Search

In this study, samples were subjected to the following surface treatment techniques: sawing with a circular saw, planing with a thickness machine, and sanding with a sanding machine (with No. 80 sandpaper). After samples were treated radially and tangentially with machines, their surface roughness values (Ra, Ry, and Rz) were measured according to ISO 4288. When statistics related to surface roughness values (for Ra, Ry, and Rz) were analyzed, it was found that surfaces processed with the thickness machine exhibited the smoothest surfaces. Also, according to the same statistical tables, the lowest surface roughness values were found for surfaces cut tangentially. [ABSTRACT FROM AUTHOR]

Copyright of Ciência Florestal (01039954) is the property of Ciencia Florestal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• Different NDE methods applied to wood and timber structures were explained. • Concept of AE and its experimentation was introduced. • Impact of wood characteristics on AE wave (velocity, attenuation) was discussed. • Applications of AE in monitoring of wood materials were critically reviewed. • Opportunities, challenges, and outline of future research were discussed. The growing interest in timber construction and using more wood for civil engineering applications has given highlighted importance of developing non-destructive evaluation (NDE) methods for structural health monitoring and quality control of wooden construction. This study, critically reviews the acoustic emission (AE) method and its applications in the wood and timber industry. Various other NDE methods for wood monitoring such as infrared spectroscopy, stress wave, guided wave propagation, X-ray computed tomography and thermography are also included. The concept and experimentation of AE are explained, and the impact of wood properties on AE signal velocity and energy attenuation is discussed. The state-of-the-art AE monitoring of wood and timber structures is organized into six applications: (1) wood machining monitoring; (2) wood drying; (3) wood fracture; (4) timber structural health monitoring; (5) termite infestation monitoring; and (6) quality control. For each application, the opportunities that the AE method offers for in-situ monitoring or smart assessment of wood-based materials are discussed, and the challenges and direction for future research are critically outlined. Overall, compared with structural health monitoring of other materials, less attention has been paid to data-driven methods and machine learning applied to AE monitoring of wood and timber. In addition, most studies have focused on extracting simple time-domain features, whereas there is a gap in using sophisticated signal processing and feature engineering techniques. Future research should explore the sensor fusion for monitoring full-scale timber buildings and structures and focus on applying AE to large-size structures containing defects. Moreover, the effectiveness of AE methods used for wood composites and mass timber structures should be further studied. [ABSTRACT FROM AUTHOR]

This study determines the influence of mechanical surfacing on tensile shear strength (TSS) and wood failure percentage (WFP) of beech wood {Fagus sylvatica L.) at the wet stage according to prEN 302-1:2011 (tensile shear tests). The wood was planed, sanded and face milled, using different qualities of cutting edges and sanding grits. Roughness and wettability of the adherends were characterised, supplemented by environmental scanning electron microscopy images. The specimens were bonded by means of a one-component polyurethane adhesive and tested at the dry stage (pretreatment A1), at the wet stage (A4) and after re-drying (mA5). Results determined that the wettability and the wood structure's integrity are considered more decisive for the TSS at the wet stage than surface roughness. Planing with very dull knives caused the lowest TSS and WFP after A4 and the most subsurface damage. Face milled and sanded batches revealed the best performance. The TSS and WFP decreased significantly from A1 to A4, but recovered after mA5. [ABSTRACT FROM AUTHOR]

The incorporation of interactive technology into the memorialization of the World War II incarceration of 120,000 Japanese Americans enables those with no prior connection to this history to role-play the internment experience. This essay compares the author's digital role-playing game Drama in the Delta with the Broadway-bound musical Allegiance, arguing that the shared impulse to use performance to walk in internees' shoes threatens to eclipse historical understanding with an uncritical form of empathy. [ABSTRACT FROM AUTHOR]

