi@put.ac.ir Assistant Professor, Faculty Member of Mechanical Engineering Department, Petroleum University of Technology, Abadan, Iran; rahim.taheri@put.ac.ir MSc. Student in Offshore Structural Engineering, Mechanical Engineering Department, Petroleum University of Technology, Abadan, Iran; E.karimipour@ait.put.ac.ir
International Journal of Maritime Technology, 2020
Flexible risers have been used widely in recent years for floating structure in shallow and deep ... more Flexible risers have been used widely in recent years for floating structure in shallow and deep water. Flexible risers have various configurations and each configuration has its specific charectresitics that helps the riser to solve the problems that exist in shallow and deep water. Selecting and designing the best configuration for flexible risers in shallow water, like deep water, present many challenges, some of these challenges can be addressed: high vessel displacement compared to the water depth, minimum riser clearance with the seabed or sea surface or the vessel keel, bending radius limitation and etc. The aim of this paper is to investigate the traditional configurations like lazy wave and pliant wave and to compare them with a new configuration like weight added wave for the riser with 15 inches internal diameter in 45m water depth connected to a turret moored floating storage unit. It is concluded that the traditional configuration can not solve the sea surface clearance...
Article History: Received: 23 Sep. 2019 Accepted: 11 Apr. 2020 Pitting is one of the most localiz... more Article History: Received: 23 Sep. 2019 Accepted: 11 Apr. 2020 Pitting is one of the most localized forms of corrosion attacks which cannot be detected easily. Pitting decreases the pipe wall thickness and also the pipeline strength against environmental and operational loads. The purpose of this article is to investigate the most common reliability methods for estimating the maximum pitting depth and the effect of internal pressure on the remaining strength of corroded pipelines at different times in its lifetime service based on different failure pressure models using first-order approximation and sampling reliability methods. To investigate the effect of pitting growth and variation of internal pressure on pipeline characteristics, sensitivity analysis with gamma index several times in pipeline lifetime was performed. It is concluded that the first-order reliability method was applicable for ASME failure pressure models, also concluding that internal pressure and pipeline wall th...
Iran University of Science & Technology, 2017
Offshore pipelines are an effective tool for transportation of oil and gas which are usually asse... more Offshore pipelines are an effective tool for transportation of oil and gas which are usually assembled by the use of girth welds. Since flaws may naturally exist at such welds, fracture assessment of girth welded offshore pipelines is substantial. Current fracture assessment procedures like BS 7910 consider identical material properties for the weld and the base metals. However the strength difference between weld and base materials has significant effect on fracture assessment results. This effect is magnified greatly for pipelines which are operated in deep waters and are subjected to large plastic loads. In this paper 3D nonlinear elastic-plastic finite element analyses using the ABAQUS software are performed in order to investigate the effect of weld mismatching at various crack geometries on fracture assessment of pipeline’s girth weld. It is noteworthy that such a quantitative study on the effect of weld mismatching condition at different crack geometries on ECA analysis has n...
Journal of Solid Mechanics, 2018
Offshore pipelines are usually constructed by the use of girth welds, while welds may naturally c... more Offshore pipelines are usually constructed by the use of girth welds, while welds may naturally contain flaws. Currently, fracture assessment procedures such as BS 7910 are based on the stress-based methods and their responses for situations with large plastic strain is suspicious. DNV-OS-F101 with limited modifications proposes a strain-based procedure for such plastic loads. In this paper 3D nonlinear elastic-plastic finite element analyses using the ABAQUS software are performed in order to compare existing stress- and strain-based procedures beside newly strain-based method which is called CRES approach in order to improve the criteria used in current guidelines particularly at large plastic strains. It is concluded that although BS 7910 values are closer to finite element results than other methods in elastic region, but it is still conservative. In the area of large plastic strain, CRES method is very less conservative in both case of with and without internal pressure in comp...
