| 1. |
|
|
| 2. |
- Adamopoulos, Stergios
(författare)
-
Acoustic emission monitoring of wood materials and timber structures: A critical review
- 2022
-
Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618. ; 350
-
Forskningsöversikt (refereegranskat)abstract
- The growing interest in timber construction and using more wood for civil engineering applications has given highlighted importance of developing non-destructive evaluation (NDE) methods for structural health monitoring and quality control of wooden construction. This study, critically reviews the acoustic emission (AE) method and its applications in the wood and timber industry. Various other NDE methods for wood monitoring such as infrared spectroscopy, stress wave, guided wave propagation, X-ray computed tomography and thermography are also included. The concept and experimentation of AE are explained, and the impact of wood properties on AE signal velocity and energy attenuation is discussed. The state-of-the-art AE monitoring of wood and timber structures is organized into six applications: (1) wood machining monitoring; (2) wood drying; (3) wood fracture; (4) timber structural health monitoring; (5) termite infestation monitoring; and (6) quality control. For each application, the opportunities that the AE method offers for in-situ monitoring or smart assessment of wood-based materials are discussed, and the challenges and direction for future research are critically outlined. Overall, compared with structural health monitoring of other materials, less attention has been paid to data-driven methods and machine learning applied to AE monitoring of wood and timber. In addition, most studies have focused on extracting simple time-domain features, whereas there is a gap in using sophisticated signal processing and feature engineering techniques. Future research should explore the sensor fusion for monitoring full-scale timber buildings and structures and focus on applying AE to large-size structures containing defects. Moreover, the effectiveness of AE methods used for wood composites and mass timber structures should be further studied.
|
|
| 3. |
- Adamopoulos, Stergios, et al.
(författare)
-
Acoustic properties of acetylated wood under different humid conditions and its relevance for musical instruments
- 2018
-
Ingår i: Proceedings of the 9th European Conference on Wood Modification 2018, Arnhem, The Netherlands. - The Netherlands : Practicum. ; , s. 236-243
-
Konferensbidrag (refereegranskat)abstract
- In musical instrument making, less expensive wood species and materials with good characteristics and acoustical properties can provide potentials to find alternatives to the traditional exotic wood species used today. Modified wood could be such a choice if shows similar sound characteristics to wood coming from endangered and expensive tropical species with problematic commercial availability. In musical instruments, the overall functionality depends on the contribution of wood to different material performance indexes like sound radiation coefficient (R), characteristic impedance (z) and acoustic conversion efficiency (ACE). In this study, the performance indexes were measured for acetylated beech, maple and radiata pine and compared with these obtained for the reference wood materials maple, mahogany, alder and ash. A non-destructive free-free flexural vibration test method was used at constant temperature (20oC) but in different humid conditions- dry (35% RH), standard (65% RH) and wet (85% RH). Dimensional changes in the different humid conditions were also taken in account. Acetylated wood showed lower EMC with higher dimensional stability at each humidity level as compared with the reference wood materials. These properties are considered important factors for making quality musical instruments. Based on the acoustical properties, acetylated wood materials, especially radiata pine, showed good potential for use for musical instruments where specific characteristics of sound are required. However, the other types of acetylated wood can also be used for specific musical instruments.
|
|
| 4. |
- Adamopoulos, Stergios, et al.
(författare)
-
Adhesive bonding of beech wood modified with a phenol formaldehyde compound
- 2012
-
Ingår i: European Journal of Wood and Wood Products. - : Springer Science and Business Media LLC. - 0018-3768 .- 1436-736X. ; 70:6, s. 897-901
-
Tidskriftsartikel (refereegranskat)abstract
- Untreated (controls) and phenol–formaldehyde (PF)-modified beech wood (10 and 25 % solid content) were glued with phenol resorcinol formaldehyde (PRF) and polyvinyl acetate (PVAc). Shear strength of PRF-bonded specimens was higher than that of PVAc-bonded ones under dry and wet conditions irrespective of the pre-treatment. Under dry conditions, only PVAc-bonded specimens exhibited reduction in shear strength due to PF-modification with 25 % PF concentration as compared to the controls. PF treated wood provided inferior bonding under wet conditions with the exception of 25 % PF concentration specimens glued with PRF adhesive. Modification with PF resulted in a decrease of adhesive penetration into the porous network of interconnected cells, especially at 25 % PF concentration.
|
|
| 5. |
|
|
| 6. |
- Adamopoulos, Stergios, et al.
(författare)
-
Dimensional changes of extracted and non-extracted small wood specimens of black locust (Robinia pseudoacacia L.)
