Growth rate of fatigue cracks in fields of residual stresses in titanium welded joints with different content of embrittling impurities

1990 ◽  
Vol 22 (11) ◽  
pp. 1562-1569 ◽  
Author(s):  
V. T. Troshchenko ◽  
V. V. Pokrovskii ◽  
V. L. Yarusevich ◽  
V. I. Mikhailov ◽  
V. A. Sher
Keyword(s):  
Growth Rate ◽  
Residual Stresses ◽  
Welded Joints ◽  
Fatigue Cracks ◽  
Different Content

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.

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.

Analysis of Fatigue Crack Propagation in Typical Welded Joints of FPSOs

2005 ◽  
Author(s):  
Bin Zhang ◽  
Torgeir Moan
Keyword(s):  
Stress Intensity ◽  
Residual Stresses ◽  
Crack Propagation ◽  
Analytical Model ◽  
Surface Crack ◽  
Welded Joints ◽  
Structural Reliability ◽  
Fatigue Cracks ◽  
Integral Approach ◽  
Initial Surface

The purpose of this paper is to predict crack propagation and especially the remaining life after through-the-thickness crack at typical joints in deck and bottom structures of FPSOs. This information can be used in planning inspection, repair and maintenance. The growth of fatigue cracks is studied in typical welded joints through the use of analytical and numerical methods. The simplified analytical model is based on the British Standard 7910 [3] and Dexter’s analytical model [1–2]. Numerical analysis is performed with the finite element method, considering the effect of residual stresses, and using the J-integral approach to determine the stress intensity factor at the crack tip during different stages of crack growth. The first stage is referred the surface crack stage, in which the crack grows from an initial surface crack of a size of about 0.1 mm in depth and 0.2mm-1.0mm in length to the through-thickness crack. The second stage is named the long crack stage, in which the crack grows from an approximately 40–100mm long through-thickness crack to the final critical long crack. The computed stress intensity factors, along with the Paris law, are used to predict the crack propagation at each stage with reasonable accuracy. The effect of welding residual stresses on fatigue behaviour is considered by introducing an effective SIF concept. It is concluded that stable crack propagation behaviour can be conservatively predicted by using relatively simple approaches. These techniques can be used in making rational decisions regarding scheduling of inspections, repairs, and allow a better prediction of the structural reliability in view of fatigue cracks.

scholarly journals Numerical simulation of laser welded joints: modern fatigue analysis methodology

2020 ◽  
Vol 53 (4) ◽  
pp. 342-355
Author(s):  
Rami Markus Kokko ◽  
Joona Vaara ◽  
Teemu Kuivaniemi ◽  
Tero Frondelius
Keyword(s):  
Numerical Simulation ◽  
Cyclic Loading ◽  
Residual Stresses ◽  
Welded Joints ◽  
Fatigue Cracks ◽  
Fatigue Behaviour ◽  
Noticeable Effect ◽  
Microstructural Changes ◽  
Analysis Methodology ◽  
Simulation Results

Welding always induces discontinuities and imperfections in the structure that allows for potential fatigue cracks. Welding effects thermal strains, which yield to residual stresses of the structure that have a noticeable effect on the fatigue behaviour of the structure. Welding inexorably leads to microstructure and geometry changes in the welding region. Material internal changes, residual stresses and microstructural changes can be simulated numerically, and the simulation results can be used in cyclic loading analysis in FEA.

Peculiarities of Formation of Residual Stresses in Welded Joints and Stellite Weld Cladding on Rail Steel

2020 ◽  
Vol 11 (3) ◽  
pp. 634-640
Author(s):  
S. Ya. Betsofen ◽  
K. V. Grigorovich ◽  
A. A. Ashmarin ◽  
A. Yu. Abdurashitov ◽  
M. A. Lebedev
Keyword(s):  
Residual Stresses ◽  
Welded Joints ◽  
Rail Steel ◽  
Weld Cladding

Thermoacoustic method for relaxation of residual stresses in welded joints

1995 ◽  
Vol 30 (4) ◽  
pp. 491-493
Author(s):  
V. V. Koshovyi ◽  
M. I. Pekhn'o ◽  
O. I. Tsykhan
Keyword(s):  
Residual Stresses ◽  
Welded Joints

Effect of Hardness and Tensile Mean Stress on Fatigue Crack Growth in Beryllium Copper

1969 ◽  
Vol 11 (3) ◽  
pp. 343-349 ◽  
Author(s):  
L. P. Pook
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Residual Stresses ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Mean Stress ◽  
Growth Data ◽  
Beryllium Copper

Some fatigue crack growth data have been obtained for age-hardened beryllium copper. The fatigue crack growth rate was found to be very dependent on the hardness and tensile mean stress. This dependence is believed to be associated with the intense residual stresses surrounding Preston-Guinier zones.

Finite Element Analyses of Residual Stresses in Typical Welded Joints Used in Nuclear Power Plants and Comparisons With Experiments

2010 ◽  
Author(s):  
Dean Deng ◽  
Kazuo Ogawa ◽  
Nobuyoshi Yanagida ◽  
Koichi Saito
Keyword(s):  
Numerical Simulation ◽  
Residual Stress ◽  
Residual Stresses ◽  
Welded Joints ◽  
Nuclear Power ◽  
Power Plants ◽  
Butt Joint ◽  
Welding Residual Stress ◽  
Dissimilar Metal ◽  
Water Reactors

Recent discoveries of stress corrosion cracking (SCC) at nickel-based metals in pressurized water reactors (PWRs) and boiling water reactors (BWRs) have raised concerns about safety and integrity of plant components. It has been recognized that welding residual stress is an important factor causing the issue of SCC in a weldment. In this study, both numerical simulation technology and experimental method were employed to investigate the characteristics of welding residual stress distribution in several typical welded joints, which are used in nuclear power plants. These joints include a thick plate butt-welded Alloy 600 joint, a dissimilar metal J-groove set-in joint and a dissimilar metal girth-butt joint. First of all, numerical simulation technology was used to predict welding residual stresses in these three joints, and the influence of heat source model on welding residual stress was examined. Meanwhile, the influence of other thermal processes such as cladding, buttering and heat treatment on the final residual stresses in the dissimilar metal girth-butt joint was also clarified. Secondly, we also measured the residual stresses in three corresponding mock-ups. Finally, the comparisons of the simulation results and the measured data have shed light on how to effectively simulate welding residual stress in these typical joints.

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