A Strength Evaluation Method of a Sharply Notched Structure by a New Parameter, "The Equivalent Stress Intensity Factor"

Kihara, Shigefumi; Yoshii, Akihiko

doi:10.1299/jsmea1988.34.1_70

Cited by 21 publications

(22 citation statements)

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“…The hypothesis of constancy of R C under mixed mode loads had been validated by by using experimental data mainly provided by Seweryn et al (1997) and Kihara and Yoshii (1991). Seweryn investigated mixedmode fracture of polymethyl-metacrylate (PMMA) specimens with a double symmetric V-notch with an opening angle 2α ranging from 20 • to 80 • .…”

Section: Analytical Preliminariesmentioning

confidence: 99%

“…At two limit conditions, the middle cross section of the specimens was loaded by pure tension (when ψ = 0˚) and by pure shear (ψ = 90 • ). Kihara and Yoshii (1991) tested under fatigue loading two materials and five geometries of plane specimens with V-shaped notches. Three geometries were characterised by single side and double side notches with 2α equal to 90 • and 120 • .…”

Section: Analytical Preliminariesmentioning

confidence: 99%

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Fatigue strength of steel and aluminium welded joints based on generalised stress intensity factors and local strain energy values

2005

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Weld bead geometry cannot, by its nature, be precisely defined. Parameters such as bead shape and toe radius vary from joint to joint even in well-controlled manufacturing operations. In the present paper the weld toe region is modelled as a sharp, zero radius, V-shaped notch and the intensity of asymptotic stress distributions obeying Williams' solution are quantified by means of the Notch Stress Intensity Factors (NSIFs). When the constancy of the angle included between weld flanks and main plates is assured and the angle is large enough to make mode II contribution non-singular, mode I NSIF can be directly used to summarise the fatigue strength of welded joints having very different geometry. By using a large amount of experimental data taken from the literature and related to a V-notch angle of 135 degrees, two NSIF-based bands are reported for steel and aluminium welded joints under a nominal load ratio about equal to zero. A third band is reported for steel welded joints with failures originated from the weld roots, where the lack of penetration zone is treated as a crack-like notch and units for NSIFs are the same as conventional SIF used in LEFM. Afterwards, in order to overcome the problem related to the variability of the V-notch opening angle, the synthesis is made by simply using a scalar quantity, i.e. the mean value of the strain energy averaged in the structural volume surrounding the notch tips. This energy is given in closed form on the basis of the relevant NSIFs for modes I and II and the radius R-c of the averaging zone is carefully identified with reference to conventional arc welding processes. Rc for welded joints made of steel and aluminium considered here is 0.28mm and 0.12mm, respectively Different values of Rc might characterise welded joints obtained from high-power processes, in particular from automated laser beam welding. The local-energy based criterion is applied to steel welded joints under prevailing mode I (with failures both at the weld root and toe) and to aluminium welded joints under mode I and mixed load modes (with mode II contribution prevailing on that ascribable to mode I). Surprising, the mean value of Delta W related to the two groups of welded materials was found practically coincident at 2 million cycles. More than 750 fatigue data have been considered in the analyses reported herein

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Section: Analytical Preliminariesmentioning

confidence: 99%

Section: Analytical Preliminariesmentioning

confidence: 99%

Fatigue strength of steel and aluminium welded joints based on generalised stress intensity factors and local strain energy values

2005

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“…transverse non-load carrying fillet welded joints with 2α = 135 degrees at the weld toe.The hypothesis of constancy of R c under mixed mode loads had been validated byLazzarin and Zambardi[15] by using experimental data mainly provided by Seweryn et al[38] and Kihara and Yoshii[39].From a theoretical point of view the material properties in the vicinity of the weld toes and the weld roots depend on a number of parameters as residual stresses and distortions, heterogeneous metallurgical micro-structures, weld thermal cycles, heat source characteristics, load histories and so on. To device a model capable of predicting R c and fatigue life of welded components on the basis of all these parameters is really a task too complex.…”

mentioning

confidence: 95%

Fatigue strength of steel rollers with failure occurring at the weld root based on the local strain energy values: modelling and fatigue assessment

Berto

Campagnolo

Chebat

et al. 2016

International Journal of Fatigue

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“…Notch stress intensity factors (NSIFs) proved to correlate the static strength of components made of brittle or quasi-brittle materials and weakened by sharp V-notches [18][19][20][21][22][23], as well as the medium and high-cycle fatigue strength of notched components made of structural materials [24,25]. Concerning welded joints, NSIFs have been used to analyze the fatigue strength both under uniaxial [26][27][28][29][30] and multiaxial cyclic loadings [31].…”

Section: Analytical Background Of the Peak Stress Methodsmentioning

confidence: 99%

Rapid Calculation of Residual Notch Stress Intensity Factors (R- NSIFs) by Means of the Peak Stress Method

Colussi¹,

Ferro²,

Berto³

et al. 2018

Residual Stress Analysis on Welded Joints by Means of Numerical Simulation and Experiments

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The intensity of the residual singular stress distribution can be quantified by the residual notch stress intensity factor (R-NSIF), which might be a useful stress parameter to include in local approaches for fatigue strength assessments of welded joints. In order to calculate the residual stress fields by means of welding process simulations, the mesh adopted in numerical models has necessarily to be very fine. Unfortunately, the nonlinear and transient behavior of the welding simulation makes numerical analyses extremely demanding in terms of computational time, particularly, if large welded structures and/or multipass welds have to be simulated. In this scenario, the use of methods aimed at reducing the computational effort to estimate local stresses and strains in welded structures can be effective. Among these, the peak stress method has been proposed to estimate the notch stress intensity factors (NSIFs) at sharp V-notches, using coarse finite element patterns. In this work, the peak stress method (PSM) has been used to calculate the R-NSIF of a full penetration welded T-joint. It has been shown that the PSM can successfully be used to estimate R-NSIFs values, provided that the stress redistribution induced by plasticity in the zone very close to the notch tip is negligible.

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A Strength Evaluation Method of a Sharply Notched Structure by a New Parameter, "The Equivalent Stress Intensity Factor"

Cited by 21 publications

References 1 publication

Fatigue strength of steel and aluminium welded joints based on generalised stress intensity factors and local strain energy values

Fatigue strength of steel and aluminium welded joints based on generalised stress intensity factors and local strain energy values

Fatigue strength of steel rollers with failure occurring at the weld root based on the local strain energy values: modelling and fatigue assessment

Rapid Calculation of Residual Notch Stress Intensity Factors (R- NSIFs) by Means of the Peak Stress Method

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