scholarly journals Influence on strain-rate history effects on the development of necking instabilities under dynamic loading conditions

2021 ◽  
Author(s):  
Nicolas Jacques ◽  
Jose Rodriguez-Martinez
Keyword(s):  
Strain Rate ◽  
Dynamic Loading ◽  
Strain Rate Sensitivity ◽  
Work Hardening ◽  
Rate Sensitivity ◽  
Neck Formation ◽  
History Effects ◽  
Instantaneous Strain ◽  
Instantaneous Strain Rate Sensitivity ◽  
Dynamic Loading Conditions

The present paper is devoted to the analysis of strain-rate history effects on neck formation under dynamic loading. For materials presenting strain-rate history effects, two different strain-rate sensitivities should be distinguished: the instantaneous strain-rate sensitivity and the work-hardening strain-rate sensitivity. We have analysed the relative contributions of these two kinds of strain-rate sensitivities to neck retardation for two different configurations: a bar under impact tension and a dynamically expanding ring. For this purpose, we have developed finite element models and, for the second configuration, an analytical model based on the linear stability analysis. The obtained results show that strain-rate history effects have a significant influence on the onset and development of necking. The reason of thisphenomenon is that, contrary to the instantaneous strain-rate sensitivity, the work-hardening strain-rate sensitivity does not contribute to delay the neck formation.

Instantaneous strain rate sensitivity of wrought AZ31 magnesium alloy

2013 ◽  
Vol 49 ◽  
pp. 173-180 ◽  
Author(s):  
E. Karimi ◽  
A. Zarei-Hanzaki ◽  
M.H. Pishbin ◽  
H.R. Abedi ◽  
P. Changizian
Keyword(s):  
Magnesium Alloy ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Az31 Magnesium Alloy ◽  
Instantaneous Strain ◽  
Instantaneous Strain Rate Sensitivity

scholarly journals Effect of Cell Wall Ductility and Toughness on Compressive Response and Strain Rate Sensitivity of Aluminium Foam

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Alexandra Byakova ◽  
Svyatoslav Gnyloskurenko ◽  
Andrey Vlasov ◽  
Nikolay Semenov ◽  
Yan Yevych ◽  
...  
Keyword(s):  
Cell Wall ◽  
Strain Rate ◽  
Dynamic Loading ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Melt Processing ◽  
Wall Material ◽  
Static Compression ◽  
Quasi Static Compression ◽  
Al Foams

The study presents the effect of cell wall ductility and toughness on the compressive behaviour of closed-cell Al foams under static and dynamic loading and localised deformation by indentation. Two kinds of Al alloys including relatively ductile AlSiMg alloy and high-strength AlZnMg alloy, which comprises a great amount of brittle eutectic domains, were used as matrix materials. Both kinds of Al foams were fabricated via newly developed melt processing using the CaCO3-foaming agent without Ca additive. Mechanical behaviour of Al foams under quasi-static compression and indentation was examined and compared with that performed under dynamic loading using direct impact tests. Characteristic events revealed in deformation patterns of Al foams at quasi-static compression were also monitored with the CCD camera. Significant differences in stress-strain response and strain rate sensitivity of Al foams arose from the difference in the microstructure, and hence, ductility and toughness of the cell wall material were investigated and discussed.

Effect of Hot Extrusion on the Flow Behaviour of a Nickel-Based P/M Superalloy

2019 ◽  
Vol 298 ◽  
pp. 43-51
Author(s):  
Jia Yong Si ◽  
Song Hao Liu ◽  
Long Chen
Keyword(s):  
Activation Energy ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Work Hardening ◽  
Rate Sensitivity ◽  
Hot Extrusion ◽  
Turbine Disk ◽  
Flow Behaviour ◽  
Strain Rates ◽  
Work Hardening Rate

