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DETERMINATION OF THE MAIN ACOUSTIC EMISSION SOURCES DURING MACHINING OF METALLIC MATERIALS

Objective


The laboratory prototype of an AE system for tool wear monitoring at machining processes (turning, drilling, grinding, etc) has been developed and built up. The system has been tested with artificial AE signals and in the frame of grinding experiments. Both the hardware and the software necessary to handle the system have proven their functionability. It is intended to apply the system not only for monitoring of machining processes but also for other areas where continuous AE is generated, e.g. for condition monitoring of bearings. For that purposes some further developments and improvements of the AE equipment have to been done. This should be performed in the frame of the construction of an industrial prototype. This goal appears to be feasible since no principal obstacles have been found.

The model of AE generation by friction has been verified by tribometer and grinding experiments. The original approaches have been modified and expanded in order to qualitatively fit the experimental results. The basic assumptions of the model were found to be justified. Additional improvements of the model in future are useful and feasible.
The proposed project deals with the basic understanding which is necessary for the development of a method for automatic monitoring of machining processes in industry.

During machining of metallic materials with geometrically defined cutting edge (turning, drilling, milling) acoustic emission (AE) is generated. As shown in a previous BRITE-project, tool wear is detectable with AE with high sensitivity. Nevertheless up to now it is not clear which mechanism gives the main contribution to AE during machining. In earlier publications plastic deformation and crack growth are assumed to be the main sources. More recent papers and also the above mentioned BRITE-project lead to the result that the friction between tool and workpiece is probably the essential source of AE. The general aim of this proposal is the clarification of this controversy, because it concerns the fundamentals of AE-techniques for tool wear monitoring in industrial manufacturing. As long as it is not clear, which is the dominating AE-source during machining, no focused development and optimisation of AE-technique for industrial application is possible.

The objectives concern the quantitative description of the different AE-sources and the experimental verification of the corresponding theoretical model. The major research tasks are: i) physical description of the generation of AE based on friction, ii) building-up an equipment which is suited for recording and analysing the AE from cutting process, iii) experimental investigations to determine the AE-sources which are relevant at cutting, iv) comparison of the experimental results with theoretical predictions. The proposal concerns focused fundamental research since the results will generate new fundamental knowledge on tool wear monitoring and will be the basis for a new automatic control system for the machining industry.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Fraunhofer-Gesellschaft zur Förderung der Angewandten Forschung eV (FhG)
Address
Im Stadtwald Gebäude 37
66123 Saarbrücken
Germany

Participants (3)

Centre Technique des Industries Mécaniques
France
Address
Avenue Felix Louat 52
60300 Senlis
FRAUNHOFER INSTITUT FÜR ZERSTOERINGSFR. PRU
Germany
Address
Krugerstraße 22
8054 Dresden
INEGI
Portugal
Address
Rua Dos Bragas
4099 Porto Codex