The measurement uncertainty of reduction in area of metals in tensile testing system

Xu, Tao; Yu, Hongying; Liu, Zhenjun; Zheng, Zongwen

doi:10.1016/j.measurement.2015.01.018

Cited by 12 publications

(9 citation statements)

References 17 publications

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“…Therefore, it is not currently possible to assign a pre-determined set of temperatures and strain rates for the determination of the original mechanical property of a specimen by tensile testing. It is unwarranted that the present technology system and standard of tensile tests posits that the original mechanical property of the specimen can be determined by testing at a fixed temperature and strain rate [17,18]. The following situation may occur due to the measurement uncertainty.…”

Section: Paradox Of Tensile Testmentioning

confidence: 99%

“…For the experimental results in Figure 11, it is pointed out in Refs. [7,17,20] that the EDT corresponding to the strain rate is longer than the critical time of the grain boundary at 700 • C. It decreases and approaches this critical time with increasing strain rate, so as to increase the grain boundary concentration of the solute and reduce the elongation. It may be inferred from Figure 23 that the EDT corresponding to the strain rate is also longer than the critical time of atmosphere at 700 • C. It decreases and approaches this critical time with increasing strain rate, so as to increase the solute concentration of the atmosphere near dislocations and raise the yield strength [20].…”

Section: Measurement Uncertainty Of Yield Strengthmentioning

confidence: 99%

“…Recently, it has been indicated in Refs. [7,17,18,36] that the microscopic theory of elastic deformation in metal reveals the measurement uncertainty of mechanical property resulting from the variation of microscopic structure during the elastic deformation stage of tensile testing when the test temperature and strain rate vary. The variation in microscopic structure, changing the solute concentration at grain boundaries and around dislocations and thus the mechanical property, induces the measurement uncertainty.…”

Section: Mechanical Property Characterizationmentioning

confidence: 99%

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Measurement Uncertainty and Representation of Tensile Mechanical Properties in Metals

Wang

Ravi

2021

Metals

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The International Organization for Standardization Technical Committee for Metallic Materials—Tensile Testing stated in 2011 that temperature and strain rate variations would induce a change in the results of tensile tests, termed as the measurement uncertainty of tensile mechanical properties in metals. The uncertainty means that the tensile testing results of a specimen at a temperature and strain rate are not the original mechanical properties possessed prior to the testing. Hence, since the time of Galileo the results of tensile testing have been incorrectly interpreted as the original mechanical properties of specimens, thereby forming a paradox. At the turn of the 21st century, the micro-theory of metallic elastic deformation was proposed, identifying that a change in microstructure at atomic level could occur during elastic deformation, leading to a change in the concentration of solute (impurity) at grain boundaries/around dislocations. The micro-theory has been used to explain the mechanism of the measurement uncertainty. Different tensile temperatures and strain rates correspond to different durations of elastic deformation during tensile testing, different concentrations of solute at grain boundaries/dislocations, and thus different mechanical properties. On this basis, a new technology system of tensile testing is suggested, i.e., a “mechanical property–tensile strain rate” curve at a given test temperature can be used to evaluate the original mechanical property. The higher the strain rate is, the closer the property on the curve is to the original property. Therefore, to determine the original mechanical property of the tested metal, a sufficiently high strain rate is required. The curve can also characterize the property variation of the tested metal in service with the service time. In addition, the property characterized by a point on the curve can represent the property of the tested metal when processing-deformed with the corresponding strain rate. As an example of the application of the new technology system, the property of high-entropy alloys is represented with a curve. The results show that the new technology system could change the conceptual framework and testing technology system of metallic mechanics.