Metals and Materials International, 2020
The effect of hydrogen on the microdamage evolution of 1200M advanced high-strength steel was eva... more The effect of hydrogen on the microdamage evolution of 1200M advanced high-strength steel was evaluated by the combination of experimental and numerical approaches. In the experimental section, the tensile test was performed under different testing conditions, i.e., vacuum, in-situ hydrogen plasma charging (IHPC), ex-situ electrochemical hydrogen charging (EEHC), and ex-situ + in-situ hydrogen charging (EIHC) conditions. The post-mortem analysis was conducted on the fracture surface of specimens to illuminate the impact of hydrogen on the microstructure and mechanical properties. The results showed that under all of hydrogen charging conditions, the yield stress and ultimate tensile strength were slightly sensitive to hydrogen, while tensile elongation was profoundly affected. While only ductile dimple features were observed on the fracture surfaces in vacuum condition, the results indicated a simultaneous action of the hydrogen-enhanced decohesion (HEDE) and hydrogen enhanced local...
هلاقم تاعلاطا هدیکچ لماک یشهوژپ هلاقم :تفایرد 22 نمهب 1396 :شریذپ 21 نیدرورف 1397 :تیاس رد هئارا ... more هلاقم تاعلاطا هدیکچ لماک یشهوژپ هلاقم :تفایرد 22 نمهب 1396 :شریذپ 21 نیدرورف 1397 :تیاس رد هئارا 21 تشهبیدرا 1397 هرهب نیگنس عیانص رد یفلاتا يامرگ تیریدم یم شیازفا یهجوت لباق روط هب ار هزوح نیا رد يرو يروانف کی ناونع هب یلآ نیکنر لکیس .دهد نیکنر لکیس درکلمع .تسا هدش یفرعم نییاپ و طسوتم ياهامد اب ییامرگ عبانم يارب هتیسیرتکلا دیلوت و یفلاتا ترارح تفایزاب تهج بسانم م یلآ نییاپ يامد ياراد عبانم زا یبایزاب تهج مک شوج يامد اب یلآ لایس زا هک توافت نیا اب تسا یلومعم نیکنر لکیس دننا یم هدافتسا رت .دوش يارب ،شکریز ود و کی اب یلآ نیکنر لکیس ود و یلآ نیکنر هیاپ لکیس هلاقم نیا رد 5 هتفرگ رارق يژرسکا و يژرنا لیلحت دروم فلتخم لایس د و هنیهب و یکیمونوکاومرت لیلحت همادا ر لکیس يزاس .تسا هتفرگ ماجنا تباث طیارش اب ییامرگ عبنم يارب کیتنژ متیروگلا طسوت هدش هراشا ياه یم ناشن جیاتن دهد R113 لایس نیب زا دوجوم ياه .دراد ار درکلمع نیرتهب لیلحت نتفرگ رظن رد اب هدمآ تسد هب هنیهب رادقم ،يداصتقا ياه لیلحت اهنت هک یتلاح اب هسیاقم رد نیبروت يدورو يامد و راشف يارب یم هتفرگ رظن رد متسیس یکیمانیدومرت ياه یم شهاک ،دوش رییغت اب .دبای دودح شکریز کی ياراد لکیس هب هداس لکیس 12.5% دودح شکریز ود ياراد لکیس هب هداس لکیس زا و 18.75% هنیزه رادقم رد رییغت دیلوت صوصخم یم هدهاشم ناوت قوف هجرد شیازفا اب .دوش يژرسکا هدزاب و شیازفا ناوت دیلوت صوصخم هنیزه رادقم زین نیبروت يدورو مرگ یم شهاک متسیس .دنبای :ناگژاو دیلک یلآ نیکنر لکیس یفلاتا ترارح يژرسکا کیمونوکاومرت کیتنژ متیروگلا
Article History: Received: 15 Nov. 2016 Accepted: 15 Mar. 2016 Offshore pipelines are an efficien... more Article History: Received: 15 Nov. 2016 Accepted: 15 Mar. 2016 Offshore pipelines are an efficient long-distance transportation method for oil and gas. These are usually constructed by the use of girth welds, while welds may naturally contain flaws. Hence, it is essential to inspect the fracture response of girth welds in order to check the structural integrity of the pipeline. One of the guidelines that is using wide spread for investigating the fracture response of steel structures is BS 7910 which is based on Engineering Critical Assessment (ECA) method. In this paper Engineering Critical Assessment (ECA) of offshore pipeline girth welds is done according to BS 7910 through Crackwise software and the influence of several parameters on ECA is presented. It is concluded that Influence of misalignment on axial internal surface flaws is more significant than on axial external flaws. Furthermore it is observed that internal surface flaws have always larger values for tolerable defect ...
