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

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.

[1]  Liviu Marsavina,et al.  Local strain energy density for the fracture assessment of polyurethane specimens weakened by notches of different shape , 2017 .

[2]  Filippo Berto,et al.  Effect of hot dip galvanization on the fatigue strength of steel bolted connections , 2017 .

[3]  Andrzej Seweryn,et al.  Brittle fracture criterion for structures with sharp notches , 1994 .

[4]  F. Berto,et al.  Estimation of Fracture Loads in AL7075-T651 Notched Specimens Using the Equivalent Material Concept Combined with the Strain Energy Density Criterion and with the Theory of Critical Distances , 2018 .

[5]  Filippo Berto,et al.  A review of the volume-based strain energy density approach applied to V-notches and welded structures , 2009 .

[6]  Filippo Berto,et al.  Fracture assessment of magnetostrictive materials , 2017 .

[7]  David Taylor,et al.  Predicting the fracture strength of ceramic materials using the theory of critical distances , 2004 .

[8]  Filippo Berto,et al.  Static Multiaxial Fracture Behavior of Graphite Components: A Review of Recent Results , 2017 .

[9]  Ted Schrecker,et al.  Changing cartographies of health in a globalizing world , 2014 .

[10]  H. Neuber.  Theory of notch stresses : principles for exact calculation of strength with reference to structural form and material , 1958 .

[11]  F. Berto,et al.  Fracture parameters determination of polyurethane materials for application of SED criteria to notched components , 2016 .

[12]  Zdeněk Knésl,et al.  A criterion of V-notch stability , 1991 .

[13]  E. Beltrami,et al.  Sulle condizioni di resistenza dei corpi elastici , 1885 .

[14]  Paolo Lazzarin,et al.  A finite-volume-energy based approach to predict the static and fatigue behavior of components with sharp V-shaped notches , 2001 .

[15]  G. Sih.  SOME BASIC PROBLEMS IN FRACTURE MECHANICS AND NEW CONCEPTS , 1973 .

[16]  David Taylor,et al.  The Theory of Critical Distances: A New Perspective in Fracture Mechanics , 2010 .

[17]  Andrzej Seweryn,et al.  Verification of brittle fracture criteria for elements with V-shaped notches , 2002 .

[18]  E. Brazel,et al.  The theory of critical distances applied to problems in fracture and fatigue of bone , 2009 .

[19]  Filippo Berto,et al.  Fracture Assessment of PEEK under Static Loading by Means of the Local Strain Energy Density , 2017, Materials.

[20]  Andrzej Seweryn,et al.  BRITTLE FRACTURE IN PLANE ELEMENTS WITH SHARP NOTCHES UNDER MIXED-MoDE LOADING , 1997 .

[21]  Filippo Berto,et al.  Local strain energy density for the fatigue assessment of hot dip galvanized welded joints: some recent outcomes , 2017 .

[22]  M. Meyers,et al.  Biomedical applications of titanium and its alloys , 2008 .

[23]  David Taylor,et al.  Geometrical effects in fatigue: a unifying theoretical model , 1999 .

[24]  Martin L. Dunn,et al.  Fracture initiation at sharp notches: Correlation using critical stress intensities , 1997 .

[25]  Torgeir Welo,et al.  40CrMoV13.9 notched specimens under multiaxial fatigue: an overview of recent results , 2017 .

[26]  Filippo Berto,et al.  The fatigue behavior of V-notches in presence of residual stresses: Recent developments and future outcomes , 2017 .

[27]  Alberto Carpinteri,et al.  Stress-singularity and generalized fracture toughness at the vertex of re-entrant corners , 1987 .

[28]  M. Williams,et al.  Stress Singularities Resulting From Various Boundary Conditions in Angular Corners of Plates in Extension , 1952 .

[29]  F. Berto,et al.  Brittle Failure of Graphite Weakened by V-Notches: A Review of Some Recent Results Under Different Loading Modes , 2015, Strength of Materials.

[30]  Marino Quaresimin,et al.  Fatigue behaviour of glass/epoxy laminates in the presence of voids , 2017 .

[31]  David Taylor,et al.  The Theory of Critical Distances Applied to the Prediction of Brittle Fracture in Metallic Materials , 2005 .

[32]  Filippo Berto,et al.  Creep behavior of v-notched components , 2017 .

[33]  Filippo Berto,et al.  Rapid calculations of notch stress intensity factors based on averaged strain energy density from coarse meshes: Theoretical bases and applications , 2010 .

[34]  G. C. Sih,et al.  Sharp notch fracture strength characterized by critical energy density , 1991 .

[35]  Luca Susmel,et al.  The theory of critical distances: a review of its applications in fatigue☆ , 2008 .

[36]  F. Gillemot,et al.  Fracture mechanics applications of absorbed specific fracture energy: Notch and unnotched specimens , 1985 .

[37]  Filippo Berto,et al.  The volume-based Strain Energy Density approach applied to static and fatigue strength assessments of notched and welded structures , 2009 .

[38]  Filippo Berto,et al.  Recent developments in brittle and quasi-brittle failure assessment of engineering materials by means of local approaches , 2014 .

[39]  Martin L. Dunn,et al.  Fracture initiation at sharp notches under mode I, mode II, and mild mixed mode loading , 1997 .

[40]  Filippo Berto,et al.  Fatigue strength of severely notched specimens made of Ti–6Al–4V under multiaxial loading , 2015 .

[41]  Filippo Berto,et al.  Mode II brittle fracture: recent developments , 2017 .

[42]  Paolo Lazzarin,et al.  A generalized stress intensity factor to be applied to rounded V-shaped notches , 2006 .

[43]  David Taylor,et al.  The effect of stress concentrations on the fracture strength of polymethylmethacrylate , 2004 .

[44]  David Taylor,et al.  The Theory of Critical Distances , 2007 .

[45]  G. Sih.  Strain-energy-density factor applied to mixed mode crack problems , 1974 .

[46]  C. Leyens,et al.  Titanium and titanium alloys : fundamentals and applications , 2005 .