Methods of determining Stress‐Strain Curves by upsetting cylindrical test‐pieces

Pöhlandt, K.; Nester, Winfried

doi:10.1002/mawe.19820130407

Cited by 4 publications

(2 citation statements)

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“…Exemplary results of the flow curve determination for two electrical steels are shown below. To evaluate the hot forming behaviour, isothermal bulk hot compression tests [ 31 ] were performed on a servo-hydraulic hot deformation simulator at constant strain rates of 0.1 s −1 , 1 s −1 and 10 s −1 in the temperature range of 800 °C to 1100 °C ( Figure 4 a–c). In the course of these experiments, bulk samples with an initial diameter of 10 mm and an initial height of 18 mm were placed in an upsetting cup and heated in an air circulation furnace up to 1200 °C.…”

Section: Best Practice For Standard Characterization Methodsmentioning

confidence: 99%

“…By holding for 10 min at 1200 °C, a homogeneous temperature distribution and similar grain size was assured in all tested samples before the compression tests at the respective deformation temperatures were conducted. Figure 4 a–c show representative hot flow curves of Fe2.4wt.%Si and Fe3.2wt.%Si ( Table 2 ) after data correction to eliminate the influence of friction and heat that occurs during deformation, as described in [ 31 ].…”

Section: Best Practice For Standard Characterization Methodsmentioning

confidence: 99%

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Characterization Methods along the Process Chain of Electrical Steel Sheet—From Best Practices to Advanced Characterization

et al. 2021

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Non-oriented (NO) electrical steel sheets find their application in rotating electrical machines, ranging from generators for wind turbines to motors for the transportation sector and small motors for kitchen appliances. With the current trend of moving away from fossil fuel-based energy conversion towards an electricity-based one, these machines become more and more important and, as a consequence, the leverage effect in saving energy by improving efficiency is huge. It is already well established that different applications of an electrical machine have individual requirements for the properties of the NO electrical steel sheets, which in turn result from the microstructures and textures thereof. However, designing and producing tailor-made NO electrical steel sheet is still challenging, because the complex interdependence between processing steps, the different phenomena taking place and the resulting material properties are still not sufficiently understood. This work shows how established, as well as advanced and newly developed characterization methods, can be used to unfold these intricate connections. In this context, the respective characterization methods are explained and applied to NO electrical steel as well as to the typical processing steps. In addition, several experimental results are reviewed to show the strengths of the different methods, as well as their (dis)advantages, typical applications and obtainable data.

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Section: Best Practice For Standard Characterization Methodsmentioning

confidence: 99%

Section: Best Practice For Standard Characterization Methodsmentioning

confidence: 99%

Characterization Methods along the Process Chain of Electrical Steel Sheet—From Best Practices to Advanced Characterization

et al. 2021

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Axi-symmetric compression of solid cylinders

Singh

Padmanabhan

1991

J Mater Sci

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Axi-symmetric compression of solid cylinders

Singh

Padmanabhan

1991

J Mater Sci

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The analytical and experimental methods of determining the compressive yield stress of materials have been reviewed briefly. Using aluminum, EN 24 steel, lead and a tin-lead eutectic alloy, the areas of applicability of the Cook and Larke method (including its modified form for strain-rate sensitive materials) and the ring compression test have been delineated. Under conditions of sliding friction, both the methods give similar values for the coefficient of friction. Under sticking or near-sticking friction conditions, the modified Cook and Larke method is more accurate, because the interpretation of the ring compression test ignores the strain-rate sensitivity of the flow stress. Within the experimental range, the coefficient of friction and the interface friction factor were unaffected by the changes in the strain level, strain rate, grain size and efficacy of lubrication. Under slow loading conditions, the effect of specimen dimensions on the flow stress could be attributed entirely to a change in the frictional contribution. The strain and/or strain-rate hardening behaviour, as well as the grain size dependence of the flow stress of the different materials, were consistent with earlier wellknown results. Earlier workFor evaluating the true stress-true strain curves of materials, axi-symmetric compression of solid cylinders is often used. In these tests friction is present and this leads to barrelling [1,2]. But the analysis of many metal-forming processes, e.g. extrusion, requires a knowledge of the compressive yield stress of a material, i.e. which is corrected for friction [3,4]. A correction for friction can be effected either analytically or experimentally.For analysing a cold-working process, Coulomb's law 9 = gN, where 9 is the frictional (shear) stress, p is the coefficient of friction and N is the normal stress, is often used. While in most analyses p is treated as constant, in reality it depends on a number of variables in a complicated way, e.g. material properties, efficacy of lubrication, rate of sliding at the interface. In hot working, on the other hand, sticking friction is assumed. Here the frictional stress is taken as equal to the shear yield stress of the material in plane strain, again an idealized picture [5,7].A barrelling correction, which is analogous to necking correction in tension, is often made. But this calculation is influenced by the specimen dimensions and the lubricant used. Additionally, some questionable assumptions are also involved in the analysis [8-113. Slip-line field solutions are often inapplicable for axi-symmetric flow problems [12][13][14][15][16][17].Early experimental methods of Rummel, Meyer and Nehl and Siebel and Pomp are only of historical significance [18][19][20][21][22][23][24]. The methods of Taylor and Quinney [25], Ford [26] and Polakowski [23] are time consuming as they require remachining (which also changes the overall mechanical history of the specimen) and cannot be used when an allotropic transformation is present in the material, e.g. a steel...

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Methods of determining Stress‐Strain Curves by upsetting cylindrical test‐pieces

Cited by 4 publications

References 6 publications

Characterization Methods along the Process Chain of Electrical Steel Sheet—From Best Practices to Advanced Characterization

Characterization Methods along the Process Chain of Electrical Steel Sheet—From Best Practices to Advanced Characterization

Axi-symmetric compression of solid cylinders

Axi-symmetric compression of solid cylinders

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