scholarly journals Fatigue life assessment regarding different influences on the HCF/VHCF behavior of a martensitic steel

2018 ◽  
Vol 165 ◽  
pp. 20004
Author(s):  
Igor Milošević ◽  
Benjamin Seisenbacher ◽  
Gerhard Winter ◽  
Florian Grün ◽  
Martin Kober
Keyword(s):  
Crack Initiation ◽  
Life Assessment ◽  
Special Treatment ◽  
Initiation Mechanism ◽  
Component Size ◽  
Fatigue Life Assessment ◽  
Fatigue Data ◽  
Gradient Based ◽  
Actual Material ◽  
Cycles To Failure

Modern applications require a special treatment when the conventional specimen size is much larger than the component size. Additional to that, high sophisticated materials are used for highly loaded components. Often the conventional fatigue limit is exceeded and loads are applied in the VHCF regime. Focus was put on the lifetime calculation and the implementation of investigated fatigue data of a X5CrNiCuNb-16-4 type steel. Two specimen geometries with diameters D7.5=7.5 mm and D2.5=2.5 mm were tested at R=-1, at room temperature and up to 109 cycles to failure. The application of different software tools (FEMFAT, fe-safe) showed several issues based on the current results. Results showed a change of crack initiation mechanism to subsurface crack initiation at approx. 2x106 cycles to failure. The gradient based correction of the reference fatigue data showed a good applicability up to 2x106 cylces. The application of fe-safe allows the flexible modification of S/N parameters over the whole cycle range. The usage of the actual material configuration introduced several important questions regarding the fatigue data and the implementation into lifetime calculation tools.

scholarly journals Fatigue life assessment regarding different influences on the HCF/VHCF behavior of a martensitic steel

2018 ◽  
Vol 165 ◽  
pp. 20004 ◽  
Author(s):  
Igor Milošević ◽  
Benjamin Seisenbacher ◽  
Gerhard Winter ◽  
Florian Grün ◽  
Martin Kober
Keyword(s):  
Crack Initiation ◽  
Life Assessment ◽  
Special Treatment ◽  
Initiation Mechanism ◽  
Component Size ◽  
Fatigue Life Assessment ◽  
Fatigue Data ◽  
Gradient Based ◽  
Actual Material ◽  
Cycles To Failure

Modern applications require a special treatment when the conventional specimen size is much larger than the component size. Additional to that, high sophisticated materials are used for highly loaded components. Often the conventional fatigue limit is exceeded and loads are applied in the VHCF regime. Focus was put on the lifetime calculation and the implementation of investigated fatigue data of a X5CrNiCuNb-16-4 type steel. Two specimen geometries with diameters D7.5=7.5 mm and D2.5=2.5 mm were tested at R=-1, at room temperature and up to 109 cycles to failure. The application of different software tools (FEMFAT, fe-safe) showed several issues based on the current results. Results showed a change of crack initiation mechanism to subsurface crack initiation at approx. 2x106 cycles to failure. The gradient based correction of the reference fatigue data showed a good applicability up to 2x106 cylces. The application of fe-safe allows the flexible modification of S/N parameters over the whole cycle range. The usage of the actual material configuration introduced several important questions regarding the fatigue data and the implementation into lifetime calculation tools.

Probabilistic Approach for Fatigue Life Assessment Based on S-N Curve

2010 ◽  
Author(s):  
Zhigang Wei ◽  
Robert E. Kurth ◽  
Thomas P. Forte
Keyword(s):  
General Trend ◽  
Standard Procedure ◽  
Probabilistic Approach ◽  
Pressure Vessels ◽  
Life Assessment ◽  
Engineering Structures ◽  
Fatigue Life Assessment ◽  
Fatigue Design ◽  
Fatigue Data ◽  
Cycles To Failure

Components in pressure vessels and pipes are usually subjected to mechanical and thermal cyclic loadings, which cause fatigue failure. The statistic and probabilistic assessment of these components based on S – N or ε–N curves is of great importance for fatigue design. Recently, the standard practice, as adopted by ASTM, BS, DNV and many other standards, for statistical analysis of linear or linearized stresslife (S – N) and strain-life (ε–N) fatigue data has been critically reviewed. The shortcomings of the standard procedure based only on the variation of cycles have been clearly demonstrated by examining the general trend of a large amount of S-N data. A new deterministic statistical method based on the equivalency between the changes of stress range and cycles to failure has been subsequently proposed and validated. In this paper a probabilistic approach based on the equivalency method is developed to quantify the uncertainty of engineering structures subjected to inherent randomness in material properties, and its effectiveness is also demonstrated.

