| 1. |
- Hosseini, Seyed, 1981, et al.
(författare)
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A Methodology for Temperature Correction When Using Two-Color Pyrometers : Compensation for Surface Topography and Material
- 2014
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Ingår i: Experimental mechanics. - : Springer Science and Business Media LLC. - 0014-4851 .- 1741-2765. ; 54:3, s. 369-377
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Tidskriftsartikel (refereegranskat)abstract
- In this investigation, the applicability of the two-color pyrometer technique for temperature measurements in dry hard turning of AISI 52100 steel was studied, where both machined surfaces as well as cutting tools were considered. The impacts of differing hard turned surface topography on the two-color pyrometer readings was studied by conducting temperature measurements on reference samples created using cutting tools with different degrees of tool flank wear. In order to conduct measurements in a controlled environment, a specially designed furnace was developed in which the samples were heated step-wise up to 1,000 °C in a protective atmosphere. At each testing temperature, the temperatures measured by the two-color pyrometer were compared with temperatures recorded by thermocouples. For all materials and surfaces as studied here, the two-color pyrometer generally recorded significantly lower temperatures than the thermocouples; for the hard turned surfaces, depending on the surface topography, the temperatures were as much as 20 % lower and for the CBN cutting tools, 13 % lower. To be able to use the two-color pyrometer technique for temperature measurements in hard turning of AISI 52100 steel, a linear approximation function was determined resulting in three unique equations, one for each of the studied materials and surfaces. By using the developed approximation function, the measured cutting temperatures can be adjusted to compensate for differing materials or surface topographies for comparable machining conditions. Even though the proposed equations are unique for the hard turning conditions as studied here, the proposed methodology can be applied to determine the temperature compensation required for other surface topographies, as well as other materials. © 2013 Society for Experimental Mechanics.
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| 2. |
- Hosseini, Seyed, 1981, et al.
(författare)
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Characterization of the Surface Integrity induced by Hard Turning of Bainitic and Martensitic AISI 52100 Steel
- 2012
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Ingår i: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 1:1, s. 494 - 499
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Konferensbidrag (refereegranskat)abstract
- Depending on the process parameters and the tool condition, hard turned surfaces can consist of a “white” and a “dark” etching layer having other mechanical properties compared to the bulk material. X-ray diffraction measurements revealed that tensileresidual stresses accompanied with higher volume fraction of retained austenite are present in the thermally induced white layer. While compressive residual stresses and decreased retained austenite content was found in the plastically created white layer. The surface temperature was estimated to be ~1200 C during white layer formation by hard turning.
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| 3. |
- Hosseini, Seyed, 1981, et al.
(författare)
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Cutting temperatures during hard turning : Measurements and effects on white layer formation in AISI 52100
- 2014
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Ingår i: Journal of Materials Processing Technology. - : Elsevier BV. - 0924-0136 .- 1873-4774. ; 214:6, s. 1293-1300
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Tidskriftsartikel (refereegranskat)abstract
- This paper concerns the temperature evolution during white layer formation induced by hard turning of martensitic and bainitic hardened AISI 52100 steel, as well as the effects of cutting temperatures and surface cooling rates on the microstructure and properties of the induced white layers. The cutting temperatures were measured using a high speed two-colour pyrometer, equipped with an optical fibre allowing for temperature measurements at the cutting edge. Depending on the machining conditions, white layers were shown to have formed both above and well below the parent austenitic transformation temperature, Ac1, of about 750 C. Thus at least two different mechanisms, phase transformation above the Ac1 (thermally) and severe plastic deformation below the Ac1 (mechanically), have been active during white layer formation. In the case of the predominantly thermally induced white layers, the cutting temperatures were above 900 C, while for the predominantly mechanically induced white layers the cutting temperatures were approximately 550 C. The surface cooling rates during hard turning were shown to be as high as 104-105 C/s for cutting speeds between 30 and 260 m/min independent of whether the studied microstructure was martensitic or bainitic. Adding the results from the cutting temperature measurements to previous results on the retained austenite contents and residual stresses of the white layers, it can be summarised that thermally induced white layers contain significantly higher amounts of retained austenite compared to the unaffected material and display high tensile residual stresses. On the contrary, in the case of white layers formed mainly due to severe plastic deformation, no retained austenite could be measured and the surface and subsurface residual stresses were compressive. © 2014 Elsevier B.V.
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| 4. |
- Ryttberg, Kristina, 1977, et al.
(författare)
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The effect of cold ring rolling on the evolution of microstructure and texture in 100Cr6 steel
- 2010
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Ingår i: Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing. - : Elsevier BV. - 0921-5093. ; 527:9, s. 2431-2436
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Tidskriftsartikel (refereegranskat)abstract
- This paper concerns the development of microstructure and texture during cold ring rolling of 100Cr6 steel rings with starting rectangular cross-sections. By interrupting the rolling process at pre-defined intervals expansion ratios ranging from 1.05 to 1.5 were achieved resulting in varying degrees of deformation of the rings. Results for rings with a simple rectangular cross-section were compared with results for a cold rolled ring with a more complex cross-section. By combining results from optical and scanning electron microscopy with hardness measurements the two different ring shapes were shown to display similar material flow during cold ring rolling. The deformation was most severe near the inner diameterof the rings decreasing towards the area of the outer diameter. By employing electron back scatter diffraction (EBSD) the ring rolling process was shown to change the {111}-fibre texture of the ring blanks to a {110} texture. This implies a mixture of both shear and compressive deformation during rolling.
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