Constitutive Modeling of Low-Temperature Superplastic Flow of Ultrafine Ti-6Al-4V Sheet Material

2010 ◽  
Vol 433 ◽  
pp. 235-240 ◽  
Author(s):  
S. Lee Semiatin ◽  
Gordon A. Sargent
Keyword(s):  
Low Temperature ◽  
Flow Behavior ◽  
Sheet Material ◽  
Superplastic Flow ◽  
Flow Softening ◽  
Flow Localization ◽  
Flow Curves ◽  
Localization Model ◽  
Simple Flow ◽  
Stress Flow

The low-temperature superplastic flow behavior of two lots of Ti-6Al-4V sheet with an ultrafine microstructure was modeled. One lot (Sheet A) had an equiaxed-alpha starting microstructure; the flow stress/flow hardening exhibited by this material was explained on the basis of the Bird-Mukherjee-Dorn constitutive equation. The other material (Sheet B), having a mixed equiaxed- and remnant-lamellar alpha microstructure, underwent flow softening, flow hardening, or steady-state flow depending on test temperature and strain rate. These behaviors were interpreted in the context of a dynamic spheroidization model. The apparent flow softening at the end of all of the flow curves was explained using a simple flow-localization model.

Application of preliminary low-temperature heating for cold forming of complex parts on cold former

2021 ◽  
pp. 396-399
Author(s):  
V.Yu. Lavrinenko ◽  
Yu.A. Lavrinenko ◽  
R.S. Fayruzov ◽  
A.S. Ayrapetyan ◽  
A.S. Kirsanov
Keyword(s):  
Low Temperature ◽  
Heating Temperature ◽  
Experimental Studies ◽  
Life Time ◽  
Cold Forging ◽  
Flow Curves ◽  
Cold Forming ◽  
40Kh13 Steel ◽  
Temperature Heating ◽  
Complex Parts

The results of experimental studies of flow curves of 32CrB4, 20G2R and 1.4034 (analogue of 40Kh13 steel) steels at different heating temperature of workpieces are presented. Rational intervals of preliminary lowtemperature heating of workpieces made of studied steels are obtained. It allows to decrease forces during cold forging, loads on the working tool and to increase of tool life time up to 2 times.

scholarly journals Rheology of THF hydrate slurries at high pressure

2020 ◽  
Vol 75 ◽  
pp. 16
Author(s):  
Paulo H. de Lima Silva ◽  
Mônica F. Naccache ◽  
Paulo R. de Souza Mendes ◽  
Adriana Teixeira ◽  
Leandro S. Valim
Keyword(s):  
High Pressure ◽  
Low Temperature ◽  
Natural Gas ◽  
Deep Water ◽  
Flow Behavior ◽  
Oil Industry ◽  
Production Lines ◽  
Oil Emulsions ◽  
Slurry Viscosity ◽  
Financial Losses

One of the main issues in the area of drilling and production in deep and ultra-deep water in the oil industry is the formation of natural gas hydrates. Hydrates are crystalline structures resembling ice, which are usually formed in conditions of high pressure and low temperature. Once these structures are formed, they can grow and agglomerate, forming plugs that can eventually completely or partially block the production lines, causing huge financial losses. To predict flow behavior of these fluids inside the production lines, it is necessary to understand their mechanical behavior. This work analyzes the rheological behavior of hydrates slurries formed by a mixture of water and Tetrahydrofuran (THF) under high pressure and low temperature conditions, close to the ones found in deep water oil exploration. The THF hydrates form similar structures as the hydrates originally formed in the water-in-oil emulsions in the presence of natural gas, at extreme conditions of high pressure and low temperature. The experiments revealed some important issues that need to be taken into account in the rheological measurements. The results obtained show that the hydrate slurry viscosity increases with pressure. Oscillatory tests showed that elasticity and yield stress also increase with pressure.

scholarly journals Low temperature superplastic flow of yttria stabilized tetragonal zirconia polycrystals

1994 ◽  
Vol 13 (2) ◽  
pp. 103-111 ◽  
Author(s):  
M.M.R. Boutz ◽  
A.J.A. Winnubst ◽  
A.J. Burggraaf ◽  
M. Nauer ◽  
C. Carry
Keyword(s):  
Low Temperature ◽  
Tetragonal Zirconia ◽  
Superplastic Flow

Rheology of Brine-Based Fuzzy-Ball Drilling Fluids in Deepwater Drilling

2019 ◽  
Author(s):  
Zhaochuan Li ◽  
Lihui Zheng ◽  
Panfeng Wei ◽  
Xiaojuan Dai ◽  
Weian Huang
Keyword(s):  
Low Temperature ◽  
Yield Point ◽  
Apparent Viscosity ◽  
High Salinity ◽  
Flow Behavior ◽  
Plastic Viscosity ◽  
Rheological Parameters ◽  
Working Fluid ◽  
Drilling Fluids ◽  
Deepwater Drilling

