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1.
Existing log grading procedures in the United States make only visual assessments of log quality. These procedures do not incorporate estimates of the modulus of elasticity (MOE) of logs. It is questionable whether the visual grading procedures currently used for logs adequately assess the potential quality of structural products manufactured from them, especially those for which MOE is of primary concern. The purpose of this study was to investigate the use of stress wave nondestructive evaluation techniques to sort red maple logs for the potential quality of lumber obtained from them. Ninety-five red maple logs were nondestructively evaluated using longitudinal stress wave techniques and sorted into four stress wave grades. The logs were then sawn into cants and lumber. The same procedure was used to obtain stress wave times in the cants and lumber. The lumber specimens were then dried and graded using a transverse vibration technique. The results of this study showed that good relationships existed between stress wave times measured in logs, cants, and the lumber produced from the logs. It was found that log stress wave grades have positive relationships with the lumber grades. Logs with high stress wave grades produced high-grade lumber. These findings indicate that the longitudinal stress wave technique has potential in sorting logs and cants for the production of high MOE products.The Forest Products Laboratory is maintained in cooperation with the University of Wisconsin. This article was written and prepared by U.S. Government employees on official time, and it is therefore in the public domain and not subject to copyright. 相似文献
2.
A mill study of 62 trees, in which boards were reassembled into their original logs, permitted the construction of wood quality maps. In this instance stiffness profiles were obtained from butt to upper-top logs, based on machine stress grading of all boards and then averaging values from the 62 trees. Traditionally the butt log has been perceived to be the most valuable log in a tree, because it is bigger and gives a higher recovery of lumber. However, it is shown to contain a wide cone of very low stiffness wood that is confined to the first 2.4–2.7 m above ground level. Above this point stiffness gradients become cylindrical with no noticeable decrease in stiffness up the tree stem. Stiffness in all logs increased radially from pith to cambium with the greatest change being associated with the wood nearest the pith. The low stiffness at the base of the tree suggests that an alternative log bucking strategy should be considered, namely cutting a short 2.4–2.7 m butt log for plywood/LVL or for bolter sawing and only cutting standard length logs above this point.The least stiff logs (lowest 20%) yielded lumber that had an average stiffness that was over 1 GPa less than the average for the population. A case can be made for separating these logs and processing them differently. 相似文献
3.
Coppice regeneration of eucalypt plantations is increasingly being used in Australia to reduce re-establishment costs. However, little is known about the impact of early coppice reduction regimes on harvester performance during clearfelling. The trial compared the productivity, time consumption, cost and fuel use of a single-grip harvester (Hyundai 210LC-9 base and SP 591LX harvesting head) clearfelling a 10.5-year-old, second-rotation coppiced Eucalyptus globulus stand in south-west Western Australia for chip logs. Coppice stems had been reduced to one stem or two stems per stool or left untreated. Time and piece counts were used to determine harvester productivity. Harvester cycle and elemental times and the number of logs and harvester head passes per stem were obtained from video recordings. Harvester fuel use was determined by refilling the fuel tank to the same point each day. Stem size was the major factor influencing harvester productivity (20.8 m3 per productive machine hour without delays [PMH0], 11.8 m3 PMH0?1 and 8.6 m3 PMH0?1 in the single-stem (mean stem volume [MSV] 0.21 m3), two-stem (MSV 0.09 m3) and untreated trial areas (MSV 0.06 m3), respectively. Estimated harvester cost (AU$ m–3) was considerably greater for the two-stem and untreated trial areas, which reflected the lower harvester productivity in these areas. Processing time represented over 60% of the total cycle time for all trial areas. Coppice characteristics resulted in significantly different moving/positioning times between trial areas. However, this difference had no impact on cycle times. Number of logs per stem was a significant variable in cycle and processing time regressions for all trial areas and felling time for the single-stem trial area. Number of harvester head passes was a significant variable in cycle and processing time regressions for the single-stem trial area and processing times for the two-stem trial area, although its effect was less than that of the number of logs per stem. Fuel consumption (L PMH0?1) was relatively constant between the trial areas, hence harvester energy intensity (L m?3) reflected the harvester productivity in each trial area. 相似文献
4.
