10 research outputs found
Robot-Based Research on Three-Layer Oriented Flakeboards
A small jointed-arm motion type robot system was introduced for wood mat formation to study the relationship between wood mat structure and panel properties. Four types of structures of three-layer oriented flakeboards with different face to core ratios and core orientations were formed using the robot as a tool. The panels were then hot-pressed and tested for horizontal density distribution (HDD) by X-ray machine, bending modulus of elasticity (MOE), internal bond (IB) and thickness swelling (TS). The results showed that the programmed robot formed panels with well-defined and reproducible structures. Linked with the existing panel simulation program, X-ray data, and real properties, the panel structure with face to core ratio of 15:70:15 and random core has been considered the most suitable panel pattern for additional research based on its superior performance and lower variation of properties
Quadratic RSM Models of Processing Parameters for Three-Layer Oriented Flakeboards
Response surface method with central composite design was used to establish quadratic regression models and surface maps to relate panel properties, including static bending modulus of elasticity, modulus of rupture, internal bond strength, and thickness swelling with flake slenderness ratio, flake orientation, and panel density. A robot mat formation system was used to form the panels with predefined processing parameters. Results indicated that nonlinear models capable of including interactions were required to relate flake slenderness ratio, flake orientation, and panel density to panel properties. An optimization model was developed to obtain the best panel performance with respect to the three factors. The optimized combination of the three factors within the experimental range is: 133 for flake slenderness ratio, 8° for surface flake orientation, and 0.62g/cm3 for board density
Analysis of OSB Mat Stucture Made From Industrially Manufactured Strands Using Simulation Modeling
Industrially manufactured oriented strandboard (OSB) furnish was characterized by scanning images of a large number of individual strands and analyzing their shape properties. A Visual Basic macro in combination with commercially available image synthesis software was utilized to carry out the task of this analysis. The scanned images of these strands were used in a model that simulates the formation of layers within an OSB mat. These layers were simulated using three different orientation scenarios: random orientation. 100% strand alignment, and strand alignment based on industrial parameters. Information provided by the model includes the number and geometrical details of voids and strand overlap. Total void area for a mat is shown to be independant of strand orientation and the aspect ratio of strands. Interestingly, noticeable differences in the number, size, orientation, and shape factor of the individual voids, which make up the total area, were shown between various mat configurations
Simulation Based Modeling of the Elastic Properties of Structural Composite Lumber
Structural composite lumber (SCL) products were introduced into the construction practice several decades ago. Their apparent advantages over traditional lumber did not generate copious research interests. However, increasing demands for structural materials coupled with the decreasing quality and quantity of raw materials are forcing the industry to introduce short rotation trees or species having unfavorable properties into the manufacturing processes. Consequently, there is a need for research to further enhance the effective use of renewable natural resources.This article describes the development of simulation models that estimate the bending and orthotropic compression modulus of elasticity (MOE) of laminated veneer lumber (LVL) and parallel strand lumber (PSL). The Monte Carlo simulation-based routines use the physical/mechanical properties of primary constituting elements, obtained from probability distributions, to calculate a particular property of the composite system. Furthermore, the orthotropic behavior of the wood constituents due to their position in the composite is modeled by well-established theoretical/empirical equations. Results and experimental validation regarding the geometric, physical, and mechanical attributes showed reasonably good agreement between simulated and experimental values. Developed models have good potential for predicting the elastic parameters of composites using new raw materials or novel design features
A Critical-Angle Ultrasonic Technique for the Inspection of Wood Parallel-to-Grain
The objective of this paper is to present a critically refracted longitudinal wave (LCR) technique that allows localized ultrasonic inspection of wood parallel-to-grain by accessing only a single side of the material. The LCR technique has been widely applied to other materials, but not to wood. The chief advantage of the LCR technique is that ultrasonic waves can be transmitted through wood at frequencies much higher than previously possible (up to 1.5 MHz), leading to potential gains in sensitivity over lower frequency methods.The LCR technique was verified using southern pine lumber. Transducer beam characteristics were examined and the influence of growth ring angle was observed. Ultrasonic wave energy was found to travel near to the inspection surface. Further, localized growth ring angle was significantly correlated to signal amplitude and frequency
Determination of Oriented Strandboard Properties from a 3D Density Distribution using the Finite Element Method
Computer modeling of Oriented Strand Board (OSB) properties has gained widespread attention with numerous models created to better understand OBS behavior. Recent models allow researchers to observe multiple variables such as changes in moisture content, density and resin effects on panel performance. Thickness-swell variation influences panel durability and often has adverse effects on a structural panel’s bending stiffness. The prediction of out-of-plane swell under changing moisture conditions was, therefore, the essence for developing a model in this research.