A Study on Fatigue and Creep-Fatigue Life Assessment Using Cyclic Thermal Tests With Mod.9Cr-1Mo Steel Structures

2012 ◽  
Author(s):  
Masanori Ando ◽  
Hiroshi Kanasaki ◽  
Shingo Date ◽  
Koichi Kikuchi ◽  
Kenichiro Satoh ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Temperature Distribution ◽  
Crack Initiation ◽  
Thermal Loading ◽  
Life Assessment ◽  
Estimation Methods ◽  
Short Term ◽  
Cyclic Thermal Loading ◽  
Fatigue Life Assessment ◽  
Creep Fatigue

In a component design at elevated temperature, fatigue and creep-fatigue is one of the most important failure modes, and fatigue and creep-fatigue life assessment in structural discontinuities is important issue to evaluate structural integrity of the components. Therefore, to assess the failure estimation methods, cyclic thermal loading tests with two kinds of cylindrical models with thick part were performed by using an induction heating coil and pressurized cooling air. In the tests, crack initiation and propagation processes at stress concentration area were observed by replica method. Besides those, finite element analysis (FEA) was carried out to estimate the number of cycles to failure. In the first test, a shorter life than predicted based on axisymmetric analysis. Through the 3 dimensional FEA, Vickers hardness test and deformation measurements after the test, it was suggested that inhomogeneous temperature distribution in hoop direction resulted in such precocious failure. Then, the second test was performed after improvement of temperature distribution. As a result, the crack initiation life was in a good agreement with the FEA result by considering the short term compressive holding. Through these test and FEA results, fatigue and creep-fatigue life assessment methods of Mod.9Cr-1Mo steel including evaluation of cyclic thermal loading, short term compressive holding and failure criterion, were discussed. In addition it was pointed out that the temperature condition should be carefully controlled and measured in the structural test with Mod.9Cr-1Mo steel structure.

Fatigue Life Analysis of Polyurethane Bending Stiffeners

2005 ◽  
Author(s):  
Fre´de´ric Demanze ◽  
Didier Hanonge ◽  
Alain Chalumeau ◽  
Olivier Leclerc
Keyword(s):  
Fatigue Life ◽  
Effective Strain ◽  
Fatigue Behaviour ◽  
Life Assessment ◽  
Test Results ◽  
Critical Areas ◽  
Fatigue Life Assessment ◽  
Fatigue Data ◽  
Life Analysis ◽  
Fatigue Life Analysis

Following some experiences of bending stiffeners fatigue failures during full scale tests performed at Flexi France on flexible pipe and stiffener assemblies, Technip decided to launch in 1999 a major research program on fatigue life analysis of bending stiffeners made of Polyurethane material. This fatigue life assessment is now systematically performed by Technip for all new design of flexible riser bending stiffeners. This totally innovative method comprises a number of features as follows: Firstly fatigue behaviour of polyurethane material is described. The theoretical background, based on effective strain intensity factor, is detailed, together with experimental results on laboratory notched samples, solicited under strain control for various strain ratios, to obtain fatigue data. These fatigue data are well fitted by a power law defining the total number of cycles at break as a function of the effective strain intensity factor. The notion of fatigue threshold, below which no propagation is observed, is also demonstrated. Secondly the design used by Technip for its bending stiffeners, and most of all the critical areas regarding fatigue for these massive polyurethane structures are presented. Thirdly the methodology for fatigue life assessment of bending stiffeners in the critical areas defined above is discussed. Calibration of the strain calculation principle is presented versus finite element analysis. Based on all fatigue test results, the size of the equivalent notch to be considered at design stage, in the same critical areas, is discussed. Finally, a comprehensive calibration of the methodology according to full and middle scale test results is presented. The present paper is therefore a step forward in the knowledge of fatigue behaviour of massive polyurethane bending stiffener structures, which are critical items for flexible risers integrity, and widely used in the offshore industry. The confidence in bending stiffeners reliability is greatly enhanced by the introduction of this innovative methodology developed by Technip.