The representative carbon footprint of product (CFP) value of “certified wood in Kyoto Prefecture” was calculated as 241?kg-CO2/m3. The CFP value was 158?kg-CO2/m3 when wood was not kiln dried and final processing was not involved, whereas that of “kiln-dried, finished wood” was 284?kg-CO2/m3. Comparisons of different types of wood were also conducted to examine CO2 emission-reducing effects of “certified wood in Kyoto Prefecture”. We compared the CFP of lumber produced (in Japan) from logs supplied from Japan and other countries and that of “certified wood in Kyoto Prefecture”; the lumber products as a target for comparison are shipped to markets throughout the country. The CFP of “certified wood in Kyoto Prefecture” was approximately 50% lower compared to that of North American wood lumbered in Japan and shipped to markets throughout the country, and about 30% lower compared to the mean CFP of lumber produced (in Japan) from logs supplied from Japan and other countries and shipped to markets throughout the country. We then compared the CFP of “products imported from other countries after being cut into lumber” to that of “certified wood in Kyoto Prefecture”. The CFPs of lumber products from North America and Europe were lower than that of “certified wood in Kyoto Prefecture” (kiln-dried, finished wood). However, when only woodchips were used as a heat source in the process of kiln drying, the CFP of “certified wood in Kyoto Prefecture” was lower than any other kiln-dried lumber products. Regarding “certified wood in Kyoto Prefecture”, the use of woodchips as a heat source in the process of kiln drying or a shift to air drying decreases the CFP. 相似文献
5.
Portable sawmilling trials with Acacia aneura (mulga) and A. cambagei (gidgee) have been undertaken to estimate the private landholder costs associated with small-scale timber production from
woodlands in western Queensland, Australia. A time study of harvesting and milling operations facilitated estimation of landholder
labour input requirements. The scarcity and small size of millable logs, coupled with the prevalence of timber defects, make
harvesting and portable sawmilling of western Queensland acacias an expensive undertaking for landholders. The cost of producing
sawn timber that meets the High Feature (HF) grade of Australian Standard AS2796 is estimated at between A$3,000/m3 and A$3,400/m3 of HF timber. 相似文献
6.
Mark Alexander Butler Joseph Dahlen Thomas L. Eberhardt Cristian Montes Finto Antony Richard F. Daniels 《Annals of Forest Science》2017,74(1):20
Key message
Loblolly pine ( Pinus taeda ) logs can be evaluated using acoustic velocity whereby threshold acoustic velocity values can be set to ensure lumber meets specified mechanical property design values for modulus of elasticity.Context
There is a need to better sort logs according to lumber quality for improved decision making and wood utilization because merchantable logs are being harvested from different stand types including natural forests, conventional plantations, and intensively managed plantations, all with differences in rotation ages, growth rates, and wood quality traits.Aims
This study aimed to link tree- and lumber-length log acoustic velocity with the resulting lumber properties as tested in static bending from five intensively managed loblolly pine stands in the Atlantic Coastal Plain of Georgia.Methods
Acoustic velocity was measured using the resonance-based approach on 87 tree-length logs and 244 lumber-length logs. The logs were then processed into 797 pieces of 38 mm by 89 mm (2×4), 140 mm (2×6), 184 mm (2×8), and 235 mm (2×10) dimension lumber, dried, and tested in static bending.Results
Mean MOE of the lumber had moderate relationships with acoustic velocity of the logs (R 2 = 0.49) whereas MOR and acoustic velocity did not have a strong relationship (R 2 = 0.20). Accounting for log position increased the performance of the mean lumber MOE model (R 2 = 0.62) which was further increased by adding green density and small-end diameter (R 2 = 0.67). Utilization of acoustics was effective for segregating logs based on lumber modulus of elasticity and did not depend on knowing tree or stand information such as age, site quality, and silviculture history.Conclusion
Acoustic velocity evaluation of tree- and lumber-length logs could be employed to segregate logs within the supply chain to ensure that lumber would meet specified design values.7.
