Predicting dwell fatigue life in titanium alloys using modelling and experiment

Xu, Yingjie; Joseph, Susmitha; Karamched, Phani; Fox, Kate; Rugg, David; Dye, David

doi:10.1038/s41467-020-19470-w

Cited by 88 publications

(29 citation statements)

References 54 publications

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“…Due to the stress level being quite low to activate basal slip in this experiment, grains oriented favourably for prism slip systems were classified as 'soft' grains. Xu et al [7] suggested that the cold dwell fatigue and the dwell debit is sensitive to the dwell stress, which agrees well with the observations in this work. The origin of the dwell debit is the activation of slip systems, resulting in an accumulation of plastic strain during the stress dwell, which leads to load shedding from 'soft' grains to neighbouring 'hard' grains.…”

Section: Discussionsupporting

confidence: 93%

“…This is also confirmed by the increase of GND density in these grains as temperature rises and shown in Figure 11(i) and 11(j). GND densities at the grain boundaries were significantly higher than that within the grains, showing a dislocation pile-up [7,41] at the grain boundaries. For the rogue grain pair, the initial stress difference across the grain boundary increases slightly for T = 120 • C compared to room temperature, then drops at higher temperature.…”

Section: Load Sheddingmentioning

confidence: 91%

“…This leads to load shedding onto grains badly orientated for slip (i.e. 'hard' grains with crystallographic c-axis of the α-Ti grain nearly parallel to the loading direction) [7]. The 'hard' oriented grain, due to higher elastic modulus, encounters a stress increase within the grain.…”

Section: Introductionmentioning

confidence: 99%

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Cold dwell behaviour of Ti$_6$Al alloy: Understanding load shedding using digital image correlation and crystal plasticity simulations

Yi¹,

Grilli²,

Karamched³

et al. 2021

Preprint

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Digital image correlation (DIC) and crystal plasticity simulation were utilised to study cold dwell behaviour in a coarse grain Ti-6Al alloy at 3 different temperatures up to 230 • C. Strains extracted from large volume grains were measured during creep by DIC and were used to calibrate the crystal plasticity model. The values of critical resolved shear stresses (CRSS) of the two main slip systems (basal and prismatic) were determined as a function of temperature. Stress along paths across the boundaries of two grain pairs, (1) a 'rogue' grain pair and (2) a 'non-rogue' grain pair, were determined at different temperatures. Load shedding was observed in the 'rogue' grain pair, where a stress increment during the creep period was found in the 'hard' grain. At elevated temperatures, 120 • C was found to be the worst case scenario as the stress difference at the grain boundaries of these two grain pairs were found to be the largest among the three temperatures. This can be attributed to the fact that the strain rate sensitivity of both prismatic and basal slip systems is at its greatest in this worst case scenario temperature.

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Section: Discussionsupporting

confidence: 93%

Section: Load Sheddingmentioning

confidence: 91%

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Cold dwell behaviour of Ti$_6$Al alloy: Understanding load shedding using digital image correlation and crystal plasticity simulations

Yi¹,

Grilli²,

Karamched³

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…Dwell fatigue has been a vital issue for several decades in aeroengine industry as it significantly reduces the lifetime of titanium-based components [1][2][3][4]. It has been known that some dual-phase Ti alloys, for example Ti6242 and IMI685, are known as dwell sensitive, while others like Ti6246 are not [5][6], where this is potentially associated with the ratesensitive deformation behaviour.…”

Section: Introductionmentioning

confidence: 99%

Local strain rate sensitivity of α+β phases within dual-phase Ti alloys

Jun

2022

J. Phys.: Conf. Ser.

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Using in-situ micropillar compression, the local strain rate sensitivity in Ti6242 and Ti6246 has been investigated to strengthen our understanding on the rate- and slip system-sensitive deformation of dual-phase Ti alloys. Electron backscatter diffraction (EBSD) was used to find target grains anticipating basal and primatic slip activities under compression test. Micropillars with similar α orientation and incomparable β morphology were made by a focused ion beam (FIB). Strain rate sensitivity (SRS) was determined based on the constant strain rate method (CSRM). The marked difference of SRS is found in the α+β of both alloys such that in Ti6242 the SRS in the basal slip is considerably higher than that in the prism whilst both slips in Ti6246 show somewhat similar SRS, inferring that either local chemical effects or the β morphology could affect rate-sensitive deformation behaviour.

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“…Also, the fatigue failure of the part was observed to be due to the creation of microvoids just before the failure. Xu et al (2020) used numerical and experimental methods to predict the dwell fatigue life of Ti834 titanium alloy using a discrete dislocation plasticity model. They investigated the effects of microstructure and its defects on the fatigue failure mechanisms that occurred on the parts representative of the jet engine spin test.…”

Section: Introductionmentioning

confidence: 99%

Improvement of Fatigue Life and Dynamic Strength of an Engine Mounting Bracket Using Experimental and Numerical Approaches

Hosseini

Kelardeh

Heidari

et al. 2021

Iran J Sci Technol Trans Mech Eng

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The engine mounting bracket is one of the most sensitive parts of an automobile that is used to connect the engine to the body of the vehicle. Under operating conditions, it is subjected to static, cyclic, and exceptional loads. Since this part is generally manufactured by the casting method, the casting-induced defects can affect its service life. In this study, an engine mounting bracket was first subjected to an experimental static load test, the results of which showed the absence of defects. The endurance limit was then measured experimentally using the high-cycle fatigue test. According to the results of the staircase-Locati fatigue test, the relative mean resistance load was obtained as 1.24 with a relative scatter of 0.07 which fell in the unsafe operating region of the engine mounting bracket. Therefore, a finite element analysis was conducted to determine the critical regions on the part and modify its geometric shape to improve its performance. The crack onset and growth regions obtained in the fatigue tests agreed well with the critical areas identified in the finite element analysis. After modifying the geometric shape and eliminating production defects, several experimental tests were performed to evaluate the endurance limit. The results showed that an increase of only 0.9% in the mass of the engine mounting bracket, decreased stress concentration up to 37%. The relative mean resistance load was increased up to 1.33 with a relative scatter of 0.06, which provided safe performance in the vehicle operating condition. Finally, the modified bracket passed the dynamic load test without any crack and loosening of the screws during the assembly process.

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Predicting dwell fatigue life in titanium alloys using modelling and experiment

Cited by 88 publications

References 54 publications

Cold dwell behaviour of Ti$_6$Al alloy: Understanding load shedding using digital image correlation and crystal plasticity simulations

Cold dwell behaviour of Ti$_6$Al alloy: Understanding load shedding using digital image correlation and crystal plasticity simulations

Local strain rate sensitivity of α+β phases within dual-phase Ti alloys

Improvement of Fatigue Life and Dynamic Strength of an Engine Mounting Bracket Using Experimental and Numerical Approaches

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