International Journal of coastal and offshore engineering, 2019
Subsea pipelines due to the reduction of transfer costs and expedite the offshore operations is o... more Subsea pipelines due to the reduction of transfer costs and expedite the offshore operations is one of the all-purpose structures in marine industries. Subsea pipelines are exposed to a variety of hazards, including corrosion and fatigue Etc. Free span exacerbates the fatigue required parameters due to a phenomenon called the Vortex Induced Vibration (VIV). In this research, the influence of the span's length on the free span subsea pipeline has been reviewed with ABAQUS standard code. In this study the previous result has been expanded. The results of the VIV fatigue life are extensible to all of the depth. Achieved Results indicate that the fatigue life of the pipeline even in the worst condition is much higher than the required amount that it represents the upstream design of DNV-RP-F105. In this study the backrest pipeline has been investigated and result show that the pipeline under the different conditions in the backrest, by creating more vibration and displacement on one side of the pipeline reduces the fatigue life of 113 percent compared to snap. The VIV fatigue life has undergone a lot of changes due to span length changes, maximum changes occur between cable and behavioral which the amount of these changes is reduced by 75%. The free span length is another factor in VIV fatigue. VIV fatigue life will be increased by reducing the span length. As well as increasing the flow velocity that is the main factor in creating the VIV is increased fatigue. Therefore, in terms of the accuracy in the choice of the existing conditions of very high importance for the pipeline. Comparison between effect parameters in VIV fatigue life was shown that span length is the most effective parameter.
Journal of Mathematics and Computer Science, 2012
In basic design of offshore or onshore structures, prediction of surface waves due to uniform mot... more In basic design of offshore or onshore structures, prediction of surface waves due to uniform motion of the floating body is essential to achieve an optimum body shape. Whereas, in the practical hydrodynamics, using of towing tanks is common and so cost and time consuming to conduct it, so a reliable numerical tank is interesting. A wide channel with constant depth constitutescomputational domain. It assumes that fluid is incompressible and non-viscous and the flow is irrotational. Therefore, Laplace's equation could describe flow field.3D Boundary Element method based on second Green's Identityis implemented to solveLaplace's equation. Impermeable boundary condition is satisfied by Image method and Cauchy integral theorem and Poisson summation formula is used to determine Principle value integral. In this study, numerical simulation is conducted for a hemisphere and added mass and generated wave profile is presented.
Materials Science and Engineering: A, 2020
Macro-and microscale investigations of hydrogen embrittlement in X70 pipeline steel by insitu and... more Macro-and microscale investigations of hydrogen embrittlement in X70 pipeline steel by insitu and ex-situ hydrogen charging tensile tests and in-situ electrochemical micro-cantilever bending test,
Thin-Walled Structures, 2018
A new analytical approach for the determination of natural frequencies of a long cylindrical shel... more A new analytical approach for the determination of natural frequencies of a long cylindrical shell containing a variably oriented semi-elliptical surface crack is presented in this paper. Equations of motion for the cracked shell are obtained based on classical shell theories and are simplified using the Donell-Mushtari-Vlasov (DMV) theory. It has been assumed that the crack length is far smaller than the radius of curvature of the shell and linespring model (LSM) is used in order to calculate crack compliance coefficients which are subsequently to be added into the equations of motion to include crack effects in the problem. An analytical solution has been developed using Hamilton's principle and the results are obtained for the shells considering clamped-clamped (C-C) and simply supported (S-S) boundary conditions at both ends. Results obtained from the proposed model are verified using a finite element model created with ABAQUS and there is an acceptable agreement between analytical and FEM results. Effects of the shell properties such as length, radius and thickness as well as the effects of the crack characteristics such as its length and orientation on the natural frequencies of the cracked shell are analyzed in this study.