《Southern Forests》2013,75(2):133-149
A study of both fibre volume loss and related opportunity cost was performed across the South African softwood sawtimber industry to gain information on the actual utilisation of useful fibre and potential loss or gain of opportunity in terms of potential revenue from both field practices and policy. The study quantified volume losses from high stumps, felling and crosscut saw kerf, log allowances, excessive removal of merchantable wood, incorrect log trimming allocation, and utilisable wood left in-field. Eight treatments were examined: four terminated with merchandising at roadside landing and four at merchandising yards. Within the treatments, felling was either motor-manual or mechanised and compartments were classed by average compartment tree size (less than or greater than 1 m3). Total wood utilisation was found to be 92.07%. Stumps were found to be 7 cm higher than necessary and volume losses because of high stumps were 0.79% and 0.07% for mechanical and motor-manual felling, respectively. For felling saw kerf losses, mechanical felling showed 0.92% loss, whereas motor-manual felling resulted in only 0.15% loss. Incorrect log trimming allowance provided for 0.60% loss. Excessive trimming of logs resulted in 2.02% loss. Volume lost because of crosscutting saw kerf was low at 0.20%, but tops not being extracted resulted in 2.57% loss. Using SIMSAW 6 simulations, these volume losses translated into an additional annual harvested volume of 421 722 m3 or additional 1 278 ha harvested area, R166 million log value and R393 million net lumber value loss. Total loss was lowest (6.49%) in the average tree size class less than 1 m3, which was mechanically felled regardless of merchandising location. For the majority of volume loss categories, motor-manual felling caused greater loss when compared to mechanical felling methods. Log trimming allowance consumed 80 604 m3 annually. The results indicate that the human element may have a greater impact on fibre and value losses than the system choice. Further research is recommended to quantify the effect of the human element. 相似文献
8.
The productivity and chipping cost of a low-investment small mobile chipper were investigated. The effect of capital cost on chipping cost reduction was analyzed by changing the service life of the chipper when assuming a target operational chipping cost set at 250 yen m?3. Productivity of the investigated chipper was found to be at 23.7 m3 h?1 in chip volume with fuel consumption at 14.6 L h?1. The results showed that the chipping cost of the investigated chipper was lower than that of a higher priced and more productive grinder. Neither chipper nor grinder, however, could achieve the assumed target cost of 250 yen m?3 even if their service lives were extended. It was necessary to withstand the initial grapple loader and the labor costs or raise the grinder’s productivity to 33 m3 h?1 in order to reach a comparable operational cost target with that of the investigated chipper. Similarly, the grinder would have to reduce its capital cost and fuel consumption to maintain the chipping cost of 250 yen m?3 ifproductivity could not be improved. Net chipping cost of the investigated chipper was relatively small compared to that of the tub grinder, especially under a shorter service lifespan. The investigation shows that it is feasible for small-scale forestry to introduce a low-investment mobile chipper because it does not require a large amount of material and has a low chipping cost. Moreover, lowering the capital cost or the price of chippers is a more realistic cost savings in the long term. 相似文献
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10.