Abstract: In this study a mutable mold for ceramic cutting tools with inserts of different cutting angles and two different injection positions was designed. Three alumina-based ceramic feedstocks with different types and amount of second phases were developed. A mold filling study was carried out for both sprue positions in order to prove the molding behavior of the feedstock and the functionality of the mold. Debindering and sintering of molded green parts was arranged for each composition, respectively. Mechanical properties, microstructure and achieved cutting edge sharpness of produced tools were investigated. Results show that the mold design and injection molding process play a key role in order to manufacture cutting tools of best possible sharpness enabling a wood machining process. Feedstocks exhibit a good mold filling behavior resulting in comparatively sharp cutting edges of ≈10μm after sintering. Mechanical properties show high potential for application of wood machining cutting tools. [Copyright &y& Elsevier]

The final quality of solid wood moulding depends on several factors, being the raw material one of the most important, but the choice of cutting conditions are a key point when processing this type of material. One of the main problems is to achieve an adequate monitoring of the cutting conditions in order to detect and correct in-time operational problems or prevent the loss of productivity due to an over chute in quality at a level that is below the required standards. The main objective of this research is to understand and limit the tool wear when appearance grade products are being produced, mainly to detect and prevent the loss of quality, but also the need to monitor the process considering different factors such as the cutting forces and the sound emitted during the process, then correlate them with surface roughness. The main findings of this study allow to conclude that the relationship between cutting speed and feed rate reflects well the changes in cutting forces, surface roughness and sound pressure. When the chip thickness increases it correlates very well with increasing cutting forces, as well as surface roughness (good levels of coefficients of determination were observed for both response parameters), rougher surfaces produced with thicker chip (higher feed rate); but it is believed that in the present state of tool wear, the results of cutting forces have not a fully appropriate behaviour; further studies are needed on this variable at different levels of wear. Also, the change of rake angle is clearly reflected on the surface roughness and sound pressure. The RMS sound pressure provides adequate results when the signals were processed using a digital high-pass filter with a cut-off frequency of 1000 Hz. [ABSTRACT FROM AUTHOR]

In this review, fundamental wood machining research is evaluated to determine the general cutting mechanics of simple, orthogonal, and oblique cutting tools. Simple tool force trends and chip formation characteristics are indentified here, along with the cause and effects of tool wear. In addition to this, specific methods of evaluating sawing processes have been investigated. These include the use of piezoelectric dynamometers to record tool forces and high speed photography to evaluate chip formation. Furthermore, regression analysis has been previously used to identify tool force trends with respect to both tooth geometry parameters and work-piece properties. This review has identified the original findings of previous research. This will allow for further original research to be conducted. [ABSTRACT FROM AUTHOR]

Abstract: The paper presents mechanical and tribological properties of CrCN/CrN and CrCN/CrN+ta-C multilayer coatings. Tetrahedral carbon (ta-C) layer formed using the pulse cathodic arc evaporation method are characterised by high hardness –45GPa, very low friction coefficient—below 0.1 and a low wear rate −1.3×10−17 m3N−1 m−1 providing promising application perspectives. Three sets of tools—planer knives for cutterheads were tested: uncoated (as reference), tools with a CrCN/CrN coating and tools with CrCN/CrN coating with additional friction-reducing tetrahedral carbon (ta-C) layer. The results of investigations indicate that the “tool life” depends on the type of coating and machining conditions. The blades covered with CrCN/CrN multilayer coating after machining of dry, seasoned pine timber showed a twofold increase of durability, and knives covered with CrCN/CrN+ta-C multilayer coating were characterised further by about 15% higher durability. Durability of knives tested in the course of rounding of wet pine timber, despite relatively high depth of machining was improved and for cutters with a CrCN/CrN coating increased more than twice, while the use of the additional ta-C layer on the multilayer coating improved durability by almost 5 times. [Copyright &y& Elsevier]

Machining operations have advanced in speed and there is an increasing demand for higher quality surface finish. It is therefore necessary to develop real-time surface inspection techniques which will provide sensory information for controlling the machining processes. This paper describes a practical method for real-time analysis of planed wood using the photometric stereo technique. Earlier research has shown that the technique is very effective in assessing surface waviness on static wood samples. In this paper, the photometric stereo method is extended to real industrial applications where samples are subjected to rapid movements. Surface profiles extracted from the dynamic photometric stereo method are compared with those from the static measurements and the results show that there is a high correlation between the two methods. [ABSTRACT FROM PUBLISHER]

