scholarly journals Multiaxial fatigue assessment of welded steel details according to the peak stress method based on tetra elements

2019 ◽  
Vol 300 ◽  
pp. 19002 ◽  
Author(s):  
Alberto Campagnolo ◽  
Giovanni Meneghetti ◽  
Vittorio Babini ◽  
Matteo Riboli ◽  
Andrea Spagnoli
Keyword(s):  
Fatigue Crack Initiation ◽  
Peak Stress ◽  
Fatigue Curve ◽  
Multiaxial Fatigue ◽  
Welded Steel ◽  
Linear Elastic ◽  
Fatigue Design ◽  
Notch Stress ◽  
Reference Design ◽  
Coarse Meshes

The Peak Stress Method (PSM) is an engineering, FE-oriented application of the notch stress intensity factor (NSIF) approach to fatigue design of welded joints, which takes advantage of the singular linear elastic peak stresses from FE analyses with coarse meshes. Originally, the PSM was calibrated by using 3D, eight-node brick elements, taking advantage of the submodeling technique. Recently, the PSM has been calibrated by using ten-node tetra elements, which are able to directly discretize complex 3D geometries without the need for submodels. The PSM was validated for pure axial or bending loadings as well as pure torsion loadings; recently it has been extended to multiaxial loadings by adopting a design stress, the so-called equivalent peak stress, in conjunction with a reference design fatigue curve. After having briefly recalled the calibration of the PSM with tetra elements, the paper presents some applications of the PSM relevant to steel plate-to-tube welded details of industrial interest under in-phase bending-torsion fatigue loadings. Experimental data have been re-analysed using the PSM based on tetra elements. Eventually a good agreement between experimental and theoretical results has been obtained in terms of fatigue crack initiation location as well as total fatigue life.

Multiaxial fatigue assessment of welded steel details according to the peak stress method: Industrial case studies

2019 ◽  
Vol 125 ◽  
pp. 362-380 ◽  
Author(s):  
Giovanni Meneghetti ◽  
Alberto Campagnolo ◽  
Vittorio Babini ◽  
Matteo Riboli ◽  
Andrea Spagnoli
Keyword(s):  
Case Studies ◽  
Peak Stress ◽  
Multiaxial Fatigue ◽  
Welded Steel ◽  
Fatigue Assessment

scholarly journals The peak stress method applied to the fatigue assessment of tube-tube steel joints with weld ends under multiaxial loadings

2019 ◽  
Vol 300 ◽  
pp. 19001
Author(s):  
Giovanni Meneghetti ◽  
Alberto Campagnolo ◽  
Michael Vormwald ◽  
Ehsan Shams
Keyword(s):  
Fatigue Strength ◽  
Welded Joints ◽  
Fatigue Crack Initiation ◽  
Peak Stress ◽  
Multiaxial Fatigue ◽  
Tube Steel ◽  
Fe Model ◽  
Present Contribution ◽  
Fatigue Assessment ◽  
Steel Joints

The Peak Stress Method (PSM) is an approximate, FE-oriented application of the notch stress intensity factor (NSIF) approach to fatigue design of welded joints, which is based on the singular linear elastic peak stresses calculated from FE analyses performed by using coarse mesh patterns. By adopting the averaged strain energy density (SED) as a fatigue strength criterion, a design stress (the equivalent peak stress) can be defined; in conjunction with a reference design curve previously defined, the fatigue strength assessment of welded joints subjected to multiaxial fatigue loadings can be performed. In the present contribution, the PSM has been applied to the fatigue assessment of tube-tube steel joints with weld ends, which have been fatigue tested in a previous contribution under combined loadings: namely pure axial, pure torsion and in-phase as well as out-of-phase axial-torsion loadings, all of which with two load ratios, i.e. R = 0 and R = -1. The experimental fatigue results have been re-converted in terms of equivalent peak stress by adopting a 3D FE model including an idealised weld end geometry. The equivalent peak stress has proved to assess the fatigue crack initiation location in agreement with experimental observations, moreover a quite good agreement has been obtained between the experimental results and the PSM-based design scatter band.

scholarly journals PWR Effect on Crack Initiation Under Equi-Biaxial Loading Development of the Experiment

2016 ◽  
Author(s):  
G. Perez ◽  
C. Gourdin ◽  
S. Courtin ◽  
J. C. Le Roux
Keyword(s):  
Biaxial Loading ◽  
Austenitic Stainless Steels ◽  
Fatigue Curve ◽  
Structural Effect ◽  
Fatigue Tests ◽  
Fatigue Lifetime ◽  
New Device ◽  
Fatigue Design ◽  
Penalty Factor ◽  
Mean Strain

Fatigue lifetime assessment is essential in the design of structures. Under-estimated lifetime predictions may generate overly conservative usage factor values and hence result in unnecessary in-service inspections. In the framework of upgrading the fatigue design rules (RCC-M, RCC-MRx), the uniaxial reference fatigue curve was altered by taking into account effects like: Multiaxiality, Mean stress or strain, Surface roughness (polished or ground), Scale effect, Loading History... In addition to this effect, Environmentally Assisted Fatigue is also receiving nowadays an increased level of attention. To formally integrate these effects, some international codes have already proposed and suggested a modification of the austenitic stainless steels fatigue curve combined with a calculation of an environmental penalty factor, namely Fen, which has to be multiplied by the usual fatigue usage factor. The aim of this paper is to present a new device “FABIME2E” developed in the LISN in collaboration with EDF and AREVA. These new tests allow quantifying accurately the effect of PWR environment on semi-structure specimen. This new device combines the structural effect like equibiaxiality and mean strain and the environmental penalty effect with the use of PWR environment during the fatigue tests.

