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Vaziri, Mojgan
Publications (10 of 25) Show all publications
Vaziri, M., Dreimol, C., Abrahamsson, L., Niemz, P. & Sandberg, D. (2023). Parameter estimation and model selection for water vapour sorption of welded bond-line of European beech and Scots pine. Holzforschung, 77(7), 515-526
Open this publication in new window or tab >>Parameter estimation and model selection for water vapour sorption of welded bond-line of European beech and Scots pine
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2023 (English)In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 77, no 7, p. 515-526Article in journal (Refereed) Published
Abstract [en]

The single exponential kinetics (SEK) and parallel exponential kinetics (PEK) models were fitted to kinetic sorption data of welded and unwelded Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.). Furthermore, diffusion coefficients of water vapour in wood were determined using two different Fickian diffusion solutions. The objective was to identify how well these models could represent the moisture contents of the specimens and to characterize differences between the sorption behaviour of welded and unwelded wood. This knowledge can be used to enhance the moisture resistance of welded wood, develop drying schedules, and improve the quality of timbers. The PEK and SEK models provided the most precise and the second most precise fits to the sorption kinetic data, respectively. The two Fickian models are equivalent when both the infinite series are truncated at n = 10. The Fickian models also exhibited the highest discrepancy with the experimental data. Nevertheless, the Fickian models fit relatively better to the sorption data of the welded wood than to that of the unwelded wood. This behaviour may be due to the rigid and less-swelling structure of the welded bond line.

Place, publisher, year, edition, pages
Walter De Gruyter, 2023
Keywords
DVS, Fick, PEK, SEK, sorption kinetics
National Category
Wood Science
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-98899 (URN)10.1515/hf-2022-0013 (DOI)001004311500001 ()2-s2.0-85162805491 (Scopus ID)
Note

Validerad;2023;Nivå 2;2023-08-16 (joosat);

Licens fulltext: CC BY License

Available from: 2023-06-26 Created: 2023-06-26 Last updated: 2023-08-16Bibliographically approved
Vaziri, M., Dreimol, C., Abrahamsson, L., Niemz, P. & Sandberg, D. (2023). Water-vapour sorption of welded bond-line of European beech and Scots pine. Holzforschung, 77(7), 500-514
Open this publication in new window or tab >>Water-vapour sorption of welded bond-line of European beech and Scots pine
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2023 (English)In: Holzforschung, ISSN 1437-434X, Vol. 77, no 7, p. 500-514Article in journal (Refereed) Published
Abstract [en]

The wood–water interactions of welded bond-lines of European beech (Fagus sylvatica L.) and Scots pine (Pinus sylvestris L.) were in this paper studied for the first time with dynamic vapour sorption equipment. The aim of this study was to characterize the water sorption in the welded bond-line and to define to which extent it deviates from water sorption of the unwelded wood. The objective was to provide deepened knowledge about water sorption of the welded bond-line, which could be used to improve the moisture resistance of welded wood in the future. The welded wood generally had lower equilibrium moisture contents than the unwelded wood. The welded bond-lines of beech and pine showed greater hysteresis than the unwelded wood from 0 to 55 % relative humidity. All specimens showed faster adsorption than desorption. However, the welded wood showed slower adsorption but faster desorption than unwelded wood. The time to complete half of the fractional change in moisture content (E(t) = 0.5) increased as the moisture content increased. The adsorption diffusion coefficients of beech and welded beech were higher than those of pine and welded pine up to 50 % and 40 % RH, respectively. In desorption, pine had a higher diffusion coefficient than beech in the whole range of 85–0 % RH. Analogously, welded pine had a higher diffusion coefficient than welded beech in the range of 85–5 % RH. In contrast to the desorption, the welded wood always had lower adsorption diffusion coefficients than the corresponding unwelded wood. The diffusion coefficients showed irregular patterns in some ranges of the RH. Therefore, it was hard to make a clear conclusion about the water-sorption behaviour of the specimens based on the defined diffusion coefficients.