Study of Fatigue Properties of Materials through Cyclic Automated Ball Indentation and Cyclic Small Punch Test Methods

2017 ◽  
Vol 734 ◽  
pp. 273-284 ◽  
Author(s):  
Raghu V. Prakash
Keyword(s):  
Fatigue Property ◽  
Test Method ◽  
Life Assessment ◽  
Remaining Life ◽  
Small Punch Test ◽  
Small Punch ◽  
Punch Test ◽  
Ball Indentation ◽  
Fatigue Data ◽  
Cycles To Failure

One of the important inputs while estimating the remaining life of critical components is the fatigue property of materials. Fatigue data, in the form of stress vs. cycles to failure (or) strain vs. cycles to failure (or) fatigue crack growth rate data is used to predict the residual life. Material’s fatigue property degrades with time and usage; hence, it is appropriate to use the current properties for remaining life assessment. Often the quantity of material available for generating fatigue data is limited, especially, if the material is scooped out of existing component of a power plant. Further, fatigue response being probabilistic in nature, requires multiple specimens to be tested at any given stress/strain levels. This has prompted us to develop test procedures to determine the fatigue data of materials from a limited volume of material. This paper presents the results of cyclic ball indentation test method as well as cyclic small punch test method that is used to generate the fatigue data at different stress levels. There are several fine details relating to these test techniques – viz., establishing a equivalent damage criteria for failure life with standard LCF/HCF test specimens. The influence of one of the variables, viz., friction at the specimen-tool interface of a small punch test is investigated through numerical simulation and the results are presented here.

Fatigue Life Assessments of the SAE 5160 Carbon Steel Subjected to Uphill and Downhill Roads Strains

2020 ◽  
Vol 402 ◽  
pp. 33-38
Author(s):  
Teuku Edisah Putra ◽  
Husaini ◽  
Hary Prakasa ◽  
Iskandar Hasanuddin ◽  
Muhammad Rizal ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Carbon Steel ◽  
Strain Gauge ◽  
Life Assessment ◽  
Coil Spring ◽  
Fatigue Life Assessment ◽  
Cycles To Failure

This study examines the fatigue life of the SAE 5160 carbon steel as the material for an automotive coil spring subjected to road strain. The strain signals were acquired by attaching a strain gauge on the component, driving a car up- and down-hill roads. The results of the fatigue life assessment based on the strain-life approach show that the downhill road resulted in a lifespan of 15,000 cycles to failure, which was 53% lower than the uphill road. This value was a result of braking when the vehicle is moving downhill, causing stress to the component leading to shorter fatigue life.

Fatigue of Composite Materials under Aircraft Service Loading

1996 ◽  
Vol 210 (1) ◽  
pp. 101-107 ◽  
Author(s):  
IR Farrow
Keyword(s):  
Composite Materials ◽  
Damage Accumulation ◽  
Local Strain ◽  
Life Assessment ◽  
Current Analysis ◽  
Fatigue Life Assessment ◽  
Analysis Methods ◽  
Fatigue Damage Accumulation ◽  
Fatigue Data ◽  
Service Loading

Fatigue damage accumulation and analysis methods are considered for composites and contrasted with metals. The failure of current analysis methods is illustrated and explained by the information missing in load idealization data. Detailed local strain operational monitoring with local strain fatigue data is proposed as a future approach to fatigue life assessment of composite materials under aircraft service loading.

Sign in / Sign up

Export Citation Format

Share Document