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Kvarstående deformation hos furu efter böjbelastning under samtidig fuktvariation.
Kungliga Tekniska Högskolan.
KTH Träteknologi.
1995 (Swedish)Report (Other academic)Alternative title
Non-recoverable Deformation in Scotch Pine after Bending and Simultaneous Variation inMoisture Content. (English)
Abstract [en]

This investigation describes the non-recoverable deformation in Scotch pine (Pinus silvestris L) specimens. The specimens have been loaded in bending and exposed to cyclic moisture content variation before unloading and subsequent resoaking in water and drying. The deformation of the unloaded specimens were recorded before resoaking and after drying and then, the degree of recovery was determined. Recovery is here defined as ratio between change of deformation during the resoaking cycle and the deformation before resoaking. Two test groups have been investigated, that is samples loaded in the radial and tangential direction, respectively. Finally, the specimens were examined in scanning electron microscope, SEM, to study the pattern of micro-cracks.

The result shows that the mean recovery is about 80 %for the specimens indepentent of direction of load. This confirm, that most of the mechano-sorptive creep is recoverable. The SEM-study show cracks in the cell walls and the nature of the cracks is dependent on the direction between the load and annual ring orientation.

 

Abstract [sv]

I detta arbete undersöks den kvarstående deformationen hos små provkroppar av furu (Pinus silvestris L) som utsatts för böjbelastning och samtidig cyklisk varierande fuktkvot. Två provgrupper har undersökts, dels prover belastade radiellt årsringama, dels prover belastade tangentiellt årsringarna. Efter avlastning uppfuktades provkroppama i vattenbad varefter de åter fick torka och återhämtningen bestämdes. Återhämtning har definierats som skillnaden i utböjning före och efter uppfuktning och torkning i förhållande till utböjningen före uppfuktning. Provema har även undersökts i svepelektronmikroskop (SEM).Resultaten visar att återhämtningen var omkring 80 % oberoende av belastningsriktning. Detta bekräftar att stor del av den krypdeformation som erhölls vid fuktcykling under belastning är reversibel. SEM-studien visar att brott uppstår i cellväggama vid mekanosorptiv krypning under relativt måttlig belastning, 30 procent av böjbrottgränsen vid 12 % fuktkvot, och att skadornas karaktär är beroende av belastningsriktningen i förhållande till årsringsorienteringen

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 1995. , 8 p.
Series
TRITA-TRÄ R-95-17, ISSN 1104-2117 ; 17
Keyword [en]
wood, Scotch pine, Pinus silvestris L, mechano-sorption, annual ring orientation, cracks, creep, cell wall, rheology
Keyword [sv]
krypning, reologi, trä, cellvägg, sprickor, deformationer, furu, Pinus sylvestris, börjning, hållfasthet
National Category
Wood Science
Research subject
Technology (byts ev till Engineering), Forestry and Wood Technology
Identifiers
URN: urn:nbn:se:lnu:diva-20796ISRN: KTH/TRÄ/R--95/17--SEOAI: oai:DiVA.org:lnu-20796DiVA: diva2:541006
Available from: 2012-08-28 Created: 2012-07-13 Last updated: 2012-08-28Bibliographically approved

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