The fatigue behavior of V-notches in presence of residual stresses: recent developments and future outcomes

Ferro, Paolo; Peron, Mirco; Razavi, S.M.J.; Berto, Filippo; Torgersen, Jan

doi:10.3221/igf-esis.42.20

Cited by 5 publications

(4 citation statements)

References 27 publications

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“…However, the volume-based approach proposed by Lazzarin and Zambardi represents a great development of all the previous strain energy density-based approaches. This method has been revealed to successfully predict both the tensile and fatigue strength of different notched materials subjected to both uniaxial and mixed-mode loading [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ]. Piccotin et al, for example, assessed with good agreements the tensile strength under mode I, II, and mixed mode I + II of polyurethane foams characterized by different densities and weakened by several notch geometries [ 32 ].…”

Section: Introductionmentioning

confidence: 99%

Rupture Predictions of Notched Ti-6Al-4V Using Local Approaches

2018

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Ti-6Al-4V has been extensively used in structural applications in various engineering fields, from naval to automotive and from aerospace to biomedical. Structural applications are characterized by geometrical discontinuities such as notches, which are widely known to harmfully affect their tensile strength. In recent years, many attempts have been done to define solid criteria with which to reliably predict the tensile strength of materials. Among these criteria, two local approaches are worth mentioning due to the accuracy of their predictions, i.e., the strain energy density (SED) approach and the theory of critical distance (TCD) method. In this manuscript, the robustness of these two methods in predicting the tensile behavior of notched Ti-6Al-4V specimens has been compared. To this aim, two very dissimilar notch geometries have been tested, i.e., semi-circular and blunt V-notch with a notch root radius equal to 1 mm, and the experimental results have been compared with those predicted by the two models. The experimental values have been estimated with low discrepancies by either the SED approach and the TCD method, but the former results in better predictions. The deviations for the SED are in fact lower than 1.3%, while the TCD provides predictions with errors almost up to 8.5%. Finally, the weaknesses and the strengths of the two models have been reported.

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Section: Introductionmentioning

confidence: 99%

Rupture Predictions of Notched Ti-6Al-4V Using Local Approaches

2018

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“…Welds represent local regions of higher stresses (i.e., stress concentrators) and fatigue failure is widely known to be sensitive to local peak stresses. Thus, over the years, several methods have been developed to assess the fatigue behavior of welds, and among these the Notch Stress Intensity Factor (NSIF) approach is worth mentioning [6][7][8]. In fact, since experimental observations have revealed that the most used welding procedures, such as arc and laser welding, are characterized by a very small weld toe radius, it is acceptable to model it as a sharp notch and the fatigue behavior can thus be correlated to the NSIFs [9,10].…”

Section: Introductionmentioning

confidence: 99%

Fatigue Strength Assessment of Steel Rollers: On the Reliability of the Strain Energy Density Approach on Real Components

Chebat¹,

Peron

Viespoli

et al. 2018

Applied Sciences

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Welded joints are one of the most widely applied methods to join different steel components. However, they introduce stress concentrators that are commonly known to reduce the fatigue strength of structures. Several methods have been developed to assess the fatigue behavior of welded components, such as the Notch Stress Intensity Factors (NSIFs) approach. However, this approach has been reported to be geometry dependent, and does not allow for a direct comparison of failures occurring at the weld toes with those occurring at the weld roots. This drawback has been overcame by considering the value of the strain energy density (SED) range averaged in a control volume ahead of the notch tip. More than 900 fatigue data of welded joints have been summarized within a single scatter band ∆W-N (strain energy range-umber of cycles to failure) using this approach. The reliability of the just mentioned scatter band in summarizing the fatigue data of real components such as steel welded rollers produced by Rulmeca is herein evaluated. The results prove the reliability of the SED approach to assess the fatigue behavior of welded rollers, paving the way to its diffusion in assessing real components.

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“…Despite these significant advances in understanding the impact of processing conditions on the mechanical behaviour of parts, the effect of geometric discontinuities such as notches is so far underexplored. Yet, this is highly relevant in the field of complex geometric design as such attempts naturally introduce such discontinuities reported to strongly affect both tensile and fatigue properties of the components [16][17][18][19][20][21][22][23][24][25][26]. In fatigue, the effect of notches is unambiguous, determining a reduction in the fatigue strength for several materials [27][28][29][30][31][32][33][34].…”

Section: Introductionmentioning

confidence: 99%

Fracture behaviour of notched as-built EBM parts: Characterization and interplay between defects and notch strengthening behaviour

Peron

Torgersen

Ferro

et al. 2018

Theoretical and Applied Fracture Mechanics

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Additive manufacturing (AM) offers the potential to economically produce customized components with complex geometries. However, the introduction of complex geometry goes hand in hand with the presence of notches. Thus, the basic understanding of the tensile behaviour of AM fabricated notched components must be substantially improved so that the unique features of this rapidly developing technology can be utilized in critical load bearing applications. This work aims to assess the tensile behaviour of different notched specimens manufactured by means of the Electron Beam Melting (EBM) technology and tested in their as-built conditions in order to reveal the interplay between notch geometry and AM specific processing. Scanning Electron Microscopy (SEM) was used to investigate the fracture surface of the broken samples, revealing the presence of process-induced defects, harmfully affecting tensile strength with a reduction of 10% and elongation to failure with 40% with respect to values reported in literature for heat treated AM parts, respectively. Interestingly, the authors have discovered an increase in the tensile strength with the severity of the stress concentrators, quite contrary to what is commonly observed for wrought Ti-6Al-4V. This notch strengthening behaviour particular to AM specimens is related to the influence of defects on the failure driving force. The authors provide a qualitative explanation for this phenomenon using 3D FE analyses together with a theoretical description via the ellipse criterion.

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The fatigue behavior of V-notches in presence of residual stresses: recent developments and future outcomes

Cited by 5 publications

References 27 publications

Rupture Predictions of Notched Ti-6Al-4V Using Local Approaches

Rupture Predictions of Notched Ti-6Al-4V Using Local Approaches

Fatigue Strength Assessment of Steel Rollers: On the Reliability of the Strain Energy Density Approach on Real Components

Fracture behaviour of notched as-built EBM parts: Characterization and interplay between defects and notch strengthening behaviour

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