Effects of Some Wood Chip Properties on Pulp Quality
A series of TMP experiments were performed at CIPP’s TMP pilot plant, and some pulp properties were measured. By comparing chip and pulp properties, and using projections to latent structures (PLS) analysis, we were able to demonstrate that on-line CMS measurements can be used to predict some pulp properties. It should be pointed out that the focus of this paper is to show how CMS measurements can be used to predict some pulp properties. This prediction will suggest ways to control chip quality so as to ensure pulp quality. We tried to explain some important chip properties included in the measurements, but did not try to model them.
Effects of log position in the stem and cutting width on size distribution of black spruce chips produced by a chipper-canter.
Fifteen stems of black spruce (Picea mariana (Mill.) B.S.P.) coming from the Abitibi-Temiscamingue region, were cross-cut into three sections: bottom, middle, and top logs. Logs were fragmented producing three faces with a chipper-canter using three cutting widths (CW) of 12.7, 19.1, and 25.4 mm. Chip dimensions were assessed by thickness, width, and length (Domtar and Williams classifications). Knot characteristics [total knot number (TKN) and area (TKA)] were assessed in the three cant faces. Growth ring attributes [earlywood density, latewood density (LWD), ring density, earlywood proportion, ring width and rings per mm (R/mm)], mechanical properties (shear, splitting, modulus of elasticity (MOE) and modulus of rupture in bending), and basic density were evaluated on samples obtained within each CW area. The results showed that most of these wood attributes were affected by the log position in the stem and/or CW. The weighted mean chip thickness (WCT) and chip size distributions were significantly affected by the log position and CW. WCT increased as CW increased. WCT variation with height could be principally associated to the number and size of knots within the stem. However, the presence of higher taper in the bottom logs produced thicker chips. Multiple linear regressions showed that CW, TKN, LWD, and TKA were significant predictors of WCT. Moreover, chip thickness distribution was affected primarily by TKA, cutting height and LWD, while the width and length distribution was mainly affected by R/mm, TKN and MOE. Chip size variation is to some point determined by knot characteristics, bending properties, growth ring width, and wood density of the raw material. These results showed the potential benefits of classifying logs in woodyards and better controlling the raw material attributes in sawmills. If the CW is combined with the knowledge of the raw material, chip dimensions can be adjusted using other fragmentation parameters to increase chip size uniformity.
Neutron Residual Stress Measurements on Rail Sections for Different Production Conditions
Rail sectioning with subsequent neutron diffraction experiments has been used to assess residual stresses in the rails. In this study we present the results of neutron stress measurements performed at the NIST Center for Neutron Research (NCNR) on rail sections from rails that were produced under various conditions. Specifically, these are air-cooled, air-cooled and roller-straightened, head-hardened and head-hardened and roller-straightened. More significantly, a head-hardened and roller-straightened rail was also studied after service to elucidate evolution of the service-induced residual stresses. In the latter case both a transverse-cut slice and the central region of a 0.53 m long piece were studied. Measurements on this piece are the first in which triaxial stresses have been determined for an intact rail. Neutron strain measurements with 3×3×3 mm3 spatial resolution were successfully employed for transversally cut slices to verify the difference in the stress state depending on the production process. Although examination of slices allows determination of only two-dimensional stresses in the plane of the slice, additional measurements on obliquely-cut slices, which were also carried out, and utilization of FEM gives the possibility of reconstructing the full triaxial stress distribution. Together, these approaches provide a better understanding of rail fabrication and the possibility of improving the durability and safety of rails in the future.Copyright © 2004 by ASME