In this study a number of work-piece variations were evaluated whilst limiting the cutting conditions. Eight wood species controlled at four moisture levels were machined along and across the wood grain. The tool used during cutting was designed to resemble a rip saw tooth with zero rake angle and narrow edge width. Each work-piece variation machined in the cutting tests was subjected to mechanical tests that evaluated bending properties across the grain and shear properties along the grain. The regression model establishes a relationship between the bending properties for cutting forces across the grain, as well as shear properties for cutting forces along the grain. F and R² values show that the elastic properties of the wood in bending and shear have less influence on the cutting forces when compared to the strength and toughness. Additionally, density is seen to have less influence on the cutting force along the grain. This is explained by the tool passing through an unquantifiable proportion of early and latewood fibers from the annual growth rings. Cutting across the grain, the tool is forced to machine through approximately the same proportion of earlywood and latewood fibres. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the results of modeling of CrCN/CrN and TiAlN/TiN multilayer coatings with a thickness of 3μm, which consist of seven bilayers, each of the thickness of ca. 400nm, and the thickness ratio of bilayers as 1:1 for both coatings, their deposition on the HS6-5-2 steel substrate using the cathodic arc evaporation method and the measurements of their mechanical properties. The mechanical properties of monolayer coatings, which are contained in the multilayer coatings were also examined. The coatings were investigated concerning the EDS hardness and adhesion. The coefficient of friction and the wear rate of the coatings were also measured. Further research includes the determination of the durability of tools for woodworking with wear resistant coatings. The coatings tested, both the multilayers and their components, are characterized by a good adhesion being not less than 80N. The lowest wear rate is characterized by the CrCN/CrN multilayer coating (8.5×10−7 mm3 N−1 m−1), the TiAlN/TiN coating has a rate being 10 times higher. Among the tested coatings TiN coating shows the lowest coefficient of friction (0.4) but the wear rate is not the lowest. It is ca. 7×10−6 mm3 N−1 m−1 and is almost 5 times higher than for the CrCN coating. Industrial research of the “lifetime” of woodworking tools with wear resistant coatings was carried out in planer knives to the head. These tools with multilayer coatings exhibit more than a twofold increase in the work life of dry pine wood cutting. Both coatings show a similar increase of durability. Further sequential re-sharpening did not change significantly the lifetime of both knives. [Copyright &y& Elsevier]

Heat concentration from wood cutting process promotes the tool premature wear, with consequent effect on the surface processed material, causing burnt areas as well as provoking larger superficial roughness than observed in machining process with absence of accumulated heat. The objective of this research was to evaluate the effect of cutting tool refrigeration during wood machining. The adopted mechanism was the use of pressurized carbon dioxide in fog form applied directly in the cutting area as a refrigeration method. The test was performed using Eucalyptus grandis and as cutting tool, a circular saw. To evaluate the wood final surface the following parameters were adopted; superficial roughness and occurrence of surface carbonization. The results showed that carbon dioxide applied in fog form, even at the smallest level (15g min-1), avoided the superficial carbonization of the processed material, as well as reduced the values of superficial roughness. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study is first to define the effect of a surface finishing such as sand-blasting on the geometry of a wood cutting tool and its wear resistance. In addition, the effectiveness of surface coatings like CrAlN deposited by physical vapor deposition (PVD) technique on conventional and sand-blasted cutting edges was studied. A reference tool and different sand-blasted ones were tested by micro-peeling of beech in a laboratory. Microscopic observations, cutting forces measurement and cutting wear tests were carried out to quantify the behaviour of these tools. The results obtained showed that the artificial wear by sand-blasting leads to an increase in the wear resistance and coating effectiveness, and completely changes the type of damage done to the tools. The sand-blasting application combined or not with CrAlN coating showed an improvement in the wear resistance of the tools and a modification of the forces during the peeling process. The effectiveness of the CrAlN layers was improved thanks to the sand-blasting treatment and then the duplex ones performed better. [Copyright &y& Elsevier]

