scholarly journals VHCF Behavior of Welded Joints with HFMI Treatment under Moisture Conditions

2022 ◽  
Vol 101 (1) ◽  
pp. 27-42
Author(s):  
ZHIWEI GAO ◽  
◽  
DONGPO WANG ◽  
BAOMING GONG ◽  
CAIYAN DENG ◽  
...  
Keyword(s):  
Welded Joints ◽  
Hydrogen Permeation ◽  
Fatigue Cracks ◽  
Initiation Site ◽  
Fatigue Tests ◽  
Water Spray ◽  
Dry Air ◽  
Weld Toe ◽  
Weld Root ◽  
Moisture Conditions

Fatigue tests of cruciform welded joints made of Q355B steel at very-high-cycle fatigue (VHCF) regimes were carried out on as-welded specimens using highfrequency mechanical impact (HFMI) treatment in dry air and water-spray environments, respectively. The influence of the environment on fatigue life was more obvious in the VHCF regime. It was found that S-N curves became flat over the range of 106–108 cycles for as-welded specimens, while a continuously decreasing S-N curve existed for HFMI-treated specimens. Fatigue cracks initiated from the weld toe of the as-welded specimens in dry air and water-spray environments. Due to residual stress, the crack initiation site transition of HFMI-treated specimens from the weld toe to the weld root and base metal was observed at lower stress levels. Moreover, hydrogen-assisted quasi-cleavage and intergranular fracture were captured using a scanning electron microscope and a hydrogen permeation test.

Fatigue study on rib-to-deck welded joint considering weld penetration rate

2019 ◽  
Author(s):  
Xiaochen Ju ◽  
Xiaogang Liu ◽  
Zhibin Zeng ◽  
Xinxin Zhao
Keyword(s):  
Welded Joints ◽  
Welded Joint ◽  
Penetration Rate ◽  
Fatigue Cracks ◽  
Element Model ◽  
Fatigue Tests ◽  
Fatigue Performance ◽  
Weld Penetration ◽  
Weld Fatigue ◽  
Weld Root

<p>The U-shaped rib-to-deck welded joint in orthotropic steel deck is a part with multiple fatigue cracks. The penetration rate which is the ratio of penetration depth to U-shaped rib thickness has an important influence on fatigue performance of partial joint penetration (PJP) welds. In this study, the influence of penetration rate on the fatigue performance of U-shaped rib-to-deck welded joints was studied. Firstly, the finite element model of U-shaped rib-to-deck welded joints with penetration rate of 65%, 75%, 85% and complete joint penetration (CJP) welds were established. The mechanical characteristics of different welding forms under typical loading conditions were analyzed. It was found that with the increase of penetration rate of PJP welds, the stress concentration at the weld root weakened. Then fatigue tests on specimens with different weld penetration rate were carried out. The fatigue cracks of CJP welds all started at the inner welding toe of the U-shaped rib. However, the fatigue cracks of PJP welds mainly started at the welding root of the unfused weld. Fatigue S-N curves for PJP and CJP were regressed, respectively, it could be found that the fatigue performance of CJP welds was superior to that of PJP welds.</p>

Full Scale Fatigue Experiment on Submarine Pipelines

2014 ◽  
Vol 633-634 ◽  
pp. 659-664 ◽  
Author(s):  
Zong Tao Fang ◽  
De Yu Tang ◽  
Yan Hua Hu ◽  
Hu Li Niu
Keyword(s):  
Welded Joints ◽  
Fatigue Property ◽  
Full Scale ◽  
Small Scale ◽  
Test Machine ◽  
Butt Joints ◽  
Weld Toe ◽  
Small Test ◽  
Weld Root ◽  
Fatigue Experiment

This paper focus on fatigue problem of submarine pipelines, four points bending full scale fatigue experiment were conducted on X65 pipelines butt joints specimens, utilizing pipeline full scale fatigue test machine developed by CNPC. Meanwhile contrast test was also carried out on small specimens. The results show that the fatigue strength of full scale welded joints is lower than the small scale joints. Owing to having no regard for the influence of residual stress and size effect, the small test would provide dangerous results. The fatigue property of full scale welded joints only meets the requirement of DNV C203 W3 curve, and meets the needs of DNV C203 F3 curve basically while not meet BS 7608 F2 curve’s requirements which relatively demand higher. Weld toe and geometric discontinuous near weld root is the weak point for the whole welded joints.

