Research on the effect of yield strength of circular saw blade on roll tensioning process
In this paper, a 2-D and 3-D finite element model of roll tensioning process of woodworking saw blade were established by Static/General module of ABAQUS software based on finite element method. The rolling force and tensioning stress distribution of circular saw blade were calculated by these two models which were proved to be true and reliable. The effects of yield strength of circular saw blade on tensioning stress distribution and rolling force were studied. The research achievements showed that a circular saw blade made with high yield strength obtained a higher tangential compressive stress and radial compressive stress in the rolled region during roll tensioning process, which has both advantages and disadvantages for the stability of the saw blade. Besides, a circular saw blade made with high yield strength also put forward higher requirements for roll tensioning equipment because of the large rolling force during roll tensioning process.
Circular saw blade is an important tool and is widely used in wood industry. Its stability, cutting precision, and material-saving ability are the most important features, especially for wood processing industry because of the shortage of precious wood. The Chinese government strongly supports the improvement of timber utilization. Therefore, TCT saw blade for wood is becoming thinner and thinner currently for reducing kerf loss and improving the utilization of materials.
However, thermal stress is produced when circular saw blade is working, because the temperature at the edge of the blade is higher than that in other regions of the blade. It will cause high tangential compressive stress on the edge of the circular saw blade, causing a buckling deformation that reduces cutting precision, increases kerf loss, and shortens the saw’s life [1, 2]. Thin TCT saw blade for wood composite is more easily affected by thermal stress. For saving materials, the stability of saw blade is very important, especially for thin circular saw blade.
Tensioning is the most important and advanced technological process for production of circular saw blade for avoiding the above-mentioned phenomenon. Among all the tensioning processes, roll tensioning process is most widely applied in the cutting tool industry. The tangential tensile tensioning stress field is produced which can compensate for the tangential compressive stress caused by thermal stress and improve the stability of circular saw blade [3–5]. However, circular saw blade can also obtain radial compressive tensioning stress during roll tensioning process which is easy for the blade to lose stability and buckle into a “dish” shape. The thin circular saw blade requires higher tangential tensile tensioning stress and lower radial compressive tensioning stress for maintaining stability, which brings a challenge to roll tensioning process of thin circular saw blade.
At present, the effects of tensioning on the dynamic stability of the blades have been mainly focused [6–16]. The generation of tensioning stress during tensioning processes has been studied by a few researchers. A theoretical model for roll tensioning process was established by Szymani and Mote [2]. A model for roll tensioning process was established by Nicoletti based on the finite element method [17]. A finite element model (FEM) for roll tensioning process, which allowed for the investigation of various roll tensioning parameters, was developed by Heisel [18]. A mathematical model of tangential tensioning stress in the edge of a circular saw blade tensioned by multi-spot pressure was established for the quality control of circular saw blades by Li [19].
Yield strength is the lowest stress value when plastic deformation is produced, which is an important indicator for metal materials and has a great effect on metal forming process such as roll tensioning process. Circular saw blade with different yield strength could obtain tangential tensile and radial compressive tensioning stress with different values, and different rolling force will be applied to the roll for making the blade to produce plastic deformation.
However, to date, for circular saw blades, there is no related research about the effect of yield strength on the generation of tensioning stress during roll tensioning process. Therefore, the effect of yield strength of circular saw blade on the generation of tensioning stress during roll tensioning process was analyzed in this paper, which can demonstrate the effect of yield strength on roll tensioning process.
In step 1, the roll moved slowly down and elastic–plastic deformation was produced to the metal cutting saw blade. In step 2, the roll slowly raised and the saw blade was no longer under any load. The residual stress of saw blade was the tensioning stress.