《Scandinavian Journal of Forest Research》2012,27(1):88-96
The aim of the study was to investigate the possibility of strength grading Norway spruce [Picea abies (L.) Karst.] saw logs on the basis of simulated X-ray LogScanner measurements and to evaluate the potential accuracy of X-ray LogScanner measurements of green heartwood density and percentage of heartwood. The study was based on 272 logs for strength grading and 29 logs for measurements of green heartwood density and percentage of heartwood. The logs were scanned using computed tomography (CT). After sawing, the modulus of elasticity (MOE) of the centre boards was measured using a strength-grading machine. The CT images were used for simulations of an X-ray LogScanner, resulting in simulated measurements of different variables such as diameter, taper, percentage of heartwood, density and density variations. Multivariate models for prediction of MOE were then calibrated using partial least squares (PLS) regression. The MOE of a log was defined as the mean value of the MOE of the two centre boards. The study showed that the simulated X-ray LogScanner measured the percentage of heartwood and green heartwood density with relatively high accuracy (R 2 = 0.94 and R 2 = 0.73, respectively, after removing two outliers) and that these and other variables measured by the simulated X-ray LogScanner could be used to predict the stiffness of the centre boards. These predictions were used to sort the logs according to the predicted MOE. When sorting out 50% of the logs (''high-strength'' logs), the percentage of C30 boards increased from 73% (all logs in the study) to 100% (only ''high-strength'' logs). The rest of the logs could then be divided into two groups, one of them with 100% C24 and C30 boards. 相似文献
11.
The purposes of this study were to accumulate fundamental data on wood properties within large Sugi logs and to take applicable variations in wood properties into consideration for sorting logs and sawing patterns. The characteristics of basic density, moisture content, growth ring width, and microfibril angle (MFA) were measured and the relationship with log and lumber quality was examined. It was considered reasonable to estimate the lumber moisture content based on the moisture content of heartwood rather than that of whole logs, especially when producing large-sized lumber. The MFA reached a constant value before the 15th ring, and within a distance of 10 cm or less from the pith. Since the E fr of lumber correlated with that of the log affected by MFA, it would be possible to produce lumber with a higher E fr from the outer position of the log, based on selecting a log above the E fr . Since the MFA would also affect the lumber warp, a sawing pattern avoiding the area around the pith or enlarging the rough sawn size when a large warp was expected could be effective in improving the lumber quality. To improve the lumber quality, not only one but also multiple wood properties must be applied to the sawing pattern. 相似文献
12.
There is increasing interest worldwide in using tree harvesting biomass as an energy source. Bark retained on logs is commonly used as an energy source, but is generally removed from eucalypt logs during harvest. In order to evaluate the potential use of eucalypt bark as fuel, there is a need for information on the productivity and cost implications of retaining eucalypt bark during harvest operations. The study examined the impact of retaining bark on logs on the productivity and costs of a whole?tree to roadside harvesting system in a short?rotation Eucalyptus nitens plantation in Australia being harvested for pulp logs. Trees were felled and bunched with a feller?buncher in spring, then left infield for four weeks to promote bark adhesion and reduce bark loss. A skidder extracted the trees to roadside where a processor processed them to predominantly 10?m logs. Machine productivities were calculated from estimated tree and log volumes and cycle times recorded from video recordings. The feller?buncher's productivity (65 m3 PMH0?1) was less than expected as it appeared to be underpowered to handle the larger trees on the study site. The skidder's productivity (56 m3 PMH0?1) was comparable to those reported in studies under similar conditions and with bark retained. The roadside processor's productivity (25 m3 PMH0?1) was lower than expected. This was believed to result from the operator separately stacking 10?m and 5?m logs, and the lower feed speed resulting from slippage due to the reduced feed roller pressure used in the study to reduce bark loss. Future research could identify feed rollers that increase feed speed while retaining bark. Harvest system costs (AUD18 GMt?1) were similar to those reported for a eucalypt roadside processing trial where bark was removed. These results suggest that retaining bark on the logs at roadside did not affect the harvesting system's productivity or costs. 相似文献
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14.
