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| 2. |
- Axsäter, Sven, et al.
(författare)
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Combining items for lot sizing in multi-level assembly systems
- 1987
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Ingår i: International Journal of Production Research. - : Informa UK Limited. - 0020-7543 .- 1366-588X. ; 25:6, s. 795-807
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Tidskriftsartikel (refereegranskat)abstract
- Many manufacturing firms are faced with the problem of planning the production/purchase quantities for items in single product, multi-level assembly production/inventory systems. Such systems are characterized by a single product, or end item, used to satisfy customer demand, which is assembled from a number of component items which, in turn, may be assembled from one or more other component items, etc. Component items may be either fabricated or purchased. This paper identifies conditions on the cost parameters which, when applicable, allow items to be combined for purpose of optimization, thereby reducing the size of the problem.
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| 3. |
- Axsäter, Sven
(författare)
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Extension of the extended basic period approach for economic lot scheduling problems
- 1987
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Ingår i: Journal of Optimization Theory and Applications. - 0022-3239 .- 1573-2878. ; 52:No 2, s. 179-189
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Tidskriftsartikel (refereegranskat)abstract
- This paper addresses the problem of choosing cyclical production patterns for several products which are produced on a common production facility. The extended basic period approach of Elmaghraby is extended by allowing more than two basic periods. The problem of dimensionality of the dynamic programming formulation is dealt with by aggregating the capacity data in different basic periods
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| 6. |
- Isaksson, Ove
(författare)
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Numerical analysis of elastohydrodynamic contacts using power-law lubricant with special reference to water-based hydraulic fluids
- 1987
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Ingår i: ASLE transactions. - : Informa UK Limited. - 0569-8197. ; 30:4, s. 501-507
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Tidskriftsartikel (refereegranskat)abstract
- A numerical solution of the elastohydrodynamic lubrication problem for pure rolling with non-Newtonian lubricants is outlined. The non-Newtonian rheological model used is a modified power-law tau equals K multiplied by (times) gamma **n. At low shear rate gamma less than gamma //b, the lubricant is Newtonian, but when gamma greater than gamma //b the lubricant becomes non-Newtonian, tau equals K multiplied by (times) gamma **n. At high shear rate ( gamma yields infinity ) the lubricant becomes Newtonian again with the same viscosity as the base lubricant. By using this rheological model a modified Reynolds' equation is derived. The influence of the n-value and gamma //b on the film thickness has been investigated. Plots of the pressure distribution and film thickness within the contact for fluids with G-values in the range 169-986 is presented. These G-values are typical for water-based hydraulic fluids. For fluids with low n-values (n less than 0. 5) the pressure profile approaches the Hertzian pressure distribution and the minimum film thickness is that given by the base fluid viscosity.
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| 7. |
- Isaksson, Ove
(författare)
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Rheology for water-based hydraulic fluids
- 1987
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 115:1-2, s. 3-17
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Tidskriftsartikel (refereegranskat)abstract
- High water-based hydraulic fluids with slightly higher viscosities than water, for instance 95-5 emulsions and micro-emulsions, do not show any significant deviation from a Newtonian fluid. Adding polymeric viscosity improvers for the purpose of increasing the viscosity will be successful as long as the shear rate is low. However, as the shear rate is increased, higher than about 10**3 s** minus **1, the viscosity will decrease and the advantage of the improver will vanish. The shear rate available was too low to break down the viscosity improvers. This is shown by the fact that the shear stress curve is reversible. Non-Newtonian fluids approach a more Newtonian behavior when the temperature is increased. The viscosity increase with pressure is much lower for water-based fluids than for a mineral oil. The pressure coefficient is about 10 times higher for mineral oils. The pressure coefficient increases if the water content of a water-based fluid is reduced.
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