Abstract: Nowadays, medium density fibreboard (MDF) composite wood is more and more used in the furniture industry to replace bulk wood such as oak, beech, etc. Indeed, this material presents good mechanical properties, is easy to machine, homogeneous, exists in different dimensions (thickness, etc.), is cheaper than bulk wood and finally can be covered by an adhesive decorative coat. Nevertheless, even if this material is homogeneous, it is abrasive enough to tend to the breakdown of the conventional carbide tools employed during its routing process. That is why it is necessary to improve the wear resistance of these tools. One solution is to protect them with a hard coating. The present study deals with the development of ternary CrAlN hard layers obtained by PVD method on carbide tools employed in second transformation of wood. CrAlN coatings have been optimized and then applied on carbide tools in routing of three types of MDF: standard, waterproof and fireproof. The aim of these wood machining tests was first to define the ability to be machined of the three kinds of MDF and second to compare the effectiveness of CrAlN coatings during the routing tests of these materials. [Copyright &y& Elsevier]

Nowadays drilling is one of the most important production processes in industrial wood machining. But this process step limits the output of flow processing machines because the workpieces have to be stopped to create the drillings etc. at relatively low feed speeds. The disadvantages of that conventional technology shall be avoided through the development of an alternative production process, by which blind holes into wooden workpieces can be punched with the use of a simple translational kinematics. Especially for machining of fiber- and particle board, which are typical materials in industrial furniture production, very good results could be achieved in the laboratory. Current research activities also deal with the punching of solid wood. A main field of investigation consists in finding the connection between punching speed (feed speed), punching force (process force) and hole quality. The primary aim is to get minimum forces at maximum qualities. Therefore several experimental setups have been developed, which enable punching with speeds of 0.001 m/s up to 150 m/s and thus different punching energies. The test of different modified punching tools was carried out with the same intention. The manufacturing of alternative (noncircular) hole geometries for fittings and assembly systems in furniture industry is currently examined. [ABSTRACT FROM AUTHOR]

Abstract: A great concern to save the amount of tungsten carbide used in various mechanical components has become important because of an increase of global demand and the resultant sharp rise in the price in recent years. Sintered tungsten carbide (WC) tools are usually used in woodworking industry because of their excellent combination of hardness and toughness. However, the actual area necessary for cutting is very small compared to the overall cutting tool body. In this work, three high-velocity oxy-fuel (HVOF) sprayed WC–Co coatings with different carbide size (0.2, 2, and 6 µm) on high speed tool steel substrates were fabricated and then grinded to produce cutting tools. Characterization of the deposited coating was done by scanning electron microscope, X-ray diffraction, hardness and indentation fracture toughness tests. The wood machining tests were performed on natural wood (Apitong) and medium density fiberboard (MDF) to study their performance as a cutting tool. The results showed that the hardness values of the coatings were approximately the same as that of sintered material, while the fracture toughness values were significantly lower. The wood machining tests on Apitong revealed that the coating tools were worn by the same level of edge recession as the sintered material. However, they showed numerous edge chippings over the worn surfaces and the level of edge chipping tended to increase with reducing the carbide size. The wood machining tests on MDF revealed that the coating tools were worn by the same level of edge recession in the low density wear zone as the sintered material but by a significantly higher level in the high density wear zone. [Copyright &y& Elsevier]

Drilling of wood is besides milling, sawing and grinding one of the most important production processes in industrial furniture manufacturing. For the body assembly and the fixing of fittings, boreholes are essential. They have immediate effect on quality and production costs. The process step drilling limits the output of stationary and throughfeed machines, because the workpieces have to be stopped to create the drillings at a relatively low feed speed. An essentially increased performance cannot be reached by the improvement of conventional drilling devices. The aim of the work presented in this paper is the development of an alternative production process in which blind holes can be punched. Thereby thin-walled, cylinder-shaped tools are pressed into different solid and derived timber workpieces by a simple translative movement. For it special experimental setups have been designed. The new production process opens possibilities for an optimization and acceleration of process cycles in industrial wood machining. [ABSTRACT FROM AUTHOR]

