A Three-Dimensional FE Approach for the Fatigue Analysis of Flexible Pipes Tensile Armors Inside End Fittings

2020 ◽  
Author(s):  
Marcelo N. R. Miyazaki ◽  
José Renato M. de Sousa ◽  
Gilberto B. Ellwanger ◽  
Vinicius R. da Silva
Keyword(s):  
Fatigue Resistance ◽  
Three Dimensional ◽  
Local Stress ◽  
Fatigue Analysis ◽  
Acceptance Test ◽  
Stress Concentrations ◽  
Flexible Pipes ◽  
Dimensional Finite Element ◽  
Operational Tests ◽  
Three Dimensional Finite Element

Abstract During the end fitting (EF) assembly, the tensile armors of flexible pipes are folded and then unfolded to allow the assessment to the inner sheath and the activation of the inner sealing system. This procedure leaves residual stresses and plastic deformations on these armors, which affect their fatigue resistance and, consequently, the overall performance of the pipe. Hence, in this work, a methodology to predict the fatigue resistance of tensile armors inside an EF is proposed. This methodology relies on stresses calculated with a previously presented three-dimensional finite element (FE) approach and is employed to analyze the fatigue response of a 6” production riser in catenary configuration. This fatigue analysis not only addresses the effects from several irregular sea states but also the local stress concentrations associated with the EF assembly and pre-operational tests (e. g., Factory Acceptance Test, FAT). The results obtained indicate that the EF entrance may be a critical point for fatigue failure and, moreover, the lower fatigue resistance is related to a region where higher alternate stresses occur despite the very high mean stresses are observed in other regions along the tensile armors.

A Three-Dimensional FE Approach for the Stress Analysis of Tensile Armors Inside End Fittings

2019 ◽  
Author(s):  
Marcelo N. R. Miyazaki ◽  
José Renato M. de Sousa ◽  
Gilberto B. Ellwanger
Keyword(s):  
Stress Distribution ◽  
Three Dimensional ◽  
Rigid Surface ◽  
Stress Concentrations ◽  
Flexible Pipes ◽  
Dimensional Finite Element ◽  
Operational Tests ◽  
Three Dimensional Finite Element ◽  
Good Agreement

Abstract In this work, a solid three-dimensional finite element (FE) approach is proposed to investigate the stress distribution along the tensile armors of flexible pipes inside their end fittings (EFs). This approach employs two different models. The first model consists of a single tensile armor, which is meshed with solid FEs, and a rigid surface that represents the EF. A toroidal template is also considered and the EF mounting process is simulated. In the second model, the deformed armor and the stress state from the first model are considered and the voids between the armor and the EF are filled with resin, which is also modeled with solid FEs. Geometric and material nonlinearities are addressed and the interaction between the different components are ensured with contact elements. A case study is conducted to observe the stress distribution along the tensile armor considering typical operational loads. The results obtained are compared to those calculated with a previously proposed analytical model showing good agreement, but also evidencing the need to adequately simulate the EF mounting process and the pre-operational tests. Moreover, intense stress concentrations at the entrance of the EF are observed thus indicating that this region can be critical in fatigue analyses.

scholarly journals A Comparative Three-Dimensional Finite Element Study of Two Space Regainers in the Mixed Dentition Stage

2020 ◽  
Vol 14 (01) ◽  
pp. 107-114
Author(s):  
Mohamed Ahmed Abdel Hakim ◽  
Nagwa Mohamed Ali Khatab ◽  
Kareem Maher Gaber Mohamed ◽  
Ahmad Abdel Hamid Elheeny
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Three Dimensional ◽  
The Other ◽  
Mixed Dentition ◽  
Von Mises Stress ◽  
Stress Concentrations ◽  
Permanent Molar ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

Abstract Objectives This study aims to compare the stress distribution and displacement that resulted from the use of a Gerber space regainer and sagittal distalizer using three-dimensional finite element analysis. Materials and Methods Three-dimensional simulated models of the appliances were developed using a software. The forces applied by the two appliances were 3N (tipping) and 15N (bodily), respectively. Displacement and von Mises stress on the compact and cancellous bone, periodontal ligament (PDL), crowns of the mandibular first, second permanent molars, and deciduous canines were calculated. Stress distribution and displacement values were measured via linear static analysis. Results Gerber space regainer showed greater displacement than that produced by the sagittal distalizer at the first permanent molar. However, such displacement was less at the other tested points when compared with that delivered by sagittal distalizer. The stresses created by Gerber appliance were higher in the crown and PDL of the deciduous canine than the crown of the first permanent molar crown. Conclusions Gerber appliance generates more distal force and less stress concentration on the crown of the mandibular first permanent molar than that created by the sagittal distalizer. On the other hand, stress concentrations produced by Gerber space regainer are found to be more on the crown and PDL of the deciduous canine. Therefore, it can be concluded that the use of Gerber appliance needs more anchorage.