Strength graded boards of Norway spruce (Picea abies (L.) Karst.) are important products for many Scandinavian sawmills. If the bending strength of the produced boards can be predicted before sawing the logs, the raw material can be used more efficiently. In previous studies it is shown that the bending strength can be predicted to some extent using discrete X-ray scanning of logs. In this study, we have evaluated if it is possible to predict bending strength of Norway spruce boards with higher accuracy using computed tomography (CT) scanning of logs compared to a combination of discrete X-ray and 3D scanning. The method was to construct multivariate models of bending strength for three different board dimensions. Our results showed that CT scanning of logs produces better models of bending strength compared to a combination of discrete X-ray and 3D scanning. The main reason for this difference was the benefit of knowing the position of where the boards were cut from the logs and therefore detailed knot information could be used in the prediction models. Due to the small number of observations in this study, care should be taken when comparing the resulting prediction models to results from other studies. 相似文献
15.
Florence Hiu Yan Lui Yoko Kurokochi Hiroe Narita Yukie Saito Masatoshi Sato 《Journal of Wood Science》2018,64(3):246-255
Binderless boards are composite boards that rely on self-bonding mechanisms for inter-fibre bonding. Quercus acutissima and Quercus serrata logs degraded by Lentinula edodes (shiitake fungi) were used in this study to investigate whether physical and chemical changes induced by shiitake fungi can enhance board mechanical properties. Binderless boards were manufactured with 0.8 g/cm3 target density, 220 °C pressing temperature, 5 MPa pressure, and pressing duration of 10 min. Boards made from logs degraded for ≥?26 months were stronger than control boards and met modulus of rupture (MOR) and internal bonding (IB) requirements for fibreboards. Chemical composition and particle size distribution of the wood powder used to make the boards were determined to elucidate the drivers of board mechanical properties. The proportion of small particles (<?150 µm) showed a strong positive correlation with MOR for both species and hot water extractives showed a strong positive correlation with IB for Q. acutissima boards. Introduction of shiitake fungi pre-treatment to the production process may enhance the mechanical strength of binderless boards. 相似文献
16.
Despite regulations introduced about two decades ago to prohibit the use of chainsaw machines for milling logs into lumber for commercial purposes in Ghana, the practice still persists in clear violation of the law. This empirical case study in the Ashanti Region of Ghana seeks to understand the motivations for such violation. The study finds that low deterrence, economic gains to be derived, high patronage of chainsaw milled lumber on the domestic and the West African sub-regional markets, apparent lack of social sanctions for violators, weak morals of the actors involved, perceived unreasonableness of the regulations that prohibit chainsaw milling and low legitimacy of the regulators have all contributed to the violation behaviour. It also highlights the importance of contextual factors particularly poverty and political support in shaping the violation behaviour. The implications of these findings for policy are discussed and recommendations put forward. 相似文献
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18.
Mohammad Reza Ghaffariyan Ramin Naghdi Ismael Ghajar Mehrdad Nikooy 《Small-Scale Forestry》2013,12(2):181-192
Time equations are derived for felling with chainsaw, skidding with cable wheeled skidder, loading with grapple hydraulic loader and trucking of logs within a cut-to-length harvesting method. The continuous time study method was applied to collect data for felling, skidding, loading and a transportation model. Multiple regression analysis via SPSS software was applied to develop the time models. Felling time was found to be highly dependent on diameter at breast height. Skidding distance, winching distance, slope of the trail and piece volume were significant variables for the skidding time prediction model. The loading time model was developed considering piece volume. Transportation distance and load volume were used as independent variables in modeling the transportation time. The net production of felling was estimated at 12 trees/h (56.65 m3/h). The net production rates for skidding, loading and traveling averaged 18.51, 41.90 and 3.32 m3/h respectively. The total cost of harvesting from stand to mill was estimated 19.70 €/m3. The skidding phase was the most expensive component of the cut-to-length method. The bucking and delimbing components were less costly than the other logging phases. The results of this study can be used for harvesting planning and productivity optimization. 相似文献
19.
联合运输机设计忽视的因素 总被引：1，自引：0，他引：1
联合运输机组的滚筒出河机在设计，试验研究过程中都忽视了原木重心与原木形心位置不一致的因素。它促使较在径级原木在滚筒出河机上打横，造成停机。 相似文献
20.