Thin-Walled Structures, 2018
The present research discusses indentation process on the oil pipelines using a rigid indenter in... more The present research discusses indentation process on the oil pipelines using a rigid indenter in the quasi-static condition by the experimental and numerical analyses. This article investigates influences of internal pressure, diameter and wall thickness of pipes and geometrical characteristics of rigid cylindrical indenters with conical nose such as cone angle, conical nose diameter and cylindrical part diameter on mechanical behavior of the circular steel pipes under concentrated lateral loading (denting). In the experimental part, some specimens made from the steel API5L L245 were prepared and they laterally compressed by a rigid cylindrical indenter with the conical nose to perform the indentation process on them. In the numerical part, some finite element models were prepared and indentation process was simulated on different models with various tube and indenter geometries in different conditions of internal pressure. By comparing the numerical and experimental results, precision and accuracy of the simulations were affirmed. The discussed results show that when tube diameter increases, bending moment arm of the concentrated applied load around the formed plastic hinge lines enhances; therefore, lower lateral load can create a certain plastic deformations in the tube wall; and also, total absorbed energy by the tube enhances. Results demonstrate that when a conical projectile with a certain mass and initial velocity laterally compresses a circular tube, increment of tube diameter causes reduction of probability of the tube failure. The results show that when cone angle of conical indenter decreases and reaches to a certain value that called critical angle, the penetration occurs during the indentation process. Furthermore, it is found that by increasing the diameter of cylindrical part of the indenter, lateral indentation load increases; and when applied internal pressure on the tube increases, ultimate lateral displacement of the indenter decreases; but, the maximum load for the tube wall fracture enhances.
Journal of Mechanical Science and Technology, 2017
Circumferential crack growth pattern in a thin-walled cylinder is studied. Thermo-elastic stresse... more Circumferential crack growth pattern in a thin-walled cylinder is studied. Thermo-elastic stresses in a cylinder subjected to thermomechanical loads are extracted. Closed form thermo-elastic stress intensity factor for cracked cylinder are derived using weight function method. An algorithm is developed to simulate different crack growth patterns utilizing a very high efficiency weight function method. This would lessen the taken time for the analyses compared to other numerical methods such as FEM. Results show that while the load effect on cylinder subjected to thermal load lead to the crack growth in small aspect ratio, in cylinder subjected to mechanical loads, it would lead to the growth of crack in large aspect ratio. The results show that, apart from load effects, the cylinders containing initial semi-circular crack have the longest life among the cylinders containing initial semi-elliptical crack with the same initial depth.
Engineering Failure Analysis, 2017
Recently, authors have developed a numerical procedure in order to predict the fatigue failure of... more Recently, authors have developed a numerical procedure in order to predict the fatigue failure of the cast iron cylinder head [Three dimensional analysis of low cycle fatigue failure in engine part subjected to multi-axial variable amplitude thermo-mechanical load, Engineering Failure Analysis 62 (2016) 128-141]. The aim of the present study is a comparative investigation on the application of the different equivalent stress and strain approaches and critical plane fatigue theories in order to accurately determine the critical zone and life cycle in the failed cylinder head. The experimental observations in engine durability test ISO 8178 E5 and some multi-axial fatigue criteria are explained in detail. Then the fatigue life predictions obtained through the developed numerical procedure are compared with the observations. Results reveal that Morrow and SWT as equivalent strain-based criteria and Fatemi-Socie as critical plane criterion would lead to more accurate predictions in comparison with others. However, in the case of engine structure analysis, there is no considerable superiority between the two last groups of multi-axial fatigue models.
Ships and Offshore Structures
Engineering Fracture Mechanics
International Journal of Coastal and Offshore Engineering, Oct 10, 2020
International Journal of Maritime Technology, 2021
A common solution for oil and gas transportation in offshore fields is long distance pipelines. F... more A common solution for oil and gas transportation in offshore fields is long distance pipelines. Flowing of High Pressure/ High Temperature (HP/HT) fluid may cause uncontrolled buckling because of material or geometry defects. In order to reduce damages and avoid buckling in unpredictable places, the controlled buckling concept is introduced. In order to trigger buckling in predetermined location, pipeline can be placed in snaked lay configuration. In this article, it is aimed to investigate the effect of geometrical parameters, i.e., laying wavelength, laying radius and offset angle of snaked lay configuration on the displacement of offshore pipelines, axial force and bending moment in post buckling stage under HP/HT condition. Then, these results are used to evaluate the global buckling failure. This work is performed by using nonlinear finite element analysis and pipe-soil interaction of as-laid pipelines is modeled by employing spring elements. The results of investigation show that different ranges of the mentioned parameters may cause the maximum difference in displacement, bending moment and axial force about 133.6%, 155%, and 30%, respectively. Investigation of global buckling failure determine the most critical section of pipelines and it is observed that as the curved section of pipeline shrinks, the possibility of global buckling failure will increase but the effect of laying wavelength is contrary and the failure will be decreased about 8.3%.
