Messung der wahre Spannung - wahre Dehnung-Kurve nach partiellem Aufschmelzen zur Ermittlung der Eigenschaften von Stahl beim Stranggieben / Measuring of the True Stress-True Strain Curve to Investigate the Properties of Steel in Continuous Casting

The Nickel-base superalloy samples were prepared by the isothermal forging in strain rate 1s-1 at deformation temperature 1070°C with different strain levels. The EBSD was carried out in order to investigate the microstructural changes that took place due to strain level. The result is the samples has no apparent dynamic recrystallization behavior in hot deformation in 1s-1 at 1070°C. The true stress-true strain curve has two peak values in the strain level of 20% and 60%, and one valley value in the strain level of 50%. The first peak value is result in the activation of slip system and the beginning of recrystallization and the second peak value of the true stress-true strain curve is result in the inhibition of activation of slip system and grain growth by the dislocation density. The work hardening behavior of P/M Nickel-base superalloy may be related to the size ratio of γ’ phase with grain size.

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A Simple and Efficient Method for Obtaining the Whole-Range Uniaxial Tensile Properties of Pipeline Steel

Metals ◽

10.3390/met8070555 ◽

2018 ◽

Vol 8 (7) ◽

pp. 555

Author(s):

Lingzhen Kong ◽

Lingbo Su ◽

Xiayi Zhou ◽

Liqiong Chen ◽

Jie Chen ◽

...

Keyword(s):

Finite Element ◽

Finite Element Model ◽

Pipeline Steel ◽

True Strain ◽

Strain Curve ◽

Element Model ◽

True Stress ◽

Material Behavior ◽

Uniaxial Tensile ◽

Output Data

To obtain the whole-range true stress-true strain curves of API X65, a method is proposed based on the equal proportion principle and digital images. The tensile elongation was obtained by tracing the gauge points on the specimen surface, and the true strain and true stress of API X65 were calculated according to the formulae. The obtained true stress-true strain curves were validated by a 3-D finite element model. The true stress-true strain curve was set as the input data, while the engineering stress-engineering strain curve was set as the output data. The output data of the finite element model was the same as that of the experiment test. The findings imply that the proposed method could acquire reliable, whole-range true stress-true stain curves. These curves, which depict the material behavior of pipeline steel from initial elongation to fracture, could provide basic data for pipeline defect tolerance limit analysis and fracture assessment.

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Mechanical Properties and Serration Behavior of a NiCrFeCoMn High-Entropy Alloy at High Strain Rates

Materials ◽

10.3390/ma13173722 ◽

2020 ◽

Vol 13 (17) ◽

pp. 3722

Author(s):

Ruoyu Liu ◽

Xianrui Yao ◽

Bingfeng Wang

Keyword(s):

Mechanical Properties ◽

Electron Microscope ◽

High Strain ◽

True Strain ◽

Strain Curve ◽

True Stress ◽

High Entropy Alloy ◽

Strain Rates ◽

High Entropy ◽

Serration Behavior

Serration behavior is a kind of plastic instability phenomenon of materials, which widely exists in the high-entropy alloys and has influence on microstructure and mechanical properties. In this work, the microstructure and mechanical properties of a NiCrFeCoMn high-entropy alloy (HEA) were studied under high-speed impact. The microstructure of a NiCrFeCoMn HEA were investigated by optical microscope (OM), scanning electron microscope (SEM), electron backscatter diffraction (EBSD), and transmission electron microscope (TEM). The dislocation density increased with the true strain at high-strain-rate deformation, and the dislocations can be hindered and released continually by the twin layers, resulting in serration on the true stress—true strain curve. When values of the strain rates are 1250, 2000 and 4800 s−1, the yield strength of the deformed NiCrFeCoMn HEA are 510, 525 and 680 MPa, respectively. Moreover, the fluctuation of the serration became more serious with the increasing of the strain rate. Compared with the as-cast NiCrFeCoMn HEA, the true stress—true strain curve of the deformed NiCrFeCoMn HEAwas smoother.

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Grain Refinement of Mg-Al-Zn Alloy Bar during Hot Compression

Materials Science Forum ◽

10.4028/www.scientific.net/msf.706-709.1267 ◽

2012 ◽

Vol 706-709 ◽

pp. 1267-1272 ◽

Cited By ~ 2

Author(s):

Akira Watazu ◽

Masataka Hakamada ◽

Hajime Iwasaki ◽

Ichinori Shigematsu ◽

Naobumi Saito

Keyword(s):

Low Temperature ◽

Continuous Casting ◽

High Strain ◽

True Strain ◽

True Stress ◽

Hot Compression ◽

Grain Sizes ◽

Compression Speed ◽

Az80 Alloy ◽

Zn Alloy

Grain refinements during hot compression of continuous casting AZ80 alloy bars and extrusive AZ61, AZ80 alloy bars were observed. The hot compression true stress-true strain curves of extrusive AZ61 and AZ80 alloy had similar tendencies, which were that the true stress increased and had a peak around 0.2 true strain, and then the stress decreased and was almost even from about 0.4 true strain. The stress peaks shifted to the high strain side as the compression speed, true strain speed, increased. However, the stress peaks did not shift at different compression temperatures. Fine grains were obtained under the condition of high strain speed and low temperature, but the grain sizes were uneven at low temperature compression. The stress peaks in the hot compression true stress-true strain curves of continuous casting AZ80 did not shift at different compression temperatures. AZ80 forging products with fine grains are expected to be formed under various conditions by using continuous casting AZ80.

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Study on Constitutive Modeling for Large Deformation Behavior of Polyethylene Considering Strain Rate Effect

Volume 6B: Materials and Fabrication ◽

10.1115/pvp2013-97778 ◽

2013 ◽

Cited By ~ 1

Author(s):

Sijia Zhong ◽

Jianfeng Shi ◽

Jinyang Zheng

Keyword(s):

Strain Rate ◽

Large Deformation ◽

Constitutive Modeling ◽

Deformation Behavior ◽

True Strain ◽

True Stress ◽

Uniaxial Tensile ◽

Pipeline System ◽

Composite Effect ◽

Time Deformation

Polyethylene (PE) pipes have been applied in transportation of key energy medium such as natural gas in the past decades. The mechanical property of PE is of great importance for better design and safer application of PE pipeline system. The large deformation behavior is a key character of PE, not only for its significant strain rate sensitivity, but also for localized necking process after yielding. In this paper, a new constitutive modeling method was proposed to charaterize the rate-denpendent large deformation behavior of PE, in which the true stress is regarded as a function of true stain and true strain rate alone. Uniaxial tensile tests of PE were conducted under various cross-head speeds, and a digital camera was used to record the real-time deformation of specimens. By separating the composite effect into respective effect of local true strain and strain rate on the local true stress in the necking region, a phenomenological model for describing the rate-dependent deformation behavior under uniaxial tension was ealstablished. Model results were validated and found in good agreement with experimental data.

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