Effect of Weld Quality and Postweld Improvement Techniques on the Fatigue Resistance of Extra High Strength Steels

Lieurade, H. P.; Huther, I.; Lefèbvre, Fabien

doi:10.1007/bf03266658

Cited by 40 publications

(27 citation statements)

References 2 publications

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“…The square of the correlation coefficient r and standard deviation of logC corresponding to logΝ f are also shown. The reported slopes for ASW tests are usually much shallower than m = 3, for example, m = 3.8-5.9 or higher, [13][14][15] and it has been presented 16 that a slope of m = 5 fits both available HFMI-treated fatigue data and existing data for hammer-peened welds. MSSPD fitting results with m = 5.85 are utilized below because the shallower slope gives better correspondence to the experimental findings, both for ASW and for mechanically treated joints (m = 5 would give C char = 10 18.59 and C mean = 10 19.26 , Fig.…”

Section: A S T E R S -N C U R V E B a S E D O N A S -W E L D E D D mentioning

confidence: 99%

A new proposal for assessment of the fatigue strength of steel butt‐welded joints improved by peening (HFMI) under constant amplitude tensile loading

Nykänen

Björk

2015

Fatigue Fract Eng Mat Struct

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A B S T R A C T Experimental fatigue data for butt-welded joints in as-welded condition and under constant amplitude tensile loading were analysed using the effective notch stress system and a new master curve analysis that takes the local stress ratio, R local , into account. The local stresses needed for computation of R local are calculated with the notch strain approach in conjunction with the reference radius concept. The main focus was to predict with the derived master curve the fatigue strength of peened butt-welded joints. The lowest surface residual stresses after peening were first estimated based on reported measurements and an analytical lower bound result. The predictions showed quite similar strength dependences and FAT values as reported for high-frequency mechanical impact treated welds for applied stress ratio R = 0.1. The benefits of peening reduce faster for higher strength steels when R increases. When R = 0.5, the FATs are practically the same for all steel grades.Keywords butt joint; effective notch stress; fatigue; improvement; local stress ratio; residual stress. N O M E N C L A T U R EASW = as-welded condition ENS = effective notch stress approach FAT = IIW fatigue class, fatigue strength corresponding to two million cycles GMAW = gas metal arc welding HAZ = heat affected zone HFMI, HFP = high frequency mechanical impact treatment (generic term) HSS = high strength steel IIW = International Institute of Welding MSSPD = minimization of the sum of squared perpendicular distances from a line NS = nominal stress approach QC = quenched and cold-formable steel SINTAP = structural integrity assessment procedure SWT = Smith-Watson-Topper approach TIG = tungsten inert gas welding UP = ultrasonic peening (device name) C = fatigue capacity E = Young's modulus f u = ultimate strength, nominal f y = yield strength H = cyclic strain hardening coefficient K f = fatigue effective fatigue stress concentration factor between notch stress and nominal stress K HP = improvement factor K m = structural stress concentration factor Correspondence: T. Nykänen.

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Section: A S T E R S -N C U R V E B a S E D O N A S -W E L D E D D mentioning

confidence: 99%

A new proposal for assessment of the fatigue strength of steel butt‐welded joints improved by peening (HFMI) under constant amplitude tensile loading

Nykänen

Björk

2015

Fatigue Fract Eng Mat Struct

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“…As a result of statistical analysis, Costa et al reported FAT 50% = 250 MPa and FAT 95% = 154 MPa with m = 5.16. Lieurade et al 7 carried out fatigue tests with the stress ratio R = 0.2 and σ max = constant = σ yield /1.5 on symmetrical MAG welded butt joints in as-welded condition (number of tests 42). Test specimens were fabricated from S700 and S960 steel plates with t equal to 8 mm.…”

Section: Fatigue Testsmentioning

confidence: 99%

“…21 In this study, new relations for the estimation of the strain-life curve are utilized, Eq. (7). 19 However, the simplification leads to a practical problem because the HB values measured on the test specimen have some variation over the weld toe volume where the crack may initiate.…”

