| 44811. |
- Krajnik, Peter, 1977, et al.
(författare)
-
Finishing
- 2018
-
Ingår i: CIRP Encyclopedia of Production Engineering. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 9783642359507 ; , s. 1-9
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Finishing is the final step in the manufacture of components which require the highest quality in terms of form, accuracy and surface integrity. Fine-finishing is an operation that adds functionality to the workpiece surface to enhance its quality characteristics.
|
|
| 44812. |
- Krajnik, Peter, 1977, et al.
(författare)
-
Grinding and fine finishing of future automotive powertrain components
- 2021
-
Ingår i: CIRP Annals - Manufacturing Technology. - : Elsevier BV. - 1726-0604 .- 0007-8506. ; 70:2, s. 589-610
-
Tidskriftsartikel (refereegranskat)abstract
- The automotive industry is undergoing a major transformation driven by regulations and a fast-paced electrification. A critical analysis of technological trends and associated requirements for major automotive powertrain components is carried out in close collaboration with industry – covering the perspectives of OEMs, suppliers, and machine builders. The main focus is to review the state of the art with regard to grinding, dressing, texturing and fine-finishing technologies. A survey of research papers and patents is accompanied by case studies that provide further insights into the production value chain. Finally, key industrial and research challenges are summarized.
|
|
| 44813. |
- Krajnik, Peter, 1977, et al.
(författare)
-
High-performance industrial grinding: recent advances and case studies from the automotive engine production
- 2016
-
Ingår i: 19th International Symposium on Advances in Abrasive Technology, ISAAT 2016; Stockholm; Sweden. ; , s. 1-13
-
Konferensbidrag (refereegranskat)abstract
- The development of new high-performance industrial grinding technologies for engine production in the automotive industry is presented. The grinding fundamentals are revisited in view of modeling and simulation to examine the effects of process design on grinding temperatures. The advantages associated with utilization of newly developed temperature-controlled grinding processes are explained via the analysis of process-control strategies. Two research-and-development projects from Scania´s engine-production plant are discussed to illustrate industrial challenges and achieved impacts. Two case studies are presented for (1) cam-lobe grinding and (2) crankpin grinding, demonstrating optimized grinding processes for achieving shorter cycle times and higher quality. Both patent-pending technologies are experimentally validated in actual production and are implemented in existing production lines.
|
|
| 44814. |
- Krajnik, Peter, et al.
(författare)
-
Method of grinding a workpiece and method for determining processing parameters
- 2017
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The present disclosure relates to a grinding method for grinding of non-circular workpieces with an improved productivity and quality of the resulting workpiece. The method comprises a first and a second stage. The rotational speed profile of the workpiece in the first stage is controlled with the purpose of maintaining a pre-selected maximum surface temperature of the workpiece during said first stage, and grinding of the workpiece in said second stage is performed while controlling an aggressiveness number of said second stage so as to achieve an intended final surface quality. The present disclosure also relates to a method for determining the processing parameters of such a grinding method wherein the first and the second stage of the grinding method are iterated to thereby determine the processing parameters leading to a high productivity and desired quality of the workpiece after grinding.
|
|
| 44815. |
- Krajnik, Peter, 1977, et al.
(författare)
-
Method of grinding a workpiece and method for determining processing parameters
- 2019
-
Patent (övrigt vetenskapligt/konstnärligt)abstract
- The present disclosure relates to a grinding method for grinding of non-circular workpieces with an improved productivity and quality of the resulting workpiece. The method comprises a first and a second stage. The rotational speed profile of the workpiece in the first stage is controlled with the purpose of maintaining a pre-selected maximum surface temperature of the workpiece during said first stage, and grinding of the workpiece in said second stage is performed while controlling an aggressiveness number of said second stage so as to achieve an intended final surface quality. The present disclosure also relates to a method for determining the processing parameters of such a grinding method wherein the first and the second stage of the grinding method are iterated to thereby determine the processing parameters leading to a high productivity and desired quality of the workpiece after grinding.
|
|
| 44816. |
- Krajnik, Peter, et al.
(författare)
-
Method of grinding a workpiece having a cylindrical bearing surface and method for determining processing parameters
- 2017
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- A method of grinding a workpiece by means of a grinding wheel is disclosed. The workpiece comprises a cylindrical bearing surface, a radially extending sidewall extending outward from the cylindrical bearing surface, and a curved transition portion connecting the cylindrical bearing surface with the sidewall. During grinding, the feed in an increment is selected so as to achieve a pre-set maximum surface temperature of the workpiece at a point of the grinding wheel resulting in the highest surface temperature of the workpiece. Furthermore, a method for determining processing parameters for such a grinding method is disclosed.
|
|
| 44817. |
- Krajnik, Peter, 1977, et al.
