scholarly journals Elasto-thermoviscoplastic finite element analyses of cold upsetting and forging processes of S25C steel with dynamic strain aging considered

2021 ◽  
Vol 2047 (1) ◽  
pp. 012001
Author(s):  
S M Ji ◽  
M K Razali ◽  
K H Lee ◽  
W J Chung ◽  
M S Joun
Keyword(s):  
Finite Element ◽  
Flow Stress ◽  
Dynamic Strain Aging ◽  
Strain Aging ◽  
Large Strain ◽  
Flow Behavior ◽  
Cold Forging ◽  
Dynamic Strain ◽  
Strain Effect ◽  
Strain And Strain Rate

Abstract A practical methodology is presented to characterize the thermoviscoplastic flow stress at larger strain over the temperature range of cold metal forming using tensile and compression tests. Its importance is emphasized for non-isothermal finite element (FE) analysis of automatic multi-stage cold forging (AMSCF) process where maximum strain and strain rate exceed around 3.0 and 200/s, respectively. The experimental compressive flow stress is first characterized using traditional bilinear C-m model with high accuracy. It is employed for describing the closed-form function model to extrapolate the experimental flow stress over the experimentally uncovered ranges of state variables. The strain effect on the flow stress is then improved using the experimental tensile flow stress accurately calculated at large strain and room temperature. A complicated flow behavior of S25C characterized by its dynamic strain aging features is expressed by the presented methodology, which is utilized to analyze the test upsetting and AMSCF processes by the elasto-thermoviscoplastic finite element method for revealing the effects of flow stresses on the process.

scholarly journals A Modified Johnson-Cook Model for Ferritic-Pearlitic Steel in Dynamic Strain Aging Regime

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 528 ◽  
Author(s):  
Ashwin Moris Devotta ◽  
P. V. Sivaprasad ◽  
Tomas Beno ◽  
Mahdi Eynian ◽  
Kjell Hjertig ◽  
...  
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Dynamic Strain Aging ◽  
Strain Aging ◽  
Experimental Testing ◽  
Flow Behavior ◽  
Pearlitic Steel ◽  
Dynamic Strain ◽  
Model Parameters ◽  
Strain Rates

In this study, the flow stress behavior of ferritic-pearlitic steel (C45E steel) is investigated through isothermal compression testing at different strain rates (1 s−1, 5 s−1, and 60 s−1) and temperatures ranging from 200 to 700 °C. The stress-strain curves obtained from experimental testing were post-processed to obtain true stress-true plastic strain curves. To fit the experimental data to well-known material models, Johnson-Cook (J-C) model was investigated and found to have a poor fit. Analysis of the flow stress as a function of temperature and strain rate showed that among other deformation mechanisms dynamic strain aging mechanism was active between the temperature range 200 and 400 °C for varying strain rates and J-C model is unable to capture this phenomenon. This lead to the need to modify the J-C model for the material under investigation. Therefore, the original J-C model parameters A, B and n are modified using the polynomial equation to capture its dependence on temperature and strain rate. The results show the ability of the modified J-C model to describe the flow behavior satisfactorily while dynamic strain aging was operative.

Dynamic Strain Aging in Biomedical Co–Cr–Mo-Based Alloys with Nitrogen Doping

2012 ◽  
Vol 508 ◽  
pp. 141-145 ◽  
Author(s):  
Kenta Yamanaka ◽  
Manami Mori ◽  
Yun Ping Li ◽  
Yuichiro Koizumi ◽  
Akihiko Chiba
Keyword(s):  
Dynamic Strain Aging ◽  
Strain Aging ◽  
Room Temperature ◽  
Electron Backscatter Diffraction ◽  
Flow Behavior ◽  
Local Strain ◽  
Dynamic Strain ◽  
Compression Tests ◽  
Partial Dislocations ◽  
Plastic Deformation Behavior

The Plastic Deformation Behavior of a Biomedical Co–29Cr–6Mo–0.2N (wt.%) Alloy with a Fully γ (fcc) Matrix Was Studied by Compression Tests from Room Temperature to 1073 K. Serrated Stress–Strain Curves Caused by Dynamic Strain Aging (DSA) Was Clearly Observed at Temperatures of 773–973 K at a Strain Rate of 10−4s−1. Such a Flow Behavior Was Not Observed Significantly in other Conditions. Electron Backscatter Diffraction (EBSD) Analysis Revealed that Deformation Microstructures with DSA Occurrence Exhibited a Large Lattice Distortion over the Grains, while Local Strain Preferentially Increased in the Vicinity of Grain Boundaries in the Specimen Deformed at Room Temperature. Dislocations Were Dissociated into Stacking Faults (SFs) Bounded by Shockley Partial Dislocations both before and after Deformation; the DSA Observed in this Alloy Would Originate from the Interactions between Nitrogen Atoms and the Partial Dislocations/SFs.

