Measurement of flow stress in hot axisymmetric compression tests

Roebuck, B; Lord, J D; Brooks, M.; Loveday, M S; Sellars, C. M.; Evans, R. W.

doi:10.1179/mht.2006.005

Cited by 98 publications

(50 citation statements)

References 7 publications

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“…The strain measurement in Gleeble testing is clearly a more direct measurement than that employed for isothermal compression testing where the crosshead displacement is usually used and converted to true strain, with some correction normally being applied in the latter case to account for test rig compliance [16].…”

Section: Stress/strain Measurement In Gleeble Testingmentioning

confidence: 99%

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A critical analysis of plastic flow behaviour in axisymmetric isothermal and Gleeble compression testing

Bennett

Leen

Williams

et al. 2010

Computational Materials Science

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Section: Stress/strain Measurement In Gleeble Testingmentioning

confidence: 99%

“…Friction at the interface between the specimen and the platens is a source of strain inhomogeneity in the compression specimen and results in non-uniform deformation of the specimen as shown in Figure 2b. This non-uniformity is known as barrelling [16].…”

Section: Interface Frictionmentioning

confidence: 99%

A critical analysis of plastic flow behaviour in axisymmetric isothermal and Gleeble compression testing

Bennett

Leen

Williams

et al. 2010

Computational Materials Science

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“…Validity of all the reported compression tests was established by ensuring barreling, and ovality of deformed specimens remained within acceptable limits [19]. Various shape coefficients, as defined in Table 1, calculated for the validity of tests are summarized in Table 2 for highest and lowest test temperature and strain rates accommodating the range of the test matrix.…”

Section: Materials and Experimental Methodologymentioning

confidence: 99%

Hot Forging of IN718 with Solution-Treated and Delta-Containing Initial Microstructures

Lalvani

Brooks

2016

Metallogr. Microstruct. Anal.

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A systematic study of the effect of d phase precipitate morphology on the hot deformation behavior and microstructural evolution in nickel superalloy Inconel 718 is presented. Isothermal compression tests at fixed nominal strain rates and temperatures relevant to industrial forging (0.001-0.3 s -1 and 990-1040°C) were used. Three distinct initial microstructures have been examined: (I) solution treated, (II) a microstructure with finely dispersed particulate d precipitates, and (III) a microstructure containing dense network of intragranular and grain boundary d platelets. The peak flow stress associated with these various microstructures has been rationalized using a single, temperature-compensated power law. This clearly demonstrates opposition of the external applied stress by an internal back stress related to the initial d phase morphology and apparent delta solvus temperature. Post-peak flow softening is attributed to dynamic recrystallization, aided by the dissolution of finer precipitates in material containing particulate d phase, and to a certain degree of mechanical grain refinement caused by distortion and offsetting of grain segments where a dense d-platelet structure exists.

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“…The data obtained were then analysed and corrected according to the axisymmetric compression testing good practice guide [6]. A moving-average correction technique was used to filter out the effects of the velocity variation on all the specimens deformed at a strain rate of 50 s -1 .…”

Section: Methodsmentioning

confidence: 99%

Determining a Flow Stress Model for High Temperature Deformation of Ti-6Al-4V

Calvert

Pollard

Jackson

et al. 2015

MSF

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In some commercial titanium extrusion practices, twisting of the extrudate can occur, which can result in the need to crop the back and front end of the extruded material, thereby reducing yield and increasing material losses. Understanding more about the behaviour of material during the extrusion process, and investigating the cause of defects such as twisting by use of finite element (FE) modelling techniques could help to reduce these losses, improve the productivity of the extrusion process, and the overall quality of the material produced.One of the most important components of FE techniques for hot deformation is the type of flow stress model that is used in the simulations. In this investigation isothermal uniaxial compression testing was performed on cylindrical specimens of Ti-6Al-4V at temperatures ranging from 950 °C to 1200°C and strain rates of 0.1 s -1 to 50 s -1 , to produce true stress against true strain and load against die travel curves which were subsequently used to develop a new specific flow stress model for use in hot deformation above the beta transus, which can ultimately be applied to the hot extrusion of Ti-6Al-4V.From analysis of this data it was concluded that flow softening and work hardening do not occur during deformation, and that low friction conditions exist between the material and the tooling. The activation energy for deformation was found to be 193178 J.mol -1 , and the flow stress model was shown to give a good fit to the raw data at low strain rates, but this relationship broke down at higher strain rates. Finally the importance of generating a flow stress model specific to a particular operation, and set of experimental data, rather than relying on existing data available in the literature is demonstrated.

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Measurement of flow stress in hot axisymmetric compression tests

Cited by 98 publications

References 7 publications

A critical analysis of plastic flow behaviour in axisymmetric isothermal and Gleeble compression testing

A critical analysis of plastic flow behaviour in axisymmetric isothermal and Gleeble compression testing

Hot Forging of IN718 with Solution-Treated and Delta-Containing Initial Microstructures

Determining a Flow Stress Model for High Temperature Deformation of Ti-6Al-4V

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