(författare)
-
Method of grinding a workpiece having a cylindrical bearing surface and method for determining processing parameters
- 2018
-
Patent (övrigt vetenskapligt/konstnärligt)abstract
- The present disclosure relates in general to a method of grinding a workpiece by means of a grinding wheel, the workpiece comprising a cylindrical bearing surface, a radially extending sidewall extending outward from the cylindrical bearing surface, and a curved transition portion connecting the cylindrical bearing surface with the sidewall. The present disclosure also relates to a method for determining processing parameters of such a grinding method.
|
|
| 44818. |
- Krajnik, Peter, 1977, et al.
(författare)
-
Optimierung von Schleif- und Abrichtprozessen mit Hilfe der Theorie der Aggressivität: Fallstudien aus der Praxis
- 2022
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In den ersten sechzig Jahren der Schleifforschung (1914-1974) wurden verschiedene dimensionslose Parameter eingeführt, um die grundlegende Mechanik eines Schleifkontakts zu beschreiben. Später wurden diese Parameter durch verschiedene Spandickenmodelle ersetzt, die eine schwierige und oft uneindeutige Quantifizierung der Schleifscheibentopographie erforderten. Der Ansatz der Grundprinzipien ist vor kurzem durch die große vereinheitlichende Theorie der Aggressivität und die praktische Aggressivitätszahl wieder aufgetaucht. Diese ist ein dimensionsloser Parameter, der sich bei der Optimierung jedes beliebigen Schleifprozesses, einschließlich Schleifen und Abrichten, als leistungsfähig erwiesen hat. Die Aggressivitätszahl erfreut sich inzwischen einer größeren Beliebtheit und wird verwendet, da sie die grundlegende Prozessgeometrie und -kinematik erfasst und gleichzeitig eine Quantifizierung der Schleifscheibentopographie überflüssig macht. In diesem Beitrag wird die Verwendung der dimensionslosen Aggressivitätszahl in mehreren Fallstudien aus der realen Produktion untersucht. Dabei wird gezeigt, wie das Konzept zur Optimierung industrieller Prozesse eingesetzt werden kann, z. B. beim Schleifen von Nocken- und Kurbelwellen, Sägespitzenschleifen, Nutenschleifen, Doppelseitenschleifen und Abrichten von Diamantscheiben.
|
|
| 44819. |
- Krajnovic, Sinisa, 1970, et al.
(författare)
-
A mixed one-equation subgrid model for large-eddy simulation
- 2002
-
Ingår i: International Journal of Heat and Fluid Flow. - 0142-727X. ; 23:4, s. 413-425
-
Tidskriftsartikel (refereegranskat)abstract
- A new mixed one-equation subgrid-scale (SGS) model for large-eddy simulation is presented. The scale-similarity part of the model is used for the description of the local energy transport (Domaradzki et al., 1993, 1994), i.e. the energy transport between scales very close to the cut-off. The eddy-viscosity part of the model represents the non-local transfer of energy, i.e. the transfer between all scales smaller than grid-filter size Delta and larger than Delta. A priori tests done by Bardina et al. (1980) have shown a high correlation between the scale-similarity model and the exact SGS stress, tau(ij). The magnitude of the scale-similarity part in the mixed one-equation SGS model is either larger than or equal to that of the eddy-viscosity part. The modeled SGS stress is thus expected to correlate well with the exact stress, tau(jj). In the proposed model, the SGS kinetic energy, k(sgs), is used to obtain the velocity scale for the eddy-viscosity part of the model. The modeled k(sgs) equation is derived and contains some additional scale-similarity parts as compared with the k(sgs) equation used in the models of Ghosal et al. (1995) or Davidson (1997). It has been shown that the model is Galilean invariant and realizable. Moreover, the approximately correct near-wall behavior of the model has been proven. The model was tested for both channel flow and the case of a surface-mounted cube (Martinuzzi and Tropea, 1993). It was found that the model gives accurate results in both cases.
|
|
| 44820. |
- Krajnovic, Sinisa, 1970, et al.
(författare)
-
A test case for large-eddy simulation in vehicle aerodynamics
- 2002
-
Ingår i: Proceedings of the 5th International Symposium on Engineering Turbulence Modelling and Measurements. ; , s. 647-656
-
Tidskriftsartikel (refereegranskat)abstract
- The flow around a simplified bus was computed using large-eddy simulation with intention to gain better understanding of this flow and to make a data base for validation of RANS and hybrid RANS-LES simulations. Transient quantities such as dominated frequencies and variance were studied as well as mean quantities. Velocity and pressure results were compared with the experimental data. Coherent structures were visualized and their positions were determined. Mean Reynolds stresses were computed and it was found that the largest resolved turbulent kinetic energy was in the recirculating flow close to the leading edges and in the lower part of the wake.
|
|