- 2003
-
Ingår i: European Journal of Wood and Wood Products. - : Springer. - 0018-3768 .- 1436-736X. ; 61:4, s. 264-268
-
Tidskriftsartikel (refereegranskat)abstract
- From straight grained heartwood of black locust (Robinia pseudoacacia L.), specimens, 3 cm×3 cm in cross section and 0.5 mm (or 10 mm) in axial direction, were cut and used for the determination of dimensional changes and the rate of tangential swelling. Mean radial, tangential and axial shrinkage was 5.30%, 6.67% and 0.16%, respectively, while the coefficient of anisotropy was 1.26. Half of the specimens for the determination of the rate of tangential swelling were extracted for 48 h with distilled hot water. The tangential dimensional change and the time taken to attain half maximum swelling in air-dry and oven-dry specimens were assessed according to a common technique. Extractive removal resulted in an increase of the total magnitude of tangential swelling in both air-dry and oven-dry specimens. However, no significant differences in time taken to attain half maximum swelling between air-dry and oven-dry specimens were observed after extraction. The rate of tangential swelling was lower in air-dry specimens than in oven-dry specimens after 30 min of immersion in water when were non-extracted and after 5 min of immersion in water when were extracted. Extracted air-dry specimens had a greater rate of tangential swelling than non-extracted air-dry specimens and the same occurred for oven-dry specimens. Extraction resulted in a higher diffusion coefficient for air-dry specimens. The diffusion coefficient calculated for non-extracted air-dry specimens (0.901×10−4 cm2/min) showed that black locust is a difficult species to impregnate.
|
|
| 7. |
|
|
| 8. |
- Adamopoulos, Stergios, et al.
(författare)
-
Effect of cambium age and ring width on density and fibre length of black locust and chestnut wood
- 2010
-
Ingår i: Wood research. - 1336-4561. ; 55:3, s. 25-36
-
Tidskriftsartikel (refereegranskat)abstract
- The relationship between wood density (WD) and fibre length (FL) with cambium age (CA) and ring width (RW) was studied in two ring-porous species, black locust and coppice-grown chestnut, collected in the Sithonia Peninsula, Chalkidiki, Greece. Using regression analysis methods, models of WD and FL in relation to CA and RW were obtained. It was found that the effect of CA and RW on WD and FL was similar for both species examined. WD of black locust and chestnut was predicted better through a model using CA and RW. A model for FL variations was also obtained with CA and RW and was more accurate than the simple models based on the two factors, CA and RW, separately. The multiple regression models suggested that the use of cambial age of growth rings together with their width might explain better their effects on WD and FL of black locust and chestnut.
|
|
| 9. |
- Adamopoulos, Stergios, et al.
(författare)
-
Effect of hot-water extractives on water sorption and dimensional changes of black locust wood
- 2012
-
Ingår i: Wood research. - 1336-4561. ; 57:1, s. 69-78
-
Tidskriftsartikel (refereegranskat)abstract
- The hygroscopicity and the dimensional changes of black locust heartwood were investigated in relation to the progressive removal of hot-water extractives. Extraction in the original specimen form removed only part of the total 8.434 % hot-water extractives, 3.601 % in first extraction and 4.642 % in second extraction. As a result, the adsorption and desorption behaviour of black locust wood was little affected by the extraction and only a small increase was observed in dimensional changes at every RH from 0 % to 97 %. The mean hysteresis coefficient was also little affected by extraction and increased from 0.75 at the unextracted stage to 0.77 at the second extraction. The initial dimensional change 3.76 % of unextracted black locust wood corresponding to RH changes between 43 % and 80 % increased after the first and second extraction to the respective values of 3.96 % and 3.97 %. Extraction had no effect on the significant, very strong linear relationships between swelling or shrinkage and equilibrium moisture content (EMC).
|
|
| 10. |
- Adamopoulos, Stergios, et al.
(författare)
-
Effect of laser drilling on mechanical properties of fir (Abies borisii regis) and spruce (Picea excelsa) wood
- 2014
-
Ingår i: Wood Structure, Properties and Quality – 2014. - : Moscow State University Press. - 9785813506253 ; , s. 7-12
-
Konferensbidrag (refereegranskat)abstract
- Fir and spruce wood specimens, 2×2 cm in cross section and 34 cm long, were pre-pared with true radial and tangential surfaces. All lateral surfaces of the wood specimens were drilled by laser beams to a depth of 0,4 cm (1/5 of specimen thickness) with two drilling pat-terns (distance between holes 1 × 1 cm and 1 × 2 cm). After drilling, static bending (MOR, MOE), axial compression strength and toughness were determined and compared with non-drilled control specimens. The effects of the two laser drilling patterns on mechanical proper-ties of fir and spruce wood specimens were measured and assessed. The results showed that the two drilling patterns created by laser beams on all lateral surfaces of fir and spruce wood specimens at 0,4 mm depth did not practically affect the mechanical properties of wood.
|
|
