A Review of DNVGL-RP-F105 Fatigue Assessment Model or Why My Free Span Has Not Failed

2021 ◽  
Author(s):  
Mário Caruso
Keyword(s):  
Fatigue Life ◽  
Exposure Time ◽  
Vibration Analysis ◽  
Direct Reference ◽  
Assessment Model ◽  
Fatigue Assessment ◽  
Fatigue Design ◽  
Fatigue Model ◽  
Key Aspects

Abstract The objective of a free span fatigue assessment is to provide a rational criterion to evaluate the long-term integrity of a free spanning pipeline, to which DNVGL-RP-F105 was developed. The Recommended Practice has a long history. Guideline 14, the foundation document to it, was released in 1998. The guidelines of the DNVGL-RP-F105 were gradually adopted by the industry for free spans analysis, and even API 1111 makes direct reference to it. Today, DNVGL-RP-F105 is the de facto Vortex Induced Vibration analysis guide for all applications where small number of bending driven modes are expected to be excited, overstepping its original purpose of free spanning pipelines and providing guidance when no other source exists. With such a long history, it is easy to forget the basis for the Recommended Practice fatigue model and obtain results that do not match expectations. A prime example is when assessing a free span based on survey and the fatigue life capacity calculated following the Recommended Practice is much smaller than the actual exposure time. In this situation one may ask “why my free span has not failed?” and conclude that the Recommended Practice is either too over conservative or plainly wrong. This paper reviews some key aspects of the DNVGL-RP-F105 fatigue model and explore their implication to fatigue design and assessment. And it hopes to clarify why your free span has not failed even when you expected it to.

Fatigue Assessment of Ship Superstructure at Expansion Joint

2013 ◽  
Vol 155 (A4) ◽  
Keyword(s):  
Stress Distribution ◽  
Block Type ◽  
Expansion Joint ◽  
Fatigue Assessment ◽  
Fatigue Design ◽  
Construction Procedure ◽  
History Of ◽  
Distribution Transformation ◽  
Selection Of

Despite the long history of application of subdivided superstructures and deckhouses, and efforts of ship designers and researchers a sensible solution in design of reliable details at the cut endings was not found yet. It may be explained as consequence of controversial requirements in design of the cut endings. Fatigue design of the superstructure details is addressed to solution of the problem. Presented is an example of fatigue design of the cut ending in a fast ship superstructure based on application of modified «Strain-Life» criterion for fatigue and subsequent approach which utilizes Neuber's formula and material cyclic properties. To realize the approach a procedure of the long-term stress distribution transformation to the block-type format is developed. Efficiency of the developed technique is illustrated by comparing the results with those of application standard S-N criteria based techniques. The results of analysis allowed selection of the expansion joint detail of the superstructure geometry and construction procedure providing necessary reliability.

Important Effects in Environmentally Assisted Fatigue (EAF) of Austenitic and Ferritic Steel Components Including Welds and Their Consideration in a Fatigue Assessment Concept

2019 ◽  
Author(s):  
Jürgen Rudolph ◽  
Matthias Herbst ◽  
Armin Roth ◽  
Christian Swacek ◽  
Tim Schopf
Keyword(s):  
Fatigue Life ◽  
Influencing Factors ◽  
Hold Time ◽  
Life Time ◽  
Operating Conditions ◽  
Experimental Program ◽  
Cooperative Research ◽  
Fatigue Assessment ◽  
Fatigue Design ◽  
Improve Fatigue

Abstract The fatigue assessment of pressure boundary components is of importance for the aging management regarding safety and reliability in nuclear power plants with light water reactors. For the evaluation of cyclic loading conditions, different country specific design codes and standards are applied to consider various mechanical and thermal loadings as well as geometrical and material effects. Those different influencing factors have also to be taken into account in the fatigue design curves. Current state of the art methods account for life time influencing factors such as temperature, surface finish, stress multi-axiality and loading history by the application of reduction factors for fatigue lives (penalty respectively margin factors) determined from fatigue design curves which are derived from laboratory test data. Other effects, such as environmental effects or hold times, are often considered with high levels of conservatism or are not taken into account at all. On the one hand, this may lead to non-conservative predictions of the materials fatigue behavior, while on the other hand, there are often large discrepancies between calculated fatigue life and practical experience from power plant operation, where the operating experience reveals much higher fatigue lifetimes as their predictions based on laboratory tests and conservative consideration of major influencing factors (plastification by Ke-factors, Environmentally Assisted Fatigue (EAF) by FEN-factors) in the calculation approach. Therefore, Framatome GmbH, Erlangen, and the Material Testing Institute MPA Stuttgart currently conducting a cooperative research program which aims to improve the understanding of environmental and loading effects as well as of welds on fatigue life time and to improve fatigue lifetime assessment methods in the framework of the well established engineering approach. Based on the results of a previous research project of the same project partners, an experimental program is performed to investigate the effect of loading parameters and hold times on environmentally assisted fatigue (EAF). Experiments on specimens of ferritic and austenitic stainless steels and austenitic stainless steel welds as well as component tests are performed under laboratory and operating conditions to improve fatigue assessment and serve to bridge the gap between specimen behavior and component fatigue in operation. Emanating from previous and ongoing cooperative research projects, the experimental results will contribute to the proposal of an engineering fatigue assessment concept, allowing more specific differentiation in the influencing factors for component fatigue life prediction. Furthermore, hold time effects are simulated based on further developed material models.

