Stress–strain curves of metallic materials and post‐necking strain hardening characterization: A review

Tu, Shengwen; Ren, Xiaobo; He, Jianying

doi:10.1111/ffe.13134

Cited by 109 publications

(66 citation statements)

References 61 publications

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“…[ 19 ] The uniform elongation was determined as the engineering strain corresponding to the maximum tensile stress, and the total elongation was determined as the elongation of the original gauge length of the tensile specimen at a fracture. [ 20 ] These elongations as well as the yield and tensile strengths of all steel grades were higher than the total elongation guaranteed by the manufacturer.…”

Section: Methodsmentioning

confidence: 89%

Analytical Approach to Failure Determination of Advanced High‐Strength Steel in Stretch‐Bending Mode

Lee

Barlat

2020

steel research int.

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Experimental and analytical studies on the stretch‐bending characteristics of advanced high‐strength steel sheets, primarily used in the automotive industry, are conducted. Herein, the stretch‐bending test, in which a specimen fixed at both ends is bent at its center with sharp punches until failure occurs, is conducted. Assuming that the failure of the material occurred at the maximum tensile force, a relationship between applied force and forming height is derived. Nine steels including high‐strength low‐alloy, dual‐phase, and transformation‐induced plasticity steels are tested, and the calculated results are compared with experimental limit‐forming heights. Finally, a failure criterion based on process variables and tensile properties of the material is proposed based on the deformation in the sheet thickness direction.

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Section: Methodsmentioning

confidence: 89%

Analytical Approach to Failure Determination of Advanced High‐Strength Steel in Stretch‐Bending Mode

Lee

Barlat

2020

steel research int.

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“…A standard procedure for the determination of trues stress and the true strain was used: = (1 + ), = (1 + ), where and are true stress and true strain, respectively, and are engineering stress and engineering strain, respectively. This approach is correct if the specimen deforms uniformly without neck formation [30,31]. In situ observations of the specimens during high-temperature tensile deformation showed that at elongations lower than 300% (~1.4), specimens deformed uniformly.…”

Section: Resultsmentioning

confidence: 99%

On the Superplastic Deformation in Vanadium-Alloyed High-Nitrogen Steel

Астафурова¹,

Moskvina²,

Panchenko³

et al. 2019

Metals

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The experimental evidence for the realization of a superplastic behavior with 900% elongation in V-alloyed high-nitrogen austenitic Fe-19Cr-22Mn-1.5V-0.3C-0.6N steel was proposed. Using thermomechanical processing, a misoriented grain/subgrain austenitic microstructure with a high density of deformation-assisted defects and precipitates was developed in the steel. During high-temperature tensile deformation in a temperature interval from 850 to 1000 • C and strain-rate range from 4 × 10 −4 s −1 to 6 × 10 −3 s −1 , this microstructure demonstrated the characteristics of superplastic flow: elongation in the interval 400-900%, strain-rate sensitivity exponent m = 0.40-0.49, grain boundary sliding mechanism. The maximum elongation to failure (900%) was reached at deformation temperature 950 • C and strain rate 4 × 10 −4 s −1 .precipitation hardening [24][25][26][27]. Despite the visible advantages of the high-nitrogen austenitic steels as a construction material, there is limited data related to the possibility of realization of superplastic flow in them. Padmanabhan [1] mentioned a result of N. Narkevich, who reported 239% elongation in Fe-20Cr-20Mn-4.7V-1.14N (mass.%) steel tested at temperature 950 • C and strain-rate 4.6 × 10 −4 s −1 . Such relatively high elongation was obtained for the steel after a solid-solution treatment followed by 50% cold-rolling and age-hardening at 700 • C for 1 h. The microstructure of the steel during high-temperature tests, probably, was not strictly single-phase austenitic but also contained Cr-based and V-based nitrides. This result lied in line with those for single-phase austenitic stainless steels, in which the superplastic-assisted elongation does not exceed 280% [1,28]. Mineura [29] reported much higher elongation (527%) for Fe-20Cr-10Ni-0.7N (mass.%) steel at temperature 800 • C and strain rate 8 × 10 −4 s −1 . They used two-step cold rolling with intermediate anneal at 1000 • C for obtaining fine-grained austenitic structure stabilized by fine chromium nitrides. Vanadium-alloying promotes a homogeneous (continuous) reaction of precipitate hardening in austenitic CrMn steels [24], and this fact could provide higher stability of the fine-grained structure during high-temperature tests as compared to chromium nitrides. Therefore, there is a potential for improvement of the values for the superplastic elongation obtained by Mineura [29].This paper aimed to find out the superplastic characteristics in high-nitrogen V-alloyed austenitic steel Fe-19Cr-22Mn-1.5V-0.3C-0.6N (mass.%).

