Flutter Instability Speeds of Guided Splined Disks: An Experimental and Analytical Investigation

“Guided splined disks” are defined as flat thin disks in which the inner radius of the disk is splined and matches a splined arbor that provides the driving torque for rotating the disk. Lateral constraint for the disk is provided by space fixed guide pads. Experimental lateral displacement of run-up tests of such a system is presented, and the flutter instability zones are identified. The results indicate that flutter instability occurs at speeds when a backward travelling wave of a mode meets a reflected wave of a different mode. Sometimes, the system cannot pass a flutter zone, and transverse vibrations of the disk lock into that flutter instability zone. The governing linear equations of transverse motion of such a spinning disk, with assumed free inner and outer boundary conditions, are derived. A lateral constraint is introduced and modeled as a linear spring. Rigid body translational and tilting degrees of freedom are included in the analysis of the total motion of the spinning disk. The eigenvalues of the system are computed numerically, and the flutter instability zones are defined. The results show that the mathematical model can predict accurately the flutter instability zones measured in the experimental tests

Erratum to “Theoretical and Experimental Verification of Dynamic Behaviour of a Guided Spline Arbor Circular Saw”

An analysis of the dynamic and stability characteristics of a guided wood cutting spline arbor circular saw is presented. A multibody dynamic model is developed to consider the idling and cutting characteristics. The model considers the interaction between the blade, the arbor, and the guide pads. The model is capable of analyzing in-plane and out-of-plane edge forces which enables simulation of the cutting performance of the saw. In order to verify the computer model, an experimental test of a guided spline saw during idling run-up is presented. The frequencies and amplitudes of the blade vibrations are documented and plotted. Cutting tests are also conducted and the cutting forces are estimated. The results of a simulation of the idling response of the blade by the computer model and the experimental results are in a good agreement. Factors that significantly affect the characteristics of guided spline saws during cutting are discussed. The computer model is shown to be capable of predicting stable cutting operations of a guided spline saw

FIBER QUALITY PREDICTION USING NIR SPECTRAL DATA: TREE-BASED ENSEMBLE LEARNING VS DEEP NEURAL NETWORKS

The growing applications of near infrared (NIR) spectroscopy in wood quality control and monitoring necessitates focusing on data-driven methods to develop predictive models. Despite the advancements in analyzing NIR spectral data, literature on wood science and engineering has mainly uti- lizedthe classic model development methods, such as principal component analysis (PCA) regression or partial least squares (PLS) regression, with relatively limited studies conducted on evaluating machine learning (ML) models, and specifically, artificial neural networks (ANNs). This couldpotentially limit the performance of predictive models, specifically for some wood properties, such as tracheid width that are both time-consuming tomeasure and challenging to predict using spectral data. This study aims to enhance the prediction accuracy for tracheid width using deep neural networks and tree-based ensemble learning algorithms on a dataset consisting of 2018 samples and 692 features (NIR spectra wavelengths). Accord- ingly, NIR spectra were fed into multilayer perceptron (MLP), 1 dimensional-convolutional neural net- works (1D-CNNs), random forest, TreeNet gradient-boosting, extreme gradient-boosting (XGBoost), and light gradient-boosting machine (LGBM). It was of interest to study the performance of the models with and without applying PCA to assess how effective they would perform when analyzing NIR spectra with- out employing dimensionality reduction on data. It was shown that gradient-boosting machines outper- formed the ANNs regardless of the number of features (data dimension). Allthe models performed better without PCA. It is concluded that tree-based gradient-boosting machines could be effectively used for wood characterization utilizing a medium-sized NIR spectral dataset

