| 51. |
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| 52. |
- Bergman, Greger, et al.
(författare)
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Verification of thermomechanical material models by thin-plate quenching simulations
- 1997
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Ingår i: Journal of thermal stresses. - : Informa UK Limited. - 0149-5739 .- 1521-074X. ; 20:7, s. 679-695
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Tidskriftsartikel (refereegranskat)abstract
- A computational model for quenching simulations of thin plates has been developed. The model is examined by comparisons with experiments with one-sided water spray cooling. With this experiment, the thermomechanical behavior of the material can be monitored throughout the time history of the test. Experiments have been performed with a material that undergoes only martensitic transformation during quenching. For the conditions examined the plate exhibits permanent deformation after quenching. In the stress calculation, transformation plasticity is included in the effective-stress-function (ESF) algorithm as an additional strain component related to the stress and to the progress of transformation. Analyses of the present experiments show that the permanent deformation of the plate is exclusively due to transformation plasticity
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| 53. |
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| 54. |
- Bergquist, Bjarne
(författare)
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Property variation in sintered steel : design of experiments
- 1997
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Ingår i: International journal of powder metallurgy (1986). - 0888-7462. ; 33:2, s. 30-40
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Tidskriftsartikel (refereegranskat)abstract
- To reduce dimensional and mechanical property variations in a component manufactured from a phosphorus alloyed P/M steel, a design of experiments approach was used to identify the most important green compact variations. Responses evaluated were unnotched Charpy impact energy total dimensional change, and sintered density. The experimental array was defined using a fractional factorial design, and the variables investigated were: phosphorus content; median particle size of Fe[3]P-powder; iron powder fines content; added graphite content; green density; and sintering temperature. The design of experiments proved powerful in detecting the most important variables; it pinpointed graphite and phosphorus content, and green density variations as being detrimental.
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| 55. |
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| 56. |
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| 57. |
- Bergquist, Karin, et al.
(författare)
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A method for dynamic measurement of the resistance to dry heat exchange by footwear
- 1997
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Ingår i: Applied Ergonomics. - 0003-6870 .- 1872-9126. ; 28:5-6, s. 383-388
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Tidskriftsartikel (refereegranskat)abstract
- Five different types of cold protective footwear have been tested with regard to their resistance to dry heat loss (i.e. the insulation) with a new electrically heated foot model. The model is able to simulate ‘walking' movements in order to provide a more realistic simulation of wear conditions. Thermal insulation of shoes with and without a steel toe cap was the same. The insulating properties during simulated walking movements were 10-25% lower compared with static conditions. For two of the shoe models a significantly lower insulation value for the sole area was obtained when adding a weight of 30 kg. A significant difference could also be found between the insulation values of two different sizes of one of the models. Measurements with the standard method (EN 344) correlated well with the local insulation value of the sole part of the thermal foot. Correlation with the insulation value for the whole shoe was much less, variation was bigger and ranking in terms of cold protection differed between methods. The electrically heated foot model appears to provide a reproducible, accurate and more realistic method for measuring the insulation properties of shoes than EN 344.
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| 58. |
- Bergström, John
(författare)
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Turbulence modeling and numerical accuracy for the simulation of the flow field in a curved channel
- 1997
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Ingår i: Proceedings, 1997 ASME Fluid Engineering Division Summer Meeting.
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Konferensbidrag (refereegranskat)abstract
- The problem of estimating the error in numerical flow simulations is very important. One case where this is particularly true is in the assessment of turbulence models, where the numerical errors must be known in order to separate them from model errors. In this paper, the three-dimensional steady turbulent flow in a curved rectangular duct has been examined. The Reynolds number was 224000 based on the channel width. At the inlet the flow pattern was already complicated, with a pair of vortices inside the top-wall boundary layer. The results from this case has already been presented (Bergstrom, 1996) but the numerical accuracy and turbulence modeling has not been studied in detail until now. The measurements for the curved channel case were extensive and well suited for checking the turbulence model. The numerical accuracy concerning iterative and grid-convergence was controlled by a grid- and iterative error, respectively. The grid error gives a way to report the number of grid cells needed for a virtually grid-independent solution. A secondary result of the error estimation is that a better approximation to the exact solution is obtained. A Reynolds stress model was used to model the turbulence. The model was seen to be able to capture the most important flow phenomena in the channel.
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| 59. |
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| 60. |
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