Assistant Professor, Faculty Member of Mechanical Engineering Department, Petroleum University of... more Assistant Professor, Faculty Member of Mechanical Engineering Department, Petroleum University of Technology, Abadan, Iran; sharifi@put.ac.ir Assistant Professor, Faculty Member of Mechanical Engineering Department, Petroleum University of Technology, Abadan, Iran; rahim.taheri@put.ac.ir MSc. Student in Offshore Structural Engineering, Mechanical Engineering Department, Petroleum University of Technology, Abadan, Iran; E.karimipour@ait.put.ac.ir
International Journal of Maritime Technology, 2020
Flexible risers have been used widely in recent years for floating structure in shallow and deep ... more Flexible risers have been used widely in recent years for floating structure in shallow and deep water. Flexible risers have various configurations and each configuration has its specific charectresitics that helps the riser to solve the problems that exist in shallow and deep water. Selecting and designing the best configuration for flexible risers in shallow water, like deep water, present many challenges, some of these challenges can be addressed: high vessel displacement compared to the water depth, minimum riser clearance with the seabed or sea surface or the vessel keel, bending radius limitation and etc. The aim of this paper is to investigate the traditional configurations like lazy wave and pliant wave and to compare them with a new configuration like weight added wave for the riser with 15 inches internal diameter in 45m water depth connected to a turret moored floating storage unit. It is concluded that the traditional configuration can not solve the sea surface clearance...
Article History: Received: 23 Sep. 2019 Accepted: 11 Apr. 2020 Pitting is one of the most localiz... more Article History: Received: 23 Sep. 2019 Accepted: 11 Apr. 2020 Pitting is one of the most localized forms of corrosion attacks which cannot be detected easily. Pitting decreases the pipe wall thickness and also the pipeline strength against environmental and operational loads. The purpose of this article is to investigate the most common reliability methods for estimating the maximum pitting depth and the effect of internal pressure on the remaining strength of corroded pipelines at different times in its lifetime service based on different failure pressure models using first-order approximation and sampling reliability methods. To investigate the effect of pitting growth and variation of internal pressure on pipeline characteristics, sensitivity analysis with gamma index several times in pipeline lifetime was performed. It is concluded that the first-order reliability method was applicable for ASME failure pressure models, also concluding that internal pressure and pipeline wall th...
Iran University of Science & Technology, 2017
Offshore pipelines are an effective tool for transportation of oil and gas which are usually asse... more Offshore pipelines are an effective tool for transportation of oil and gas which are usually assembled by the use of girth welds. Since flaws may naturally exist at such welds, fracture assessment of girth welded offshore pipelines is substantial. Current fracture assessment procedures like BS 7910 consider identical material properties for the weld and the base metals. However the strength difference between weld and base materials has significant effect on fracture assessment results. This effect is magnified greatly for pipelines which are operated in deep waters and are subjected to large plastic loads. In this paper 3D nonlinear elastic-plastic finite element analyses using the ABAQUS software are performed in order to investigate the effect of weld mismatching at various crack geometries on fracture assessment of pipeline’s girth weld. It is noteworthy that such a quantitative study on the effect of weld mismatching condition at different crack geometries on ECA analysis has n...