Place, publisher, year, edition, pages
De Gruyter, 2023
Keywords
isotherm, moisture content, relative humidity, sorption kinetic, wood-moisture relations
National Category
Wood Science
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-98278 (URN)10.1515/hf-2022-0012 (DOI)000995019600001 ()2-s2.0-85160816337 (Scopus ID)
Note

Validerad;2023;Nivå 2;2023-08-16 (joosat);

Licens fulltext: CC BY License

Available from: 2023-06-13 Created: 2023-06-13 Last updated: 2023-08-16Bibliographically approved
Vaziri, M. & Sandberg, D. (2021). Welding of thermally modified wood and thermal modification of the welded wood: Effects on the shear strength under climatic conditions. BioResources, 16(2), 3224-3234
Open this publication in new window or tab >>Welding of thermally modified wood and thermal modification of the welded wood: Effects on the shear strength under climatic conditions
2021 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 16, no 2, p. 3224-3234Article in journal (Refereed) Published
Abstract [en]

This work investigated how thermal modification affects the shear strength of welded joints under different climatic conditions. The order of the thermal modification, before or after the welding, was investigated for its effect on the shear strength of the welded wood. Two groups of thermally modified specimens were prepared in a laboratory kiln under controlled conditions, one thermally modified before welding and the other after welding of the specimens. The shear strength of the specimens were measured at four different moisture contents of 10%, 12%, 16%, and 18%, and the results for the two different approaches were compared. Moreover, observations of the X-ray computed tomography scanning and digital microscopy were used to study the density profile and the structural details of the welded joints. The results showed that thermal treatment of the wood either before or after welding had a negative influence on the shear strength, and the modes of failure of the joints in mechanical tests were in most cases brittle. In the weld interface of the wood modified before welding, a rigid material similar to charcoal was produced as a result of the further degradation of wood by welding pressure and frictional motion. Welding of wood before thermal modification, however, yielded thicker and more densified joints with less susceptibility to higher moisture variations than the joints obtained by welding the thermally modified wood.

Place, publisher, year, edition, pages
NC State University, 2021
Keywords
CT scanning, Digital microscopy, Shear strength, Thermal modification, ThermoWood
National Category
Wood Science
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-83258 (URN)10.15376/biores.16.2.3224-3234 (DOI)000647769700008 ()2-s2.0-85137724817 (Scopus ID)
Funder
Swedish Research Council Formas, 2017-01157
Note

Validerad;2021;Nivå 2;2021-03-15 (johcin)

Available from: 2021-03-14 Created: 2021-03-14 Last updated: 2022-12-02Bibliographically approved
Vaziri, M., Karlsson, O., Abrahamsson, L., Lin, C.-F. & Sandberg, D. (2021). Wettability of welded wood-joints investigated by the Wilhelmy method: part 1. Determination of apparent contact angles, swelling, and water sorption.. Holzforschung, 75(1), 65-74
Open this publication in new window or tab >>Wettability of welded wood-joints investigated by the Wilhelmy method: part 1. Determination of apparent contact angles, swelling, and water sorption.
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2021 (English)In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 75, no 1, p. 65-74Article in journal (Refereed) Published
Abstract [en]

This study presents a novel application of the Wilhelmy plate method on welded joints of Scots pine sapwood and beech. Welding resulted in an increase in the contact angle (increased hydrophobicity) as well as a decrease in the water uptake and swelling of the welded pine-joint compared to non-welded pine. When the welding time was extended from 4 to 5 s, these properties were further pronounced. Welding of beech, on the other hand, led to an increase in the contact angle and a decrease in the water uptake, but an increase in the swelling.

Fourier Transform Infrared spectroscopy showed that welding increased the aliphatic C-H and unsaturated C=C stretching absorption bands in pine and beech. Scanning electron microscopy showed a dense structure at the welded joints of the both species, giving evidence of a lower porosity that leads to a lower permeability as a result of the welding.

Place, publisher, year, edition, pages
De Gruyter Open, 2021
National Category
Wood Science
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-80328 (URN)10.1515/hf-2019-0308 (DOI)000600064600007 ()2-s2.0-85089449904 (Scopus ID)
Funder
Swedish Research Council Formas
Note

Validerad;2021;Nivå 2;2021-01-11 (johcin)

Available from: 2020-08-07 Created: 2020-08-07 Last updated: 2021-01-11Bibliographically approved
Vaziri, M., Karlsson, O., Abrahamsson, L., Moghaddam, M. & Sandberg, D. (2021). Wettability of welded wood-joints investigated by the Wilhelmy method: part 2. Effect of wollastonite additive. Holzforschung, 75(1), 79-86
Open this publication in new window or tab >>Wettability of welded wood-joints investigated by the Wilhelmy method: part 2. Effect of wollastonite additive
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2021 (English)In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 75, no 1, p. 79-86Article in journal (Refereed) Published
Abstract [en]

