Creat membership Creat membership
Sign in

Forgot password?

Confirm
  • Forgot password?
    Sign Up
  • Confirm
    Sign In
home > search

Now showing items 1 - 9 of 9

  • Vers une meilleure valorisation des chênes de qualité secondaire

    Croisel, Jean   Collet, Robert  

    Download Collect
  • Analysis of chip formation mechanisms and modelling of slabber process

    Pfeiffer, Renaud   Collet, Robert   Denaud, Louis Etienne   Fromentin, Guillaume  

    During the primary transformation in wood industry, logs are faced with conical rough milling cutters commonly named slabber or canter heads. Chips produced consist of raw materials for pulp paper and particleboard industries. The process efficiency of these industries partly comes from particle size distribution. However, chips formation is greatly dependent on milling conditions and material variability. Thus, this study aims at better understanding and predicting chips production in wood milling. The different mechanisms of their formation were studied through orthogonal cutting experiments at high cutting speed for beech and Douglas fir. Under these conditions, ejection of free water inside wood can be observed during fragmentation, particularly on beech. As previously seen in quasi-static experiments, chip thickness is proportional to the nominal cut thickness. Moreover, the grain orientation has a great influence on the cutting mechanisms, so as the nominal cut and the growth ring widths. This chip fragmentation study finally allows the improvement of the cutting conditions in rough milling. In order to optimize machine design as well as cutting geometry, a geometrical model of a generic slabber head was developed. This model allows the study of the effective cutting kinematics, the log-cutting edges interactions and the effective wood grain direction during cutting. This paper describes the great influence of the carriage position on cutting conditions. The results obtained here can be directly used by milling machine manufacturers.
    Download Collect
  • A Method of Lathe Checks Measurement; SMOF device and its software

    Palubicki, Bartosz   Marchal, Remy   Butaud, Jean-Claude   Denaud, Louis-Etienne   Bleron, Laurent   Collet, Robert   Kowaluk, Grzegorz  

    In the present paper, a novel method for veneer checks measurement and description based on digital image analysis is evaluated. According to this method, the camera is located sideways to the veneer allowing for viewing the checks geometry in the cross-section of the veneer. Checks are opened by bending the veneer on a roller of a specific diameter and they are exposed in such a way that good visibility of checks is assured. The algorithm used reproduces the checks by finding their coarse positions on the rescaled image and then migrating to the original, full resolution image to precisely localize the checks' bottom. The method is automatic and delivers the most important information on checks of veneer, namely distances between checks and their depths.
    Download Collect
  • Prediction of Oak Wood Mechanical Properties Based on the Statistical Exploitation of Vibrational Response

    Faydi, Younes   Brancheriau, Loic   Pot, Guillaume   Collet, Robert  

    In the European Union, timber is used in structural applications and must be graded with a Conformite Europeene (CE) mark. To achieve standard, machine strength grading is used. A common technology for these machines is based on using the vibrational response of each wood board to estimate the timber modulus of elasticity and modulus of rupture. The first Eigen frequency is usually used to predict these mechanical properties. However, in heterogeneous wood species such as oak, this parameter is less correlated with mechanical properties. The current study proposes two new methods based on an extended exploitation of the vibrational response that predicts oak wood mechanical properties. The first method was based on the mechanical parameters deduced from several Eigen frequencies that were chosen with regards to a stepwise regression. The second method was based on the full vibrational spectrum and used a partial least squares method. The first method slightly improved the prediction of the modulus of elasticity compared with the first Eigen frequency in edgewise transversal vibration. Both methods significantly improved the prediction of the modulus of rupture.
    Download Collect
  • Automatic measurement of wood fiber orientation and knot detection using an optical system based on heating conduction

    Daval, Vincent   Pot, Guillaume   Belkacemi, Mohamed   Meriaudeau, Fabrice   Collet, Robert  

    In this paper, a new approach to computing the deviation of wood grain is proposed. To do this, the thermal conduction properties of timber are used (higher conduction in the fiber direction). Exciting the surface of the wood with a laser and capturing the thermal conduction using a thermal camera, an ellipse can be observed. Using a method similar to the tracheid effect, it is possible to extract information from this ellipse, such as the slope of grain and the presence of knots. With this method it is therefore possible to extend the mechanical model (assessing the mechanical properties of timber) to take certain singularities into account. Using this approach, the slope of grain can be estimated for any wood species, either hardwood or softwood, which was not possible with the existing tracheid effect. (C)2015 Optical Society of America
    Download Collect
  • Evaluation of the visual stress grading standard on French Spruce (Picea excelsa) and Douglas-fir (Pseudotsuga menziesii) sawn timber