Journal of Solid Mechanics, 2018
Offshore pipelines are usually constructed by the use of girth welds, while welds may naturally c... more Offshore pipelines are usually constructed by the use of girth welds, while welds may naturally contain flaws. Currently, fracture assessment procedures such as BS 7910 are based on the stress-based methods and their responses for situations with large plastic strain is suspicious. DNV-OS-F101 with limited modifications proposes a strain-based procedure for such plastic loads. In this paper 3D nonlinear elastic-plastic finite element analyses using the ABAQUS software are performed in order to compare existing stress- and strain-based procedures beside newly strain-based method which is called CRES approach in order to improve the criteria used in current guidelines particularly at large plastic strains. It is concluded that although BS 7910 values are closer to finite element results than other methods in elastic region, but it is still conservative. In the area of large plastic strain, CRES method is very less conservative in both case of with and without internal pressure in comp...
Metals and Materials International, 2020
The effect of hydrogen on the microdamage evolution of 1200M advanced high-strength steel was eva... more The effect of hydrogen on the microdamage evolution of 1200M advanced high-strength steel was evaluated by the combination of experimental and numerical approaches. In the experimental section, the tensile test was performed under different testing conditions, i.e., vacuum, in-situ hydrogen plasma charging (IHPC), ex-situ electrochemical hydrogen charging (EEHC), and ex-situ + in-situ hydrogen charging (EIHC) conditions. The post-mortem analysis was conducted on the fracture surface of specimens to illuminate the impact of hydrogen on the microstructure and mechanical properties. The results showed that under all of hydrogen charging conditions, the yield stress and ultimate tensile strength were slightly sensitive to hydrogen, while tensile elongation was profoundly affected. While only ductile dimple features were observed on the fracture surfaces in vacuum condition, the results indicated a simultaneous action of the hydrogen-enhanced decohesion (HEDE) and hydrogen enhanced local...
هلاقم تاعلاطا هدیکچ لماک یشهوژپ هلاقم :تفایرد 22 نمهب 1396 :شریذپ 21 نیدرورف 1397 :تیاس رد هئارا ... more هلاقم تاعلاطا هدیکچ لماک یشهوژپ هلاقم :تفایرد 22 نمهب 1396 :شریذپ 21 نیدرورف 1397 :تیاس رد هئارا 21 تشهبیدرا 1397 هرهب نیگنس عیانص رد یفلاتا يامرگ تیریدم یم شیازفا یهجوت لباق روط هب ار هزوح نیا رد يرو يروانف کی ناونع هب یلآ نیکنر لکیس .دهد نیکنر لکیس درکلمع .تسا هدش یفرعم نییاپ و طسوتم ياهامد اب ییامرگ عبانم يارب هتیسیرتکلا دیلوت و یفلاتا ترارح تفایزاب تهج بسانم م یلآ نییاپ يامد ياراد عبانم زا یبایزاب تهج مک شوج يامد اب یلآ لایس زا هک توافت نیا اب تسا یلومعم نیکنر لکیس دننا یم هدافتسا رت .دوش يارب ،شکریز ود و کی اب یلآ نیکنر لکیس ود و یلآ نیکنر هیاپ لکیس هلاقم نیا رد 5 هتفرگ رارق يژرسکا و يژرنا لیلحت دروم فلتخم لایس د و هنیهب و یکیمونوکاومرت لیلحت همادا ر لکیس يزاس .تسا هتفرگ ماجنا تباث طیارش اب ییامرگ عبنم يارب کیتنژ متیروگلا طسوت هدش هراشا ياه یم ناشن جیاتن دهد R113 لایس نیب زا دوجوم ياه .دراد ار درکلمع نیرتهب لیلحت نتفرگ رظن رد اب هدمآ تسد هب هنیهب رادقم ،يداصتقا ياه لیلحت اهنت هک یتلاح اب هسیاقم رد نیبروت يدورو يامد و راشف يارب یم هتفرگ رظن رد متسیس یکیمانیدومرت ياه یم شهاک ،دوش رییغت اب .دبای دودح شکریز کی ياراد لکیس هب هداس لکیس 12.5% دودح شکریز ود ياراد لکیس هب هداس لکیس زا و 18.75% هنیزه رادقم رد رییغت دیلوت صوصخم یم هدهاشم ناوت قوف هجرد شیازفا اب .دوش يژرسکا هدزاب و شیازفا ناوت دیلوت صوصخم هنیزه رادقم زین نیبروت يدورو مرگ یم شهاک متسیس .دنبای :ناگژاو دیلک یلآ نیکنر لکیس یفلاتا ترارح يژرسکا کیمونوکاومرت کیتنژ متیروگلا
Article History: Received: 15 Nov. 2016 Accepted: 15 Mar. 2016 Offshore pipelines are an efficien... more Article History: Received: 15 Nov. 2016 Accepted: 15 Mar. 2016 Offshore pipelines are an efficient long-distance transportation method for oil and gas. These are usually constructed by the use of girth welds, while welds may naturally contain flaws. Hence, it is essential to inspect the fracture response of girth welds in order to check the structural integrity of the pipeline. One of the guidelines that is using wide spread for investigating the fracture response of steel structures is BS 7910 which is based on Engineering Critical Assessment (ECA) method. In this paper Engineering Critical Assessment (ECA) of offshore pipeline girth welds is done according to BS 7910 through Crackwise software and the influence of several parameters on ECA is presented. It is concluded that Influence of misalignment on axial internal surface flaws is more significant than on axial external flaws. Furthermore it is observed that internal surface flaws have always larger values for tolerable defect ...
