Assessing the integrity of steel structural components with stress raisers using the Theory of Critical Distances

Abstract

Please cite this article as: Li Wenchao, Susmel Luca, Askes Harm, Liao Fangfang, Zhou Tianhua, Assessing the integrity of steel structural components with stress raisers using the Theory of Critical Distances, (2016), doi: 10.1016/j.engfailanal.2016.07.007 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Abstract: This paper assesses and evaluates the detrimental effect of standard and complex geometrical features on the static strength of samples made of Q460 steel. The experimental results generated by testing four types of notched specimens were analyzed using the Theory of Critical Distances (TCD). The considered configurations included uniaxial tension tests on standard notched round bars and double-side U-notched flat plate specimens. In particular, our attention was focused on the fracture behavior of two specimens containing complex geometrical features subjected to pure-shear and tensile-shear local stress states. The common feature of these two notched specimens was that cracks were seen to initiate, within the material, away from the stress raisers, even though obvious stress concentrations existed at notch tip. The performed validation exercise confirms the accuracy and reliability of the linear-elastic TCD in estimating the fracture initiation position and static strength of standard notched round bars and double-side U-notched flat plate specimens. In the meantime, the linear-elastic method proposed in this paper can also be used as an effective approach to assess the fracture behavior of metallic components having complex geometry. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPTKey words: notches; Theory of Critical Distances; static failure; fracture; structural steel A C C E P T E D M A N U S C R I P TACCEPTED MANUSCRIPT 2 1.IntroductionMany engineering investigations have demonstrated that failure of engineering components takes place in the vicinity of notches, cracks and complex geometrical features. Further, micro defects due to manufacturing usually tend to concentrate themselves in these regions with a weakening effect on the overall strength of the components. In parallel, stress concentration phenomena and the resulting local multiaxial stress states accelerate the crack initiation process. In this context, it is key to provide structural engineers with design methods suitable for evaluating the detrimental effect of notches on the overall strength of engineering components.The Theory of Critical Distances (TCD) [1] is a group of failure criteria which make use of the local linear-elastic stress fields in the vicinity of the assumed crack initiation locations to estima...

A material length scale–based methodology to assess static strength of notched additively manufactured polylactide (PLA)

“…As far as static assessment of notched components is concerned, much experimental evidence suggests that the so-called Theory of Critical Distances (TCD) 1 is certainly the most powerful candidate to be used in situations of practical interest to design AM notched components against static loading. The key advantage of the TCD is that its usage does not require complex non-linear constitutive models, [2][3][4] with this holding true independently of the level of ductility characterising the material being assessed. 5,6 Further, since the TCD takes directly into account the morphology of the assessed material via suitable length scale parameters, 1 it is capable of accurate estimates regardless of shape and sharpness of the geometrical features being designed.…”

Determination of the fatigue critical distance according to the Line and the Point Methods with rounded V-notched specimen

“…where l 0 is the PM counterpart of the previously defined l 0 for the LM. The fatigue stress concentration factor is then introduced and related to this length: 20) and this equation can be solved for l 0 :…”

“…For these reasons, as an alternative to fracture mechanics testing, one of the critical distance methods can be considered in order to be able to find the length that matches the notched and the plain specimen strengths, or two notches with different severities. This approach can be found in several papers, especially those regarding monotonic fracture, such as Li et al [20], Yin et al [21], Cicero et al [22], Voiconi et al [23], where the threshold is replaced by the fracture toughness K Ic , and the inherent strength σ 0 has to be considered rather than the fatigue limit. Susmel and Taylor [24] extensively applied this principle both for monotonic fracture and fatigue loadings, and they found and validated a large material database of K Ic and ∆K th .…”

Requirements for stress gradient‐based fatigue assessment of notched structures according to theory of critical distance

“…Because of increased computational power, such methods are more easily applicable nowadays. The point (PM) and line (LM) methods—based on the gradient of the stress acting perpendicular to the expected crack path—have gained especial interest, judging by the variety of investigated applications 8–29 …”