The effect of wollastonite on the wetting properties of welded Scots pine-joints was studied using the multicycle Wilhelmy plate method and by observation of the chemical composition of the welded joints. Welding pine with wollastonite for 5 s resulted in a decrease in the water uptake and the swelling, and an increase in the contact angle of the welded joint compared to welded wood without wollastonite. High-performance liquid chromatography and gas chromatography/mass spectrometry showed the presence of dehydration products such as furfural, 5-hydroxymethylfurfural, and levoglucosan in methanol extracts from welded joints of specimens welded with and without wollastonite. Phenols were also found by analysis using the Folin-Ciocalteu method and High-performance liquid chromatography. The importance of such compounds in relation to the wetting properties of the welded joint is discussed.

Place, publisher, year, edition, pages
De Gruyter Open, 2021
Keywords
apparent contact angle (CA), gas chromatography/mass spectrometry (GC/MS), high-performance liquid chromatography (HPLC), liquid sorption, pine, swelling, welding time
National Category
Wood Science
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-80595 (URN)10.1515/hf-2019-0310 (DOI)000600064600008 ()2-s2.0-85089107202 (Scopus ID)
Funder
Swedish Research Council Formas
Note

Validerad;2021;Nivå 2;2021-01-11 (johcin)

Available from: 2020-08-27 Created: 2020-08-27 Last updated: 2021-01-11Bibliographically approved
Zor, M., Vaziri, M. & Sandberg, D. (2020). Water Resistance of Welded Birch Wood Produced by Linear Friction. Paper presented at III. International Mediterranean Forest and Environment Symposium (IMFES-2019), 3-5 Ocotber, 2019, Kahramanmaraş, Turkey. Kastamonu University Journal of Forestry Faculty, 20(3), 266-271
Open this publication in new window or tab >>Water Resistance of Welded Birch Wood Produced by Linear Friction
2020 (English)In: Kastamonu University Journal of Forestry Faculty, ISSN 1303-2399, Vol. 20, no 3, p. 266-271Article in journal (Refereed) Published
Abstract [en]

Aim of study: In this study, it was aimed to determine the shear strength after water immersion and observe bond-line density of the welded birch wood.

Material and methods: 24 welded samples of dimensions 200x20x20 mm3 (LxTxR) were prepared from sapwood of birch wood (Betula pendula). Shear strength of welded birch at 24h and 48h water soaking were investigated.X-Ray CT-scanning was used to monitor the density profile of welded bond-line.

Main results: The results showed that shear strength decreased slightly with increasing water immersion time. The decreasing of the average shear strength, caused by immersion for 24h and 48h were 60.25% and 78.9%, respectively, compared to control sample. With the welding process, a significant change in density was observed in the welding bond-line. As a result, the X-Ray CT scanner shows that it works effectively on wood material.

Highlights: The results of this research revealed the applicability of a new method alternative to traditional mechanical fasteners (nail, screw etc.) or gluing. The availability of welding combining method in the field of wood engineering should be explored widely and more studies are recommended for appropriate parameters.

Abstract [tr]

Çalışmanın amacı: Bu çalışmada, kaynaklanmış huş odunun su daldırma sonrası makaslama dayanımının belirlenmesi ve kaynak birleşim hattı yoğunluğunun gözlemlenmesi amaçlanmaktadır.

Materyal ve yöntem: Huş odunun diri odunlarından 200x20x20 mm3(boyuna x radyal x teğet boyutlarında 24 örnek hazırlanmıştır. 24 saatlik ve 48 saatlik suya daldırma sonrası kaynaklanmış huş odunun makaslama dayanımları incelenmiştir. Odun kaynak birleşim hattının yoğunluk değişimi için X-Ray bilgisayarlı tomografi tarayıcısı kullanıldı.

Temel sonuçlar: Sonuçlara göre, suya daldırma süresi arttıkça makaslama dayanımı azda olsa azalma göstermiştir. Kontrol örneğine göre, makaslama dayanımındaki azalış, 24 saatte ortalama %60.25, 48 saatte ortalama %78,9 oranındadır. Kaynak işlemi ile kaynak hattında yoğunlukta önemli derecede değişiklik gözlenmiştir. Sonuç olarak, kullanılan X-Ray CT tarayıcısı, ahşap malzeme üzerinde etkili bir şekilde çalıştığını göstermektedir.

