High Cycle Fatigue of Pipelines With Plain Dents: Simulations, Experiments and Assessment

2007 ◽  
Author(s):  
Se´rgio B. Cunha ◽  
Bianca C. Pinheiro ◽  
Ilson P. Pasqualino
Keyword(s):  
Stress Concentration ◽  
High Cycle Fatigue ◽  
Fatigue Tests ◽  
Test Material ◽  
Small Scale ◽  
Test Results ◽  
Cycle Fatigue ◽  
Concentration Factors ◽  
Stress Concentration Factors

The objective of this work is to propose a methodology for assessing the fatigue life of dented pipelines according to the current high cycle fatigue theory. The proposed methodology employs S-N curves obtained from tensile test material properties and includes an expression to estimate stress concentration factors for spherical dents. Finite element analyses are carried out to determine stress concentration factors for different pipe and dent geometries. Using the numerical results, an expression to estimate stress concentration factors of dented pipelines is developed. Additionally, fatigue tests are conducted with the application of cyclic internal pressure on small-scale dented steel pipe models. Different pressure levels are employed, resulting in failures ranging from around 6000 to more than 106 cycles, enabling the determination of the endurance limit and of the finite life behavior of dented pipes. Furthermore, the Goodman and Gerber criteria to account for the mean stress are evaluated in view of the experimental results. The fatigue test results are used to validate the proposed assessment methodology for the analyzed conditions.

Stress Concentration Factors of Longitudinal and Transverse Plain Dents on Steel Pipelines

2008 ◽  
Author(s):  
Bianca C. Pinheiro ◽  
Ilson P. Pasqualino
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Internal Pressure ◽  
High Cycle Fatigue ◽  
Element Model ◽  
Small Scale ◽  
Assessment Methodology ◽  
Cycle Fatigue ◽  
Concentration Factors ◽  
Stress Concentration Factors

The objective of this work is to evaluate the stress concentration induced by longitudinal and transverse plain dents on steel pipelines under cyclic internal pressure. This work is within a study to propose a new methodology to assess the fatigue life of dented steel pipelines based on the current high cycle fatigue theory. This methodology employs stress concentration factors induced by plain dents, which are used to modify material S-N curves of metallic structures under high cycle fatigue loadings. The proposed assessment methodology was validated according to small-scale fatigue test results of steel pipe models with spherical dents under cyclic internal pressure. Here, stress concentration factors induced by longitudinal and transverse plain dents on steel pipes under internal pressure are obtained from a previously developed finite element model. Several finite element analyses are carried out in a parametric study. Analytical expressions are developed to estimate stress concentration factors for these two different dent geometries as function of pipe and dent geometric parameters. With the inclusion of these expressions, the proposed assessment methodology is improved and is now able to deal with three different plain dent geometries: spherical, longitudinal and transverse dents.

Fatigue Life Analysis of Steel Pipelines With Plain Dents Under Cyclic Internal Pressure

2008 ◽  
Author(s):  
Bianca de Carvalho Pinheiro ◽  
Ilson Paranhos Pasqualino ◽  
Se´rgio Barros da Cunha
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Stress Concentration ◽  
Internal Pressure ◽  
Fatigue Tests ◽  
Small Scale ◽  
Concentration Factors ◽  
Life Analysis ◽  
Fatigue Life Analysis ◽  
Stress Concentration Factors

This work is within an ongoing study, which aims to propose a new methodology for fatigue life analysis of steel pipelines with plain dents under cyclic internal pressure. This methodology follows the current high cycle fatigue theory and employs stress concentration factors induced by plain dents to modify standard S-N curves. A previously developed and validated finite element model is extended to generate stress concentration factors for longitudinal and transverse dents, in addition to spherical dents. Several finite element analyses are carried out in a parametric study to evaluate stress concentration factors induced by the three dent types studied: spherical, longitudinal and transverse dents. Analytical expressions are developed to estimate stress concentration factors for these three dent types as function of pipe and dent geometric parameters. Small-scale fatigue tests are conducted to evaluate the finite life behavior of dented steel pipes under cyclic internal pressure. The methodology is validated in view of the fatigue tests results. Including expressions to estimate stress concentration factors for three different dent types (spherical, longitudinal and transverse dents), the proposed methodology can then be used for fatigue life analysis of dented steel pipelines under cyclic internal pressure.