Section: Estimation Of the Materials Parametersmentioning

confidence: 99%

Fatigue strength prediction of ultra high strength steel butt‐welded joints

Nykänen

Björk

Laitinen

2012

Fatigue Fract Eng Mat Struct

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A B S T R A C T First, fatigue tests were performed on butt-welded joints made of novel direct quenched ultra high strength steel with high quality welds. Two different welding processes were used: MAG and Pulsed MAG. The weld profiles, misalignments and residual stresses were measured, and the material properties of the heat-affected zone were determined. Fatigue tests were carried out with constant amplitude tensile loading both for joints in as-welded condition and for joints after ultrasonic peening treatment. Finally, in fatigue strength predictions, the crack initiation phase was estimated using the procedures described by Lawrence et al. [Lawrence F V, Ho N J and Mazumdar P K (1981) Predicting the fatigue resistance of welds. Annu. Rev. Mater. Sci,11,. The propagation phase was simply estimated using S-N curves for normal quality butt welds, which may contain pre-existing cracks or crack-like defects eliminating the crack initiation stage.Keywords fatigue; local approach; ultra high strength steels; weld profile. N O M E N C L A T U R Ea * = material parameter ASW = as-welded condition A 5 = elongation, permanent extension of the gauge length after fracture, % b = fatigue strength exponent c = fatigue ductility exponent C = fatigue capacity CEV = carbon equivalent value e = axial misalignment E = Young's modulus FAT = fatigue class, fatigue strength corresponding to two million cycles GMAW = gas metal arc welding HAZ = heat-affected zone HB = Brinell hardness number [kg/mm 2 ] HV10 = Vickers hardness number obtained using a 10 kgf force [kg/mm 2 ] IIW = International Institute of Weldingnotch factor K m = stress concentration factor caused by misalignments K m,e = axial magnification factor K m,α = angular magnification factor K t = stress concentration factor Correspondence: T. Nykänen. Fatigue Fract Engng Mater Struct 36, 469-482 469 470 T. NYKÄNEN et al.K w = stress concentration factor of weld l = half distance between clamps LCF = low cycle fatigue LEFM = linear elastic fracture mechanics m = exponent of S-N curve n = static strain-hardening exponent n = cyclic strain hardening exponent NDT = non-destructive testing N f = total life N i = initiation life N p = propagation life QC = quenched and cold-formable steel R = stress ratio, the ratio of minimum to maximum applied stress in a cycle R p0.2 = 0.2% proof stress R m = ultimate tensile strength SLM = structured light method t = plate thickness t 8/5 = cooling time between 800 • C and 500 • C UP = ultrasonic peening treatment α = angular misalignment angle, survival probability β = two-sided confidence interval ε = local strain range ε e = elastic strain range ε p = plastic strain range K = stress intensity factor range S = nominal stress range σ = local stress range ε f = fatigue ductility coefficient θ = weld notch angle ρ = notch root radius ρ c = critical notch root radius σ f = fatigue strength coefficient σ m = mean stress, a combination of applied and residual stresses σ res = residual stress Sub indexes: geo = mean value of log-normal distrib...

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“…However, the efficiency of these processes seems to be lower than hammer and ultrasonic penning [7,11]. The fatigue strength improvement achieved through these techniques, increases with nominal yield stress and therefore the greatest benefits are obtained for high strength steels [7,9,12,14,15]. Recently, some work has been focused on the application of these steels and post-weld treatments in the medium cycle regime, i.e.…”

Section: Introductionmentioning

confidence: 99%

“…However, to obtain the desired improvements with the post-weld techniques, it is necessary that the as welded joints and the improved welded joints, in case of rewelding treatments, have certain quality requirements, to ensure the absence of welding defects, or its limitation, as well as the fulfillment of certain requirements on bead geometry [14,27,28]. Although the existing weld class system [29,30] will guarantee the requirements of industrial quality control, it doesn't allow relating the quality of the weld joint with its fatigue strength in an efficient way [31].…”

Section: Introductionmentioning

confidence: 99%

Fatigue behaviour of T welded joints rehabilitated by tungsten inert gas and plasma dressing

Ramalho

Ferreira

Branco³

2011

Materials & Design

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This paper concerns a fatigue study on the effect of tungsten inert gas (TIG) and plasma dressing in non-load-carrying fillet welds of structural steel with medium strength. The fatigue tests were performed in three point bending at the main plate under constant amplitude loading, with a stress ratio of R=0.05 and a frequency of 7 Hz.Fatigue results are presented in the form of nominal stress range versus fatigue life (S-N) curves obtained from the as welded joints and the TIG dressing joints at the welded toe. These results were compared with the ones obtained in repaired joints, where TIG and plasma dressing were applied at the welded toes, containing fatigue cracks with a depth of 3-5 mm in the main plate and through the plate thickness. A deficient repair was obtained by TIG dressing, caused by the excessive depth of the crack. A reasonable fatigue life benefits were obtained with plasma dressing. Good results were obtained with the TIG dressing technique for specimens with shallower initial defects (depth lesser than 2.5 mm).The fatigue life benefits were presented in terms of a gain parameter assessed using both experimental data and life predictions based on the fatigue crack propagation law.

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Effect of Weld Quality and Postweld Improvement Techniques on the Fatigue Resistance of Extra High Strength Steels

Cited by 40 publications

References 2 publications

A new proposal for assessment of the fatigue strength of steel butt‐welded joints improved by peening (HFMI) under constant amplitude tensile loading

A new proposal for assessment of the fatigue strength of steel butt‐welded joints improved by peening (HFMI) under constant amplitude tensile loading

Fatigue strength prediction of ultra high strength steel butt‐welded joints

Fatigue behaviour of T welded joints rehabilitated by tungsten inert gas and plasma dressing

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