Karakterizacija parametara elastičnosti ploče s orijentiranim makroiverjem (OSB) proizvedene od iverja drva topole (Populus deltoides) uz pomoć ultrazvučnoga kontaktnog prijenosa impulsa

When using wood and wood-based composites, it is necessary to determine the elastic constants of these engineered materials. Oriented strand board (OSB), as structural wood based panel, plays a significant role in the building sector, but the accessibility of such elastic constants of OSB is mostly limited. For this purpose, this study aimed at determining the elastic wave velocity, stiffness and all elastic constants of OSB made from Poplar (Populus deltoides) strands using ultrasonic through–transmission technique. Laboratory OSBs with the mean density of 760 kg/m3 were made with the average strand sizes of 0.6 mm in thickness, 120 mm in length and 30 mm in width. 8 % phenol-formaldehyde (PF) resin was used with the pressing conditions of 3.43 N/mm2, 190 °C and 600 s as pressure, temperature and time of pressing, respectively. The OSBs were assumed as an orthotropic model. Three modulus of elasticity (E1, E2, and E3), three shear modulus (G12, G13 and G23), and six Poisson’s ratios (v12, v21, v13, v31, v23, v32) were calculated by longitudinal, transversal and quasi-transversal waves velocities. Ultrasonically determined stiffness coefficients of OSB were investigated by representative volume elements (RVE). Therefore, the separation of scales requirement is satisfied, and the measured velocities can be applied to determine the engineering elastic parameters of the examined OSB. The results indicate that modulus of elasticity and shear modulus are in the same order of magnitude in comparison with other references, and the values of Poisson’s ratios are valid in ultrasonic range measurement. In conclusion, the ultrasonic contact pulse transmission shows great potential to determine the characterization of elastic wave velocity, stiffness and engineering elastic parameters.Za primjenu drva i kompozita na bazi drva iznimno je važno odrediti konstante elastičnosti tih konstrukcijskih materijala. Ploča s orijentiranim makroiverjem (OSB ploča), kao strukturna ploča na bazi drva, ima široku primjenu u građevnom sektoru, a pristup takvim konstantama elastičnosti OSB ploča uglavnom je ograničen. Stoga je cilj ove studije bio odrediti brzinu elastičnog vala, krutost i sve konstante elastičnosti OSB ploča proizvedenih od makroiverja topole (Populus deltoides) primjenom ultrazvučne tehnike. Od iverja prosječne debljine 0,6 mm, duljine 120 mm i širine 30 mm laboratorijski su izrađene OSB ploče srednje gustoće 760 kg/m3. Upotrijebljena je 8 %-tna fenol-formaldehidna (PF) smola u ovim uvjetima prešanja: tlak je bio 3,43 N/mm2, temperatura 190 °C, a proces prešanja trajao je 600 s. Pretpostavljeno je da su OSB ploče ortotropni modeli. Na temelju srednjih vrijednosti uzdužne, poprečne i kvazipoprečne brzine valova izračunana su tri modula elastičnosti (E1, E2 i E3), tri modula smicanja (G12, G13 i G23) i šest Poissonovih omjera v12, v21, v13, v31, v23, v32). Ultrazvučno utvrđene krutosti OSB ploča ispitivane su reprezentativnim volumnim elementima (RVE). Dakle, ispunjen je zahtjev za odvajanje skala, a izmjerene se brzine mogu primijeniti za određivanje inženjerskih parametara elastičnosti ispitivanih OSB ploča. Rezultati pokazuju da su moduli elastičnosti i moduli smicanja istog reda veličine u usporedbi s drugim referencama, a vrijednosti Poissonovih omjera vrijede u mjerenjima ultrazvučnog raspona. Zaključno, ultrazvučni kontaktni prijenos impulsa pokazuje velik potencijal za određivanje brzine elastičnih valova, krutosti i konstrukcijskih parametara elastičnosti materijala

Numerical modeling in timber engineering – moisture transport and quasi-brittle failure

With the rising popularity of timber structures and the increasing complexity of timber engineering projects, the need for numerical simulation tools specific to this building material is gaining rapidly in importance. in particular, moisture transport processes and the quasi-brittle failure behavior, both difficult to describe, present major challenges and are of great relevance in practical construction. For these reasons, this article presents numerical modeling concepts for predicting moisture gradients, estimating effective stiffness and strength, and numerically identifying potential cracking mechanisms in wooden components. These concepts are validated through experimental test programs, and the associated challenges are addressed. selected results ultimately demonstrate the capabilities and relevance of such methods for timber engineering

Proceedings of the 29th EG-ICE International Workshop on Intelligent Computing in Engineering

