Galling wear detection and measurement in sheet metal forming




Voss, Brendan Michael

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Galling wear of sheet metal stamping tooling is an expensive issue for sheet metal forming industries. Forming of high strength steels, particularly in the automotive industry, has led to accelerated tool wear rates. These wear rates lead to product quality and die maintenance issues, making galling wear an expensive issue for automotive manufacturers and the sheet metal forming industries in general. Process monitoring allows for the continuous monitoring of tooling condition so that wear development can be detected. The aim of this investigation was to develop an in-depth understanding of the relationship between punch force variation and wear for implementation in future process monitoring regimes. To achieve this aim, the effect of wear and other friction influencing factors on punch force signatures were investigated. This required the development of an accurate method for quantifying galling wear severity so that the relationship between galling wear progression and punch force signature variation could be quantified. Finally, the specific effects of wear and friction conditions on the punch force signatures were examined. An initial investigation using a statistical pattern recognition technique was conducted on stamping force data to determine if the presence of galling wear on press tooling effected punch force variation. Galling wear on tooling, changes in lubrication type, and changes in blank holder pressure were all found to effect variation in punch force signatures shape. A new galling wear severity measurement methodology was developed based on wavelet analysis of 2D surface roughness profiles that accurately provided an indication of the location and severity of galling wear damage. Using the new method for quantifying galling wear severity in the relationship between punch force variation and galling wear progression was investigated, and a strong linear relationship was found. Finally, two prominent vii forms of punch force signature shape variation were linked to friction conditions driven by wear, lubrication, and blank holder pressure. This work describes and quantifies the relationship between galling wear and punch force signature variation. A new methodology for accurate measurement of galling wear severity is presented. Finally, specific forms of punch force signature variation are linked to different friction conditions. These results are critical for future implementation of punch force based galling wear process monitoring and a significant reduction in costs for the metal forming industries.



Sheet metal forming, galling, wear, process monitoring, wear measurement




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