The finite element model accounted for both vertical and horizontal density variations, the three-dimensional (3D) density variation of the board. The density variation, resulting from manufacturing processes, affects the uniformity of thickness-swell in OSB and is often exacerbated by continuous sorption of moisture that leads to potentially damaging internal stresses in the panel. The overall thickness-swell (the cumulative swell from non- uniform horizontal density profile, panel swell from free water, and spring-back from panel compression) was addressed through the finite element model in this research.
The pursued goals in this study were, first and foremost, the development of a robust and comprehensive finite element model which integrated several component studies to investigate the effects of moisture variation on the out-of-plane thickness-swell of OSB panels, and second, the extension of the developed model to predict panel stiffness. It is hoped that this paper will encourage researchers to adopt the 3D density distribution approach as a viable approach to analyzing the physical and mechanical properties of OSB
Ultrasonic characterization of engineering performance of oriented strandboard
Direct-contact (DC) and non-contact (NC) ultrasonic transmission (UT) methods were developed to characterize the structural performance of oriented strandboard (OSB). The UT variable velocity was shown to be sensitive to the physical impediments caused by flake interfacial boundaries and embedded voids. Both attenuation and root mean square (RMS) voltage were good indicators of the “zero void” densification level for OSB, a point of the greatest transmissivity of the stress wave energy. For both DC and NC methods, the predicted densities of the model were validated for spatial distribution over each OSB type. Based on the EN300 standard for panel manufacturing, the control limits were ±10% of the panel average density. The density prediction was found to improve with higher resin content (RC) and higher nominal density (ND) levels. From the out-of-limits plots, the predicted in-situ densities produced a reasonably spatial coherence to the measured values. All panels made with ND 0.60 g/cm3 or greater conformed well within the limits, with declining conformity towards lower RC panels. For each composite type made of different particle sizes, the equilibrium moisture content showed a decreasing trend toward smaller particle panels. The attenuation and RMS were good indicators for moisture change and densification level for each composite type. The velocity, sensitive to physical resistance of particle sizes, increased with increasing IB strength and sample density, manifesting the positive influence of layering, resin content, and the negative effect of bark as a constituent. The results of the creep rupture tests on commercial OSB using an acoustic emission (AE) technique indicated that the cumulative AE event count parameter was highly correlated with deflection parameter and appropriately represented the accumulation of incipient damage. Under high stress levels, specimens with high moisture content (MC) sustained the worse damages having the shortest creep rupture time followed by specimens with dynamically rising MC. Defects on the compression-side of the bending specimen were found critical to creep rupture than those on the tension-side. The in-plane fracture patterns tended to follow the defect trenches of low-density valleys, and worsened with greater variability of the horizontal density, indicating the need to measure and control the horizontal density variation within reasonable limits
Reframing wood construction : innovation in architecture through activating material properties with the use of digital technologies
Reframing Wood Construction. Innovation in architecture through activating material properties with the use of digital technologies.
This thesis focuses on the relationships between material-centred design, digital technologies and environmentally-responsible practice with respect to wood construction. It argues that computational design methods and digital manufacturing have the capacity to reframe wood construction, open new opportunities for design, and lead to more sustainable practices.
Wood is the building material that frames this research. The long tradition of using wood in construction and its cultural connotations, as well as its heterogeneous structure and its often-unpredictable behaviour, make it a case in point for material-centred design. Today, the predominant approach to wood construction is adaptation to industrialised processes that suppress individual material properties. The thesis proposes to reframe wood construction in order to offer an alternative design method that uses material properties and behaviours as valid design factors.
The monograph comprises two main parts: (i) Experiments, and (ii) Perspectives. (i) The first part describes three experimental projects with wood in which inherent material properties and material behaviours are used as a starting point, and computational design techniques and digital fabrication are the main methods. (ii) The second part theorises the approach presented in the experiments. It comprises three perspectives: (1) design methodology that outlines the proposed framework of innovation in wood architecture, (2) design theory that positions the proposed approach within discussion surrounding relationships of form and matter in the history and theory of architecture, and (3) design and technology that discusses the development of technology related to wood architecture and its impact on design and construction. Together, the three perspectives form a discussion of the approach to reframing wood construction.