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“…The slight advantage of FepiM is expected, as it explicitly considers the temperature inhomogeneity in the specimen and that is captured only in an average sense in the analytical methods [10]. Additionally, flow curves with several recrystallization cycles are reproduced well, which is difficult to achieve using conventional inverse modeling based on flow curve equations [5]. Finally, the FepiM approach proved to be more versatile than other piecewise approaches like IFD [16], as it was successfully applied to compression tests where a strain measurement inside the specimen using DIC is impossible.…”

Section: Discussionmentioning

confidence: 99%

“…Cao et al [15] recently determined flow curves beyond necking from tensile test experiments by optimizing parameters of a modified Swift constitutive law. However, the accuracy of these models highly depends on the a priori chosen constitutive model [5]. In addition, flow curve description for materials exhibiting complex flow behavior like multiple dynamic recrystallization cycles cannot typically be captured by these models.…”

Section: Inverse Methods For Isothermal Flow Curve Determinationmentioning

confidence: 99%

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FepiM: A Novel Inverse Piecewise Method to Determine Isothermal Flow Curves for Hot Working

Vuppala

Krämer

Lohmar

2021

Metals

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In forming simulations, flow curves are cardinal inputs to predict features, such as forming forces and material flow. The laboratory-scale experiments to determine them, like compression or tensile tests, are affected by deformation heating, restricting direct flow curve determination. In principle, the current analytical and inverse methods determine flow curves from these tests, but while the analytical methods assume a simplified temperature profile, the inverse methods require a closed-form flow curve equation, which mostly cannot capture complex material behavior like multiple recrystallization cycles. Therefore, the inverse piecewise flow curve determination method “FepiM” previously developed and published by the current authors is extended by introducing a two-step procedure to obtain isothermal flow curves at elevated temperatures and different strain rates. Thereby, the flow curve is represented as tabular data instead of an equation to reproduce complex flow curve shapes while also compensating the effect of inhomogeneous temperature profiles on the flow stress. First, a flow curve at the highest temperature is determined. In the second step, using this first flow curve as a reference, the flow curves at lower temperatures are obtained via interpolation. Flow curves from conventional compression tests for aluminum and copper in the temperature range of 20–500 °C are predicted, and it is shown that these flow curves can reproduce the experimental forces with a maximum deviation of less than 1%. Therefore, the proposed new piecewise method accurately predicts isothermal flow curves for compression tests, and the method could be further extended to highly inhomogeneous methods in the future.

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Stress–strain curves of metallic materials and post‐necking strain hardening characterization: A review

Cited by 109 publications

References 61 publications

Analytical Approach to Failure Determination of Advanced High‐Strength Steel in Stretch‐Bending Mode

Analytical Approach to Failure Determination of Advanced High‐Strength Steel in Stretch‐Bending Mode

On the Superplastic Deformation in Vanadium-Alloyed High-Nitrogen Steel

FepiM: A Novel Inverse Piecewise Method to Determine Isothermal Flow Curves for Hot Working

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