FATIGUE ASSESSMENT OF SHIP SUPERSTRUCTURE AT EXPANSION JOINT

2021 ◽  
Vol 155 (A4) ◽  
Author(s):  
S V Petinov ◽  
R V Guchinsky
Keyword(s):  
Stress Distribution ◽  
Block Type ◽  
Expansion Joint ◽  
Fatigue Assessment ◽  
Fatigue Design ◽  
Construction Procedure ◽  
History Of ◽  
Distribution Transformation ◽  
Selection Of

Despite the long history of application of subdivided superstructures and deckhouses, and efforts of ship designers and researchers a sensible solution in design of reliable details at the cut endings was not found yet. It may be explained as consequence of controversial requirements in design of the cut endings. Fatigue design of the superstructure details is addressed to solution of the problem. Presented is an example of fatigue design of the cut ending in a fast ship superstructure based on application of modified «Strain-Life» criterion for fatigue and subsequent approach which utilizes Neuber’s formula and material cyclic properties. To realize the approach a procedure of the long-term stress distribution transformation to the block-type format is developed. Efficiency of the developed technique is illustrated by comparing the results with those of application standard S-N criteria based techniques. The results of analysis allowed selection of the expansion joint detail of the superstructure geometry and construction procedure providing necessary reliability.

scholarly journals On the Statistical Size Effect of Cast Aluminium

Materials ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1578 ◽  
Author(s):  
Roman Aigner ◽  
Sebastian Pomberger ◽  
Martin Leitner ◽  
Michael Stoschka
Keyword(s):  
Size Effect ◽  
Statistical Distribution ◽  
Assessment Model ◽  
Validation Data ◽  
Stressed Volume ◽  
Fatigue Assessment ◽  
Fatigue Design ◽  
Critical Defect ◽  
Cast Alloys ◽  
Set Up

Manufacturing process based imperfections can reduce the theoretical fatigue strength since they can be considered as pre-existent microcracks. The statistical distribution of fatigue fracture initiating defect sizes also varies with the highly-stressed volume, since the probability of a larger highly-stressed volume to inherit a potentially critical defect is elevated. This fact is widely known by the scientific community as the statistical size effect. The assessment of this effect within this paper is based on the statistical distribution of defect sizes in a reference volume V 0 compared to an arbitrary enlarged volume V α . By implementation of the crack resistance curve in the Kitagawa–Takahashi diagram, a fatigue assessment model, based on the volume-dependent probability of occurrence of inhomogeneities, is set up, leading to a multidimensional fatigue assessment map. It is shown that state-of-the-art methodologies for the evaluation of the statistical size effect can lead to noticeable over-sizing in fatigue design of approximately 10 % . On the other hand, the presented approach, which links the statistically based distribution of defect sizes in an arbitrary highly-stressed volume to a crack-resistant dependent Kitagawa–Takahashi diagram leads to a more accurate fatigue design with a maximal conservative deviation of 5 % to the experimental validation data. Therefore, the introduced fatigue assessment map improves fatigue design considering the statistical size effect of lightweight aluminium cast alloys.

scholarly journals Impact of Prolonged Exposure of Eleven Years to Hot Seawater on the Degradation of a Thermoset Composite

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2154
Author(s):  
Amir Hussain Idrisi ◽  
Abdel-Hamid I. Mourad ◽  
Muhammad M. Sherif
Keyword(s):  
Exposure Time ◽  
Prolonged Exposure ◽  
Mechanical Performance ◽  
Matrix Cracking ◽  
Pull Out ◽  
Strength Based ◽  
Different Temperatures ◽  
River Line ◽  
Composite Samples

This paper presents a long-term experimental investigation of E-glass/epoxy composites’ durability exposed to seawater at different temperatures. The thermoset composite samples were exposed to 23 °C, 45 °C and 65 °C seawater for a prolonged exposure time of 11 years. The mechanical performance as a function of exposure time was evaluated and a strength-based technique was used to assess the durability of the composites. The experimental results revealed that the tensile strength of E-glass/epoxy composite was reduced by 8.2%, 29.7%, and 54.4% after immersion in seawater for 11 years at 23 °C, 45 °C, and 65 °C, respectively. The prolonged immersion in seawater resulted in the plasticization and swelling in the composite. This accelerated the rate of debonding between the fibers and matrix. The failure analysis was conducted to investigate the failure mode of the samples. SEM micrographs illustrated a correlation between the fiber/matrix debonding, potholing, fiber pull-out, river line marks and matrix cracking with deterioration in the tensile characteristics of the thermoset composite.