Fatigue Strength of Three Dimensional Welded Joints: A Synthesis Based on the Strain Energy Density over a Control Volume

2007 ◽  
Vol 348-349 ◽  
pp. 413-416
Author(s):  
M. Zappalorto ◽  
Filippo Berto ◽  
Paolo Lazzarin
Keyword(s):  
Experimental Data ◽  
Energy Density ◽  
Welded Joints ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Complex Geometry ◽  
Control Volume ◽  
Three Dimensional ◽  
Weld Toe ◽  
Weld Root

A recent approach based on the local strain energy density (SED) averaged over a given control volume is applied to well documented experimental data taken from the literature, all related to steel welded joints of complex geometry. This small size volume embraces the weld root or the weld toe, both regions modelled as sharp (zero notch radius) V-notches with different opening angles. The SED is evaluated from three-dimensional finite element models by using a circular sector with a radius equal to 0.28 mm. The data expressed in terms of the local energy fall in a scatter band recently reported in the literature, based on about 650 experimental data related to fillet welded joints made of structural steel with failures occurring at the weld toe or at the weld root.

Residual Stress and Strain Responses of Welded Piping Joints Under Low-Cycle Fatigue Loading

2009 ◽  
Author(s):  
Pei-Yuan Cheng ◽  
Tasnim Hassan
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Fatigue Failure ◽  
Welded Joints ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Stress And Strain ◽  
Weld Toe ◽  
Strain Responses

It is well known that residual stress of welded joints influence their fatigue lives. This influence of residual stress is manifested through strain ratcheting response at the weld toe. Among many other reasons, strain ratcheting at the weld toe is anticipated to be a reason of many premature fatigue failure of welded joints. Hence, accurate simulations of weld toe residual stress and strain responses are essential for fatigue life simulation of welded joints. This paper presents results form an ongoing study on fatigue failure of welded piping joints. A modeling scheme for simulating weld toe residual stress and strain response is developed. Uncoupled, thermo-mechanical, finite element analyses are employed for imitating the welding procedure, and thereby simulating the temperature history during welding and initial residual stresses. Simulated residual stresses are validated by comparing against the measured residual stresses. Finite element simulations indicate that both residual stress and resulting strain responses near the weld toe are the key factors in inducing fatigue cracks at the weld toe. Research needs in revealing the fatigue failure mechanisms at the weld toe are discussed.

Fatigue Design of Welded Joints by Local Approaches: Comparison between Fictitious Notch Rounding and Strain Energy Averaging

2007 ◽  
Vol 348-349 ◽  
pp. 449-452 ◽  
Author(s):  
Paolo Lazzarin ◽  
Filippo Berto ◽  
D. Radaj
Keyword(s):  
Welded Joints ◽  
Strain Energy ◽  
Control Volume ◽  
Local Strain ◽  
Stress Distributions ◽  
Good Correspondence ◽  
Load Carrying ◽  
Weld Toe ◽  
Weld Root ◽  
Coarse Meshes

The paper demonstrates the close correspondence between two local approaches to assess the fatigue strength of welded joints: Radaj’s approach based on fictitious notch rounding and a recently proposed approach based on the local strain energy density (SED) averaged over a given control volume. This volume surrounds the weld root or weld toe, both modelled as sharp (zero radius) V-notches with different opening angles. The two approaches are applied to load carrying and non-load carrying cruciform joints and the theoretical fatigue notch factors Kf are compared. The SED averaged over the control volume is determined from finite element models with very fine meshes, as typically designed to evaluate the intensity of the asymptotic stress distributions, and also from coarse meshes, showing a surprisingly good correspondence.

scholarly journals Microstructure and Fatigue Behavior of 2205/316L Stainless Steel Dissimilar Welded Joints

Metals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 93
Author(s):  
Saúl Leonardo Hernández-Trujillo ◽  
Victor Hugo Lopez-Morelos ◽  
Marco Arturo García-Rentería ◽  
Rafael García-Hernández ◽  
Alberto Ruiz ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Welded Joints ◽  
316L Stainless Steel ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Base Material ◽  
Fatigue Tests ◽  
Solidification Mode ◽  
Tension And Compression ◽  
Weld Toe