    Roblot, Guillaume   Coudegnat, Damien   Bleron, Laurent   Collet, Robert  

    In this paper an evaluation of the visual grading standard for softwood sawn timber was made. In order to do so, visual grading according to EN 518 and theoretical grading according to EN 338 and EN 384 (measurements of MOE, MOR and density) were applied to lumber. Two batches of 111 and 102 French boards were graded, respectively, of Spruce (Picea excelsa) and Douglas-fir (Pseudotsuga menziesii). For the visual grading the most discriminant criterion was noted: knots, cracks, wane, etc. Finally, the results of the two grading methods were compared, and it was shown that the visual stress grading gave quite low results for our two French species.
    Download Collect
  • Numerical study of the influence of veneer lathe checks on the elastic mechanical properties of laminated veneer lumber (LVL) made of beech

    Pot, Guillaume   Denaud, Louis-Etienne   Collet, Robert  

    Laminated veneer lumber (LVL) is a well-known high-performance engineered wood product suitable for structural applications. However, the peeling process can induce lathe checks of the veneer with various depth and spatial frequencies. In this study, a finite element model (FEM) is proposed to describe and to analyze the influence of veneer lathe checks on the elastic properties of LVL. Firstly, the typical lathe check depths and frequencies were determined by means of different compression rates of the pressure bar when peeling. These experimental results served as input to the model to compare the influence of check depth and frequency on the elastic behavior of an LVL beam in four-point bending. The checks were modeled as free spaces in the cross-section that can be partially filled with glue. The results show that the longitudinal modulus of elasticity is marginally affected by checking, while the shear rigidity of the LVL beam is significantly reduced in edgewise bending if checks are not glued. Gluing checks, even under consideration of a low Young's modulus of glue, highly reduces the effect of checking on the elastic mechanical properties of LVL.
    Download Collect
  • Resistance of thermally modified ash (Fraxinus excelsior L.) wood under steam pressure against rot fungi,soil-inhabiting micro-organisms and termites

    Candelier, Kevin   Hannouz, Simon   Thevenon, Marie-France   Guibal, Daniel   Gerardin, Philippe   Petrissans, Mathieu   Collet, Robert  

    Thermal modification processes have been developed to increase the biological durability and dimensional stability of wood. The aim of this paper was to study the influence of ThermoWood(A (R)) treatment intensity on improvement of wood decay resistance against soil-inhabiting micro-organisms, brown/white rots and termite exposures. All of the tests were carried out in the laboratory with two different complementary research materials. The main research material consisted of ash (Fraxinus excelsior L.) wood thermally modified at temperatures of 170, 200, 215 and 228 A degrees C. The reference materials were untreated ash and beech wood for decay resistance tests, untreated ash wood for soil bed tests and untreated ash, beech and pine wood for termite resistance tests. An agar block test was used to determine the resistance to two brown-rot and two white-rot fungi according to CEN/TS 15083-1 directives. Durability against soil-inhabiting micro-organisms was determined following the CEN/TS 15083-2 directives, by measuring the weight loss, modulus of elasticity (MOE) and modulus of rupture (MOR) after incubation periods of 24, 32 and 90 weeks. Finally, Reticulitermes santonensis species was used for determining the termite attack resistance by non-choice screening tests, with a size sample adjustment according to EN 117 standard directives on control samples and on samples which have previously been exposed to soil bed test. Thermal modification increased the biological durability of all samples. However, high thermal modification temperature above 215 A degrees C, represented by a wood mass loss (ML%) due to thermal degradation of 20%, was needed to reach resistance against decay comparable with the durability classes of ''durable'' or ''very durable'' in the soil bed test. The brown-rot and white-rot tests gave slightly better durability classes than the soil bed test. Whatever the heat treatment conditions are, thermally modified ash wood was not efficient against termite attack neither before nor after soft rot degradation.
    Download Collect
  • Robert Bosch GmbH; Researchers Submit Patent Application, "Bi-Directional Quick Change Tool-Less Lever and Wedge Actuated Collet Chuck, System And/Or Method for Using the Same", for Approval

    Download Collect
1

Contact

If you have any feedback, Please follow the official account to submit feedback.

Turn on your phone and scan

Submit Feedback