Differences in Fatigue Strength Between Arc and Laser Hybrid Welded Joints

2008 ◽  
Vol 24 (03) ◽  
pp. 139-146
Author(s):  
H. Remes ◽  
P. Varsta
Keyword(s):  
Fatigue Strength ◽  
Welded Joints ◽  
Fatigue Tests ◽  
Notch Depth ◽  
Butt Joints ◽  
Fatigue Design ◽  
Notch Stress ◽  
Notch Geometry ◽  
Laser Hybrid ◽  
Fatigue Endurance

This paper presents the results of fatigue tests, including tests of laser hybrid and arc welded butt joints, for two plate thicknesses, 6 and 12 mm. Pure laser welded joints were also tested. The S-N curves based on nominal stresses for the different welded joints are presented. The results were further analyzed using the notch stress approach, where the fatigue notch factors were determined from the measured geometries of the welded joints. Unexpected differences in the S-N curves based on the notch stresses were found between the laser hybrid and arc welded joints and between the laser hybrid and pure laser welded joints. The reasons for this difference were studied with the help of extensive measurements of weld notch geometries. Significant differences in the geometries were observed. Taking into account the notch geometry and the notch depth, the notch stress approach partially explains the differences between the fatigue endurance limits of the laser hybrid and arc welded joints. The applicability of the notch stress approach to the fatigue design of laser hybrid welded joints is also discussed.

scholarly journals A fatigue crack initiation and growth life estimation method in single-bolted connections

2019 ◽  
Vol 54 (2) ◽  
pp. 79-94 ◽  
Author(s):  
Arash P Jirandehi ◽  
TN Chakherlou
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Initiation ◽  
Crack Growth ◽  
Fatigue Crack Initiation ◽  
Multiaxial Fatigue ◽  
Estimation Accuracy ◽  
Life Estimation ◽  
Lower Error ◽  
Fatigue Life Estimation

Fatigue life estimation accuracy of mechanical parts and assemblies has always been the source of concern in different industries. The main contribution of this article lies in a study on the accuracy of different multiaxial fatigue criteria, proposing and investigating the accuracy of four optimized fatigue crack initiation life estimation methods—volume, weighted volume, surface and point, thereby improving the multiaxial fatigue life estimation accuracy. In order to achieve the goal, the fatigue lives of bolt clamped specimens, previously tested under defined experimental conditions, were estimated during fatigue crack initiation and fatigue crack growth and then summed together. In the fatigue crack initiation part, a code was written and used in the MATLAB software environment based on critical plane approach and the different multiaxial fatigue criteria. Besides the AFGROW software was utilized to estimate the crack growth share of fatigue life. Experimental and numerical results showed to be in agreement. Furthermore, detailed study and comparison of the results with the available experimental data showed that a combination of Smith–Watson–Topper approach and volume method results in lower error values, while a combination of Fatemi–Socie criterion and surface or point method presents estimated lives with lower error values. In addition, the numerical proposed procedure resulted in a good prediction of the location of fatigue crack initiation.

Random Load Fatigue: Theory and Experiment

1985 ◽  
Vol 199 (3) ◽  
pp. 249-257 ◽  
Author(s):  
J M Tunna
Keyword(s):  
Traditional Method ◽  
Laboratory Tests ◽  
Stress Range ◽  
Constant Amplitude ◽  
Random Load ◽  
Welded Steel ◽  
Random Loads ◽  
Fatigue Design ◽  
Stress Signal ◽  
Theory And Experiment

This paper is concerned with the problem of fatigue design for random loads. A theory is outlined which allows the fatigue life to be predicted from the constant amplitude stress range–life curve and the standard deviation and ruling frequency of the stress signal. Laboratory tests are described which verify the theory for welded steel constructions in a railway environment. The results are also analysed by a more traditional method. Areas where the theory might usefully be extended are identified.

Pipe Elbows Under Strong Cyclic Loading

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
George E. Varelis ◽  
Spyros A. Karamanos ◽  
Arnold M. Gresnigt
Keyword(s):  
Cyclic Loading ◽  
Low Cycle Fatigue ◽  
Seismic Loading ◽  
Fatigue Curve ◽  
Design Codes ◽  
Loading Conditions ◽  
Cycle Fatigue ◽  
Finite Element Analyses ◽  
Fatigue Design ◽  
Process Piping

Motivated by the response of industrial piping under seismic loading conditions, the present study examines the behavior of steel process piping elbows, subjected to strong cyclic loading conditions. A set of experiments is conducted on elbow specimens subjected to constant amplitude in-plane cyclic bending, resulting into failure in the low-cycle-fatigue range. The experimental results are used to develop a low-cycle-fatigue curve within the strain-based fatigue design framework. The experimental work is supported by finite element analyses, which account for geometrical and material nonlinearities. Using advanced plasticity models to describe the behavior of elbow material, the analysis focuses on localized deformations at the critical positions where cracking occurs. Finally, the relevant provisions of design codes (ASME B31.3 and EN 13480) for elbow design are discussed and assessed, with respect to the experimental and numerical findings.

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