Fig 13 - uploaded by Miran Merhar
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Circular saw deflection at a lateral force of 40 N and different rolling forces: a) rolling force of 15,500 N; b) rolling force of 18,300 N; c) rolling force of 21,800 N
Source publication
A commercial woodcutting circular sawblade was analysed in this work. The lateral stiffness on the periphery was measured, and the natural frequencies were determined by modal analyses. The sawblade was modelled by the finite element method, where the influence of the internal stresses caused by roll-tensioning of the sawblade was considered. The r...
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In this study, forced vibration of a rotating disk is investigated. The disk is clamped at the inner and free at the outer circumferences. A time varying excitation force is applied to a spacefixed point on the disk surface perpendicularly. The presence of multiple excitation forces is also considered in the paper. These forces can be applied to an...
Citations
... On a normal working situation (cutting operational process), the tool is susceptible to different type mechanical requests. These requests which are generally, of torsion and of heating due to friction, have its origin from the rotational blade movement when in contact to the wood [4], which are caused by the advance of the wood in the cutting operation. ...
The band saw blade, used on the wood log cutting, is exposed in service manufacturing to applications which can cause mechanical damages and affect the quality of the tool and the wood produced. To related applications, the shear stress is essential to the correct wood machining. the proposal of this paper was the numerically analyze the influence of the parallel shear force, applied vertically at the saw blade tooth, in response to the normal longitudinal tensions (σy) in service. A numeric model was constructed, by using of the commercial software based on the Finite Elements Method (FEM). In a first analysis, only a tensile stress was applied to the model on the upper edge of the blade, the deformation results obtained were used in the secondary analysis, with the simultaneous application of vertical point loads on the saw teeth.
... These can be fixed in clamp flanges or guided. Natural frequencies of saws and their dependent critical rotational speeds were determined in [21][22][23][24] . The impact of the design of the circular saw blade on its dynamic characteristics was described by Cheng and others 25 . ...
The shrinking global forest area limits the supply of industrially usable raw resources. This, in combination with the ever-increasing consumption of timber due to population growth can lead to the lack of a positive balance between the annual volumetric growth and consumption of wood. An important innovation toward increasing environmental and economic sustainability of timber production is to reduce the volume of wood residues by minimizing the sawing kerf. It results in higher material yield but may impact the dimensional accuracy of derived products. Therefore, the cutting tool geometry as well as the sawing process as a whole must be carefully optimized to assure optimal use of resources. The goal of this study is to better understand the causes of machining errors that occur when sawing wood with saws of varying thickness of kerf, with a special focus on re-sawing thin lamellae performed on the gang saw. Numerical simulations were tested against experimental results, considering influence of diverse components of cutting forces, in addition to the initial and operating stiffness coefficients of the saw blade. It has been demonstrated that asymmetric loads from the cutting process for the scraper saw blade can cause sawing inaccuracies. The simulation methodology developed in this research can be straightforwardly extended towards determination of optimal geometry of other cutting tools, particularly with the reduced sawing kerf. This may lead to more sustainable use of natural resources as well as an increase in economic gain for the wood processing industries.
... This is an analytical method, which is only suitable for circular saw blades with ideal disk structure. A finite element model of the roll tensioning process was established and proven correct by experimental verification (Nicoletti et al. 1996, Heisel et al. 2014, Merhar et al. 2017. The finite element method is a numerical method, which is suitable for circular saw blades of any structure, but it requires a lengthy calculation process. ...
In this paper, a concise and fast 2D model of the roll tensioning process was built using the finite element method. Elastic thermal expansion is used to simulate rolling plastic deformation. A 3D model considering contact between roller and circular saw blade was also built. Through comparison of residual stress results obtained by the 2D model, 3D model, and X-ray stress test method, the correctness and feasibility of the 2D model were proven. While accounting for the diversity of circular saw blade structure, this paper provided an idea for rapidly predicting the residual stress field of a roll-tensioned circular saw blade.
... Szymani and Mote 5,6 built a theoretical model for roll tensioning process and got the residual stress of saw blade body. A finite element model for roll tensioning process was established by Nicoletti et al., 7 Heisel et al., 8 and Merhar et al. 9 The influence of material properties of saw blade body on residual stress field of roll tensioned saw blade body was studied by Li and Zhang 10 based on finite element method (FEM). Generation and regulation mechanism of residual stress field of circular saw blade after multi-spot pressure tensioning was analyzed by Li et al. [11][12][13] Research Institute of Wood Industry, Chinese Academy of Forestry, Beijing, China analysis model of laser shock tensioning process was built by Li and Zhang 14-16 based on laser shock wave theory. ...