Wood machining parallel to the grain (90-0 direction) of Blackwood was performed using piezo-electrical transducer to record the acoustic emission (AE) signals generated during the cut process, considering the type of wood (heartwood and sapwood), and the relationship with surface roughness (Rz). A good relationship it was found between cutting conditions and acoustic emission signals, where an increase of the chip thickness results in a major consumption of cutting energy. Also, it was detected an increase of AE signals with the change of wood type, passing from sapwood to heartwood (increase of density). Finally, a good relationship it was found between surface roughness (Rz) and acoustic emission (AE). [ABSTRACT FROM AUTHOR]

In recent years parallel kinematic machines for wood machining have come into use more frequently. Despite first promising prototypes, these machines are single solutions for specific applications. To meet the requirements of shorter product life cycles and higher product diversity, high flexibility is demanded of the machining system. This paper presents a new wood machining center obtaining both, the reduction of the primary and secondary processing times. The machine concept, based on a parallel kinematic structure, allows high operating speeds and accelerations not only for workpiece machining but also for handling. Thus, the machine can be used without any external handling devices. The kinematic structure originates from a plane closed five-bar chain with two linear drives and additional drive axes for stroke and rotation. In order to increase the useable workspace a continuous motion between different assembly modes is realized. To guarantee a high feed rate and to minimize set-up times, an optimized dust exhaustion is included. [ABSTRACT FROM AUTHOR]

With rising feed rates of wood working machines, it is important to realize a process-integrated quality assurance. The quality control of produced workpieces is mainly carried out by the operator. As his capabilities are limited, an automated quality control system can help to assure a constant quality level. Due to the high production speeds, only an optical measurement can be used. While CCD-camera-based control systems are generally applied in wood working, no approach has been made so far to measure the surface roughness which is caused by the machining of the workpiece. This paper presents two different quality control systems for an assessment of the surface quality of a workpiece. In planing of solid wood, the size of the waves on the surface is most significant for workpiece quality. An image processing system has been developed which measures the width of the waves by means of a special illumination. In machining chipboards, the size and number of cracks in the edge are very important. Here, a camera-based system is presented which is able to measure the complete workpiece edge even at high feed rates with a sufficient resolution. [ABSTRACT FROM AUTHOR]

Abstract: This study was carried out to determine the planing properties and surface roughness of naturally grown Oriental beech (Fagus orientalis Lipsky.), Anatolian chestnut (Castenea sativa Mill), Black alder (Alnus glutinosa subsp. Barbata (C.A.Mey.) Yalt.), Scotch pine (Pinus sylvestris L.), and Oriental spruce (Picea orientalis (L.) Link.) grown in the eastern Black sea region of Turkey. The tests were conducted according to ASTM 1666 and DIN 4768. Test specimens were prepared from the lumber cut tangentially from logs. The machining process was carried out on a cabinet planer machine. Mainly, the effects of the rake angle and the feed speed were investigated. The cutting depth was constant with 1.6mm. The Oriental spruce resulted in the lowest machining performance among the samples. The machining performance of the specimen increased as the feed speed or the rake angle decreased. All of the samples except the Anatolian chestnut showed lower surface roughness values. The surface roughness is found not to be affected by the feed speed, but by the rake angle. In addition, lower surface roughness values were observed for the latewood than the earlywood. [Copyright &y& Elsevier]

Abstract: Industrial wood-cutting inserts were produced from both Si3N4- and Si3N4-based ceramic matrix composites (CMC), subjected to industrial wood-cutting conditions and compared to tungsten carbide (WC). Relevant material properties for this particular application were collected and compared to the results obtained from the cutting tests. The results show that Si3N4/30wt.% SiC gives the best balance between fracture toughness and wear. An yttria/lanthana sintering aid system allows the production of a very fine-grained microstructure without decreasing the fracture toughness. Post-hipping and crack-healing operations have been shown to be of paramount importance for the survivability of the cutting edges. An extrapolation from the lifetime prediction test gives a potential lifetime for the CMC material three times that obtained from the WC. [Copyright &y& Elsevier]

