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- Girlanda, Orlando, et al.
(författare)
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Characterization and Modelling of the Mechanical Properties of Pressboard
- 2013
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Ingår i: 2013 IEEE Conference on Electrical Insulation and Dielectric Phenomena (CEIDP). - : IEEE. - 9781479925964 ; , s. 563-566
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Konferensbidrag (refereegranskat)abstract
- Cellulose-based components constitute the bulk of the current insulation for transformers. Cellulose is an organic polymer material which combines excellent electrical properties and good mechanical performance. As a polymeric material, cellulose is very sensitive to moisture and temperature. These factors can influence the electrical and mechanical performance of a transformer throughout its lifetime. In order to ensure the quality of the product during transformer manufacturing, as well as during transformer life-time services, adequate models for predicting the physical properties of its constituents are needed. The present investigation tackles the mechanical description of pressboard. For this purpose, a three dimensional mechanical model is developed for simulating the in-plane and out-of-plane behavior of the pressboard material. The model is based on an anisotropic viscoelastic-viscoplastic constitutive law, which includes features that are particular for cellulose-based materials, e.g. the peculiar double nature of fiber-network-based and porous material. The material is orthotropic by nature, i.e. the in-plane mechanical properties markedly differ from the out-of-plane ones. Particular regard is taken when considering the effect of out-of-plane stresses which both cause viscous deformation and permanent compaction. The analyses on the mechanical behavior of pressboard are performed by comparing the experimental data on pressboard and the results of model simulations.
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| 2. |
- Girlanda, Orlando, et al.
(författare)
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Modeling and experimental validation of the mechanical behavior of pressboard
- 2014
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Ingår i: Proceedings of the 2014 Electrical Insulation Conference. - : IEEE conference proceedings. ; , s. 203-207
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Konferensbidrag (refereegranskat)abstract
- High density (HD) pressboard is an essential element in power transformers combining good electrical insulation properties with effective mechanical characteristics that well suit design requirements of power transformers. In order to ensure a correctly functioning transformer, it is therefore very important to characterize and to understand the mechanical properties of pressboard under different operating conditions. Pressboard is composed of natural polymeric chains, whose mechanical properties are affected by moisture and temperature. Moreover, temperature and moisture conditions in power transformers vary throughout manufacturing process and service/operation life-time. An accurate definition of the mechanical properties is, therefore, necessary.The present article focuses on the effect of different combinations of temperature/moisture and mechanical load on the deformation behavior of HD pressboard samples. A mechanical constitutive model is developed for finite element (FEM) simulation based on a viscoelastic–viscoplastic material description. Special attention is given on the complex through-thickness deformation behavior of HD pressboard. Thorough analyses are performed based on the comparisons between the results of experimental characterization and FEM modeling and simulations. The good agreement between experimental and modeling results shows a great potential for application in mechanical design of transformer insulation.
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