Background for New Revision of DNV-RP-C203 Fatigue Design of Offshore Steel Structures

2010 ◽  
Author(s):  
Inge Lotsberg
Keyword(s):  
Steel Structures ◽  
Electronic Version ◽  
Fatigue Assessment ◽  
Fatigue Design ◽  
Different Types ◽  
Background Material ◽  
Made In

The DNV-RP-C203 Fatigue Design of Offshore Steel Structures is being used by a number of different companies for fatigue assessment of different types of structures. This has resulted in questions to DNV about background for the different sections in the document. It is therefore important that the basis for this document is open to the industry. Quite a lot of the background material has also been published earlier at conferences and in journals. In some situations it has been found that the content can be improved to better suite the industry. The document is presented in an electronic version making revisions easy. Therefore it has been revised several times since the last official presentation of a revision in 2005. The present paper gives an overview of the most significant changes made in the document since the 2005 revision. Some of these changes are already included in the present version of DNV-RP-C203. The remaining changes will be included in a revision dated 2010.

Power Transformer Fault Diagnosis Based on Vibration Correlation Analysis

2014 ◽  
Author(s):  
Kaixing Hong ◽  
Hai Huang
Keyword(s):  
Fault Diagnosis ◽  
Correlation Analysis ◽  
Fundamental Frequency ◽  
Vibration Analysis ◽  
Laboratory Tests ◽  
Power Transformer ◽  
Assessment Model ◽  
Vibration Method ◽  
Proposed Model ◽  
Transformer Fault

In this paper, a condition assessment model using vibration method is presented to diagnose winding structure conditions. The principle of the model is based on the vibration correlation. In the model, the fundamental frequency vibration analysis is used to separate the winding vibration from the tank vibration. Then, a health parameter is proposed through the vibration correlation analysis. During the laboratory tests, the model is validated on a test transformer, and manmade deformations are provoked in a special winding to compare the vibrations under different conditions. The results show that the proposed model has the ability to assess winding conditions.

The Influencing Factors and Assessment Rule of Fatigue Life of Shaft Based on Product Lifecycle Management

2007 ◽  
Vol 561-565 ◽  
pp. 2253-2256 ◽  
Author(s):  
You Tang Li ◽  
Ping Ma ◽  
Jun Tian Zhao
Keyword(s):  
Fatigue Life ◽  
Influencing Factors ◽  
Axial Stress ◽  
Assessment Method ◽  
Product Lifecycle Management ◽  
Product Lifecycle ◽  
Fatigue Design ◽  
Main Factors ◽  
Set Up ◽  
Lifecycle Management

Product lifecycle management is one of the main developmental aspects of advanced manufacturing technology. Anti-fatigue design is the key content in product lifecycle management. For designing the fatigue life of shaft exactly and determining the assessment method, the influencing factors must be realized roundly. The mechanical model of shaft is set up at first, and then the main factors that affect the fatigue life of shaft is discussed, the interrelations of the main factors and the framework are founded. The assessment equation of fatigue life for shaft is put forward and the influencing coefficient of multi-axial stress to fatigue life is analyzed. The results of this paper will establish the base of anti-fatigue and assessment life of shaft.

Using system dynamics to evaluate renewable electricity development in Malaysia

Kybernetes ◽  
2014 ◽  
Vol 43 (1) ◽  
pp. 24-39 ◽  
Author(s):  
Salman Ahmad ◽  
Razman bin Mat Tahar
Keyword(s):  
System Dynamics ◽  
Fossil Fuels ◽  
Systems Approach ◽  
Capacity Expansion ◽  
Assessment Model ◽  
Flow Diagram ◽  
Content Type ◽  
The Government ◽  
Policy Targets

Purpose – The purpose of this paper is to provide an assessment of Malaysia's renewable capacity target. Malaysia relies heavily on fossil fuels for electricity generation. To diversify the fuel-mix, a technology-specific target has been set by the government in 2010. Considering the complexity in generation expansion, there is a dire need for an assessment model that can evaluate policy in a feedback fashion. The study also aims to expand policy evaluation literature in electricity domain by taking a dynamic systems approach. Design/methodology/approach – System dynamics modelling and simulation approach is used in this study. The model variables, selected from literature, are constituted into casual loop diagram. Later, a stock and flow diagram is developed by integrating planning, construction, operation, and decision making sub-models. The dynamic interactions between the sub-sectors are analysed based on the short-, medium- and long-term policy targets. Findings – Annual capacity constructions fail to achieve short-, medium- and long-term targets. However, the difference in operational capacity and medium- and long-term target are small. In terms of technology, solar photovoltaic (PV) attains the highest level of capacity followed by biomass. Research limitations/implications – While financial calculations are crucial for capacity expansion decisions, currently they are not being modelled; this study primarily focuses on system delays and exogenous components only. Practical implications – A useful model that offers regulators and investors insights on system characteristics and policy targets simultaneously. Originality/value – This paper provides a model for evaluating policy for renewable capacity expansion development in a dynamic context, for Malaysia.

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