Araştırma vurguları: Bu araştırmanın sonuçları, geleneksel ahşap mekanik bağlantı elemanlarına (çivi, vida vb.)ya da yapıştırmaya alternatif yeni bir yöntemin uygulanabilirliği ortaya çıkmıştır. Ahşap mühendisliği alanında kaynak birleştirme yönteminin kullanılabilirliği geniş çapta irdelenmeli ve uygun parametreler için daha çok çalışmalar yapılması önerilmektedir.

Place, publisher, year, edition, pages
Kastamonu University, 2020
Keywords
Birch Wood, X-Ray CT Scanner, Linear Welding, Water Resistance, Huş Odunu, X-Ray CT Tarayıcı, Doğrusal Kaynaklama, Su Dayanımı
National Category
Wood Science
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-82595 (URN)10.17475/kastorman.849500 (DOI)000603995000007 ()
Conference
III. International Mediterranean Forest and Environment Symposium (IMFES-2019), 3-5 Ocotber, 2019, Kahramanmaraş, Turkey
Note

Godkänd;2021;Nivå 0;2021-01-21 (alebob);Konferensartikel i tidskrift;

Finansiär: Scientific and Technological Research Council of Turkey (TUBITAK- 2219/BIDEB, 2019)

Available from: 2021-01-21 Created: 2021-01-21 Last updated: 2021-01-21Bibliographically approved
Vaziri, M., Abrahamsson, L., Hagman, O. & Sandberg, D. (2020). Welding of wood in the presence of wollastonite. BioResources, 15(1), 1617-1628
Open this publication in new window or tab >>Welding of wood in the presence of wollastonite
2020 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 15, no 1, p. 1617-1628Article in journal (Refereed) Published
Abstract [en]

The use of wollastonite as a natural additive for the welding of Scots pine improved the water resistance and shear strength of the welded joint. The X-ray computed tomography images revealed that the welding of Scots pine with wollastonite could postpone crack formation in the welded joints. The specimens welded for a longer time (5 s) had a more uniform distribution of wollastonite particles in welded joints. The microstructure of the wood and the thickness of the wood cell walls also had a great influence on the thickness and strength of the welded joints. Water immersion tests showed that the use of wollastonite in wood joints was able to meet the requirement of resistance to frequent short-term and long-term exposure to water.

Place, publisher, year, edition, pages
NC State University, 2020
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-78020 (URN)10.15376/biores.15.1.1617-1628 (DOI)000511129100112 ()2-s2.0-85088261735 (Scopus ID)
Note

Validerad;2020;Nivå 2;2020-03-10 (johcin)

Available from: 2020-03-10 Created: 2020-03-10 Last updated: 2020-12-04Bibliographically approved
Zor, M., Vaziri, M. & Sandberg, D. (2019). Shear strength of welded birch wood produced by linear friction. In: Turgay Dindaroğlu (Ed.), III. International Mediterranean Forest And Environment Symposium: Full-paper proceedings. Paper presented at III. International Mediterranean Forest and Environment Symposium(IMFES 2019), Kahramanmaraş, Turkey, October 3-5, 2019 (pp. 109-112). Turkey: Kahramanmaras Sutcu Imam University, Faculty of Forestry
Open this publication in new window or tab >>Shear strength of welded birch wood produced by linear friction
2019 (English)In: III. International Mediterranean Forest And Environment Symposium: Full-paper proceedings / [ed] Turgay Dindaroğlu, Turkey: Kahramanmaras Sutcu Imam University, Faculty of Forestry , 2019, p. 109-112Conference paper, Published paper (Refereed)
Abstract [en]

Friction welding of wood is a joining technique that has the advantage of being a fast process that does not require the utilization of additional material such as mechanical fastener or synthetic adhesives. The water resistance, as well as shear strength of the welded joints of birch (Betula pendula) at 24 and 48 hours water-soaking time were investigated. Additionally, an X-ray Computed Tomography (CT) scanning was used to monitor the density profile of the welded bond-line. The LT-surfaces of specimens measuring 200 × 20 × 20 mm (L × T × R) were welded two-by-two. The results showed that the shear strength decreased slightly with increasing immersion time. The reduction of the shear strength caused by immersion in water for 24h and 48h compared to non-soaked specimens, were 60% and 79%, respectively. The X-ray CT-scanning results revealed that the average density of the Birch (530 kg/m3) increased to 700 kg/m3 in the welded bond line, i.e. the wood also undergo densification during the welding process.

