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Gundersen, Martin Flyum - One of the best experts on this subject based on the ideXlab platform.
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Utmatting som følge av OPB i fortøyningsliner av kjetting : FEM analyse av topp-kjedet utsatt for OPB i henhold til retningslinjer av Bureau Veritas : Beregning og evaluering av utmattingslevetid for kjettingen, der effekten av en innfestningsarm med
Universitetet i Agder ; University of Agder, 2019Co-Authors: Gundersen, Martin FlyumAbstract:Offshore structures are exposed to harshenvironments where there are many kinds of loads acting on the structure. These loads lead to complicated conditions with many possible load combinations. In addition, they are changing in both time and spacesince the intensity and orientation varies with time.Mooring lines in floating structures consists of mooring system where chains are widely used in what is called catenary and semi taut mooring. The mooring line is a key part in the station-keeping system thatforms a connection between the structure on the surfaceto the seabed.Here it will keep floating structures stable with the least possible movementover a point of interest. This means that the response from the loads on the structure must be absorbed by the mooring lines.Since the timespan in which the offshore structure is to be stationed often will be around 20 years, the mooring lines are significantly subjected to fatigue damage. This is because of the dynamic motion of the structures where the varying displacements induces tension cycles in the mooring system.In the 20 first chain links from the connection point at the floating structure, we will have a combined stress state with tension and bending stress because of tension-tension load, in plane bending and out of plane bending. This phenomenon occurs because of the angular differences between connection point on the floating structureand chain, Friction between the links and changes in geometry from proof load that will help resist rolling and the sliding effect between the links. This results inbending moments to the first links of the top chain.To reduce the effect of OPB in the top chain, a “hang off” configuration can be implemented in the system. This configuration consists of anattachment arm which are free to rotatehorizontally and vertically throughlow-Friction-Bearings.The rod at the coupling point will relieve the chain by curving and unburdensrotations and stressesfrom the chain. The tensions and curvature here will be related to moments that occur when theyare belowor equal tothe sliding boundary of the Bearing configuration linkage. The sliding boundary for the low Friction Bearing will also lie at a lower level relative to the momentthan the sliding boundary in the chain. This means that when using such an arm with rotational properties, the potential for moment is reduced just byimplementation.To obtain stresses due to theloads,stress concentrations, OPB interlinkmoments and IPB interlink moments are to be evaluatedthrough FEM calculations.The rod is also evaluated through FEM analysis.The fatigue damage accumulated in a mooring component due to cyclic loads will be the sum of the fatigue damage from occurring cycles.In this report one uses a wave period T of 6.3 seconds, thismeans that in a year you will have 5005714.286 cycles.This is further used with S-N curves given through standards from Bureau Veritas and DNVto calculate the lifetime of the top chain and attachment arm.The attachment arms influence on the mooring line has shown to have animposing effect in terms of OPB. Friction coefficient, pretension and length are all factors that is decisive in this matterandfor the arm itself in terms of fatigue.It can also be seen that the fatigue life of the attachment arm will be lower in relation to the fatiguelife of the chain with corresponding parameters. This means that when designing mooring lines based onthis report, the fatigue properties of the attachment arm will bedecisive for the choice of parameters
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Utmatting som følge av OPB i fortøyningsliner av kjetting : FEM analyse av topp-kjedet utsatt for OPB i henhold til retningslinjer av Bureau Veritas : Beregning og evaluering av utmattingslevetid for kjettingen, der effekten av en innfestningsarm med
Universitetet i Agder ; University of Agder, 2019Co-Authors: Gundersen, Martin FlyumAbstract:Masteroppgave bygg BYG508 - Universitetet i Agder 2019Offshore structures are exposed to harshenvironments where there are many kinds of loads acting on the structure. These loads lead to complicated conditions with many possible load combinations. In addition, they are changing in both time and spacesince the intensity and orientation varies with time.Mooring lines in floating structures consists of mooring system where chains are widely used in what is called catenary and semi taut mooring. The mooring line is a key part in the station-keeping system thatforms a connection between the structure on the surfaceto the seabed.Here it will keep floating structures stable with the least possible movementover a point of interest. This means that the response from the loads on the structure must be absorbed by the mooring lines.Since the timespan in which the offshore structure is to be stationed often will be around 20 years, the mooring lines are significantly subjected to fatigue damage. This is because of the dynamic motion of the structures where the varying displacements induces tension cycles in the mooring system.In the 20 first chain links from the connection point at the floating structure, we will have a combined stress state with tension and bending stress because of tension-tension load, in plane bending and out of plane bending. This phenomenon occurs because of the angular differences between connection point on the floating structureand chain, Friction between the links and changes in geometry from proof load that will help resist rolling and the sliding effect between the links. This results inbending moments to the first links of the top chain.To reduce the effect of OPB in the top chain, a “hang off” configuration can be implemented in the system. This configuration consists of anattachment arm which are free to rotatehorizontally and vertically throughlow-Friction-Bearings.The rod at the coupling point will relieve the chain by curving and unburdensrotations and stressesfrom the chain. The tensions and curvature here will be related to moments that occur when theyare belowor equal tothe sliding boundary of the Bearing configuration linkage. The sliding boundary for the low Friction Bearing will also lie at a lower level relative to the momentthan the sliding boundary in the chain. This means that when using such an arm with rotational properties, the potential for moment is reduced just byimplementation.To obtain stresses due to theloads,stress concentrations, OPB interlinkmoments and IPB interlink moments are to be evaluatedthrough FEM calculations.The rod is also evaluated through FEM analysis.The fatigue damage accumulated in a mooring component due to cyclic loads will be the sum of the fatigue damage from occurring cycles.In this report one uses a wave period T of 6.3 seconds, thismeans that in a year you will have 5005714.286 cycles.This is further used with S-N curves given through standards from Bureau Veritas and DNVto calculate the lifetime of the top chain and attachment arm.The attachment arms influence on the mooring line has shown to have animposing effect in terms of OPB. Friction coefficient, pretension and length are all factors that is decisive in this matterandfor the arm itself in terms of fatigue.It can also be seen that the fatigue life of the attachment arm will be lower in relation to the fatiguelife of the chain with corresponding parameters. This means that when designing mooring lines based onthis report, the fatigue properties of the attachment arm will bedecisive for the choice of parameters
Pieter Martin Lugt - One of the best experts on this subject based on the ideXlab platform.
