The Effect of Material Properties on the Accuracy of Superplastic Tensile Test
Abstract
:1. Introduction
2. Models and Methods
2.1. Finite Element Model
2.2. The Constitutive Models
2.3. Calculation of the Output Stress and Strain
3. Results
3.1. The Adjustment and Verification of the Model
3.2. The Effect of Specimen Thickness and Friction
3.3. The Distributions of Strain Rate
3.4. The Effects of Material Properties on the Output Stress
3.4.1. Backofen Material Model
3.4.2. The Effect of Strain Hardening
3.4.3. The Effect of Strain Rate
3.5. Measurement of the Strain-Rate Sensitivity
4. Discussion
5. Concluding Remarks
- Higher strain-rate sensitivity values provide lower initial output stresses and larger apparent strain hardening effect.
- Apparent strain softening effect occurs long before the observable necking of a specimen.
- Equal values of the strain-rate sensitivity index do not guarantee equal elongations prior to necking, if the strain-rate sensitivity is strain-rate-dependent. In particular, if the material behavior is described by the sigmoidal log stress vs. log strain rate relation, higher elongations are produced by the lower strain rate associated with the same strain-rate sensitivity.
- A larger variation of strain-rate sensitivity with the strain rate provides larger errors in the determination of . For the strain rates corresponding to the edges of the quasi-SPF strain-rate range, this error may reach 25%. Lower variations of provide lower errors, which become neglectable if the material flow behavior follows the Backofen power law.
- The variation of friction between the specimen and the grip shoulders and the initial specimen thickness has an insignificant effect on the evolution of output stress in tensile testing.
Author Contributions
Funding
Conflicts of Interest
References
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Number | Initial Thickness | Friction Coefficient | Nominal Strain Rate | Deviation of the Output Stress | |
---|---|---|---|---|---|
1 | 1 mm | 0.4 | 0.01 s−1 | 300 | reference test |
2 | 1 mm | 0.0 | 0.01 s−1 | 300 | 0.26% |
3 | 1 mm | 0.2 | 0.01 s−1 | 300 | 0.18% |
4 | 2 mm | 0.4 | 0.01 s−1 | 300 | 0.09% |
5 | 4 mm | 0.4 | 0.01 s−1 | 300 | 0.73% |
6 | 6 mm | 0.4 | 0.01 s−1 | 300 | 1.95% |
7 | 1 mm | 0.4 | 0.01 s−1 | 150 | 0.05% |
8 | 1 mm | 0.4 | 0.001 s−1 | 300 | 0.08% |
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Aksenov, S.; Mikolaenko, V. The Effect of Material Properties on the Accuracy of Superplastic Tensile Test. Metals 2020, 10, 1353. https://doi.org/10.3390/met10101353
Aksenov S, Mikolaenko V. The Effect of Material Properties on the Accuracy of Superplastic Tensile Test. Metals. 2020; 10(10):1353. https://doi.org/10.3390/met10101353
Chicago/Turabian StyleAksenov, Sergey, and Vadim Mikolaenko. 2020. "The Effect of Material Properties on the Accuracy of Superplastic Tensile Test" Metals 10, no. 10: 1353. https://doi.org/10.3390/met10101353