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Section: Paradox Of Tensile Testmentioning

confidence: 99%

Section: Measurement Uncertainty Of Yield Strengthmentioning

confidence: 99%

Section: Mechanical Property Characterizationmentioning

confidence: 99%

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Measurement Uncertainty and Representation of Tensile Mechanical Properties in Metals

Wang

Ravi

2021

Metals

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“…In early studies, Xu [4] proposed the concept of strain rate brittleness and gave a theoretical explanation of the influence of tensile strain rate on the reduction rate or elongation of a section, also giving a more in-depth explanation of this theory. [5] The strain rate brittleness is closely related to the solute atomic interface segregation. During the elastic deformation stage in tensile testing, the concentration of the grain boundary segregation of solute atoms reaches a maximum at a certain moment, and strain rate brittleness occurs when tensile testing enters the plastic deformation stage.…”

Section: Introductionmentioning

confidence: 99%

Tensile Properties and Fracture Mechanism of Strain Rate Brittleness on Quenched Cold‐Rolled Carbon Steel

Zhao

Wang

et al. 2021

steel research int.

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For metal materials, the corresponding mechanical indicators obtained by tensile experiments at different strain rates are different. Herein, after the quenching and cold‐rolling process, a deformed lath martensite structure is obtained in low‐carbon steel. A scanning electron microscope (SEM), transmission electron microscope (TEM), and 3D atom probe (3DAP) analyses are used in this research. The results show that measurement uncertainty exists and when the strain rate is 0.0021 s−1 at room temperature, the elongation is at its minimum value, which gets into an extreme point. C atoms segregate into the martensite boundary when the strain rate brittleness occurs from 3DAP analysis. This phenomenon indicates that the supersaturated C atoms in the steel undergo nonequilibrium segregation at the lath boundary during the elastic phase of stretching, which results in strain rate brittleness.

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“…International Standard ISO 6892-2 shows that for a metal, which underwent a same thermal cycle the variations of strain rate in tensile test system can produce change of stress-strain curves which indicates a large difference in testing results, named as measurement uncertainty of mechanical properties relative to strain rate variations in tension test system [11]. It was demonstrated [12,13,14] with the micro-theory of elastic deformation of metals that the stress will change the micro-structure and mechanical properties during the stage of elastic deformation in tension test to induce the measurement uncertainty of mechanical properties. In this paper, the measurement uncertainty of reduction in area relative to strain rate, called as strain rate embrittlement (SRE), is first described experimentally for IN718 alloy.…”

Section: Introductionmentioning

confidence: 99%

Elastic Deformation Induced Non-equilibrium Segregation of P in IN718 Alloy

Du¹

2016

IJMSA

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IN718 alloy is a precipitation hardened, nickel-based superalloy that is used extensively in the aircraft engine industry. The excellent cyclic fatigue resistance, high tensile strength, fracture toughness and oxidation resistance allow the alloy to be safely used at maximum useful service temperature of about 650ºC. Many researchers improve the alloy's high-temperature strength through adding of P. However, segregation of P at grain boundary can be induced the grain boundary embrittlement, decreased the tension reduction in area. In this paper, intermediate-temperature embrittlement (ITE) for a IN718 alloy has been experimentally studied by elevated-temperature tension tests. International standard ISO 6892-2 (Metallic Materials Tensile Testing) indicates that the variations in temperature of this measurement system have been found to have a larger potential effect on test results, which is a kind of uncertainty contribution not related to test equipment. International standard ISO 6892-2 maintains that strain rate variations can induce the measurement uncertainty of mechanical properties in tensile testing, which will imperil the reliability of tension tests. The measurement uncertainty of reduction in area relative to strain rate, called as strain rate embrittlement (SRE), is first described experimentally for IN718 alloy in this paper. Then the measurement uncertainty is clarified based on microscopic theory of elastic deformation in metals. It is shown that the elastic deformation of tension test induced the segregation of impurities to grain boundaries and the relevant embrittlement which produces the measurement uncertainty of reduction in area.

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The measurement uncertainty of reduction in area of metals in tensile testing system

Cited by 12 publications

References 17 publications

Measurement Uncertainty and Representation of Tensile Mechanical Properties in Metals

Measurement Uncertainty and Representation of Tensile Mechanical Properties in Metals

Tensile Properties and Fracture Mechanism of Strain Rate Brittleness on Quenched Cold‐Rolled Carbon Steel

Elastic Deformation Induced Non-equilibrium Segregation of P in IN718 Alloy

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