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Modern advancements in lubricating grease technology
Tribology International, 2016Co-Authors: Pieter Martin LugtAbstract:Grease is one of the major Bearing components and the performance of a grease lubricated Bearing is strongly determined by the performance of the grease. This paper describes how grease knowledge is linked to improved rolling Bearing performance. First the various performance indicators will be described such as rolling Bearing life, sealing performance, Bearing Friction, Bearing noise and grease life. Next, the dominating grease parameters and specifications on these aspects will be given. It will also be shown how re-lubrication will enhance the Bearing performance. There is synergy between grease formulation and Bearing design. In the last years new generation grease lubricated Bearings have been developed where grease technology was used to provide significantly lower Friction and longer grease life. This was achieved by developing better greases but also by improving the internal Bearing design, which could be done by using modern advancements in understanding the lubrication mechanisms. Finally, an outlook will be given on future developments in lubricating greases for rolling Bearings. The various test methods are not described in this paper. For an extensive list the reader is referred to [67] (Lugt et al., 2013).
Erich Hodes - One of the best experts on this subject based on the ideXlab platform.
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a self lubricating Bearing material and roller Bearings with such a Bearing material
1995Co-Authors: Achim Adam, Karlheinz Dr Gruenthaler, Erich HodesAbstract:A self-lubricating Bearing material and a Friction Bearing made of such a material are disclosed. Their performance in lubricant-free conditions is so clearly improved that pressure-volume values of up to 6 Mpa/m/s may be reached in a medium load and speed range. The self-lubricating Bearing material has a PTFE-containing plastic matrix with fillers that comprise PbO and at least one metal fluoride. The PbO proportion lies between 15 and 55 % by volume and the metal fluoride proportion between 0.1 and 14 % by volume. CaF2, PbF2 and MgF2 are preferably used as metal fluorides. The admixture of other fillers such as hard substances, pigments of fibrous materials is also possible. The proportion of other additives may amount to up to 40 % by volume of the PbO and metal fluoride fillers.
Achim Adam - One of the best experts on this subject based on the ideXlab platform.
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a self lubricating Bearing material and roller Bearings with such a Bearing material
1995Co-Authors: Achim Adam, Karlheinz Dr Gruenthaler, Erich HodesAbstract:A self-lubricating Bearing material and a Friction Bearing made of such a material are disclosed. Their performance in lubricant-free conditions is so clearly improved that pressure-volume values of up to 6 Mpa/m/s may be reached in a medium load and speed range. The self-lubricating Bearing material has a PTFE-containing plastic matrix with fillers that comprise PbO and at least one metal fluoride. The PbO proportion lies between 15 and 55 % by volume and the metal fluoride proportion between 0.1 and 14 % by volume. CaF2, PbF2 and MgF2 are preferably used as metal fluorides. The admixture of other fillers such as hard substances, pigments of fibrous materials is also possible. The proportion of other additives may amount to up to 40 % by volume of the PbO and metal fluoride fillers.
Ya B Sachek - One of the best experts on this subject based on the ideXlab platform.
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the method of prediction of the life of the dry Friction Bearing unit with a solid grease coating
Journal of Friction and Wear, 2008Co-Authors: M N Dobychin, Ya B SachekAbstract:The method is considered of prediction of wear of full-scale Friction units by the temperature dependence of the integral parameter (Φ, the factor of wear) governed by the conditions of operation derived from the respective type of interactions. The temperature dependence of this parameter can be found from the results of laboratory tests of a model random-configured pair. It is shown that the calculated life of the bush-shaft coupling with the solid-grease VNIINP-212 determined from the factor of wear of this coating obtained with end-to-end tests is 4–45% different from the actual life.