The ultimate goal of the thesis is to reorient architecture towards sustainable construction methods. The thesis identifies that digital technologies have not yet embraced materiality and that digital advances in architecture provide an opportunity for including material parameters as valid design factors. This thesis proposes that digital technologies have the potential to access various latent and palpable potentialities of the material that can deliver design solutions with lower environmental impact.publishedVersio
Recommended from our members
Computed tomography analysis of wood-adhesive bonds
The importance of wood bonding increased in the last decades due to the
increased usage of wood composites whose performance depends to a large extent on
the adhesive penetration and subsequent bonding of the adherends. The presented
research used XMT (x-ray microtomography) to perform a non-destructive, threedimensional
analysis of the adhesive bondline and wood-structure of Southern yellow
pine, Douglas-fir and yellow-poplar samples. A phenol-formaldehyde adhesive was
used. The sodium hydroxide catalyst was replaced with rubidium hydroxide during
resin formulation. This was done to improve the image contrast. The reconstructions
of the wood structure of Southern yellow pine showed tracheids, rays, fusiform rays,
resin canals and pits. On the Douglas-fir sample tracheids, pits and rays were
displayed clearly. The yellow-poplar images showed vessels, fibers, bordered pits,
scalariform sieve plates and rays.
The renderings of the adhesive-bondline of Southern yellow pine proved the
dominant role of tracheids for the adhesive flow and showed rays as a secondary
pathway of adhesive flow. The results revealed no adhesive flow occured through
bordered pits, while simple pits permitted some adhesive flow through ray
parenchyma. The results for Douglas-fir showed a similar result; the tracheids were
the predominant path of adhesive penetration, while rays played a secondary role and
no adhesive flow through the pit aperture was visible. The adhesive flow through the
microstructure of yellow-poplar wood occured mainly through vessels and also
through rays, but no adhesive flow through the pits was directly observed. The
segmentation of the images in three phases: void space, cell wall substance and
adhesive, enabled the calculation of the effective bondline thickness based on the
adhesive, as well as the volumetric measurement of all three elements and their share
on the sample volume.
Subsequent experiments showed that the exposure of the Southern yellow pine
and yellow-poplar bondlines to cyclic moisture did not cause delaminations or cracks.
However, there were some indicators that the samples experienced some irreversible
swelling.
Finally, the generation of 3-D animations of wood samples and bondlines of
Southern yellow pine, Douglas-fir and yellow poplar was achieved. This animation
was a way to present the results of this research in a quick and accessible way that
illustrates the three-dimensional microstructure of a wood-adhesive bond
Robot-based research on three-layer oriented flakeboards
The rapid development and continued worldwide production growth of Oriented Strand Board
(OSB) since the early 1980's has led to the realization that the better understanding and
improved of the theoretical description of OSB manufacturing processes are important. This
knowledge is needed to improve the present day mat forming, quality control technology and
effective design and engineering of the next generation of composite wood products. Horizontal
density distribution (HDD) is one of the most important factors determining the presence of
voids and high density areas inside mat that greatly influences the board properties. However the
formation mechanism of HDD and how it influences the panel properties are not fully
understood.
This project focuses on studying the influence of the spatial organization of wood elements
inside a three-layer oriented flake mat on the manufacturing process, HDD, and end-use
properties of OSB. Unlike previous studies with limitation of one or two variables at one time
which results in difficulties when comparing and applying the results to production practices, this
study reveals the combined effect of three important processing parameters — flake slenderness
ratio, flake orientation, and panel density on panel properties. Also, with the help of a robot mat
formation system and a X-ray machine, the mat simulation model established by Dai and Steiner
(1994) is verified.
The research program was divided into two parts. A pilot study was conducted first to verify the
possibility of using a robot mat formation system to manufacture panels. Four types of structures
structures with different face-to-core ratios and core flake arrangements for three-layered OSB
were formed using the robot as a tool. The panels were then hot-pressed and tested for horizontal
density distribution (HDD), bending modulus of elasticity (MOE), internal bond (IB) and
thickness swelling (TS). Linked with the existing panel simulation program and X-ray density
data, a suitable panel structure was selected for further research. The results showed that the
programmed robot formed panels with well-defined and reproducible structures. Also the
validity of the simulation program describing the 2-dimensional mat structure is verified by
robot-made mats.
The second part of the study involved the use of Response Surface Method (RSM) to study the
relationship between strength and physical properties of robot formed panels and the defined
structure of the panels with different combinations of three processing parameters, namely,
flake slenderness ratio, flake orientation and panel density. Regression models were established
relating each panel property including MOE, MOR, IB and TS with flake aspect ratio, flake
orientation and panel density. Results indicated that nonlinear models capable of including
interactions were required to relate the three factors studied to panel properties. By applying
FIACCO AND McCORMICK (SUMT Algorithm) and Linear Combination method, an
optimization model is developed. The best combination of the three factors which can provide
the optimum overall properties of the panels studied in the project is: 143 for slenderness ratio,
0° for flake orientation angle and 0.6g/cm³ for board density.Forestry, Faculty ofGraduat