A Study On Residual Stresses Of Wood Circular Saws In Manufacture

This thesis systematically studied residual stress change of wood circular saws in manufacture for the first time, basing upon experiment analysis and technological processes in the enterprises that can represent saw industry in China. It also studied on roll tensioning process by a finite element. The all studying works are built up on one starting point which is taken the entire technological steps in making saws as a system engineering. The results of this thesis will improve and consummate the technology in manufacturing saw by controlling the residual stress state of circular saws so that high quality of domestic saws can be achieved.Circular saw blades must be under heat treatment, the first main step to infect the residual stress change of the blades in saw manufacturing processes for getting required mechanical properties and hardness. If oil or other quenching mediums which have similar cooling rate with oil used, the blades of 65Mn steel would have lower quenching stresses. Tempering after quenching is necessary for quenching stress release. For circular saws, the first 7 minutes in tempering is the time for quenching stress rapid release, so the tempering time could be cut down appropriately according to required mechanical properties and temper furnace output in order to economize energy consumption and raise production efficiency. Tempering stresses should fluctuate at ±20 MPa. Even hardness and lower tempering stresses in saw blades will lay a sound foundation for following technological processes.Grinding and roll tensioning are two key processes for the final stresses of a saw blade. Any single one of the two processes can not respectively achieve tension effect at present technological conditions. Taking the two processes as a combined one, the sequence of grinding and roll tensioning have no connection with tension effect. Some of the domestic blades do have certain tangential tensile stress, that is because of help from grinding rather than roll tensioning. Besides, magnitude and nature of stresses produced by grinding and roll tensioning depend on their technological parameters.The relationships between half width of X-ray diffraction and technological processesare analyzed here for the first time. Using the curve of half width and tempering time or temperature, the residual stress releasing process will be expressed directly and briefly. After tempering, half width date of the blades is about 2.2°.Half width date of the blades will increase nearing 1.0° after grinding, but half width date will change little after rolling. Taking grinding and rolling as a combined technological process, the effect of the process would be expressed clearly and briefly in the comparison of half width of the combined process with tempering. Because of a little fluctuation of half width, the test would be simplified and the test data would be got easily.A finite element model in analyzing rolling process by using ANSYS is built in this thesis. The model directly simulate the blade material and rolling conditions, the key factors in rolling process for the first time. The results of tensioning stresses comparatively agree with the experiment measurements. Besides, the model is also used to compare the deformation under different rolling conditions.