Theoretical And Experimental Study Of Blanking Process Noise Emission And Its Control

Pressworking is one of the production technology used widely in modern manufacturing. However, there exist noise, vibration and insecurity problems in pressworking technology, which are more and more attentioned in the world, and pressworking noise has become an acknowledged environmental pollution. Obviously, it is highly significant whether in social benefit or in technical economic value or in academic theory to research pressworking noise.Blanking process noise is the most serious and the most typical among noise caused in various pressworking processes. Therefore, in this dissertation, process noise caused in the general blanking is selected to be researched, then some systemic and detailed research work have finished with theoretical analysis and experimental methods, where theoretical disciplinarian and characteristic of its noise emission are probed and dicussed, and finally some countermeasures are introduced to reduce its maximum noise actively. The research work includes these aspects:Establishment of the blanking process noise testing system, analysis of the general blanking noise testing results, and the research of blanking process noise emission mechanism; Deduction of a punch's unrestricted vibration differential equation and a mathematic expression on blanking process noise sound pressure level and blanking force on the break-through stage of blanking deformation, the construction of prediction model on maximum blanking process nose emission; The FEM analysis of sheet metal blanking processing and blanking deformation stage, the theoretic analysis of noise reduction effect in two steps blanking process, the design of progressive dies for two steps blanking process, and the experimental study on noise produced in two steps blanking process with progressive dies compared with that produced in general blanking process; The design and intensity verification of blanking dies while adding counterforce on punch's head, the experimental study on noise produced in the blanking process with adding counterforce on punch's head. The main research results are as follows:(1) Using an advanced testing method, some typical blanking force curves and noise emission sound pressure wave graphs are obtained; Through the whole profile description for the blanking process noise emission sound pressure wave graph with contour lines, a physical model—blanking process noise emission tree is constructed, which quantificationally proves the conclusion that noise produced on the break-through stage is the maximum among that produced in the whole blanking deformation, and which can describe noise emission status in the whole blanking processing.(2) A mathematic expression on blanking process noise sound pressure level and blanking force on the break-through stage of blanking deformation is deduced systematically, that is the mathematic calculable model of maximum blanking process noise emission, which shows that blanking force is bigger, blanking noise sound level is higher.(3) For the first time, this dissertation presents two mathematic model that can predict maximum blanking process noise emission sound level, respectively by sheet metals' tensile strength limit and by sheet metals' HV hardness, and typically suggests the model predicting blanking process noise produced on the break-through stage by sheet metals' HV hardness.(4) Through the simulation results of blanking deformation of these three kind of sheet metals that are respectively sheet steels, sheet brass and sheet aluminum, accurately locating the sheet metal's break-through; an important conclusion can be drawn theoretically, which shows that sheet metal's deformation is on the break'through stage while proportion of punch's cut-in deep to sheet metals' thickness is almost 0.5 to 0.6.(5) On basis of theoretical analysis to two steps blanking process, a blanking process with progressive dies for noise reduction is introduced, which can be steered by the simulation results of sheet metal's blanking deformation and has been tested in the experiments. Finally, four sets different progressive dies are introduced for two steps blanking process.(6) Presenting a new blanking process with adding the counterforce on punch's head to reduce noise level, which equals to general blanking process in operation, practicability, and productivity, and also has been tested in the experiments. So, it is another new blanking process for noise reduction.