Abstract: The paper presents a study on the performances of innovative coatings for steel cutting tools in machining wood. A series of steel tools with different surface modifications, such as nitriding, application of antiwear DLC and CrN mono and multilayer coatings, has been applied to HSS18 and alloy steel 90CMV8 substrates. Tribological and erosion resistance of the samples was evaluated and related to the cutting performance, while surface analysis was carried out on the workmaterial at the end of the cutting tests. The overall tests indicated that the modified tools are promising in secondary transformation of wood. Furthermore, combined tribological and erosion studies allowed to individuate a wear mechanism and the possibility to foresee cutting performance in this application. [Copyright &y& Elsevier]

Abstract: The aim of this study is to optimise the application of duplex treatments by modifying the nitriding conditions and using a new kind of PVD coating like ZrBN compound. The influence of gas mixture (composed of N2, H2) and time of nitriding on the mechanical and structural properties of 32CrMoV13 low alloy steel was studied. An optimisation of a ZrBN coating was also conducted. After the characterisation of the nitrided layers and coatings (XRD, SEM, EDS, hardness profiles,…), different kind of cutting knives were treated and tested in the peeling of non-defect beech wood. It appears that the duplex treated knives (nitriding with 80% of N2 and a ZrBN coating) performed best and allowed an increase of almost twice the tools'' service life. [Copyright &y& Elsevier]

Abstract: The aim of this study is to show the behaviour of modified knives by ion nitriding, hard coatings and duplex treatments (nitriding+hard coating) in peeling of beech (for the production of veneer and plywood) and in pulp chips production (used for the production of particle boards). These surface treatments were tested within the framework of a European project where laboratories and SME working in the primary transformation of wood were involved. After optimization of the surface treatments, we applied the best ones on knives and we tested them in laboratory and directly in industry. The results showed that the application of surface treatments on wood cutting knives increased their wear and shocks resistance and also the quality of the final product. [Copyright &y& Elsevier]

Abstract: The influence of CrN coating on the thermal phenomena during wood composite (MDF—medium density fiberboard) peeling is investigated. The heat flux in the knife is used as the thermal indicator of the coating impact. The heat flux estimation is obtained through the resolution of the inverse heat conduction problem in the tool. The difficulty encountered in this problem comes from the great uncertainty in the sensors location and on the nonlocal measurement. The noninteger system identification method is used in order to obtain an accurate heat transfer model in the tool that rely the spatial average heat flux on the cutting edge to the temperature of the sensors embedded in the tool along the time. This average heat flux is then estimated during machining using the classical constant function specification method. The spatial variation of the heat flux on the cutting edge is reached using a finite element approach and its magnitude is adjusted with respect to the value of the estimated average heat flux. [Copyright &y& Elsevier]

Today, for wood industries, a better knowledge of material behaviour during machining is needed for economical and productive reasons: with equipment adapted to manufacturers’ needs. Woodworking machinery and tools manufacturers, as well as their users, urgently require reliable information on the main factors influencing wood cutting and above all on the magnitude of the force required to separate a chip, i.e. the cutting force and its variations in different cases. This is the main aim of this work.This investigation deals with the study of 14 wood species in the following cutting process: routing, i.e. peripheral milling parallel to the longitudinal direction. The influence of main mechanical characteristics was studied and a formulation was obtained which allowed us to estimate more precisely strains involved and the general behaviour of wood during machining. [Copyright &y& Elsevier]