The relation among microstructure and fatigue behavior of 2205/316L stainless steel dissimilar welded joints was investigated. Plates of 6.35 mm in thickness with a single-V joint configuration were gas metal arc welded (GMAW) in a single pass by feeding at 6 m/min an ER2209 filler wire with a heat input of 1.2 kJ/mm. Grain growth in the high temperature-heat affected zone (HT-HAZ) occurred mostly at the mid-height of the plates, delimiting the width of this region up to ~1.28 and ~0.73 mm of the 2205 and 316L plates, respectively. Dilution of the 316L plate with the ER2209 filler altered the solidification mode in this side of the weld and led to a significant content of austenite along the fusion line. Fatigue tests were performed using sinusoidal waveform at room temperature applying uniaxial cyclic loading, between constant stress limits within the elastic deformation of tension and compression (Δσ) with stress ratio R = −0.3. With stress ranges of 98% and 95% the fatigue specimens rapidly failed in much less than 106 cycles. The failure crack initiated at the surface of the 316L in the HT-HAZ near the weld toe. Surface analyses of unbroken specimens before and after fatigue testing revealed a significant increment in roughness of the 316L base material owing to the formation of intrusions and extrusions.

A Fatigue Failure Mechanism of Welded Piping Joints

2005 ◽  
Author(s):  
Tasnim Hassan ◽  
Xiangyang Lu
Keyword(s):  
Residual Stresses ◽  
Fatigue Failure ◽  
Welded Joints ◽  
Power Plants ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Pipe Length ◽  
Welding Sequence ◽  
Weld Toe ◽  
Weld Fatigue

Fatigue failures of small bore piping systems have historically occurred in nuclear power plants, resulting in unanticipated plant downtime and substantial financial loss. If the failures were not caused by defects, the reasons of the initiation of fatigue cracks were not clear in many cases. This paper presented a set of weld fatigue response data which pointed to the strain ratcheting response as a probable reason for weld fatigue failure. A systematic set of low-cycle fatigue tests on butt- and socket welded piping joints in the cantilever set up is conducted. A new observation made in these tests is that the recorded strains near the weld toe ratchet continuously, which results in the initiation of fatigue crack(s). Comparison of these ratcheting responses with those from the cyclic bending of straight pipe and ratcheting experiments at the material level indicates that the residual stresses at welded joints may induce the ratcheting responses. This observation is further supported by the symmetric strain response (no ratcheting) at the mid-pipe length, which is located away from the welded joint. At this location, there are no residual stresses to induce ratcheting. It is observed that the fatigue cracks in all experiments occurred at the weld toe location where the ratcheting strain is the largest. The experimental data indicate that the fatigue life of materials is reduced in the presence of ratcheting. It is also observed that the ratcheting is influenced by the welding sequence. One interesting aspect of the weld fatigue data developed is that the ratcheting at the weld joints occurred under a displacement-controlled loading cycle. This study with its limited time and resource could not explore this issue. A plausible reason could be due to material heterogeneity at the welded joints.

Advanced Local Concepts for Assessing the Fatigue Durability of Welded Joints

2007 ◽  
Vol 348-349 ◽  
pp. 565-568
Author(s):  
C.M. Sonsino ◽  
D. Radaj ◽  
W. Fricke
Keyword(s):  
Fracture Mechanics ◽  
Welded Joints ◽  
Thin Sheet ◽  
Plate Thickness ◽  
Lap Joints ◽  
Structural Stress ◽  
Notch Stress ◽  
Weld Toe ◽  
Mechanics Concepts ◽  
Weld Root

Some recently developed variants of local concepts for assessing the fatigue strength and structural durability of welded joints are reviewed. These comprise structural stress, notch stress or strain and fracture mechanics concepts. New variants of the structural stress concept are Dong’s gradient stress approach and Xiao-Yamada’s ‘one millimetre stress’ approach. FE meshing rules have been developed for welded joints in thin sheet structures. The concept of fictitious notch rounding is now better substantiated for aluminium alloys. The small-size notch concept is applicable to thin sheet lap joints. The new notch stress intensity factor concept is based on the singular stresses at the sharp weld toe notch. Advanced fracture mechanics concepts combine crack initiation at the seam weld root or nugget edge and crack propagation over the plate thickness resulting in endurable FK values as function of cycles per unit thickness, N/t.

Fatigue assessment of weld toe and weld root failures in steel welded joints according to the peak stress method

2016 ◽  
Vol 60 (3) ◽  
pp. 559-572 ◽  
Author(s):  
Giovanni Meneghetti ◽  
Davide Marini ◽  
Vittorio Babini
Keyword(s):  
Welded Joints ◽  
Peak Stress ◽  
Fatigue Assessment ◽  
Weld Toe ◽  
Weld Root
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