This publication is the Proceedings of the 29th EG-ICE International Workshop on Intelligent Computing in Engineering from July 6-8, 2022. The EG-ICE International Workshop on Intelligent Computing in Engineering brings together international experts working on the interface between advanced computing and modern engineering challenges. Many engineering tasks require open-world resolution of challenges such as supporting multi-actor collaboration, coping with approximate models, providing effective engineer-computer interaction, search in multi-dimensional solution spaces, accommodating uncertainty, including specialist domain knowledge, performing sensor-data interpretation and dealing with incomplete knowledge. While results from computer science provide much initial support for resolution, adaptation is unavoidable and most importantly, feedback from addressing engineering challenges drives fundamental computer-science research. Competence and knowledge transfer goes both ways. &nbsp

Proceedings of the 29th EG-ICE International Workshop on Intelligent Computing in Engineering

This publication is the Proceedings of the 29th EG-ICE International Workshop on Intelligent Computing in Engineering from July 6-8, 2022. The EG-ICE International Workshop on Intelligent Computing in Engineering brings together international experts working on the interface between advanced computing and modern engineering challenges. Many engineering tasks require open-world resolution of challenges such as supporting multi-actor collaboration, coping with approximate models, providing effective engineer-computer interaction, search in multi-dimensional solution spaces, accommodating uncertainty, including specialist domain knowledge, performing sensor-data interpretation and dealing with incomplete knowledge. While results from computer science provide much initial support for resolution, adaptation is unavoidable and most importantly, feedback from addressing engineering challenges drives fundamental computer-science research. Competence and knowledge transfer goes both ways. &nbsp

Simulating failure mechanisms in wooden boards with knots by means of a microstructure-based multisurface failure criterion

(VLID)279048

A numerical approach to describe failure of wood - From the wood cell level up to wood-based products

For the description of the failure processes in clear-wood, a multiscale approach, based on the Finite Element (FE) method, was performed. In a previous work, failure mechanisms at the single wood cell level were identified by using a unit cell approach in combination with the eXtended Finite Element Method (XFEM). Finally, a multisurface failure criterion was obtained. Within this work, these results were combined in another unit cell at the annual year ring level, where late-(LW) and earlywood (EW) cells form a layered structure. Subsequently, a single multisurface failure criterion with predefined global crack directions at the clear-wood level could be won, which will be implemented into the commercial FE software Abaqus through a subroutine. In combination with a previously developed FE simulation tool, which allows the 3D virtual reconstruction of different wood-based products, including knots and the surrounding fiber deviations, the main failure mechanisms in such products can now be captured realistically. Thus, the influences of knot configurations on several effective properties, like modulus of elasticity or bending strength, can be determined. Moreover, the resulting effective stiffness properties are used to study strengthening and load-transfer effects between lamellae in Glulam and CLT elements

Linear response of a planar FGM beam with non-linear variation of the mechanical properties

Full paper from the proceedings of SMART2017, which are available at the conference website http://congress.cimne.com/smart2017/.This contribution aims at proposing an effective First order Shear Deformation Theory (FSDT) capable to tackle the non-trivial effects that a continuous variation of the mechanical properties induces on stresses, displacement, and stiffness distributions within a planar beam made of Functionally Graded Material (FGM). In greater detail, the beam model assumes the Timoshenko beam kinematics and it results naturally expressed by six Ordinary Differential Equations (ODEs) considering both cross-section displacements and internal forces as unknowns. Furthermore, exploiting a recently proposed analysis tool, the paper provides also effective tools for the accurate reconstruction of cross-section stress distributions (with special emphasis on shear stresses) and the beam stiffness estimation. A simple numerical example demonstrates that the proposed beam model can catch with good accuracy the main effects induced by variations of the mechanical properties, allowing for a simple and effective modeling of a large class of structures and opening the doors to a new family of enhanced beam models.Austrian Science Funds (FWF

Experimental study on glued laminated timber beams with well-known knot morphology

Nowadays, the impact of knots on the failure behaviour of glued laminated timber (GLT) beams is considered by subjecting the single lamellas to a strength grading process, where, i.a., tracheid effect-based laser scanning is used to obtain information about knot properties. This approach single-handedly defines the beam’s final strength properties according to current standards. At the same time, advanced production processes of such beams would allow an easy tracking of a scanned board’s location, but, at this point, previously obtained detailed information is already disregarded. Therefore, the scanning data is used to virtually reconstruct knot geometries and group them into sections within GLT beams. For this study, a sample of 50 GLT beams of five different configuration types was produced and tested under static four-point-bending until failure. As for each assembled lamella the orientation and position within the corresponding GLT beam is known, several parameters derived from the reconstructed knots can be correlated to effective GLT properties. Furthermore, the crack patterns of the tested beams are manually recorded and used to obtain measures of cracks. A detailed analysis of the generated data and their statistical evaluation show that, in the future, dedicated mechanical models for such timber elements must be developed to realistically predict their strength properties. A potential approach, using fluctuating section-wise effective material properties, is proposed.Vienna Business Agenc