scholarly journals Dynamic Plasticity Model for Rapidly Heated 1045 Steel Up to 1000°C

2021 ◽  
Vol 126 ◽  
Author(s):  
Steven P. Mates ◽  
Sheng-Yen Li
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Dynamic Strain Aging ◽  
Strain Aging ◽  
Gaussian Function ◽  
Machining Process ◽  
Dynamic Strain ◽  
Plasticity Model ◽  
Aging Effects ◽  
1045 Steel

The National Institute of Standards and Technology (NIST) developed an experimental technique to measure the dynamic flow stress of metals under rapid heating to study their time-dependent plastic response when heating times are short enough to interrupt or bypass thermally driven microstructural evolution. Such conditions may exist as chips are formed in the machining process. Measurements of American Iron and Steel Institute1045 steel behavior up to 1000 °C showed complex thermal softening due to dynamic strain aging effects and the diffusion-limited austenite transformation process beginning at the A1 temperature (712 °C). This paper proposes a constitutive model to capture the flow stress and hardening evolution of 1045 steel under rapidly heated conditions for simulating metal cutting. The model combines the Preston-Tonks-Wallace plasticity model, which uses five parameters to capture complex rate- and temperature-sensitive strain hardening, with a dual-rate-sensitivity model to capture the response of rapidly heated 1045 steel. Finally, a strain-rate-dependent Gaussian function is introduced to capture dynamic strain aging effects, which act over a narrow range of temperatures that change with strain rate. The proposed model is compared to existing plasticity models for 1045 steel over the range of data available and at a representative machining condition.

Dynamic strain aging and serrated flow behavior of Cr-Ti-B low carbon steel during warm deformation

2021 ◽  
Vol 172 ◽  
pp. 110828
Author(s):  
Ankang Huang ◽  
Zhigang Wang ◽  
Xin Liu ◽  
Qiangqiang Yuan ◽  
Jieyun Ye ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Dynamic Strain Aging ◽  
Strain Aging ◽  
Flow Behavior ◽  
Low Carbon Steel ◽  
Dynamic Strain ◽  
Low Carbon ◽  
Warm Deformation ◽  
Serrated Flow

Dynamic Strain Aging during the Plastic Flow of Metals

2007 ◽  
Vol 340-341 ◽  
pp. 823-828 ◽  
Author(s):  
Wei Guo Guo
Keyword(s):  
Experimental Data ◽  
Flow Stress ◽  
Plastic Flow ◽  
Dynamic Strain Aging ◽  
Strain Aging ◽  
Testing Machine ◽  
Strain Curve ◽  
Dynamic Strain ◽  
Polycrystalline Materials ◽  
Strain Rates

In the present paper, in order to better understand the third type “dynamic strain aging” occurring during the plastic flow of metals, the uniaxial compressive experimental data ever obtained in University of California, San Diego using an Instron servo-hydraulic testing machine and the Hopkinson technique are systematically analysed. These experimental data cover the plastic flow stress of several fcc, hcp, bcc polycrystalline materials and several alloys at a broad range of temperatures (77K – 1,100K) and strain rates (0.001/s – 10,000/s). In analysis, the appearing region of the “dynamic strain aging ” under different temperatures and strain rates are respectively plotted by the curves of stress vs temperature, and stress vs strain for fcc, hcp and bcc metals. The results show that: (1) this third type “dynamic strain aging ” occurs in all hcp, bcc and fcc polycrystalline or alloy materials, and there are different profiles of stress-strain curve; (2) the “dynamic strain aging ”occurs in a matching coincidence of the temperature and strain rate, its temperature region will shift to higher region with increasing strain rates; (3) bcc materials do not have an initial pre-straining strain as the onset of work-hardness rate change for the “dynamic strain aging ”; and (4) based on the explanations of dynamic strain aging with serration curves (Portevin-Lechatelier effect) and other explaining mechanisms of references, The mechanism of third DSA is thought as the rapid/continuous formation of the solute atmospheres at the mobile dislocation core by the pipe diffusion along vast collective forest dislocations to result in a continuous rise curve of flow stress. Finally, several conclusions are also presented.

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