Abstract In deepwater drilling, the rheology of traditional drilling fluid is uncontrollable since the fluid usually mixes with brine and encounters low temperature. A solution may be to use the newly designed brine-based fuzzy-ball drilling fluids (BFDFs) since these have a well-adapted rheology under high salinity and low temperature condition. This has the potential to make drilling safer and more efficient. In this experiment, the rheological properties of BFDFs under test conditions were characterized with a rheometer by varying salinity (2 to 20 mass%) and temperature (4 to 80 °C). The rheological parameters considered are apparent viscosity (AV), plastic viscosity (PV), yield point (YP), and θ6 reading. To characterize the magnitudes of changes of the rheological parameters and their low temperature dependence, their ratios at 4 and 25 °C, and 4 and 80 °C were calculated. The results showed that the apparent viscosity (AV), the plastic viscosity (PV), the yield point (YP), and θ6 reading of BFDFs increased slightly with the decrease of salinity and temperature. The ratios of rheological parameters at 4 and 25 °C were close to unity, while the ratios at 4 and 80 °C were about two. The flow behavior of BFDFs under high salinity and low temperature condition was stable. Therefore, brine could be used as the base fluid for BFDFs. Theoretically, the flow behavior of BFDFs under low temperature condition seems to follow the Herschel-Bulkley model. Practically, the tests indicated that the BFDFs possess a strong tolerance to sandstone cuttings and Cabentonite, an excellent inhibitive property to shaly cuttings, weak corrosive characteristics against N80 casing steel, excellent lubricity properties, and remarkable biodegradability. In summary, the empirical results showed that the newly designed fuzzy-ball working fluid can use brine instead of fresh water as based fluid and maintain remarkable properties under high salinity and low temperature condition. Properties of BFDFs could basically satisfy the requirement of deepwater drilling work.

scholarly journals Constitutive Relationship for Hot Deformation of TB18 Titanium Alloy

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Qiang Fu ◽  
Wuhua Yuan ◽  
Wei Xiang
Keyword(s):  
Titanium Alloy ◽  
Flow Stress ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Hot Deformation ◽  
Flow Behavior ◽  
Peak Stress ◽  
Constitutive Relationship ◽  
Flow Localization ◽  
Phase Zone

In the present work, the hot deformation behavior of TB18 titanium alloy was investigated by isothermal hot compression tests with temperatures from 650 to 880°C and strain rates from 0.001 to 10 s−1. The flow curves after friction and temperature correction show that the peak stress decreased with the temperature increase and the strain rate decrease. Three typical characteristics of flow behavior indicate the dynamic softening behavior during hot deformation. At a strain rate of 0.001∼0.01 s−1, the flow stress continues to decrease as the strain rate increases after the flow stress reaches the peak stress; the flow softening mechanism is dynamic recovery and dynamic recrystallization at a lower temperature and dynamic recrystallization at a higher temperature. The discontinuous yielding phenomenon could be seen at a strain rate of 1 s−1, dynamic recrystallization took place in the β single-phase zone, and flow localization bands were observed in the α + β two-phase zone. At a higher strain rate of 10 s−1, the flow instabilities were referred to as the occurrence of flow localization by adiabatic heat. Constitutive equation considering the compensation of strain was also established, and the results show high accuracy to predict the flow stress with the correlation coefficient of 99.2% and the AARE of 6.1%, respectively.

Low temperature flow behavior of B2 intermetallic phase in Ti–Al–Nb system

2006 ◽  
Vol 424 (1-2) ◽  
pp. 71-76 ◽  
Author(s):  
Hari Shankar ◽  
N. Eswara Prasad ◽  
A.K. Singh ◽  
T.K. Nandy
Keyword(s):  
Low Temperature ◽  
Flow Behavior ◽  
Intermetallic Phase

Modelling of Flow Behaviour of Magnesium Alloys

2016 ◽  
Vol 716 ◽  
pp. 360-367
Author(s):  
Carlo Bruni
Keyword(s):  
Numerical Simulation ◽  
High Temperature ◽  
Low Temperature ◽  
Magnesium Alloys ◽  
Flow Curve ◽  
Flow Behaviour ◽  
Temperature Deformation ◽  
Flow Curves ◽  
High Deformation ◽  
Modelling Approach

The present investigation aims at studying the flow behaviour of magnesium alloys under different conditions in terms of temperature, deformation velocities and deformation. The modelling approach was based on a proposed equation to model the shape of each flow curve through different variables. The modelled flow curves were subsequently compared with those obtained with experiments. The models were validated on flow curves not used in the building stage. It was observed that, for low temperature values, high deformation velocities and deformations the final part of the flow curve has to be adapted in order to be adopted for the description of material in the numerical simulation. In other words it needs to be extrapolated. Also for the high temperature, the flow softening has to be limited in order to allow the extrapolation queue required for elevated deformations. The deformation value at which the extrapolation can start can be predicted with an other proposed equation detailed in the paper.

A Suitable Criterion for Precise Determination of Incipient Necking in Sheet Materials

2006 ◽  
Vol 519-521 ◽  
pp. 111-116 ◽  
Author(s):  
Q. Situ ◽  
Mukesh K. Jain ◽  
M. Bruhis
Keyword(s):  
Strain Rate ◽  
Sheet Material ◽  
Forming Limit Diagram ◽  
Precise Determination ◽  
Forming Limit ◽  
Strain History ◽  
Flow Localization ◽  
Major Strain ◽  
Strain Paths

Forming limit diagram (FLD) is a measure of the formability of a sheet material. The major-minor strain pairs that are closest to the neck on multiple specimens of various strain paths are utilized to construct a boundary between safe and unsafe zones. The challenge to obtain the FLD is the determination of incipient necking. Three approaches to determine the limit strains have been investigated and compared in this research in order to establish the optimal one for implementation: (1) commonly used Bragard criterion ( 1)e Br with periodic grids; (2) tracking the region of large local strains from strain history to locate the instance when critical major strain ( 1)e cr happens; (3) post-processing of strain history to locate the inflection in the major strain rate curve 1 max (e&&) at the onset of localization. The last criterion of inflection in strain rate 1 max (e&&) carries both a numerical and a physical meaning towards developing an understanding of flow localization, formability and fracture.

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