... A three-dimensional (3D) roll tensioning elastoplastic model was built by finite element method, which referred to the previous research results. [8][9][10] Previous studies had proved the accuracy of finite element method. The 3D model was shown in Figure 2 and the roll was analytical rigid body. ...
In this paper, 3D roll tensioning elastoplastic model was built by finite element method and the research object was a common circular saw blade body with hole, slot, and scraper structure. The theoretical calculation results show that there are areas dominated by tangential compressive stress near slot and scraper of roll tensioned saw blade body, which is not the expected result. It is proved that residual stress of saw blade body can be regulated by combining roll tensioning and local plastic compression process in this paper. The theoretical calculation results show that the outer edge of saw blade body near slot and scraper becomes area dominated by tangential tensile stress after the improved tensioning process. The improved tensioning process has little effect on stiffness and waist strength of circular saw blade.
... The effect of a solid saw blade's geometry (such as its diameter, clamping ratio and blade thickness) on the saw dynamic behaviour was described by Schajer [1], Stakhiev [2], Droba et al. [3], Kaczmarek et al. [4], and Li et al. [5]. Optimization of saw blade tensioning by rolling [6][7][8][9][10], the potential for the use of internal pressure in the saw blade as an alternative tensioning method [11] and application of a laser beam for straightening and tensioning circular saws [12] were also researched. Furthermore, Münz [13] revealed that there is a correlation between the critical speeds and residual stresses in the saw blade caused by technological process (grinding). ...
Dynamical properties of rotating circular saw blades are crucial for both production quality and personnel safety. This paper presents a novel method for monitoring circular saw vibrations and deviations. A machine vision system uses a camera and a laser line projected on the saw’s surface to estimate vibration range. Changes of the dynamic behaviour of the saw were measured as a function of the rotational speed. The critical rotational speed of the circular saw blade as well as the optimal rotational speed of the saw were detected.
Tensioning is an important manufacturing process of circular sawblade, which can effectively improve the critical rotation speed of the sawblade. With the development of tensioning technology, the comprehensive research of each technology is of great significance. In this paper, the elastic-plastic numerical simulation models of roll and multi-spot pressure tensionings were established. The natural frequency and critical rotation speed of the tensioned sawblade were obtained through modal analysis and analytical calculation, using no buckling of the sawblade as the limiting condition. The results show that with the increase of the mold reduction, the anti-plane displacement, critical rotation speed, and high-order natural frequency of the sawblade increased, while the low-order natural frequency decreased. After the multi-spot pressure tensioning process, the critical rotation speed was higher, and the tensile tangential stress at the edge of the sawblade was greater. The post buckling forms of the roll tensioned and multi-spot pressure tensioned sawblades were a dish and saddle, respectively. Through this study, the upper limit critical rotation speed of the sawblade under different tensioning methods could be found, which could be used for the selection of tensioning methods and parametric optimization.
Circular saw blades have many states, before and during the sawing process, depending on the different residual stresses and flatness of the circular saw blades. Based on the different states of circular saw blades, the effect of rotating centrifugal stress on the dynamic stability of circular saw blades is different, mainly reflected in flattening and stiffening effects. In this article, three representative states of circular saw blades were chosen and studied. The finite element method was chosen to simulate the deformation behavior of circular saw blades in the three states. The flattening and stiffening effects of centrifugal stress on circular saw blades in the three states were systematically studied. The axial stiffness of the outer edge of circular saw blades is increased with rotating speed. The rotating speed has a flattening effect on the circular saw blade, as a result of a centrifugal stress field. When the circular saw blade is in a different state, there are some differences in the flattening and stiffening effect of centrifugal stress.
When cutting wood, heat is generated in the cutting zone and in the gullet due to the friction between the teeth of the blade and the material that is being cut. Since the wood is hydrophilic, the saw blade cannot be cooled with liquids, as is usual when cutting metals. The only way to remove the heat from the source is by conductivity to the centre of the saw blade and then by convection into the air. This research presents an analytical model to calculate the natural frequencies of circular saw blades exposed to different temperature distributions. The model confirmed experimental findings of many authors, i.e. the heating of the saw blade cutting edge reduces its natural frequencies, the rate of the reduction depending on the temperature difference between the cutting edge and the rest of the blade and on the shape of the temperature distribution. In contrast, heating the centre of the saw blade increases its natural frequencies, the rate of increase depending on the temperature difference and the shape of the temperature distribution. With the presented model, the most favourable temperature distribution can be calculated from the point of view of the critical saw blade speed, which can be achieved by heating or cooling the centre of the saw blade.
