scholarly journals Mechanistic basis of temperature-dependent dwell fatigue in titanium alloys

2017 ◽  
Vol 107 ◽  
pp. 185-203 ◽  
Author(s):  
Zebang Zheng ◽  
Daniel S. Balint ◽  
Fionn P.E. Dunne
Keyword(s):  
Titanium Alloys ◽  
Temperature Dependent ◽  
Dwell Fatigue ◽  
Mechanistic Basis

scholarly journals On the mechanistic basis of deformation at the microscale in hexagonal close-packed metals

2015 ◽  
Vol 471 (2178) ◽  
pp. 20140881 ◽  
Author(s):  
T. B. Britton ◽  
F. P. E. Dunne ◽  
A. J. Wilkinson
Keyword(s):  
Single Crystal ◽  
Titanium Alloys ◽  
State Of The Art ◽  
Plastic Anisotropy ◽  
Deformation Mechanisms ◽  
Hexagonal Close Packed ◽  
Dwell Fatigue ◽  
Crystallographic Slip ◽  
Rate Effects ◽  
Mechanistic Basis

This is an overview of micromechanical deformation mechanisms in hexagonal close-packed metals. We start with an in-depth discussion of single-crystal behaviour concerning crystallographic slip, plastic anisotropy and deformation twinning. We move on to discuss some complexities involved in polycrystalline deformation and modelling approaches, focusing on rate effects in titanium alloys that are thought to play a significant role in dwell fatigue. We finish our review with a brief commentary on current understanding and state-of-the-art techniques, and outline some key areas where further study is recommended.

scholarly journals Towards a better understanding of the dynamics of Aphis spiraecola Patch (Homoptera: Aphididae) populations in commercial alpine yarrow fields

2010 ◽  
Vol 42 (2) ◽  
pp. 103 ◽  
Author(s):  
Zulfaidah Penata Gama ◽  
Pablo Morlacchi ◽  
Giuseppe Carlo Lozzia ◽  
Johann Baumgärtner ◽  
Anna Giorgi
Keyword(s):  
Natural Enemy ◽  
Distributed Delay ◽  
Structured Populations ◽  
Temperature Dependent ◽  
Optimum Sample Size ◽  
Aphis Spiraecola ◽  
Different Temperatures ◽  
Mechanistic Basis ◽  
Age Structured ◽  
Optimum Sample

The spatial distribution of Aphis spiraecola Patch was studied in two commercial yarrow fields located in the Swiss and Italian Alps and represented by Taylor’s (1961) power law. The respective parameters indicate a highly aggregated distribution and lead to a high optimum sample size of 400-500 plants in the design of a sampling program. Opportunities for reducing the sampling efforts are discussed. The infestation patterns were studied on the basis of Vansickle’s (1977) time varying distributed delay adequate for modelling the dynamics of age-structured populations. Published literature data were used to parametrize the functions representing the temperature-dependent duration and survival of the nymphal and adult stage. Likewise, literature data were available to obtain reliable estimates for the parameters of the fecundity function comprising the reproductive profile and the number of nymphs produced at different temperatures. The field data were used to parametrize the functions for wing formation and a compound mortality compromising the effects of plant senescence, stem cutting and natural enemies. The model satisfactorily represented the observed infestation patterns. However, there are opportunities for improving parameter estimation and validation. Moreover, the separation of the compound mortality into host plant and natural enemy effects would improve the mechanistic basis of the model and lead towards a tool that could be used to study bottom-up and top-down effects in the yarrow-aphid-natural enemy system.

scholarly journals Mechanistic basis of oxygen sensitivity in titanium

2020 ◽  
Vol 6 (43) ◽  
pp. eabc4060
Author(s):  
Yan Chong ◽  
Max Poschmann ◽  
Ruopeng Zhang ◽  
Shiteng Zhao ◽  
Mohammad S. Hooshmand ◽  
...  
Keyword(s):  
Titanium Alloys ◽  
Oxygen Sensitivity ◽  
Poisoning Effect ◽  
Extreme Sensitivity ◽  
Mechanistic Basis ◽  
Oxygen Poisoning ◽  
Temperature Strain ◽  
Mechanistic View ◽  
Oxygen Impurities ◽  
Solute Strengthening

One of the most potent examples of interstitial solute strengthening in metal alloys is the extreme sensitivity of titanium to small amounts of oxygen. Unfortunately, these small amounts of oxygen also lead to a markedly decreased ductility, which in turn drives the increased cost to purify titanium to avoid this oxygen poisoning effect. Here, we report a systematic study on the oxygen sensitivity of titanium that provides a clear mechanistic view of how oxygen impurities affect the mechanical properties of titanium. The increased slip planarity of Ti-O alloys is caused by an interstitial shuffling mechanism, which is sensitive to temperature, strain rate, and oxygen content and leads to the subsequent alteration of deformation twinning behavior. The insights from our experimental and computational work provide a rationale for the design of titanium alloys with increased tolerance to variations in interstitial content, with notable implications for more widespread use of titanium alloys.

scholarly journals Understanding thermal alleviation in cold dwell fatigue in titanium alloys

2018 ◽  
Vol 111 ◽  
pp. 234-252 ◽  
Author(s):  
Zebang Zheng ◽  
Adam Stapleton ◽  
Kate Fox ◽  
Fionn P.E. Dunne
Keyword(s):  
Titanium Alloys ◽  
Dwell Fatigue

Temperature-Dependent Tension Plastic Deformation and Fracture Behavior of Ti-6.6Al-3.3Mo-1.8Zr-0.29Si Alloy at High Strain Rates

2014 ◽  
Vol 626 ◽  
pp. 115-120
Author(s):  
Jun Zhang ◽  
Qi Wei Zhang ◽  
Yang Wang
Keyword(s):  
Strain Rate ◽  
Titanium Alloys ◽  
High Strain ◽  
Impact Resistance ◽  
Strain Rates ◽  
Temperature Dependent ◽  
High Strain Rates ◽  
Tension Tests ◽  
Deformation And Fracture ◽  
Split Hopkinson

Titanium alloys have received great interest in the engineering applications requiring light weight and high impact resistance components. It is necessary to understand the mechanical properties of titanium alloys at high strain rates and various temperatures in the structural design. In the present paper, uniaxial tension tests at strain rates of 190, 500 and 1150s-1 and temperatures of 20, 150, 300°C are carried out using a modified split hopkinson tension bar system to investigate the effects of strain rate and temperature on tension behavior of the Ti-6.6Al-3.3Mo-1.8Zr-0.29Si alloy. Experimental results indicate that the alloy has the rate and temperature sensitivity and still keeps high strengths and toughness at temperature up to 300°C under high strain rate. SEM observations reveal that ductile fracture is the major fracture mode when the alloy is deformed at high strain rates.

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