Influence of specimen dimensions and strain measurement methods on tensile stress–strain curves

Zhao, Yaohua; Guo, Yuan‐ji; Wei, Qian; Topping, Troy D.; Dangelewicz, Andrea M.; Zhu, Yuntian; Langdon, Terence G.; Lavernia, Enrique J.

doi:10.1016/j.msea.2009.06.031

Cited by 218 publications

(100 citation statements)

References 55 publications

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“…For example, experiments have shown that the measured elongations to failure in tensile testing tend to increase with decreasing gauge length [47,48] and this is because the area of necking constitutes a major fraction of the gauge length in samples with very short gauge lengths so that much of the measured elongation in simple tensile testing is related to flow in the necked region. This suggests, therefore, that it may be unreasonable to make a direct comparison between the total elongations achieved in conventional tensile testing with longer gauge lengths with the results obtained in tensile testing using HPT samples with gauge lengths only of the order of ~1 mm.…”

Section: Significance Of Using Miniature Configurations In the Testinmentioning

confidence: 99%

Using heat treatments, high-pressure torsion and post-deformation annealing to optimize the properties of Ti-6Al-4V alloys

Shahmir

Langdon

2017

Acta Materialia

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Experiments were conducted to investigate the processing parameters that may be used to optimize the properties of Ti-6Al-4V alloys. The alloy was initially subjected to two different heat treatments leading to the formation of martensitic αʹ and lamellar α+β microstructures and then both materials were processed by high-pressure torsion (HPT) for 10 turns at room temperature. This gave significant grain refinement to the nanometer range in both conditions and the occurrence of an allotropic hcp to fcc phase transformation in the martensitic alloy.These nanostructured alloys were subjected to post-deformation annealing (PDA) at temperatures in the range of 473 to 1023 K. The results show the hardness increases slightly to 773 K due to αʹ+fcc→α+β+fcc and α→α+β phase transformations in the martensitic αʹ and lamellar α+β alloys and then decreases up to 1023 K due to recrystallization and grain growth.An optimum property of a very high yield strength (~1120 MPa) and ultimate tensile strength (~1200 MPa), together with excellent ductility (elongation to failure of ~26%), was achieved in the Ti-6Al-4V martensitic alloy processed by a combination of HPT followed by PDA at 873 K for 60 min.

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Section: Significance Of Using Miniature Configurations In the Testinmentioning

confidence: 99%

Using heat treatments, high-pressure torsion and post-deformation annealing to optimize the properties of Ti-6Al-4V alloys

Shahmir

Langdon

2017

Acta Materialia

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“…The most common method used to produce miniature tensile specimens is wire electro discharge machining ('wire EDM') [1,7,8,10,11,[13][14][15][16][17] (note that one study used water jet cutting [18]). The advantage of EDM over traditional machining processes is that it can produce the small work piece accurately and to close tolerances with very little wasted material.…”

Section: Tensile Testing Of Miniature Specimensmentioning

confidence: 99%

“…In an attempt to avoid that the boundary effects of the end shoulders influence the response of the test section, these ratios can be adopted for miniature tensile test specimens. In studies [17,19] the importance of some of these ratios in miniature tensile test specimens is investigated. The consensus is that an important ratio is G/W and the best results are obtained when adhering to a ratio of 4, just as the standard prescribes for traditional specimens.…”

Section: Tensile Testing Of Miniature Specimensmentioning

confidence: 99%

Characterisation of weld heterogeneity through hardness mapping and miniature tensile testing

Bally

Waele

Verleysen

et al. 2015

SCAD

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Abstract:Welding is a widely adopted industrial process used for joining components. A fusion weld has a highly heterogeneous microstructure and characterisation of strength heterogeneity is difficult because of the potentially large variations over a limited distance. Hardness mapping and miniature tensile tests are two distinct approaches to this problem. This paper reports on the possibilities and limitations of both techniques. Hardness mapping is a well-documented procedure as opposed to miniature tensile testing, where the dimensions of the dogbone shaped specimens are smaller than what standards prescribe. A particular challenge is the measurement of strains in such small specimens. The authors have achieved this measurement by means of Digital Image Correlation (DIC). To that end, a sufficiently fine speckling method has been developed.Keywords: heterogeneity; hardness mapping; miniature tensile testing; DIC INTRODUCTIONWelding is one of the most common joining methods due to its generally high production speed and low associated costs. It is often associated with flexibility, integrity and reliability [1]. An example application showing the economic importance of welding is pipeline installation. Costs associated to fusion welding are estimated to make up 20% of the total cost of pipe laying. These include aligning the pipe sections, cleaning and grinding, welding, checking the weld for flaws and coating the weld [2].Notwithstanding the economical appeal of welding, the localized application of heat and melting results in a high susceptibility to material discontinuities, flaws and residual stresses, whose presence may lead to structural failure and lifetime reduction. The prediction of weld flaw acceptability ('structural integrity') is hampered by the potential presence of strongly heterogeneous microstructures. Modern day weld flaw assessment ignores this heterogeneity by assuming a homogeneous weld. As such, a generally accepted method to characterise weld heterogeneity does not yet exist. STATE OF THE ARTHeterogeneity is inherent to fusion welds, because in order to melt the weld metal and fuse it with the base metal, heat has to be locally applied. For thicker sections, weldments are created in several passes (deposition of multiple layers), resulting in a variety of zones undergoing a succession of particular heat cycles. The heat cycle determines what the microstructure transforms into, each structure having a different stress-strain response. Not only the weld metal is heterogeneous due to this, but the heat affected zone (HAZ) of the base metal (heated but non-melted metal in close vicinity of the weld) also transforms.Many conventional steel welds show a hardened HAZ due to the occurrence of stronger microstructures. In contrast, a broad range of high strength low alloy steels obtain their properties from a fine grain size, resulting from a specific heat treatment, often combined with mechanical deformation. These steels may show a softened HAZ due to grain coarsening. To quantify variations ...

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“…Zhao et al (2009) discussed the limitations and issues in correctly interpreting micro tensile experiments. This work (GPa) 57 ± 1 5 7 ± 1 5 2 ± 3 5 7 ± 1 Elongation (%) 30 ± 3 2 6 ± 2 2 7 ± 2 2 5 ± 3 Fig.…”

Section: Sintering and Micro-tensile Testsmentioning

confidence: 99%

Water soluble Invar 36 feedstock development for μPIM

Hidalgo

Jiménez-Morales

Barrière

et al. 2014

Journal of Materials Processing Technology

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Micro powder injection moulding Invar 36 Solid loading optimisationA water soluble binder system based on cellulose acetate butyrate (CAB) and polyethylene glycol (PEG) is proposed and investigated to carry out a micro powder injection moulding (PIM) process with an Invar 36 alloy powders. The overall process was optimised with an emphasis on the determination of the optimal solid loading. Several methodologies were evaluated and compared to determine this parameter. A full PIM was performed with different powder content feedstocks. Dog bone-type micro test parts were fabricated thereof and their mechanical properties were evaluated. Solid loadings up to 65 vol.%resulted to have the most equilibrated properties to successfully fabricate Invar 36 micro parts with the selected powder and binder system.

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Influence of specimen dimensions and strain measurement methods on tensile stress–strain curves

Cited by 218 publications

References 55 publications

Using heat treatments, high-pressure torsion and post-deformation annealing to optimize the properties of Ti-6Al-4V alloys

Using heat treatments, high-pressure torsion and post-deformation annealing to optimize the properties of Ti-6Al-4V alloys

Characterisation of weld heterogeneity through hardness mapping and miniature tensile testing

Water soluble Invar 36 feedstock development for μPIM

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