Use of Sub-Modeling Techniques to Calculate Peak Stresses in Bolt Head-to-Shank Fillet Radius

2008 ◽  
Author(s):  
Richard E. Smith ◽  
Stephen J. Speicher
Keyword(s):  
Three Dimensional ◽  
Structural Response ◽  
Peak Stress ◽  
Finite Element Models ◽  
Stress Concentrations ◽  
Sufficient Detail ◽  
Structural Details ◽  
Modeling Techniques ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

There is an ever-increasing use of three-dimensional finite element models in the field of structural analysis to simulate structural response of complex geometries. Although these models are effective in simulating gross structural behavior, they are oftentimes not able to include sufficient detail to simulate small structural details where stress concentrations can occur. To overcome this limitation, sub-models can be used to calculate stresses in areas of peak stress. This paper discusses the process involved in calculating peak stresses in bolt head-to-shank interfaces using sub-modeling methods.

scholarly journals Understanding the influence of laminate stacking sequence on strain/stress concentrations in thin laminates at repair holes with large scarf angles

2019 ◽  
Vol 53 (28-30) ◽  
pp. 4273-4284 ◽  
Author(s):  
Mahdi Damghani ◽  
Jerzy Bakunowicz ◽  
Adrian Murphy
Keyword(s):  
Three Dimensional ◽  
Equivalent Diameter ◽  
Stacking Sequence ◽  
Stress Concentrations ◽  
Foreign Object Damage ◽  
Fastener Hole ◽  
Dimensional Finite Element ◽  
Strain Stress ◽  
Laminate Thickness ◽  
Three Dimensional Finite Element

Scarf repair is widely used in the restoration of structural performance of damaged aircraft secondary structures. Such repairs result in reduced thickness sections which are significantly larger than those associated with typical fastener holes. Significant literature exists on the distribution of strain/stress concentration in fastener hole geometries, both straight sided and countersunk, but is lacking for the geometries associated with shallow scarf angles and thin laminates. Hence, herein three-dimensional finite element models are developed to understand the influence of stacking sequence and scarf angle on strain/stress concentrations. The results demonstrate and quantify for the first time that strain concentrations are not only dependant on the laminate membrane stiffness but also on laminate bending stiffness, due to the anisotropy created as a result of scarfing angle, hole geometry and laminate thickness. Scarfing is demonstrated, for typical repair geometry associated with foreign object damage (hole diameter 20 mm, scarf angles 3° to 7°), to elevate strains by up to 2.5 times when compared to equivalent diameter straight-sided holes in laminates of thickness ≈1 mm.

Dynamic Cyclic Stress Analysis of Rolling of a Diametrically Loaded Helical Test Specimen

2017 ◽  
Author(s):  
Don Metzger ◽  
Mark Paulseth ◽  
Andre Gagnon
Keyword(s):  
Cyclic Loading ◽  
Stress Analysis ◽  
Test Specimen ◽  
Three Dimensional ◽  
Cyclic Stress ◽  
Fatigue Analysis ◽  
Rolling Motion ◽  
Structural Components ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

In a particular nuclear application, separation between structural components is maintained by a helical spring such that the separating load bears across the diameter of the spring coils. Relative motion between the structural components due to changing load and temperature is accommodated by rolling of the spring. This rolling motion while under radial load results in cyclic loading of the spring material. Fatigue analysis of the cyclic loading must take into consideration the material degradation due to the unique operating environment, so testing of ex-service material is required. Standard fatigue test specimens are not possible due to the small dimensions of the spring component, so cyclic stress is applied to the material via a reciprocating rolling motion between two platens. Stress analysis of this arrangement provides the stress range and mean stress necessary for fatigue analysis. A three dimensional finite element dynamic simulation of the test process is applied to a nominal test specimen to determine detailed history of the stress distribution. Numerical challenges are addressed to ensure representative loading conditions are properly applied, and that steady-state response is achieved. Bounding stress ranges are determined, and the implications of the results in fatigue analysis are discussed. It is concluded that response at the ends of the specimens is important in properly evaluating test data.

Three-Dimensional Analyses of Single Rivet-Row Lap Joints — Part II: Elastic-Plastic Response

1999 ◽  
Author(s):  
K. Iyer ◽  
C. A. Rubin ◽  
G. T. Hahn
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Lap Joints ◽  
Finite Element Analyses ◽  
Lap Joint ◽  
Stress Concentrations ◽  
Elastic Plastic ◽  
Linear Elastic ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

Abstract Three-dimensional finite element analyses of an elastic-plastic, single rivet-row, aluminum lap joint are presented and compared with previous results for linear elastic models. The calculations treat non-countersunk aluminum and steel rivets, 3 different configurations of countersunk rivets as well as two values of the friction coefficient. The compliance of the connection, rivet tilt, the stresses in the panels, peak plastic strains and the contact pressures and slip amplitudes at the rivet-panel and panel-panel interfaces are evaluated. The transverse, axial, and shear stress distributions and the stress concentrations generated in four different rivets are derived from the linear elastic models and related to the rivet geometry. Laboratory measurements of the lap joint compliance and local out-of-plane displacements that support the reliability of the finite element analyses are presented.

Mechanical Characteristic Analysis of Dredger Crane Based on ABAQUS

2013 ◽  
Vol 821-822 ◽  
pp. 1406-1409
Author(s):  
Jian Bo Wang ◽  
Xun Qian Xu ◽  
Yong Zhu
Keyword(s):  
Finite Element ◽  
Theoretical Calculations ◽  
Reaction Force ◽  
Three Dimensional ◽  
Structure Design ◽  
Stress Concentrations ◽  
Characteristic Analysis ◽  
Design And Optimization ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

In order to improve the safety and stability of dredger crane (DC), three dimensional finite element models for the DC were established. By applied loads and boundary conditions, the area of stress concentrations, the axis force of jib cylinder and the reaction force of the king structure was obtained under four typical working conditions. Meanwhile, the related theoretical calculations were accomplished to comparing finite element results and at last some suggestions were given. The conclusions can provide a theoretical reference for the further structure design and optimization of DC.

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