Place, publisher, year, edition, pages
Turkey: Kahramanmaras Sutcu Imam University, Faculty of Forestry, 2019
Keywords
Birch wood, X-ray CT-scanner, Friction linear welding, Shear test
National Category
Wood Science
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-83382 (URN)
Conference
III. International Mediterranean Forest and Environment Symposium(IMFES 2019), Kahramanmaraş, Turkey, October 3-5, 2019
Funder
Swedish Research Council Formas, 2017-01157
Note

Finansiär: Scientific and Technological Research Council of Turkey (TUBITAK- 2219/BIDEB, 2019)

Available from: 2021-03-24 Created: 2021-03-24 Last updated: 2021-03-26Bibliographically approved
Vaziri, M. & Sandberg, D. (2019). Water resistance of welded pine. Pro Ligno, 15(4), 200-205
Open this publication in new window or tab >>Water resistance of welded pine
2019 (English)In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 15, no 4, p. 200-205Article in journal (Refereed) Published
Abstract [en]

Wood welding is a novel technology to join wood elements based on friction between two wood surfaces. The crack formation in the welded joint was visualized and studied using X-ray Computed Tomography. Increasing the welding time from 4 s to 5 s could either make no difference or decrease the cracking time i.e. the time from water exposure of the specimen to the crack appearance in the welded joint, whereas increasing the welding time could improve the water resistance and shear strength of the welded joint. The incompatibility between the CT-scanning results with immersion test and the shear strength results lead to the idea that the cracking time may not be an indicator of durability and strength of the welded wood

Place, publisher, year, edition, pages
Brasov, Rumania: Transilvania University of Brasov, 2019
Keywords
cracking, CT scanning, Micro CT scanning, shear strength, welding time
National Category
Wood Science
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-83383 (URN)
Funder
Swedish Research Council Formas, 2017-01157
Note

Godkänd;2021;Nivå 0;2021-03-24 (alebob)

Available from: 2021-03-24 Created: 2021-03-24 Last updated: 2021-03-24Bibliographically approved
Berg, S., Sandberg, D., Ekevad, M. & Vaziri, M. (2015). Crack influence on load-bearing capacity of glued laminated timber using extended finite element modelling (ed.). Wood Material Science & Engineering, 10(4), 335-343
Open this publication in new window or tab >>Crack influence on load-bearing capacity of glued laminated timber using extended finite element modelling
2015 (English)In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 10, no 4, p. 335-343Article in journal (Refereed) Published
Abstract [en]

Most of the cracks are caused by changes in temperature and relative humidity which lead to shrinkage and swelling of the wood and thereby induce stresses in the structure. How these cracks influence the strength of the wooden structure, especially the shear strength, is not well understood. However, it is reasonable to expect that cracks have an impact on the shear strength as they preferably run along the beams in the direction of grain and bond lines. The purpose of this study was to investigate the load-bearing capacity of cracked glulam beams and to find a model that could predict the failure load of the beams due to the cracks. Three-point bending tests were used on glulam beams of different sizes with pre-manufactured cracks. An orthotropic elastic model and extended finite element method was used to model the behaviour of the cracked beams and to estimate the load-bearing capacity. The conclusions were validated by numerical simulations of the mechanical behaviour of three-point bending of glulam beams with different crack locations. The crack initiation load was recorded as the failure load and compared to the experimental failure load. The results of the compaction simulations agree well with the experimental results.

Keywords
Fundamental properties of wood and wood-based materials, wood processing
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-7608 (URN)10.1080/17480272.2015.1027268 (DOI)000368718400003 ()2-s2.0-84945452586 (Scopus ID)5ff81246-b07d-4875-b725-2b03c5e2df47 (Local ID)5ff81246-b07d-4875-b725-2b03c5e2df47 (Archive number)5ff81246-b07d-4875-b725-2b03c5e2df47 (OAI)
Note

Validerad; 2015; Nivå 1; 20150417 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2022-08-30Bibliographically approved
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