Te-Hsin Yang

A thermal model of the wet grinding process

Abstract A thermal model of the wet grinding process is presented. The thermal effect of the grain–workpiece interface and the shear plane between the workpiece and the chip is taken into account. By taking all of the parameters needed in the model from the experimental results, the temperature of the workpiece surface in the grinding zone can be predicted. It is shown that the flow rate of the grinding fluid under general grinding conditions is sufficient to cover the thermal boundary layer of the coolant in the grinding zone. The predicted workpiece surface temperatures have been compared to experimental data for some grinding conditions. Good agreement is obtained except for the creep-feed grinding process, when water-based grinding fluid is used. The differences between the theoretical values and experimental results are attributed to constant thermal properties, and neglect of transverse conduction in the development of the thermal model.

Compressive strength of young Taiwania (Taiwania cryptomerioides) trees grown with different thinning and pruning treatments

Taiwania (Taiwania cryptomerioides Hay) is an important timber species in Taiwan. Growth in generally improved trees under intense silvicultural practice is so rapid that rotations or the practice of thinning trees may be as short as 20–30 years. Thus, the wood properties of young plantation trees need to be characterized to effectively use this resource. The effects of different thinning and pruning methods on the compressive strength parallel to grain of young Taiwania trees were explored. Average compressive strengths with various thinning treatments revealed the trend of no thinning > medium thinning > heavy thinning and in the pruning treatments showed the trend of medium pruning > no pruning > heavy pruning. However, most results showed no statistically significant differences among thinning and pruning treatments.

Effects of ACQ preservative treatment on the mechanical properties of hardwood glulam

The purpose of this study is to examine the mechanical properties of ACQ-treated glulam made from three hardwood lumbers. Two nondestructive methods, ultrasonic wave and tap tone method, were also used in this study. The results showed that the dynamic MOE and static MOE of lumbers decreased with increased ACQ preservative retention. ANOVA showed no significant difference in the MOE values of glulam between untreated and ACQ-treated group. However, it was also found that glulam made from red oak lumbers had the highest bending strength retention ratio. The shear strength of the glulam also showed similar results. Finally, no delaminating was found in all glulams after the specimens under soaked and boiled delamination tests.ZusammenfassungIn dieser Studie werden die mechanischen Eigenschaften von mit ACQ behandeltem Brettschichtholz aus drei verschiedenen Laubholzarten untersucht. Dabei wurden auch zwei zerstörungsfreie Methoden, nämlich Ultraschall- und Längsschwingungsmessung, verwendet. Die Ergebnisse zeigten, dass der dynamische und der statische Elastizitätsmodul (MOE) von Schnittholz mit zunehmender ACQ-Schutzmittelaufnahme abnahmen. Die ANOVA-Analyse ergab keine signifikanten Unterschiede zwischen den MOE Werten der unbehandelten und der behandelten Prüfkörpergruppe. Daneben hat sich gezeigt, dass die Biegefestigkeit bei Brettschichtholz aus Roteiche am geringsten beeinträchtigt war. Die Scherfestigkeit von Brettschichtholz zeigte ähnliche Ergebnisse. Delaminierungsprüfungen ergaben bei allen untersuchten Brettschichtholzgruppen keine Delaminierungen.

Effect of laminate configuration on the modulus of elasticity of glulam evaluated using a strain gauge method

The purpose of this study was to measure the strain of glulam laminae by affixing a strain gauge at the central axis of the lateral face in order to determine the effect of the configuration of the glulam. Japanese cedar and southern pine were used in the study. The strain and stress of the laminae during the bending test were recorded, and the modulus of elasticity (MOE) was calculated. The influence of the MOE of the adhesive layers was also considered. Results showed that the MOE of the laminated elements increased as its specific gravity increased, although the specific gravity was not the only factor evaluated. The MOE of glulam (Ebsg) measured by the strain gauge method was very close to the observed MOE of glulam (Eb) and a significant linear relationship was identified. The MOE (e) of laminae measured by the strain gauge method was very close to that determined (E) under the “free condition” before bonding. The difference between the modified MOE (Ebsa) and Ebsg was not significant. The MOE of glulams made of heterogeneously graded lumbers were about 23% and 31% larger than the average MOE of their laminae for Japanese cedar and southern pine, respectively. The actual neutral axis was just below the longitudinal center line. It shifted slightly within the proportional limit range and moved downward when the load increased.

Application of the fractometer for crushing strength: juvenile-mature wood demarcation in Taiwania (Taiwania cryptomerioids)

The fractometer is a device that breaks a radial increment core along the fiber for the measurement of crushing strength, which is a direct wood quality indicator for structural lumber. In this study, the crushing strength of Taiwania (Taiwania cryptomerioides Hay) trees using the fractometer was investigated and the data were used to determine the position of demarcation between juvenile and mature wood. Segmented regression and variance component analysis were used to estimate the demarcation position. With increasing cambium age, the core wood improves the crushing strength in the outer wood area. Within-tree variations in wood properties were greater than between-tree variations. In this experiment, the position of demarcation between juvenile and mature wood occurred at an approximate distance of 10.8cm to 13.2cm from the pith at about 18–20 years of cambium age.

Fire retardancy and CO/CO2 emission of intumescent coatings on thin plywood panel with waterborne vinyl acetate-acrylic resin

Using intumescent coatings on wood-based materials is an effective method for fire safety. Previous studies have demonstrated that the formulation of components strongly influences the performance of coatings. This study investigated the effect of intumescent formulation of vinyl acetate-acrylic coating on flame retardancy of plywood. The fire retardancy of materials was assessed by both heat release and CO and CO2 emissions. The CO and CO2 emissions have not been used frequently to rank materials; the highly toxic CO and CO2 may cause most fire fatalities. The fire retardancy of coatings on plywood was assessed by a cone calorimeter. Total heat release and time to peak heat release rate were the two primary parameters. The data show that low contents of binder resin (BR) and foam producing substance (FPS) decreased total heat release and lengthened time to peak heat release rate. Additionally, low BR and FPS content can form an ideal char layer. The ideal char layer significantly decreased the CO and CO2 emission. The mechanism to achieve better fire performance was verified by thermogravimetrical analysis exhibiting lower weight loss. Moreover, evaluated by 31P NMR, the low BR and FPS content can extend the survival duration of phosphor-carbonaceous chars. The results provide information for designing vinyl acetate-acrylic emulsion coating.