Analysis of Stress Concentrations in Thick Cylinders With Sideholes and Crossholes

1972 ◽  
Vol 94 (3) ◽  
pp. 815-824 ◽  
Author(s):  
J. C. Gerdeen
Keyword(s):  
Stress Concentration ◽  
Stress Concentrations ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Experimental Values ◽  
Pressure Stress ◽  
Shrink Fit ◽  
Outside Diameter ◽  
Theoretical Results

An approximate theoretical analysis is presented for the determination of stress concentration factors in thick walled cylinders with sideholes and crossholes. The cylinders are subjected to both internal pressure and external shrink-fit pressure. Stress concentration factors are plotted as functions of the geometrical ratios of outside diameter-to-bore diameter, and bore diameter-to-sidehole diameter. Theoretical results are compared to experimental values available in the literature and results of experiments described in a separate paper.

High-cycle fatigue tests of pretensioned concrete beams

PCI Journal ◽  
2022 ◽  
Vol 67 (1) ◽  
Author(s):  
Jörn Remitz ◽  
Martin Empelmann
Keyword(s):  
Fatigue Life ◽  
High Cycle Fatigue ◽  
Concrete Beams ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Design Methods ◽  
Test Results ◽  
Cycle Fatigue ◽  
Pretensioned Concrete ◽  
Current Design

Pretensioned concrete beams are widely used as bridge girders for simply supported bridges. Understanding the fatigue behavior of such beams is very important for design and construction to prevent fatigue failure. The fatigue behavior of pretensioned concrete beams is mainly influenced by the fatigue of the prestressing strands. The evaluation of previous test results from the literature indicated a reduced fatigue life in the long-life region compared with current design methods and specifications. Therefore, nine additional high-cycle fatigue tests were conducted on pretensioned concrete beams with strand stress ranges of about 100 MPa (14.5 ksi). The test results confirmed that current design methods and specifications overestimate the fatigue life of embedded strands in pretensioned concrete beams.

Design Curves for High-Cycle Fatigue Loaded Structural Elements

2013 ◽  
Vol 752 ◽  
pp. 135-144 ◽  
Author(s):  
Zsuzsanna Koncsik ◽  
János Lukács
Keyword(s):  
High Cycle Fatigue ◽  
Empirical Method ◽  
Fatigue Tests ◽  
Structural Elements ◽  
Cycle Fatigue ◽  
Structural Element ◽  
Fatigue Design ◽  
Structural Details ◽  
Important Design

Frequently, the cause of the failure of different structures or structural elements is the cyclic loading. Both fatigue design curves and methods for determination of these curves can be found in the literature. Even so, there are structural details whereabouts executing of examinations is necessary. The aims of the study are as follows: to give a short summary of important design curves can be found in different standards or specifications; and to demonstrate of own high cycle fatigue tests on a soldered structural element and the comparing of our results and the results of an empirical method.

The Influence of Corrosion Pits and Cold Expanded Fastener Holes on the Fatigue Life Aluminium 7075-T651

2014 ◽  
Vol 891-892 ◽  
pp. 87-92 ◽  
Author(s):  
Benjamin Withy ◽  
Stephen Campbell ◽  
Glenn Stephen
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Stress Concentration ◽  
Air Force ◽  
Fatigue Tests ◽  
Expansion Process ◽  
Cold Expansion ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Corrosion Pits

The Royal New Zealand Air Force (RNZAF) utilised the split sleeve cold expansion process to increase the fatigue life of fastener holes in the wings of the C130 transport fleet. As part of the validation of the fatigue improvements offered by the process the Defence Technology Agency conducted a series of fatigue tests on cold expanded fastener holes in aluminium 7075-T651, including specimens with corrosion induced after the cold expansion process had been performed. This research conducted an analysis of fatigue crack origins and modelled the stress concentration factors generated as a result of the corrosion pits. These results were used to explain the differing fatigue life and s-n curves produced by corroded and non-corroded fatigue specimens and the location of crack initiation sites around corroded cold expanded fastener holes.

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