International Journal of coastal and offshore engineering, 2019
Subsea pipelines due to the reduction of transfer costs and expedite the offshore operations is o... more Subsea pipelines due to the reduction of transfer costs and expedite the offshore operations is one of the all-purpose structures in marine industries. Subsea pipelines are exposed to a variety of hazards, including corrosion and fatigue Etc. Free span exacerbates the fatigue required parameters due to a phenomenon called the Vortex Induced Vibration (VIV). In this research, the influence of the span's length on the free span subsea pipeline has been reviewed with ABAQUS standard code. In this study the previous result has been expanded. The results of the VIV fatigue life are extensible to all of the depth. Achieved Results indicate that the fatigue life of the pipeline even in the worst condition is much higher than the required amount that it represents the upstream design of DNV-RP-F105. In this study the backrest pipeline has been investigated and result show that the pipeline under the different conditions in the backrest, by creating more vibration and displacement on one side of the pipeline reduces the fatigue life of 113 percent compared to snap. The VIV fatigue life has undergone a lot of changes due to span length changes, maximum changes occur between cable and behavioral which the amount of these changes is reduced by 75%. The free span length is another factor in VIV fatigue. VIV fatigue life will be increased by reducing the span length. As well as increasing the flow velocity that is the main factor in creating the VIV is increased fatigue. Therefore, in terms of the accuracy in the choice of the existing conditions of very high importance for the pipeline. Comparison between effect parameters in VIV fatigue life was shown that span length is the most effective parameter.
Journal of Mathematics and Computer Science, 2012
In basic design of offshore or onshore structures, prediction of surface waves due to uniform mot... more In basic design of offshore or onshore structures, prediction of surface waves due to uniform motion of the floating body is essential to achieve an optimum body shape. Whereas, in the practical hydrodynamics, using of towing tanks is common and so cost and time consuming to conduct it, so a reliable numerical tank is interesting. A wide channel with constant depth constitutescomputational domain. It assumes that fluid is incompressible and non-viscous and the flow is irrotational. Therefore, Laplace's equation could describe flow field.3D Boundary Element method based on second Green's Identityis implemented to solveLaplace's equation. Impermeable boundary condition is satisfied by Image method and Cauchy integral theorem and Poisson summation formula is used to determine Principle value integral. In this study, numerical simulation is conducted for a hemisphere and added mass and generated wave profile is presented.
Materials Science and Engineering: A, 2020
Macro-and microscale investigations of hydrogen embrittlement in X70 pipeline steel by insitu and... more Macro-and microscale investigations of hydrogen embrittlement in X70 pipeline steel by insitu and ex-situ hydrogen charging tensile tests and in-situ electrochemical micro-cantilever bending test,
Thin-Walled Structures, 2018
A new analytical approach for the determination of natural frequencies of a long cylindrical shel... more A new analytical approach for the determination of natural frequencies of a long cylindrical shell containing a variably oriented semi-elliptical surface crack is presented in this paper. Equations of motion for the cracked shell are obtained based on classical shell theories and are simplified using the Donell-Mushtari-Vlasov (DMV) theory. It has been assumed that the crack length is far smaller than the radius of curvature of the shell and linespring model (LSM) is used in order to calculate crack compliance coefficients which are subsequently to be added into the equations of motion to include crack effects in the problem. An analytical solution has been developed using Hamilton's principle and the results are obtained for the shells considering clamped-clamped (C-C) and simply supported (S-S) boundary conditions at both ends. Results obtained from the proposed model are verified using a finite element model created with ABAQUS and there is an acceptable agreement between analytical and FEM results. Effects of the shell properties such as length, radius and thickness as well as the effects of the crack characteristics such as its length and orientation on the natural frequencies of the cracked shell are analyzed in this study.