This research investigated the effect of hot extrusion on the flow behaviour of nickel-based superalloy FGH4096 by hot compression experiments in the temperature range from 1020 to 1110 °C and strain rates ranging from 0.1 to 0.001 s-1. The influence of the hot extrusion on the initial microstructures, work hardening rate, strain rate sensitivity, and activation energy of deformation were discussed. The results show that the extruded microstructure is constituted by the fine dynamic recrystallisation of grains. The true strain-true stress curves show that the as-HIPed and as-HEXed FGH4096 superalloy present double flow stress peaks and discontinuous flow softening. The as-HEXed FGH4096 is easily dynamically softened at high temperatures and high strain rates compared with as-HIPed microstructures. As for the work hardening rate, the as-HEXed FGH4096 exhibits higher θ values than that of as-HIPed. It is beneficial to the homogenous deformation and grain refinement during subsequent turbine disk forging. Comparing to as-HIPed FGH4096, the highest strain rate sensitivity value of as-HEXed is 0.306 at 1110 °C. The isothermal superplastic forging of a P/M turbine disk may be carried out at this temperature. The deformation activation energy value of the as-HIPed FGH4096 is lower which means that dislocation sliding and climbing can be easily initiated in the as-HIPed alloy.

Work-hardening effect and strain-rate sensitivity behavior during hot deformation of Ti–5Al–5Mo–5V–1Cr–1Fe alloy

2015 ◽  
Vol 82 ◽  
pp. 84-90 ◽  
Author(s):  
Yang Nan ◽  
Yongquan Ning ◽  
Houquan Liang ◽  
Hongzhen Guo ◽  
Zekun Yao ◽  
...  
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Work Hardening ◽  
Hot Deformation ◽  
Rate Sensitivity ◽  
Hardening Effect

Strain Rate Dependence of the Flow Stress and Work-Hardening of Single Crystals of NI3(Al,Hf)B

1994 ◽  
Vol 364 ◽  
Author(s):  
S. S. Ezz ◽  
Y. Q. Sun ◽  
P. B. Hirsch
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Temperature Dependence ◽  
Single Crystals ◽  
Yield Stress ◽  
Strain Rate Sensitivity ◽  
Work Hardening ◽  
Room Temperature ◽  
Rate Sensitivity ◽  
Controlling Mechanism

AbstractThe strain rate sensitivity ß of the flow stress τ is associated with workhardening and β=(δτ/δln ε) is proportional to the workhardening increment τh = τ - τy, where τy is the strain rate independent yield stress. The temperature dependence of β/τh reflects changes in the rate controlling mechanism. At intermediate and high temperatures, the hardening correlates with the density of [101] dislocations on (010). The nature of the local obstacles at room temperature is not established.

Effect of Annealing Treatments on Strain Rate Sensitivity and Anisotropy in a Magnesium Alloy Processed by Severe Rolling

2010 ◽  
Vol 638-642 ◽  
pp. 1524-1529 ◽  
Author(s):  
J.A. del Valle ◽  
Oscar A. Ruano
Keyword(s):  
Magnesium Alloy ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Work Hardening ◽  
Basal Slip ◽  
Plastic Anisotropy ◽  
Rate Sensitivity ◽  
Az61 Magnesium Alloy ◽  
Work Hardening Rate ◽  
R Value

The effect of annealing treatments on the evolution of the strain rate sensitivity with strain of AZ61 magnesium alloy processed by severe rolling was investigated and related to previous results on normal plastic anisotropy (r-value). The various annealing treatments produce two effects on the microstructure: grain coarsening and slight weakening of the texture. In addition, these treatments produce a noticeable decrease in strain rate sensitivity and an increase of work hardening rate that is related to the decrease of the anisotropy. It is concluded that these effects are related to an enhanced contribution of basal slip as a consequence of the microstructural changes induced by the annealing treatments.

Microstructures with extraordinary dynamic work hardening and strain rate sensitivity in Al0.3CoCrFeNi high entropy alloy

2018 ◽  
Vol 734 ◽  
pp. 42-50 ◽  
Author(s):  
Sindhura Gangireddy ◽  
Bharat Gwalani ◽  
Kaimiao Liu ◽  
Rajarshi Banerjee ◽  
Rajiv S. Mishra
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Work Hardening ◽  
Rate Sensitivity ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Dynamic Work
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