Cubic CrN coatings were deposited by magnetron sputtering onto carbide tools and tested in wood machining operations. The coatings composition was determined by Energy Dispersive Spectroscopy. SEM cross-section observations verified their morphology. The phase structure of the layers was determined by XRD analyses. In the first step, the mechanical properties of the chromium nitride coatings were characterised by hardness measurements and scratch adhesion tests. In the second step, carbide tools were tested in machining of Oriented Strand Board (OSB) up to 10 km of cutting distance using an industrial router. The tool wear was quantified by recording and analysing the cutting edge profiles at increasing cutting distances. These observations were performed using the Vertical Scanning Interferometry technique on 3D surface profiler (Wyko NT 2000). Parameters such as, the bevel width at 0.1 mm depth from the tip and the nose loss were computed for each profile. The influence of deposition conditions, such as the coatings thickness, the working pressure and the target power, on the mechanical and structural properties of coatings and the wear of the coated carbide tools was studied. It has been found that CrN coatings, obtained with a thickness of 2 μm at working pressure of 0.2 Pa, and a target power of 650 W performed the best in OSB machining. A good agreement was observed between the tribological properties and the wear rate in wood machining tests. An influence of the layer structure was also observed: CrN crystallised with (111) and (200) orientations, performed better in OSB machining than the one presenting (200)-preferred orientation. [Copyright &y& Elsevier]

The efficiency of hard coatings, such as CrxNy, in increasing abrasion resistance of cutting tools for peeling has been shown in previous studies [Surf. Coat. Technol. 74–75 (1995) 625–633; Me´ca. Indus. 3 (2002) 333–342]. Furthermore, it has also been demonstrated that this efficiency was increased by a previous thermal treatment of the steel cutting knife that means by a duplex treatment consisting in nitriding followed by CrN-sputtered coatings [Me´ca. Indus. 3 (2002) 333–342].The aim of the study is to optimise the application of duplex treatments by modifying the nitriding gas mixture in high temperature process. The influence of gas mixture (composed of N2, H2 and CH4) on the mechanical and structural properties of 32CrMoV13 low alloy steel samples was studied. The composition and structure of the nitriding layer was determined by the EDS and the XRD, respectively. Vickers microhardness profiles were also performed to study the influence of the gas mixture. The morphology of the nitriding layers was observed by optical microscopy. Cubic CrxNy coatings have been realised by triode sputtering on both faces of the cutting knives. The EDS analyses permitted to verify the composition of the layers while their structure was determined by the XRD.Different kind of cutting knives were tested in peeling of non-defect beech wood: non-treated, nitrided, CrN-triode sputtered and CrN-duplex treated cutting knives. The friction coefficient between the cutting material and the wood was determined and the wear of the knive edge (reduction of the edge) was also measured.It was obvious that increasing the nitrogen contents from 20 to 80% in the nitriding gas mixture N2 + H2 or adding 5% of methane permit to increase the nitrided layer’s thickness and hardness. The nitrided cutting knives and CrN-triode sputtered duplex based treated knives were tested and compared in peeling of beech. The duplex treated knives obtained with 80% of N2 or 5% of CH4 performed best and allowed to increase almost twice the tools service life. [Copyright &y& Elsevier]

In this paper an analytical investigation of the possibility of employing damping elements to prevent chatter instability in wood machining is presented. A simplified model of a two-degree-of-freedom machine for wood cutting is first established. Then, the stabilizing effect of damping on the initially unstable and undamped system is investigated. The influence of damping on flutter and divergence instability is analyzed separately following different approaches. Some simplified assumptions are made to facilitate the analysis and a set of explicit conditions ensuring stability is found. Since the studied system is nonconservative, not only the effect of damping on the initially unstable system is investigated, but also its effect on the initially stable system. In particular, a condition preventing the destabilization of the system is achieved through the eigenvalue sensitivity analysis. The results attained might ensure important productivity improvements in real wood machining applications. [Copyright &y& Elsevier]

Experimental results from fixed abrasive diamond wire machining of wood and foam ceramics are presented. Three types of wood—pine, oak, and fir, and three types of foam ceramic—silicon carbide, zirconia, and zirconia toughened alumina, are tested. The research investigates the life of diamond wire and effects of process parameters on the cutting forces, force ratio, and surface roughness. A scanning electron microscope is used to study the worn diamond wire, machined surfaces, and debris. The diamond wire saw is demonstrated to be very effective in machining foam ceramics. The wire life for cutting wood at slow feed rates is low. The short tool life for dry cutting of wood indicates that more research in new fixed abrasive diamond wire and wire saw machining technologies is necessary. [Copyright &y& Elsevier]