Thin-Walled Structures, 2018
The present research discusses indentation process on the oil pipelines using a rigid indenter in... more The present research discusses indentation process on the oil pipelines using a rigid indenter in the quasi-static condition by the experimental and numerical analyses. This article investigates influences of internal pressure, diameter and wall thickness of pipes and geometrical characteristics of rigid cylindrical indenters with conical nose such as cone angle, conical nose diameter and cylindrical part diameter on mechanical behavior of the circular steel pipes under concentrated lateral loading (denting). In the experimental part, some specimens made from the steel API5L L245 were prepared and they laterally compressed by a rigid cylindrical indenter with the conical nose to perform the indentation process on them. In the numerical part, some finite element models were prepared and indentation process was simulated on different models with various tube and indenter geometries in different conditions of internal pressure. By comparing the numerical and experimental results, precision and accuracy of the simulations were affirmed. The discussed results show that when tube diameter increases, bending moment arm of the concentrated applied load around the formed plastic hinge lines enhances; therefore, lower lateral load can create a certain plastic deformations in the tube wall; and also, total absorbed energy by the tube enhances. Results demonstrate that when a conical projectile with a certain mass and initial velocity laterally compresses a circular tube, increment of tube diameter causes reduction of probability of the tube failure. The results show that when cone angle of conical indenter decreases and reaches to a certain value that called critical angle, the penetration occurs during the indentation process. Furthermore, it is found that by increasing the diameter of cylindrical part of the indenter, lateral indentation load increases; and when applied internal pressure on the tube increases, ultimate lateral displacement of the indenter decreases; but, the maximum load for the tube wall fracture enhances.
Journal of Mechanical Science and Technology, 2017
Circumferential crack growth pattern in a thin-walled cylinder is studied. Thermo-elastic stresse... more Circumferential crack growth pattern in a thin-walled cylinder is studied. Thermo-elastic stresses in a cylinder subjected to thermomechanical loads are extracted. Closed form thermo-elastic stress intensity factor for cracked cylinder are derived using weight function method. An algorithm is developed to simulate different crack growth patterns utilizing a very high efficiency weight function method. This would lessen the taken time for the analyses compared to other numerical methods such as FEM. Results show that while the load effect on cylinder subjected to thermal load lead to the crack growth in small aspect ratio, in cylinder subjected to mechanical loads, it would lead to the growth of crack in large aspect ratio. The results show that, apart from load effects, the cylinders containing initial semi-circular crack have the longest life among the cylinders containing initial semi-elliptical crack with the same initial depth.
Engineering Failure Analysis, 2017
Recently, authors have developed a numerical procedure in order to predict the fatigue failure of... more Recently, authors have developed a numerical procedure in order to predict the fatigue failure of the cast iron cylinder head [Three dimensional analysis of low cycle fatigue failure in engine part subjected to multi-axial variable amplitude thermo-mechanical load, Engineering Failure Analysis 62 (2016) 128-141]. The aim of the present study is a comparative investigation on the application of the different equivalent stress and strain approaches and critical plane fatigue theories in order to accurately determine the critical zone and life cycle in the failed cylinder head. The experimental observations in engine durability test ISO 8178 E5 and some multi-axial fatigue criteria are explained in detail. Then the fatigue life predictions obtained through the developed numerical procedure are compared with the observations. Results reveal that Morrow and SWT as equivalent strain-based criteria and Fatemi-Socie as critical plane criterion would lead to more accurate predictions in comparison with others. However, in the case of engine structure analysis, there is no considerable superiority between the two last groups of multi-axial fatigue models.