Flutter instability speed of guided splined disks, with applications to sawing

In this thesis the vibration characteristics of guided splined saws are studied, both analytically and experimentally. Significant insights into the complex dynamic behavior of guided splined saws are presented by analytical investigation of the dynamic behaviour of spinning splined disks and then by conducting idling and cutting experimental tests of guided splined saws. Cutting tests are conducted at different speeds, at critical, supercritical, and post flutter speeds of a guided splined saw. The cutting results are compared to determine the stable operation speeds for guided splined saws. For the analytical studies, the governing linear equations are derived for the transverse motion of a constant speed spinning splined disk. The disk is subjected to lateral constraints and loads. Rigid body translational and tilting degrees of freedom are included in the analysis of total motion of the spinning disk. Also considered in the analyses are applied conservative in-plane edge loads at the outer and inner boundaries. The numerical solution of these equations is used to investigate the effect of the loads and constraints on the natural frequencies, critical speeds, and stability of the spinning disk. The sensitivity of the eigenvalues of the splined spinning disk to the in-plane edge loads is analyzed by taking the derivative of the spinning disk’s eigenvalues with respect to the applied loads. This analysis contains an evaluation of the energy transfer from the applied loads to the disk vibrations and is used to examine the role of critical system components in the development of instability. Experimental results are presented that support the validity of the analysis. The experimental results indicate that flutter instability occurs at speeds when a backward travelling wave of a mode meets a reflected wave of a different mode. The maximum stable operating speed of the rotating splined disk is defined as the initiation of flutter. Flutter instability speeds of splined saws of various sizes were computed and verified experimentally. Then flutter speed charts of splined saws were developed which provides primary practical guide lines for sawmills to choose optimum blade diameter, eye size, blade thickness, and a stable rotation speed.Applied Science, Faculty ofMechanical Engineering, Department ofGraduat

Idling and cutting vibration characteristics of guided circular saws

In this thesis the vibration characteristics of guided circular saws are studied, both analytically and experimentally. Significant insights into the complex dynamic behavior of guided circular saws are presented first by numerical investigation of rotating disks and then by conducting idling and cutting experimental tests of splined saws with different guide configurations. For the numerical investigations, the governing linear equation of transverse vibration of a rotating disk is used. As a primary interest, the variation of disk natural frequencies with rotation speed and the disk response to applied external force are calculated. Also, the steady state response of the disk at different speeds is calculated. The effects of elastic lateral constraints are investigated in this section. A comprehensive experimental investigation of idling tests of splined saws with different guide configurations is presented. The frequencies and amplitudes of the blade vibrations are documented and the mean deflections of the disks are plotted. The dynamic characteristics of a rotating blade when subjected to the stationary lateral constant force are discussed. Extensive cutting tests are conducted and the effect of different guide configurations on cutting accuracy is presented. Cutting tests are conducted at different speeds, below and above the lowest critical speed for different guide configurations. The cutting results are compared to determine the guide configuration which results in the best cutting accuracy.Applied Science, Faculty ofMechanical Engineering, Department ofGraduat

Flutter Instability Speeds of Guided Splined Disks: An Experimental and Analytical Investigation

“Guided splined disks” are defined as flat thin disks in which the inner radius of the disk is splined and matches a splined arbor that provides the driving torque for rotating the disk. Lateral constraint for the disk is provided by space fixed guide pads. Experimental lateral displacement of run-up tests of such a system is presented, and the flutter instability zones are identified. The results indicate that flutter instability occurs at speeds when a backward travelling wave of a mode meets a reflected wave of a different mode. Sometimes, the system cannot pass a flutter zone, and transverse vibrations of the disk lock into that flutter instability zone. The governing linear equations of transverse motion of such a spinning disk, with assumed free inner and outer boundary conditions, are derived. A lateral constraint is introduced and modeled as a linear spring. Rigid body translational and tilting degrees of freedom are included in the analysis of the total motion of the spinning disk. The eigenvalues of the system are computed numerically, and the flutter instability zones are defined. The results show that the mathematical model can predict accurately the flutter instability zones measured in the experimental tests

Theoretical and Experimental Verification of Dynamic Behaviour of a Guided Spline Arbor Circular Saw

An analysis of the dynamic and stability characteristics of a guided wood cutting spline arbor circular saw is presented. A multibody dynamic model is developed to consider the idling and cutting characteristics. The model considers the interaction between the blade, the arbor, and the guide pads. The model is capable of analyzing in-plane and out-of-plane edge forces which enables simulation of the cutting performance of the saw. In order to verify the computer model, an experimental test of a guided spline saw during idling run-up is presented. The frequencies and amplitudes of the blade vibrations are documented and plotted. Cutting tests are also conducted and the cutting forces are estimated. The results of a simulation of the idling response of the blade by the computer model and the experimental results are in a good agreement. Factors that significantly affect the characteristics of guided spline saws during cutting are discussed. The computer model is shown to be capable of predicting stable cutting operations of a guided spline saw