Abstract:Abstract:The mechanical behavior of API 5L X52 steel with planar type laminations was studied in the present work. Planar laminations were proposed in the base metal (BM), heat affected zone (HAZ) and welding bead (WB). Three-dimensional finite element (FE) models, kinematic hardening and mechanical properties for BM, HAZ, and WB were activated in the finite element program. The results showed that crack propagation corresponds to the direction of the main stress. For a crack length (2a) of 10.01 mm, crack pro… Show more
“…The above situation agrees with the fracture mechanics postulate because the direction of cracking corresponds to the direction of the main stresses. For pipeline internal pressure values, the mode of the main stress at the crack tips corresponds with the field stress of the plastic zone for mode I 4 [34], which agrees with the model proposed by Ikeda [10].…”
Section: Mechanical Behavior Of a Pipeline With An Induced Cracksupporting
The mechanical resistance of API 5L X52 steel with stepping lamination in the base metal (BM), heat affected zone (HAZ) and welding bead (WB) was studied by using the finite element method (FEM) in the present work. Both internal working pressure in the pipelines and internal pressure in the stepping laminations were studied to analyze the mechanical behavior of the pipelines. 3D FEM models and kinematic hardening were activated in the software used, while tests for the mechanical properties (true stress-strain curve) of BM, HAZ and WB were also conducted. The results demonstrated that stepping laminations in the BM-HAZ-WB zone reduced the ability to support internal pressure; therefore, the failure pressure (P f ) is also reduced. Pipeline failures occurred when the Von Mises stresses reached or exceeded the ultimate tensile stress (σ UTS ) of the material in the outer and inner wall and the stepping lamination sizes were too large. Failure in pipelines with stepping laminations occurred on the left side of the crack on the outer wall of the BM-HAZ zone; on the inner right side of the stepping laminations, the failure takes place on the inner wall in the WB.
“…The above situation agrees with the fracture mechanics postulate because the direction of cracking corresponds to the direction of the main stresses. For pipeline internal pressure values, the mode of the main stress at the crack tips corresponds with the field stress of the plastic zone for mode I 4 [34], which agrees with the model proposed by Ikeda [10].…”
Section: Mechanical Behavior Of a Pipeline With An Induced Cracksupporting
The mechanical resistance of API 5L X52 steel with stepping lamination in the base metal (BM), heat affected zone (HAZ) and welding bead (WB) was studied by using the finite element method (FEM) in the present work. Both internal working pressure in the pipelines and internal pressure in the stepping laminations were studied to analyze the mechanical behavior of the pipelines. 3D FEM models and kinematic hardening were activated in the software used, while tests for the mechanical properties (true stress-strain curve) of BM, HAZ and WB were also conducted. The results demonstrated that stepping laminations in the BM-HAZ-WB zone reduced the ability to support internal pressure; therefore, the failure pressure (P f ) is also reduced. Pipeline failures occurred when the Von Mises stresses reached or exceeded the ultimate tensile stress (σ UTS ) of the material in the outer and inner wall and the stepping lamination sizes were too large. Failure in pipelines with stepping laminations occurred on the left side of the crack on the outer wall of the BM-HAZ zone; on the inner right side of the stepping laminations, the failure takes place on the inner wall in the WB.
“…In the further analysis, numerical verification of coefficients for specimens C1-1 and P1-1 is shown for strains immediately before the fracture: The values obtained in ABAQUS for the quarter of the specimen C1-1 and P1-1 at the characteristic points (1 and 2) are shown in Figure 9. Stress for specimen C1-1, the maximum equivalent stresses (von Misses) are: The equivalent stress values, obtained by ABAQUS and the stresses calculated by the formulas (10)(11)(12)(13)(14)(15), are given in Table 5. One should notice difference between stress values in points 1 and 2 for specimen C1-1 and almost the same stress values in these two points for specimen P1-1.…”
Section: Resultsmentioning
confidence: 99%
“…The true stress–strain curve was developed by using the modified version of the weighted average method. Yet another overmatched welded joint was considered in [ 12 ], where mechanical behavior with planar type laminations in the base metal (BM), heat-affected zone (HAZ), and welding bead (WB) was studied. By using HV data, an equivalent true stress–strain curve in the HAZ was estimated, based on corresponding hardness value obtained from the BM and WB.…”
This paper presents new methodology for determining the actual stress–strain diagram based on analytical equations, in combination with numerical and experimental data. The first step was to use the 3D digital image correlation (DIC) to estimate true stress–strain diagram by replacing common analytical expression for contraction with measured values. Next step was to estimate the stress concentration by using a new methodology, based on recently introduced analytical expressions and numerical verification by the finite element method (FEM), to obtain actual stress–strain diagrams, as named in this paper. The essence of new methodology is to introduce stress concentration factor into the procedure of actual stress evaluation. New methodology is then applied to determine actual stress–strain diagrams for two undermatched welded joints with different rectangular cross-section and groove shapes, made of martensitic steels X10 CrMoVNb 9-1 and Armox 500T. Results indicated that new methodology is a general one, since it is not dependent on welded joint material and geometry.
“…In the Level 2 assessment, lamination zones are considered as local thinner areas or a crack-like flaw and evaluated by criteria such as remaining strength factor (RSF) and failure assessment diagram (FAD) [19]. The Level 3 assessment also is done using the Finite Element Method (FEM) for explicit modeling and the most accurate stress analysis of lamination zones, considering defects geometry and loading conditions [17,20]. The equipment's Owners/Users often question the assessment criteria of API 579 and request FFS engineers to provide technical advice for modifying the system due to the high financial cost.…”
Improvement of nondestructive inspection techniques has allowed more frequent detection of closely spaced zones of non-metallic inclusions in pressure vessels made of low carbon steel. In the present study, closely spaced inclusions in an in-service cylindrical horizontal pressure vessel were detected by Scan-C ultrasonic inspection and considered as laminations to be assessed by Part 13 of the API 579-1/ASME FFS-1 2016 standard. The outcoming results were considered as a rejection for Level 1 assessment, and a repair or replacement of the component was required, even though it retained a significant remaining strength. Thus, an alternative procedure to assess the mechanical integrity of pressure vessels containing zones of non-metallic inclusions is proposed by adopting some criteria of the API 579-1/ASME FFS-1 Part 13 standard procedure and taking into consideration the dimensions and grouping characteristics of the inclusion zones.
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