A microstructure-based multisurface failure criterion for the description of brittle and ductile failure mechanisms of clear-wood

Lukacevic, Markus; Lederer, Wolfgang; Füssl, Josef

doi:10.1016/j.engfracmech.2017.02.020

Cited by 54 publications

(37 citation statements)

References 32 publications

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“…They already showed, by using linear traction-separation laws in combination with constant fracture energies, good fits to experiments could be obtained. In future, more realistic, variable fracture energies for knot sections might be obtained by simulating those sections with a multisurface failure criterion (Lukacevic and Füssl 2016;Lukacevic et al 2017), whose combination with the mentioned fiber deviation model shows promising results. Furthermore, in such an approach, additional strength reducing or failure inducing factors, like finger joints, could be easily implemented by introducing additional weak sections.…”

Section: Resultsmentioning

confidence: 99%

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

2018

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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.

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Section: Resultsmentioning

confidence: 99%

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

2018

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“…Lukacevic et al [10] propose microstructural modelling based on unit cells of cell walls for EW and LW, arranged in separate layers. This allows the identification of brittle and ductile failure mechanisms on the annual ring scale and the derivation of a multisurface failure criterion in reference [11]. The present contribution uses a mapping method for a direct discretization of the varying structural properties of veneer sheets.…”

Section: Materials Composition and Testing Methodsmentioning

confidence: 99%

“…Different works deal with the failure modelling of wood. Multisurface criteria were introduced with high accuracy for orthotropic failure of clear wood [11,15,18]. Furthermore, some general criteria such as the Tsai-Wu hypothesis were applicable with sufficient estimations of failure [19].…”

Section: Materials Modelmentioning

confidence: 99%

Modelling Inhomogeneity of Veneer Laminates with a Finite Element Mapping Method Based on Arbitrary Grayscale Images

Zerbst

Liebold²,

Gereke

et al. 2020

Materials

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Failure and deformation behavior of veneer laminates of ring porous wood species vary with the individual arrangement of early- and latewood zones over a veneer sheet. Therefore, a method is presented, where local failure and damage modes are considered for finite element models with respect to forming simulations, during the development process of automotive interior trim parts. Within the mapping tool Envyo, a routine has been realized for the discretization of early- and latewood zones from ash wood veneer surfaces to finite element meshes. The routine performs the following steps: reading a grayscale image of known size and generation of a point cloud based on the number of pixels; transformation and scaling of the generated point cloud to align with a target finite element mesh; nearest neighbor search and transfer of grayscale values to the target mesh element centroids; assigning part and therefore material properties to the target elements based on the mapped grayscale value and user-defined grayscale ranges. Due to the absence of measurement data for early- and latewood, optimization was used to identify locally varying material constants. A set of material input parameters for early- and latewood was created, calibrating the force-displacement response of tensile test simulations to corresponding experimental curves. The numerical results gave a very good agreement to the failure behavior of tensile tests in the loading directions longitudinal and transverse to the fiber orientation. Furthermore, in a stochastic analysis the characteristic distribution of tensile strength and ultimate strain could be verified for the suggested procedure. The introduced modelling approach can be applied for the discrete implementation of inhomogeneity to numerical simulations.

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“…At the author's institute, Lukacevic and Füssl (2014); Lukacevic et al (2014a); Lukacevic and Füssl (2016); Lukacevic et al (2017) have established the basis for a crack initiation and propagation criterion in the framework of the eXtended Finite Element Method (XFEM) in recent years, which has been implemented into a numerical simulation tool for wooden boards. The implementation of such an approach poses two questions: (i) which stress states cause the initiation of a crack?…”

Section: Prediction Tools For the Ultimate Strength Of Woodmentioning

confidence: 99%

“…);Bader et al (2011);Lukacevic et al (2014b);Lukacevic and Füssl (2016);Lukacevic et al (2017) and is currently in elaboration at the author's institute.Until now, this model has mainly been developed for the prediction of effective elastic material properties. The extension to strength predictions represents the next big challenge, and the limit analysis formulations presented above are expected to play a major role in this development.In this paper, the limit analysis formulations have been applied to selected observation scales as illustrated inFigure 1.…”

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Strength predictions of clear wood at multiple scales using numerical limit analysis approaches

Füssl

Lukacevic

et al. 2018

Computers & Structures

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This work aims at a new approach to understand failure mechanisms and to predict wood strengths, which are strongly influenced by the complex hierarchical material system of wood. Thus, a mechanical concept, where different microstructural characteristics are incorporated, appears to be necessary, based on the division of wood into meaningful scales of observation. At each scale, effective strength properties are to be determined and a multiscale approach is applied, for which conventional numerical methods appear to be inefficient. Thus, within this work, numerical limit analysis approaches are further developed and applied for the first time to wood, complementing conventional methods successfully at certain scales of observation in a multiscale 'damage' concept. Limit analysis belongs to the group of direct plastic analysis methods, exclusively focusing on the time instant of structural collapse, and delivering the ultimate strength. Compared with conventional numerical approaches, limit analysis approaches are much more stable and efficient. In this work, orthotropic failure criteria and periodic boundary conditions have been implemented into numerical limit analysis formulations. As numerical results, effective failure surfaces are obtained at both annual ring scale and clear wood scale. A validation at clear wood scale renders this new approach as very promising.

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A microstructure-based multisurface failure criterion for the description of brittle and ductile failure mechanisms of clear-wood

Cited by 54 publications

References 32 publications

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

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

Modelling Inhomogeneity of Veneer Laminates with a Finite Element Mapping Method Based on Arbitrary Grayscale Images

Strength predictions of clear wood at multiple scales using numerical limit analysis approaches

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