Effects of surface roughness and notch on fatigue properties for Ti–5Al–2.5Sn ELI alloy at cryogenic temperatures

Yuri, Tetsumi; Ono, Yumie; Ogata, Tetsuya

doi:10.1016/s1468-6996(03)00058-5

Cited by 33 publications

(12 citation statements)

References 12 publications

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“…In the manufacture of test specimens close attention is paid to the surface finish in the gauge section, as surface flaws can influence the test result, for example [34] specifies that the specimen be polished prior to testing. Other studies of the effect of surface finish on mechanical properties include [35,36]. Since, in general, this level of surface modification is not carried out on in-service components; one focus of the present paper is to quantify the effect of this surface polishing process.…”

Section: Geometry and Materials Considerationsmentioning

confidence: 99%

A computational study of the influence of surface roughness on material strength

et al. 2018

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In machine component stress analysis, it usually assumed that the geometry specified in CAD provides a fair representation of the geometry of the real component. While in particular circumstances, tolerance information, such as minimum thickness of a highly stressed region, might be taken into consideration, there is no standard practice for the representation of surface quality. It is known that surface roughness significantly influences fatigue life, but for this to be useful in the context of life prediction, there is a need to examine the nature of surface roughness and determine how best to characterise it. Non-smooth geometry can be represented in mathematics by fractals or other methods, but for a representation to have a practical value for a manufactured component, it is necessary to accept that there is a lower limit to surface profile measurement resolution. Resolution and mesh refinement also play a part in any computational analysis undertaken to assess surface profile effects: in the analyses presented, a nominal axi-symmetric geometry has been taken, with a finite non-smooth region on the boundary. Various surface roughness representations are modelled, and the significance of the characterized surface roughness type is investigated. It is shown that the applied load gives rise to a nominally uni-axial stress state of 90% of the yield, although surface roughness features have the effect of modifying the load path, and give rise to localized regions of plasticity near to the surface. The material of the test model is assumed to be elasto-plastic, and the development and evolution of plastic zones formed within the geometry are shown for multiple load cycles.

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Section: Geometry and Materials Considerationsmentioning

confidence: 99%

A computational study of the influence of surface roughness on material strength

et al. 2018

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“…It should be noted that the fatigue notch sensitivity q is variable with both K t and R. Since these selected data under R=−1 in refs. [14,27,[29][30][31][32][33][34][35][36][37][38][39][40][41][42] were measured with different K t , the q under the identical condition of K t =4 (Fig. 8) has to be calculated by the Kuhn-Hardrath equation [25]:…”

Section: Comparison Of Fatigue Notch Properties With Other Metallic Mmentioning

confidence: 99%

“…Comparing fatigue notch sensitivity and strength-modulus ratio of Ti2448 alloy with other metallic materials, including Mg alloys [30], Al alloys [31][32][33], Ti alloys [27,29,[34][35][36][37][38] and steels [14,[39][40][41][42]. modulus β type biomedical titanium alloys are potential for load-bearing applications to ensure long-term service safety because they are tolerant to notch, as evidenced by the decreased q of the α, (α+β) and β type alloys under the identical σ/E ratio.…”

Section: Figurementioning

confidence: 99%

Weak fatigue notch sensitivity in a biomedical titanium alloy exhibiting nonlinear elasticity

et al. 2017

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It is well known that metallic materials exhibit worse fatigue damage tolerance as they behave stronger in strength and softer in modulus. This raises concern on the long term safety of the recently developed biomechanical compatible titanium alloys with high strength and low modulus. Here we demonstrate via a model alloy, Ti-24Nb-4Zr-8Sn in weight percent, that this group of multifunctional titanium alloys possessing nonlinear elastic deformation behavior is tolerant in fatigue notch damage. The results reveal that the alloy has a high strength-to-modulus (σ/E) ratio reaching 2% but its fatigue notch sensitivity (q) is low, which decreases linearly from 0.45 to 0.25 as stress concentration factor increases from 2 to 4. This exceeds significantly the typical relationship between σ/E and q of other metallic materials exhibiting linear elasticity. Furthermore, fatigue damage is characterized by an extremely deflected mountain-shape fracture surface, resulting in much longer and more tortuous crack growth path as compared to these linear elastic materials. The above phenomena can be explained by the nonlinear elasticity and its induced stress relief at the notch root in an adaptive manner of higher stress stronger relief. This finding provides a new strategy to balance high strength and good damage tolerance property of metallic materials.

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“…Normally, the attained sheet edge roughness after machining is a function of the material property (texture) [5] and in some cases the technique used to process the sheet material [6]. Machining induced edge defects also act as stress raisers thereby optimizing the fatigue and fracture life [7][8][9], residual stress and hardness [10] of components. Electric discharge machining (EDM) and Abrasive water jet (AWJ) cutting are non-traditional cutting techniques adopted by industry mainly due to their better surface finish and versatility compared to their conventional counterparts [11].…”

Section: Introductionmentioning

confidence: 99%

Examining Failure Behaviour of Commercially Pure Titanium During Tensile Deformation and Hole Expansion Test

Kwame¹,

Yakushina²,

Blackwell³

2020

J. Mater. Appl.

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Hole expansion ratio is a material parameter which defines the extent to which sheet metals are formed. Research has shown that, the stress state observed at the hole edge after hole expansion test is similar to those observed during conventional uniaxial tensile test. However, conventional tensile test methods are not efficient in evaluating material edge formability. This work utilised optical non-contact measuring techniques to examine failure behaviour during tensile test and hole expansion test of commercially pure titanium sheet, fabricated with either abrasive water jet cutting or electric discharge machining. The work found that, the deformation mode in conventional tensile testing are governed by localised necking and subsequently diffused necking prior to failure. Deformation mode observed in hole expansion test is characterised by localised necking with no visible occurrence of diffused necking prior to failure. The highest strains are concentrated at the hole edge during hole expansion test due to their sensitivity to the hole preparation method with accompanying multiple localised necking sites resulting in non-uniform deformation. Strains become concentrated in the bulk material microstructure rather than the machined edge during tensile testing resulting in single localised deformation site and a more homogenous deformation.

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Effects of surface roughness and notch on fatigue properties for Ti–5Al–2.5Sn ELI alloy at cryogenic temperatures

Cited by 33 publications

References 12 publications

A computational study of the influence of surface roughness on material strength

A computational study of the influence of surface roughness on material strength

Weak fatigue notch sensitivity in a biomedical titanium alloy exhibiting nonlinear elasticity

Examining Failure Behaviour of Commercially Pure Titanium During Tensile Deformation and Hole Expansion Test

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